Tuatara
Journal of the Biological Society
Victoria University of Wellington
New Zealand
Victoria University of Wellington
New Zealand
Volume14
Part1
April1966
Tuatara aims to stimulate and widen interest in the natural sciences in New Zealand, by publishing articles which (a), review recent advances of broad interest; or (b), give clear, illustrated, and readily understood keys to the identification of New Zealand plants and animals; or (c), relate New Zealand biological problems to a broader Pacific or Southern Hemisphere context. Authors are asked to explain any special terminology required by their topic. Address for contributions: Editor of Tuatara, c/o. Victoria University of Wellington, Box 196, Wellington, New Zealand. Enquiries about subscriptions or advertising should be sent to: Business Manager of Tuatara, c/o. Victoria University of Wellington, Box 196, Wellington, New Zealand.
Contents
(This issue edited by
Tuatara
is the journal of the Biological Society, Victoria University of Wellington, New Zealand, and is published three times a year. Joint Editors:
Botany Department, Victoria University of Wellington
The GenusNothofagus has been known in temperate lands bordering the South Pacific since the mid-nineteenth century, but it is only relatively recently that botanists have become aware that an equal or larger number of species also occurs in montane situations in New Guinea and New Caledonia (Van Steenis 1953, 1954). The latter are regarded as a distinct group within the genus—‘brassii group’—and are distinguished from the two temperate groups—‘menziesii’ and ‘fusca’—by differences in pollen form, and in anatomy and external morphology. Some authors (Baumann-Bodenheim 1953, Hjelmquist 1953) suggest that all or some of the brassii group should be regarded as a separate genus.
Fossil evidence (Couper, 1961) has shown, firstly, that species of the Western Australia and Grahamland Peninsula, Antarctica.brassii group formerly occurred in all higher latitude land areas within and beyondNothofagus, becoming extinct there during the Pleistocene glaciations; secondly, that Nothofagus appears to have reached New Guinea, presumably from the south and conceivably overland, only late in the Tertiary in the wake of Pliocene cooling. Nothing is known of the history of Nothofagus in New Caledonia, but if the genus migrated there at a similarly late stage then it must have traversed considerable stretches of ocean from New Zealand or Australia. Another possibility is that Nothofagus has been in New Caledonia since the
Up to the present time five species of Nothofagus have been described from New Caledonia (Baumann-Bodenheim, 1953). On a recent visit I was able to collect and observe three species and I found them to be surprisingly different in appearance from those of New Zealand. The most striking differences were in the leaves, which were relatively large in size, thick and coriaceous in texture and, at the adult stage, revolute at the margins and recurved at the tips.
In Nothofagus sp. (probably undescribed) adult leaves were about 3 X 1 inches; Nothofagus balansae 3 1/2 X 1 inches; and Nothofagus codanandra 8 1/2 X 2 inches. Juvenile leaves were noticeably different in the last two species, being quite flat and larger than the adult. In Nothofagus codanandra juvenile leaves were seen which measured 10 X 3 1/2 inches! It does not seem, however, that leaf size can be used as one of the distinguishing features of the brassii group as several of the New Guinea species within the group have quite small leaves and some South American species outside it have large leaves.
Other notable differences from the New Zealand species were the attachment of the stipules near their mid-points (peltate) rather than at one end and the large bi-lobed cupules at the fruiting stage each containing three large, markedly flattened and winged seeds. Examination of the bud scale scars in the three species showed that each leaf lasts for two or three years. This is in agreement with Nothofagus menziesii in New Zealand, but in the three other New Zealand species, all in the ‘fusca group’, the leaves last for only one year. Other species of the ‘fusca group’ in South America and Tasmania are deciduous.
Ecologically, one of the New Caledonian species of Nothofagus, N. balansae, where it occurred in a non-serpentine area, displayed many interesting similarities with the species in New Zealand and elsewhere.
The area referred to was near the centre of the island just south of the Col des Roussettes, where the main road from the west to the east coast crosses the island. The terrain was steep and comprised a series of ridges rising gradually to an average height of about 2,000 feet. Milling was in progress in the area and for this reason, as well as periodic fires, the vegetation nearest the
Fig 1: Some Nothofagus species of New Caledonia (A-E) and New Zealand (F-J) × 3/5. A-C. N. codanandra (A-juvenile leaf, B-adult leaf, C-twig with cupule containing 3 seeds); D. N. sp. (adult leaf); E. N. balansae (adult leaf); F. N. fusca; G. cata; H. N. solandri var. cliffortioides; I. N. menziesii; J. N. solandri var. Photo: M. D. KingMelaleuca leucadendron), although the original vegetation was probably rain forest of which only scattered regenerating patches remained. Near a ridge crest small patches of Nothofagus balansae occurred alongside a milling road. The individual plants were mostly young and slender, although in places there were groups of trees with trunks up to about one foot in diameter. Nothofagus seedlings were locally abundant on clay banks edging the road.
With increasing distance from the main road the Melaleuca woodland diminished and the area of rain forest increased. The Melaleuca became restricted to scattered patches within the rain forest, often leading from a timber road to a ridge crest. On one occasion I walked from a campsite at about 1,700 feet up a ridge which levelled off at about 2,000 feet. The lower parts of the ridge were in rain forest, but this gave way at higher levels to Melaleuca woodland showing obvious signs of a recent undergrowth fire. The Melaleuca was extensively developed on one side of the ridge, over the crest and for a short distance down the other side, where it formed a sharp boundary with rain forest. Prominent along this boundary were a number of small trees of Nothofagus balansae.
Continuing further along the ridge the Melaleuca gave way to an almost pure ridge crest stand of Nothofagus at a point where the ridge began to slope down into a saddle. The trees were young and of two size classes — on the ridge crest no more than five or six inches in diameter and just to one side of the ridge mostly about 10 inches in diameter.
In the saddle itself Nothofagus gave way to rain forest, but the long, level ridge on the far side supported a narrow belt of apparently undisturbed Nothofagus forest in which Nothofagus balansae appeared to be the only tree species. The trunks were mostly a foot or less in diameter, but there were also scattered larger trees with trunks two to three feet in diameter and standing about 40 to 50 feet high. Some of the latter were dead and there were also a number of large logs, some recently fallen, others much older. It almost seemed as if an older generation of trees were being replaced by a newer generation. No vascular epiphytes or lianes were noted and shrubs and sapling Nothofagus were rare. The ground was open and completely covered with a leaf litter entirely derived from the Nothofagus. Nothofagus seedlings were numerous, only a few inches high, and predominantly at the three leaf stage.
In slight hollows and level areas there was a layer of fine fibrous roots about an inch thick with leaf litter above and pure clay below. This root layer held a certain amount of dry, humus-like material. In slightly raised places the leaf litter lay directly on
Nothofagus in New Zealand. The upturned root systems were flat and plate-like with masses of pure clay still attached to them.
This pattern of Nothofagus forest occurring on poor skeletal ridge crest soils with rain forest on the deeper soils of the valleys and valley sides can also be seen in New Zealand, for example near Wellington, and in South Queensland (Nothofagus moorei). Robbins (1961) states that in some places in New Guinea Nothofagus dominates on the ridges with podocarp-broadleaf forest below.
The other locality where I saw Nothofagus (N. codanandra) in abundance was above about 2,000 feet in the Montagne des Sources area, which forms part of the large southern serpentine region. The Montagne des Sources was to a large extent clothed with short xeromorphic shrubby vegetation, but there were also considerable areas of forest, particularly at higher elevations. The main type of forest was very distinctive being fairly open and dominated by species of Araucaria, Agathis and Casuarina. It differed in many respects from the rain forests dominated by broad-leaved angiosperms. The Nothofagus forest occurred as apparently randomly scattered patches within the predominant forest type and differed from the Col des Roussettes forest in exhibiting no particular preference for ridge crests. Some of these patches were quite large and were readily discernable from a distance owing to the distinctly reddish colouration of the new vegetative growth. Unlike the ridge crest Nothofagus balansae forests at the Col des Roussettes, N. codanandra was here not the only canopy tree, although it was certainly the commonest. Several other tree species were present including scattered Araucarias.
Schmid (pers. comm.) has studied Nothofagus on serpentine mountains further to the north—Mt. Mou (Nothofagus baumannii) and the massifs of Me Maoya at about 4,500 feet and Boulinda at about 3,500 to 4,000 feet (at both localities, there was the same, probably undescribed species of Nothofagus). He reports that, as was the case at the Montagne des Sources, Nothofagus forest mostly occurred on the side slopes of ridges, on soils of medium depth, rather than along their crests. Schmid also notes that the Nothofagus at these localities was frequently intermixed with other species, mostly belonging to the genera Araucaria, Podocarpus and Dacrydium.
Smaller groups of Nothofagus were seen at localities further south in the serpentine region. On the road leading to the Montagne des Sources a group of young Nothofagus balansae was noted and scattered river margin trees of N. codanandra were seen at quite low elevations along the Riviere Bleu, which arises from the Montagne des Sources. In the Plaine des Lacs area Nothofagus
balansae was seen again, at low elevation, as a forest margin species. The forest occupied a hillside valley system and appeared to be second growth comprising mostly broad-leaved angiosperm species. The third Nothofagus species seen by me, apparently also undescribed, was also growing here as a forest margin species, although I saw only one mature and one young tree. The leaves of this species differed from those of the other two in having shallow marginal teeth.
For further information on Nothofagus on serpentine see Hurlimann 1962.
Another interesting ecological similarity between the New Zealand and New Caledonian Nothofagus species lies in periodicity of flowering. In both countries species of the genus flower and set seed in abundance only at intervals of several years. Such heavy flowering apparently follows unusually warm preceding summers in New Zealand (Poole, 1948; Kirkland, 1961) and has been recorded throughout the country or regionally in 1935, 1938, 1944, 1948, 1951, 1956, 1959, 1965. In New Caledonia Corbasson (pers. comm.) reports heavy flowering in Nothofagus in 1950, 1957 and 1964. Nothing is known of the cause or causes of this apparently seven-year cycle.
In conclusion, from the ecological pattern displayed in New Caledonia and the other regions already referred to, it would appear that where the climate is suitable for rain forest, and where there is no very special edaphic factor such as serpentine parent rock, Nothofagus tends to be restricted to situations where the soil is poor, particularly along ridge crests. At higher altitudes and latitudes, where climates are less favourable or unfavourable for rain forest Nothofagus may then form continuous and much more extensive forests.
I should like to thank M. Schmid of the Laboratoire de Botanique, Centre Orstom, and M. Corbasson, Director of the Bureaux des Eaux et Forets, for their assistance to me in New Caledonia and also for reading the manuscript of this article and providing valuable additional information.
Bull. du. Mus. Nat. d'Hist. Naturelle.Ser. 2, 25: 419-421.
Proc. Roy. Soc. Lond. B.152: 491-500.
Nothofagusfrom New Guinea and New Caledonia.
Botaniska Notiser116: 225-237.
Proc. 9th Pac. Sci. Cong. 4.
N.Z. Jour. For.8: 482-497.
N.Z. Jour. For.5: 422-427.
Tuatara8: 121-133.
Nothofagus. Jour. Arn. Arb.34: 301-374.
27 Merchiston Street, Dunedin
The Lichen FamilyParmeliaceae is represented in New Zealand by six genera with an approximate total of eighty species. Hypogymnia and Menegazzia, formerly included in Parmelia as subgenera, are today generally accorded full generic rank. They are represented by seven and fourteen named species respectively, but there are several new species of Menagazzia awaiting determination and description. Parmelia has approximately fifty species, Cetraria six, and Anzia and Chondropsis one each.
The status and even the validity of several named Parmeliae may be open to question, as many early descriptions were meagre and inadequate, while much relevant literature, almost all types, and even authentic specimens are not available in the Dominion. These factors make the preparation of an accurate Key very difficult.
The late Dr. Parmelia in which he included both Hypogymnia and Menegazzia—40 species in all—part of which I have incorporated in the following Key. As this Key is based in part on published descriptions only, inaccuracies may well be present; but the lack of suitable Keys in many genera makes ecological studies in particular exceedingly difficult: and as the completion by Dr. Mason E. Hale of his monograph of the genus Parmelia may be expected to take some considerable time yet, it is felt that circumstances warrant the present Key, always realizing that final determinations cannot safely be made solely from a Key.
In his ‘Conspectus Systematicus Lichenum Novae Zelandiae’ of 1894 Dr. J. Muller has already eliminated some sixty species erroneously classified as Parmeliae, or attributed to the wrong species of Parmelia. It may be that one or two species retained by me are also synonyms. Several other recorded species have been omitted for lack of detailed information.
For a glossary of the terms used in these keys see Tuatara 10: 124-128, 1962.
(Note: K and C refer to aqueous solutions of caustic potash and calcium hypochlorite respectively, and P to an alcoholic solution of para-phenylene diamine. The + sign implies a colour reaction, y-r indicates a yellow colour turning to red. All reactions refer to the medulla unless otherwise indicated. The use of a lens may be necessary to detect pseudocyphellae.)
I am indebted to Mr.
Omitted from the Key for various reasons are the following reported species:— Parmelia furfuracea, P. limbata, P. linkolae, P. pyracea, P. ruditor, P. schweinfurthii, P. subalbicans P. subconspersa. The New Zealand species of the other genera are listed below.
a. Dispora (2-4 spores in each ascus).
M. aucklandica, M. cincinnata M. circumsorediata, M. dispora, M. foraminulosa, M. nigrescens, M. nothofagi, M. opuntioides (?) and M. pertusa.
b. Octosporae (6-8 spores in each ascus).
M. amabilis, M. dielsii, M. inflata, M. pertransita, M. stirtonii, M. weindorferi.
a. Lobes hollow.
H. enteromorpha, H. lugubris, H. physodes, H. subphysodes, H. turgidula.
b. Lobes solid.
H. billardieri, H. subteres.
C. corallophora, C. dermatoidea, C. glauca, C. islandica, C. novae-zelandiae, C. sepincola.
Anzia angustata, Chondropsis semiviridis.
Fisheries Research Division, Marine Department, Wellington
Present address: Museum of Comparative Zoology, Harvard University, Cambridge, Massachusetts 02138, U.S.A.
The Most Widely Recognised Species of whitebait in New Zealand is the juvenile of Galaxias attenuatus (Jenyns) but it is now known that other New Zealand Galaxiidae also have marine whitebait. The whitebait stages of G. attenuatus, G. postvectis Clarke, G. fasciatus Gray, and G. brevipinnis Gunther have been described (McDowall, 1964b) and it was suggested that G. argenteus (Gmelin), because of its similarity to some of these other species, would also be found to have a marine whitebait stage. This paper describes the whitebait of G. argenteus and discusses the relationship between the marine existence of some Galaxias species and the distribution of the family Galaxiidae. The distribution of the Galaxiidae around the southern hemisphere land masses was discussed by McDowall (1964a).
During a survey to determine the composition of the commercial whitebait catch in New Zealand (McDowall, 1965), a sample of whitebait was collected from the Buller River and the fish reared
G. attenuatus which was well known to have a marine whitebait. G. attenuatus can be distinguished from other Galaxias whitebait by the more extensive trunk pigmentation. One of the survivors of this sample was, in fact, G. attenuatus. The fish were captured by a whitebaiter using a scoop net about half a mile upstream from the mouth of the Buller River and well within the tidal reaches. Eleven fish survived until they were identifiable, and one of these was G. argenteus, strongly suggesting that this species has a marine whitebait. Definite proof that the whitebait of G. argenteus is marine, and not merely estuarine, is lacking. However, in view of the strong evidence that G. postvectis and G. fasciatus have marine whitebait (McDowall, 1964b), and the close relationships between these two species and G. argenteus, it is considered highly probable that the whitebait of G. argenteus is marine.
It is remarkable that the eleven survivors of the sample comprised 5 G. fasciatus. They thus represent all five species of Galaxias known to have marine whitebait in New Zealand. G. argenteus was subsequently identified in many samples from rivers on the west coast of the South Island.
1 G. attenuatus, 1 G. brevipinnis, 1 G. argenteus, 3 G. postvectis and
G. argenteus
G. argenteus whitebait were found to be more heavily built than the whitebait of other species. Measuring between 50 and 55mm length to caudal fork (L.C.F.), they were deep and thick bodied, with broad long head, a deep caudal peduncle and an expansive caudal fin. The pigmentation of G. argenteus whitebait is similar to that of G. fasciatus and G. postvectis, consisting of rather indistinct dorsal, ventral and mid-lateral series of melanophores, with further melanophores on the head and opercular margins (Fig. 1). Soon after the fish enter fresh-water, pigmentation begins to intensify and the young G. argenteus becomes a dark grey-brown colour, and later 8-10 distinct pale blotches or bands develop on the sides of the trunk (Fig 1). This pattern is quite different from G. fasciatus juveniles in which the bands are narrower and much more numerous, and from G. postvectis in which the bands are dark on a paler body colour.
The adult of G. argenteus has a mass of yellow-gold spots, rings, crescents and lines on the dorsum of the head, the trunk and the fin bases (Fig. 2). These markings are superimposed on the bands of the juveniles, which may still be visible in younger adults, but become obscured in older fish. The body colour of the adult ranges from light brown to dark chocolate.
Fig. 1: Galaxias argenteus (Gmelin). Upper: whitebait, 54mm. L.C.F. Lower: banded juvenile 58mm. L.C.F.
Some writers have expressed the view that the family Galaxiidae is primarily a fresh-water one. Stokell (1950) suggested that some form of land connection between the areas of galaxiid distribution was necessary until the Galaxiidae had evolved. Although it has been known for a long time that G. attenuatus has a marine whitebait, it has been thought by some that the marine stage of G. attenuatus is atypical of the Galaxiidae (e.g. Phillipps, 1919). The distribution of G. attenuatus around the southern land masses may be quite recent, but the existence of further species of Galaxias with marine larval stages shows that the marine life of G. attenuatus is not atypical.
The distinctive life-cycle of G. attenuatus, more particularly the persistent shoaling habits (found only in the juveniles of other species) and the characteristic habit of breeding amongst vegetation above normal water levels suggest that G. attenuatus is not a typical galaxiid. Ogilby (1899) drew attention to the distinctness of G. attenuatus when he removed it to the new genus Austrocobitis. The validity of using G. attenuatus to explain the dispersal of the ancestral Galaxiidae is thus doubtful, but the knowledge that
G. attenuatus as a pointer to Galaxias distribution patterns and means of dispersal.
Fig 2: G. argenteus adult, 260mm. L.C.F.
G. attenuatus appears to be differentiating in several land-locked lakes where the marine larval stage is eliminated. Stokell (1964) described a form of Galaxias (G. parrishi) from Lake Bullen Merri, Australia, and noted another similar form from Lake Colac. The author has specimens of ‘G. attenuatus’ collected from Lake Modewarre in Australia by Mr. G. parrishi Stokell and G. attenuatus. In a survey of the coastal dune lakes of New Zealand (Cunningham et al, 1953), specimens of a fish very similar to G. attenuatus were collected from Lake Waiparera, a small land-locked lake near Kaitaia, and these showed differences from G. attenuatus similar in degree to the differences described by Stokell for G. attenuatus and G. parrishi.
The ability to forsake a partially marine life and adopt a purely fresh-water one where circumstances are suitable appears also to be true for G. fasciatus which has been collected from the Kaihoka Lakes, near Collingwood; neither of these small lakes has an outlet stream yet there are large populations of G. fasciatus in them. The similarities in the form and life history patterns of the partially marine G. brevipinnis and the two lake Galaxiidae G. lynx Hutton and G. koaro Phillipps, suggest that these lake species may be derived from a species with a marine whitebait. The marine whitebait is replaced by a lake whitebait with subsequent diversification isolated from the parent stock. It appears that the family Galaxiidae can be regarded as a euryhaline fresh-water family in which there is capacity for adaptation to a purely fresh-water existence when isolated by some barrier from the sea.
The fact that certain species of Galaxias have marine whitebait is reflected in their New Zealand distribution. G. fasciatus is particularly widespread and occurs from North Auckland to Southland on both the east and west coasts of New Zealand; it is also known from the Chatham Islands (Stokell, 1950), the Chicken Islands, Stewart Island (Stokell, 1949), Little Barrier Island, Cavalli Island. Mercury Island, D'Urville Island and Kapiti Island. G. argenteus and G. postvectis are less widely recorded, but this may partially be attributed to the difficulty in capturing these species from the dense cover they live in. However, G. argenteus is known from the Bay of Plenty, Taranaki, Wellington, Wairarapa, Canterbury, Westland, Fiordland, Otago and Southland. G. postvectis is not commonly collected, but is now known from North Auckland, Bay of Plenty, Taranaki, Wellington, Marlborough and Westland. Many of these localities are from the author's records. With further collecting it seems likely that both G. argenteus and G. postvectis will be found in New Zealand wherever suitable habitat is accessible to them.
G. brevipinnis is as widely distributed on the mainland of New Zealand as G. fasciatus. It has been found in North Auckland, Waikato. Bay of Plenty, Hawke's Bay, Taranaki, Wanganui-Manawatu, Wellington, Westland and Otago, and has also been recorded from Kapiti Island (Wilkinson and Wilkinson, 1952). G. campbelli Sauvage, from the sub-antarctic islands of New Zealand is regarded by Stokell (1954 and 1960) as con-specific with G. brevipinnis. G. attenuatus occurs throughout New Zealand and is known from some of the offshore islands and from the Chatham Islands.
Other species are more restricted in their distribution. G. divergens Stokell and Neochanna apoda Gunther occur in the southern North Island and the Nelson-West Coast area; these regions were connected as recently as the Pleistocene glaciations (Fleming, 1962). Galaxias lynx occurs in the mountain lakes of the South Island, and is also recorded by Stokell from Lake Waikaremoana in the North Island. Apart from this apparent anomaly and the cases of G. divergens and Neochanna apoda, all New Zealand Galaxiidae not having marine whitebait are confined to one or other of the major islands, and present data indicate that many have very restricted distributions, e.g. G. burrowsius Phillipps is recorded only from Mid-Canterbury, G. paucispondylus Stokell and G. prognathus Stokell are known only from mountainous Canterbury streams. G. koaro Phillipps occurs only in the thermal lakes of the central North Island.
The much broader distribution of G. attenuatus, G. postvectis, G. fasciatus, G. argenteus and G. brevipinnis appears to be closely
The hypothesis that the genus Galaxias has been distributed amongst the southern land masses by oceanic routes is supported by the discovery that several species, apart from G. attenuatus, have marine whitebait. The fact that G. attenuatus is present in three widely separated land masses (Australia, New Zealand, South America) shows that its larvae and juveniles are capable of oceanic dispersal, and that this dispersal could have taken place quite recently. The presence of marine larvae in several species now restricted to New Zealand indicates that the family has had a potentiality for oceanic dispersal for a long time, i.e. long enough to allow the evolution of distinct species in New Zealand.
Any doubts about the validity of G. attenuatus as an index for the early distribution of the family are no longer of consequence as more ‘typical’ species of Galaxias support the hypothesis of oceanic dispersal equally strongly. However, although at least three species in Australia (Lynch, 1965) and five species in New Zealand have marine juveniles, only one species is found to occur in more than one faunal region. This suggests that in the past, success in movements of these fishes across these gaps must have been infrequent. Apart from the comparatively recent dispersal of G. attenuatus, all species were apparently dispersed sufficiently long ago to allow divergence to bring endemism to all the other forms of Galaxias in each area. It is possible that some change in the marine life, such as a reduction in the length of the marine stage, has affected the ease with which the marine tolerant Galaxiidae are dispersed.
In the previous paper (McDowall, 1964a) it was suggested that the New Zealand Galaxiidae had Australian origins. If this is the case, then the presence of five species with marine juveniles in New Zealand is probably a result of diversification of Australian form(s) in a New Zealand fresh-water environment almost uninhabited by fish. Because dispersal in the south-temperate region is probably west to east, these marine tolerant New Zealand species would be unlikely to reach Australia. That only one of the five species is known to have crossed the South Pacific from New Zealand to South America is not surprising in view of the great distance involved.
The author is indebted to the following for their assistance: Mr.
Aust. J. Mar. Freshw. Res.4 (2) 343-386, 2 pl.
Aust. Fish. Newslett.24 (4): 13 and 15, 1 fig.
Tuatara12 (2): 59-67, 1 fig.
Tuatara12 (3): 134-146, 4 figs.
N.Z.J. Sci.8 (3): 285-300, 10 figs.
Proc. Linn. Soc. N.S.W.24 (1): 154-186.
Galaxias attenuatus. Aust. Zool.1 (7): 211-213.
Trans. Roy. Soc. N.Z.77 (4): 472-496, 12 figs.
Cape Exped. Ser. Bull.9: 1-8, 1 fig.
Trans. Roy. Soc. N.Z.82: 411-418, 2 figs.
Galaxias postvectisClarke with notes on other species.
Rec. Dom. Mus. N.Z.3 (3): 235-239.
Galaxiasfrom Victoria, Australia.
Rec. Dom. Mus. N.Z.5 (6): 45-48, 1 fig.
Kapiti Bird Sanctuary, a natural history of the island.Masterton, Masterton Printing Co., 190 pp., 24 pl.
With the Development of statistical methods ecology is graduating to a more exact science. The days when the preparation of a species list or a vegetation map was the prime objective of an ecological study are now almost past. Closer attention is being given to the correlation of plants with their habitats, to the influence of the biotic factors on vegetation and to the microclimates in which the different communities develop. Consequently techniques by which data are accumulated are becoming more objective, with the result that different observers obtain similar records from a given ecological community, and the subjective or personal factor in making records is reduced to a minimum.
The following data were obtained by Botany students of Victoria and Auckland Universities in the course of their practical field work in Ecology during May, 1965. Data obtained from the same area by the 1963 (Victoria University) class have been included.
The scheme of work was designed to illustrate the Importance Value Index technique of Curtis and Macintosh (1951), and to study the vegetation above the timber-line on the Bruce Road, Mount Ruapehu. A preliminary examination indicated that, at any given altitude, the vegetation changed considerably with the shelter or exposure of the habitat, and was greatly influenced by cold air drainage and snow drifts of varying persistence. It was decided to study the vegetation of only one aspect, the north-west aspect in the neighbourhood of the Bruce Road. The graphs indicate that a reasonable uniformity of trend was achieved in the data obtained from each station, and the changes in the index for each species would seem to be related to its reaction to the habitat and the changing altitudes: but it should be stressed that the data as presented are applicable only to slopes facing north-west.
The class was divided into five groups of ten or more students, and a different group worked on the sub-alpine vegetation each day over a period of ten days. On the site each group was divided
The groups were instructed to ignore mosses (other than Rhacomitrium lanuginosum) and lichens; but in some cases these have been included though without specific determination. They have been grouped together in the tabulated data as ‘Sundry mosses and lichens’, since, having been included in the calculations, their omission would prevent checking of the total of the indices at each station. However no weight can be given to records of ‘mosses and lichens’, in Table I, since they were not recorded uniformly by all groups.
The practical details in the field, the checking of altitude and assistance in the identification of species were the responsibility of a member of staff or his deputy who supervised and co-ordinated the work of successive parties throughout the week.
The observations of abundance, dominance and sociability were carded and put on a computer as an experimental attempt at rapid analysis. The totals of each of these statistics for each species at each altitude were available the week after the cards had been completed, and a table for interpolating the ‘relative’ data was provided. With more efficient programming the Importance Value Index (I.V.I.) could have been obtained in the same time. Because absences were not carded, frequency and relative frequency were calculated manually from the summaries of the original data. The I.V.I. was obtained on a calculating machine by adding the figures for relative abundance, relative dominance and relative frequency for each species at each altitude. The sums of each of the contributing statistics and of the index were checked to confirm the accuracy of the calculations.
Importance Value Indices are presented both in tabular form (Table 1) and as graphs (Table 2) for each species at each different altitude. The species are arranged in the graphs according to three criteria: first, those species that are common throughout the range of altitudes sampled: secondly, according to the sequence in which they disappeared from the record as the altitude increased: and finally, in the approximate order in which they appeared in the record as the altitude increased above 4000 feet.
Though these data were obtained as part of an undergraduate field course in ecology, I am confident that most of the work was done conscientiously, and this is confirmed by the uniformity of the
C. B. Williams (1950), stresses that the relation between the distributions of species and individuals in the original population and in a series of quadrats depends on three variables, namely:
To increase the size of the quadrats, whether measured by individuals or by area, will cause more species to be included in each and so the number of species that are common to all quadrats will be more. To study a greater number of quadrats increases the number of species that occur in but a few quadrats. Thus both size and number of quadrats will affect frequency and especially relative frequency.
The effect of size can be eliminated if the quadrat size in different plant communities is related to the minimum homogeneous floristic area as determined from the species area curve. In the area under consideration the homogenous floristic area at 4.100ft. appears to be about 16 square metres; and at 4,700ft. about 12 square metres. Thus square quadrats on a side of two metres (four square metres) are between one-third and one-quarter of the homogeneous floristic area. This relationship permits the more common species to achieve 100 per cent. frequency and avoids confusing them with those less common plants which would nevertheless appear in most of the minimum homogenous floristic areas. A finer calibration of the distribution of a species in the community is thus possible.
The large number of quadrats at some altitudes has resulted in the sampling of a larger area, and has thus included more species in the data for that station, but since these contribute little volume to the vegetation and have low frequency the variation in the number of quadrats at any one site has not greatly affected the I.V.I. of the major species at that site.
Some slight allowance must be made for the assessment of alitude. Most of the plots recorded at any given altitude were placed within 12 or 15 feet of that altitude, as determined by a sensitive aneroid altimeter.
Table 1. Importance Indices of Species Recorded on North-West Aspects of Bruce Road Mount Ruapehu, Tongariro National Park.
Table 1 (continued)
Table 2. Graphical Presentation of Importance Indices for Prominent Species on North-West Slopes, Bruce Road, Mount Ruapehu.
Table 2 (continued)
This method of analysis has permitted a clear-cut assessment of each of the 74 species that were encountered in some 270 quadrats studied at 18 altitudes between 4,000 and 5,600 feet on Bruce Road, Mount Ruapehu. No species were recorded at every one of the 18 altitudinal stations, and only six species (Dracophyllum recurvum, Anisotome aromatica, Senecio bidwillii, Gaultheria colensoi, Celmisia spectabilis, Rhacomitrium lanuginosum and another unidentified moss), were recorded over the whole of the altitudinal range. Three other species were recorded regularly between 4,100 and 5,600 feet, namely Wahlenbergia pygmaea, Helichrysum bellidioides and Drapetes dieffenbachii. These nine species contribute a total of 2283 I.V.I. units out of a possible 5,100 units for the whole analysis, and may be considered as the most important species in the community since they contribute jointly 44.8 per cent. of the total I.V.I. Only three other species, Notodanthonia setifolia, Gentiana bellidifolia and Coprosma pumila are recorded regularly between 4,100 and 5,500 feet. Of these the first would be about three times as important as either of the other two.
An examination of the graph indicates that a number of species seem to have an upper limit of 4,500 to 4,600 feet. Among these species may be listed Neopanax colensoi, Pimelea buxifolia, Olearia nummularifolia, Hypolaena lateriflora, Gleichenia circinata, Dracophyllum filifolium, D. subulatum, Hebe odora and H. venustula.
Within this range of altitudes (4,000-4,500 feet) the ten species that contribute most to the vegetation in the order of their importance are Gleichenia circinata, Chionochloa rubra, Dacrydium laxifolium, Dracophyllum recurvum, Celmisia spectabilis, Coprosma cheesemanii, Hebe odora, H. venustula, Rhacomitrium lanuginosum and Dracophyllum filifolium, which together contribute 944 of the possible 1,800 I.V.I. units attributed to this region.
Between 4,500 and 5,000 feet at which altitude such species as Podocarpus nivalis, Dacrydium laxifolium, Chionochloa rubra, Hebe tetragona, Myrsine nummularia and Gaultheria antipoda reach or approach their upper limit of growth, the plants that contribute most to the I.V.I. in the order of their importance are Dracophyllum recurvum, Rhacomitrium lanuginosum, Celmisia spectabilis, Anisotome aromatica, Notodanthonia setifolia, Gaultheria colensoi, Pentachondra pumila, Dacrydium laxifolium, Senecio bidwillii, Chionochloa rubra and Wahlenbergia pygmaea. These eleven species contribute together 1,000 I.V.I. units of a possible 1,800 distributed through the six stations in this region.
Above 5,000 feet the most obvious change is in the increased importance of Helichrysum bellidioides and Drapetes dieffenbachii, in an area where the vegetation is becoming very sparse and
Rhacomitrium lanuginosum, Dracophyllum recurvum and Gaultheria colensoi; each of which contributes more than 180 units to the total 1800 I.V.I. ratings in this area. These with Anisotome aromatica, Helichrysum bellidioides and Notodanthonia setifolia contribute 59 per cent. of the possible I.V.I. units of the area.
A few species extend from lower altitudes into this highest region and seem to find their maximum altitude at 5,200 feet. Included in these are Pentachondra pumila, Euphrasia cuneata, Ourisia vulcanica, Poa caespitosa, and Hebe tetragona. The sharpness of the exclusion of these species from the records at this altitude may be due to the fact that the next station is at 5,380 feet, an increase of 180 feet in elevation.
It is thus clear that there are two regions where changes in the plant communities can be discerned. That at 4,500-4,600 feet is not so readily obvious; but that between 4,900 and 5,000 feet was anticipated by the field parties, though it was defined by them as a change in the floristic lists, rather than as a change in physiognomy of the vegetation.
Physiognomically, the vegetation between 4,000 and 5,600 feet on the north-west aspects of the Bruce Road, Mt. Ruapehu, would appear to be one plant association in which Dracophyllum recurvum, Rhacomitrium lanuginosum, Celmisia spectabilis, Senecio bidwillii, Anisotome aromatica and Gaultheria colensoi are the most important species. This may be divided into perhaps three plant communities separated by the presence or absence of certain species. These communities may be described as follows.
The Gleichenia-Chionochloa-Dacrydium laxifolium community that exists between 4,000 and 4,600 feet would owe its physiognomic appearance to Gleichenia circinata, Chionochloa rubra, Hebe odora, H. venustula and Phyllocladus alpinus. The Dracophyllum recurvum-Rhacomitrium-Celmisia spectabilis community, differs physiognomically by the absence of Gleichenia, Hebe odora, H. venustula and Phyllocladus whose places are taken by Podocarpus nivalis, Pentachondra pumila and Hebe tetragona. This latter group is present but less prominent in the previous community. This community appears to lie between 4,500 and 5,100 feet on north-west slopes of the Bruce Road.
The third community, above 5,100 feet, would be Rhacomitrium-Dracophyllum recurvum-Gaultheria colensoi. It is notable because of the increased importance of Helichrysum bellidioides and Drapetes dieffenbachii; but in spite of the moss present the community is very open, and provides a very poor coverage of the ground.
It will be noted in the graphs that the record of a species at its highest altitude is often graphed as a high peak out of character with the rest of the graph. This is probably because, in most cases, the working parties were taken to the highest altitude and worked their way downwards. As a new species was observed in the vegetation at the new station it was natural that each party wished to include it in their records, and so it was consciously included in the plots at that altitude. It was no longer a novelty at the next station down the mountain, and so fell into its natural place as a species in the random placing of quadrats. These peaks therefore show a bias when the species is first observed as a new species in the record — a human touch — but the bias is not continued in subsequent stations. When this interpretation was put to the students it was confirmed and admitted as a course that had been adopted by several parties.
One aspect that must be recognised in interpreting these results is that the Importance Index is just what it is called. It is in fact the sum of the relative abundance, the relative dominance and the relative frequency attributable to each species for which data were obtained at each station. These statistics represent the contribution that a species makes to the community in respect of (a) the number of plants within the quadrats (abundance), (b) its influence on the other species through its shading, competition or aggressiveness (dominance), and (c) its contribution to the community through its distribution (frequency). There is no estimate or measurement of the volume or productivity of a species in the quadrat, and no absolute assessment of the space occupied by the plant. Consequently the Index is not a measure of production. In fact, the plots at the highest altitudes were very sparsely covered by vegetation. Thus, in the absence of any data concerning the amount of bare ground, the Index is purely a measure of the contribution of a species to that vegetation which is present, regardless of whether the ground is completely covered (as it was at the lowest altitudes) or very sparsely covered, as at the highest.
In the three communities ten or eleven species contributed more than half the I.V.I. of the important vegetation. Dominance was shared by several species at each altitude, and, with the possible exception of Gleichenia circinata, no one species exerted complete dominance over any appreciable area. Importance, as indicated by I.V.I., was shared by several species, and, though these may change from station to station, they are not necessarily the physiognomic species of the community.
Some 270 quadrats were distributed over eighteen stations at different altitudes between 4,000 and 5,600 feet on north-western slopes adjoining the Bruce Road, Mt. Ruapehu, Tongariro National Park, and abundance, dominance and frequency ratings obtained for each species encountered.
Importance Value Indices were calculated for each species at each station. These have been graphed against increasing altitude.
Some twelve species were found to have their upper limit of growth about 4,500 feet, six others at 5,000 feet, while only seven species were recorded throughout the range from 4,000 feet to 5,600 feet.
On the basis of these changes in floristic composition, and changing importance of species as altitude increased, three subcommunities have been proposed within the one plant association that was studied.
I wish to acknowledge the contribution of the students of the Victoria University of Wellington Botany II and III classes of 1963 and 1965 who gathered the basic data that made this analysis possible. The 1965 class was joined for a week by the contemporary classes from Auckland University who contributed their share of data. The reliability of the data may be reasonably attributed to the leaders of the student groups who conscientiously endeavoured to assure that each party in their group followed instructions, and to the staff member, Mr.
Assistance has also been received from individual students, who wish to remain anonymous, in determining frequencies, carding the data for the computer, and drawing the initial graphs of Indices. Most of the 1965 Wellington class assisted at one time or another in working out various of the indices. Finally, in both 1963 and 1965 most of the staff of the V.U.W. Botany Department spent at least a week on the ecology field work, and if they did not actually take part in this project, they were in charge of other projects that kept those students not on Bruce Road busy.
Ecol.32: 476-496.
Journal of Ecology, 38: 107-138.
Botany Department, Victoria University of Wellington.
In the First Article of this series (Johnston 1965), we dealt with the importance of algae as producers of organic matter—the fuel of the biological world. While this is of fundamental importance to Man, it is not of such direct and personal concern as some of the other algal roles with which we intend to deal. As stated earlier, the range of their influence is rather astonishing and because of this it is difficult to know where to begin — where to make the incision into this corpus of fact and phenomenon.
Algae are photosynthetic, and together with their more highly evolved counterparts on dry land, are the only organisms which can lay aside the vast quantities of food reserves on which the animal world is entirely and irrevocably dependent. It is to be expected therefore that algae will initiate all animal food-chains in the seas and freshwaters, in much the same way as land plants initiate terrestrial animal food-chains. So our next section will deal with algae as articles of food.
Since food is the most important requirement of the human body and eating an ever enjoyable pastime, it is perhaps natural enough if we broach this huge topic by considering the algae that Man has used directly as food for himself. Many things that Nature does, Science tries to emulate or do better. Having seen how easily planktonic algae yield to laboratory culture, Science has tried to cultivate algae industrially for food — hoping through advanced technology to be able to improve on Nature's productivity. We must therefore see to what extent Science has been successful in improving on Nature in this sphere. Most important of all we must see how the algae fit into the scheme of things by acting as the biological protyle for aquatic animal foodchains, since these ultimately support the fishing industry — still the second largest industry in the world. It must not be forgotten that fish and not land-animal flesh is the major source of food protein for many millions of people.
In the present article we will deal with naturally-occurring algae as food for man, and the macroscopic marine algae called seaweeds will be our main concern.
For the production of food, people living on continents and large island masses have mostly been accustomed to what we regard as “conventional agriculture” with its cereal crops, pastures and grazing animals. Consequently, the use of seaweeds as food would usually be foreign to such societies except for those folk living on a seacoast — and these would use algae only to allay hunger in times of dire necessity such as crop-failure, to follow a fad, or to perpetuate the practice of an older indigenous population. It so happens that most if not all of the textbooks on algae have been written by people from societies living on land masses pedologically and climatically suited to conventional agriculture. Thus in these books the use of seaweeds as food finds little mention, and one might form the erroneous opinion that they are rather insignificant as articles of diet.
But outside the European, Eurasian, African, Australian and American continents and the larger islands capable of supporting agriculture as we know it, we find many millions of people living on islands where conventional agriculture can never be adopted. For this reason, those people inhabiting myriads of islands in the Pacific and Indian Oceans, the South China Sea and the seas around Borneo, New Guinea and Indonesia have traditionally and of necessity relied on the sea as their major source of food. For this reason, many of these island people have come to rely on seaweeds as an important element in their diet. In certain areas such as Japan this reliance have been so great and the demand so constant that methods of seaweed cultivation have been evolved and put into practice (see later). Acquired knowledge and skill have finally produced specialists in this technique, and given rise throughout time to a thriving industry employing considerable labour. Heavy outside demands have led over the years to the development of an export market.
East and West differ enormously in their use of seaweeds as food; and we can get some idea of this difference by referring to lists of the seaweeds eaten by peoples of each hemisphere. Tables I, II and III should help to establish a truer perspective of what seaweeds mean to people who cannot practice agriculture as we know it. The information in Table I (originally compiled by Zaneveld) has been rearranged in chart form to show more clearly the known distribution and consumption of the seaweeds he listed. One emergent feature is that most of the data come from larger countries or islands with well-established research institutions, who employ people interested in such esoteric things as seaweeds and their dietary and commercial significance. Zaneveld lists mainly warmwater seaweeds whose distribution must be much wider than recorded: and conceivably therefore their consumption is more widespread than is shown. For these reasons this Table should be regarded as
In Zaneveld's article, Japan does not feature as a great consumer of seaweeds; but the algae listed are mainly warm-water ones. Okamura lists more than fifty which are eaten by the Japanese (see Table III). Among these we recognise the cool-water ones familiar to us in temperate waters. The Koreans are just as keen on eating seaweeds as the Japanese and use almost all those quoted in Table III as well as ‘young fronds of Costaria turneri and Pelvetia wrightii’ (Okamura). The earliest reference to the culinary use of seaweed is found in Chinese writings. The Chinese have always regarded seaweeds as a delicacy; yet according to Table I China uses hardly any at all, despite the fact that much of her coastline lies below 32° latitude. This apparent anomaly calls for comment; but this is delayed till near the end of the article.
Before considering the value of seaweed as food, we must answer the question —‘What do we derive from food?’ Lamentably, the human body is neither photosynthetic nor nitrogen-fixing; so among the first things we need are sugars to provide us with energy for our body functions, and proteins whose constituents we can dismantle and remodel into the types of protein the human body requires. As well as the carbon, hydrogen, oxygen and nitrogen contained in sugars and proteins, we also need about a dozen inorganic elements — sodium, potassium, magnesium, calcium, phosphorus, sulphur, iron, copper, zinc, manganese, cobalt, chlorine, and iodine. Since we are unable to manufacture our own vitamins, we must also acquire a ready-made set of these too — which include vitamins A (or its precursor), B1-6, B12, C and D. So, when assessing seaweeds as a source of food, we must evaluate them in terms of what they can provide in the way of sugars, vitamins, fats, proteins and the elements mentioned, apart from any piquancy or flavour which might endear them to our palate.
It would be as well at this point to review one or two important properties of carbohydrates (a better term to use than sugars) before we consider seaweed carbohydrates as a source of energy. We can classify carbohydrates into three major groups:
References: Brook, Chapman, Kirby(1950), Newton (1951, 1963), Tiffany.
The monosaccharides can be directly assimilated by the human body and hence are of immediate food value without further modification; the oligosaccharides must be dismantled to their constituent monosaccharide building-units before they are of use; the polysaccharides, likewise, have to be broken down into their monosaccharide units. Being insoluble, the latter group in any case could not be digested before being broken down. If we examine higher plant carbohydrates we find that most occur as polysaccharides, and in not very many plants do we find mono- or oligosaccharides in plenty. The two major exceptions are sugarcane and sugar-beet. We must therefore focus our attention on polysaccharides in greater detail. In assessing polysaccharides in terms of food value, we must consider whether they can be hydrolysed to their monosaccharide units and thus be useful as a source of food, and therefore energy. The human body can hydrolyse the polysaccharide starch to its structural monomer very easily; but the body cannot attack cellulose. To see why this is so, we must look at the structures of cellulose and starch — remembering that both substances are built entirely of glucose units. Why, then, the difference in digestibility?
Glucose can exist in two forms, alpha-glucose and beta-glucose, whose formulae are:
Alpha-glucose Beta-glucose
Starch is a polymer of alpha-glucose — as follows:
Cellulose is a polymer of beta-glucose, and its formula is:
Both of these polymers are broken down by enzymes: starch — by glycolytic enzymes such as the amylases, which are fairly common;
Reference: Okamura
Table III: Seaweeds eaten by the Japanese.
cellulose— by cellulolytic enzymes called cellulases which are quite rare and not possessed by many organisms be they plant or animal.
Despite the hundreds of different kinds of herbivorous animals, we at present know of very few possessing cellulase in their kit-bag of enzymes. These biochemical elite include the silverfish, the snail (Helix pomatia), the limpet (Patella patella) and the chiton. There may be others; but these seem to be the only ones whose oddity has up to the present been recorded in the literature. And yet most of the world's agriculture relies (as does almost the whole of New Zealand's export income) on the digestion of cellulose in the gut of cows, beef cattle and sheep, and other hoofed animals. However, all these are ruminant animals and maintain in their rumen intestinal bacteria and protozoa which excrete a cellulase capable
It appears that the stability of cellulose may be due to its being composed of beta-glucose units, which seem to have a much more stable structure electronically than those of the alpha-glucose form. Maybe this is why cellulose was the carbohydrate selected during evolution as the structural material of plant-life after the latter had appeared on dry land. The difference in stability between the alphatype linkage and beta-type linkage is even reflected in their ease of hydrolysis in acid conditions: alpha-linkage is broken by dilute hydrochloric, but the fracture of beta-linkage requires the use of concentrated sulphuric acid and prolonged boiling. The structural stability of cellulose is not a feature of starch — with its polymerised array of alpha-glucose units whose unions are so easily severed.
Funnily enough, if we cross the border into the zoological world, we see a similar demonstration of the choice on biochemical grounds of the right material for the right job. Glycogen, the main metabolic polysaccharide of animals, is a polymer of glucose units joined by alpha-1:4 and 1:6 linkages. Chitin, the structural material of the insects and crustacea, is a polymer of a nitrogen-containing glucose derivative called N-acetylglucosamine. This polymer consists of N-acetylglucosamine units joined together in beta-1:4 linkage — just as we see in cellulose. This similarity is perhaps more easily appreciated after comparing the formulae of these two structural substances.
Cellulose
Chitin
In both plant and animal worlds, the metabolic polysaccharides which must be broken down very quickly for immediate release of energy are built on the alpha-linkage pattern — i.e. starch and glycogen. But the structural polysaccharides which must ‘stand four-square against all the winds that blow,’ even to the extent
In our digestive interiors we produce the following polysaccharide-splitting enzymes: salivary amylase (ptyalin) which acts to a limited extent on starch and glycogen and breaks them down to dextrin and maltose by hydrolysing alpha-1:4 linkages; pancreatic amylase (diastase or amylopsin) which attacks the alpha-1:4 links of starch and glycogen: and finally the intestinal enzymes for splitting carbohydrates. The latter include maltase for hydrolysing maltose (alpha-1:4 linkage); a specific sucrase or invertase for splitting sucrose; a specific enzyme for hydrolysing lactose: and an oligo-1:6 glucosidase for hydrolysing the alpha-1:6 linkages of the dextrins formed as a result of salivary amylase working on starch and glycogen (Cantarow and Schepartz). Not being ruminants, we cannot break down cellulose; but we can handle starch quite readily and reduce it to its constituent glucose molecules: i.e., we cannot hydrolyse the 1:4 links between beta-glucose units, but we can rupture the 1:4 and 1:6 links between alpha-glucose units. Armed with this information, let us now look at seaweeds as a source of food in terms of hydrolysable polysaccharides, since this class of substance is the main supplier of energy for our metabolic reticulation system.
When assessing the major carbohydrates of seaweeds as energy sources, we should use the same classification for these carbohydrates as we used above.
Monosaccharides
There appear to be no free monosaccharides in seaweeds, but we do find some polyhydric alcohols related to monosaccharides e.g. dulcitol, sorbitol, mannitol and one or two derivatives. Also found are mannoglyceric acid and floridoside, the former being a compound between mannose and glyceric acid, and the latter a compound between galactose and glycerol (Meeuse). These two chemicals have alpha-glycoside links and are not difficult for humans to hydrolyse.
Oligosaccharides
Sucrose has been found in Chlorophyta and Rhodophyta but not in Phaeophyta. This sugar we can handle very easily. Trehalose, also a disaccharide, is found in a few algae but has not yet been reported from the usual edible seaweeds.
Polysaccharides
As in land plants, we find that glucose is a major building unit; but we also find polymers of galactose and a few of xylose and
-
alpha-1:4 and alpha-1:6 linkage between glucose units: here, as in higher plants, we find storage products, e.g. starch and floridean starch.
-
beta-1:3 linkage between glucose units — again the compound is a storage product, e.g. laminarin.
-
beta-1:4 linkage between
— glucose units, e.g. cellulose
— mannose units, e.g., mannan
— mannuronic acid units) i.e. alginic
— guluronic acid units) acid
-
beta-1:3 alternating with beta-1:4 linkage between galactose and 3:6-anhydrogalactose and sulphated derivatives, e.g. agar, carrageenin and iridophycin.
beta-1:3 occurring with beta-1:4 linkage between xylose units, e.g. dulsin.
-
beta 1:2 alternating with beta-1:3 linkage between fucose units, e.g. fucoidin.
The first point to emerge from this classification is the exotic nature of some of the linkage types which the seaweeds seem to specialise in. These are quite unlike any types found in land plants and therefore quite foreign to the human digestive system's enzyme complement. Let's take each of these linkages and see what the chances are of digesting such polysaccharides.
The first group contains alpha-1:4 and alpha-1:6 linkages. This is well known to our gastronomy because starch and glycogen molecules are based on this pattern. True starches identical with those of higher plants are found in the green seaweeds. This group includes floridean starch, the usual product of photosynthesis in a number of red seaweeds such as Rhodymenia pertusa. It appears to be very closely related to the higher-plant amylopectins. Apparently there are a few 1:3 linkages as well. Myxophycean starch also belongs within this group; but very few blue-greens are used as food and they therefore hardly warrant further consideration.
In the second group we find those polysaccharides with a beta-1:3 linkage. It is now thought that these are probably the most abundant polysaccharides on earth — even usurping the exalted position of cellulose. ‘the greatest’ of the organic carbon compounds. They are also found in highe ‘plants — as callose in grapevine phloem, as a deposit in the cell walls of other plant tissues, and as yeast glucan from yeast cell walls. In algae they are found in the cell walls of some greens such as Caulerpa—but more particularly
Euglena, as chrysolaminarin in certain diatoms and possibly all Chrysophyta (Meeuse). The compound of interest to us is laminarin — not that it is widespread in the browns, since it has so far been found in quantity only in Laminaria and Fucus, though it has also been isolated from Eisenia bicyclis (Nisizawa 1938).
The enzyme laminarase which degrades laminarin is rather infrequently encountered. It has been identified in wheat, barley, oats, potato, malt, and in hyacinth bulbs — to match, no doubt, the distribution in these plants of a glucan of this nature. It has also been found in snail juice (Helix potmatia or H. aspersa) (Barry 1941) and in the sea-hare, Tethys punctata (Nisizawa 1939); and laminarin can also be degraded by enzymes in the fore-and midgut of the herbivorous marine snail, Tegula funebralis (Galli and Giese). The question arises — can laminarin be broken down easily in the human body or is it like cellulose in being difficult to degrade because of these beta-linkages? Remembering that the polysaccharide-attacking enzymes produced by humans can operate only on alpha-1:4 and alpha-1:6 linkages, we are forced to admit that a feast of laminarin seems synonymous with a famine of monosaccharide — particularly since it is impregnable to diastase (i.e. amylase) and ptyalin (Barry 1938).
The next group for review contains carbohydrates with beta-1:4 linkage. Here we are amongst old friends — cellulose, xylan and mannan: the newcomer is alginic acid which is a mixture of a polymer of mannuronic acid units and a polymer of guluronic acid units. Cellulose is not common in seaweeds. It has been found in Chondrus crispus (2.2% D.W.), Rhodymenia palmata (2.1% D.W.), Laminaria saccharina (5.7% D.W.), and Laminaria digitata (3.7% D.W.), Mannan occurs in Porphyra umbilicalis — the only record so far in the reds. It has also been found in some of the greens e.g. Codium fragile. This compound consists of beta-1:4 linked mannose units. Xylan (of beta-1:4 xylose units) as we know it in higher plants occurs in red seaweeds too. We are already aware of our inability to do anything with cellulose; and it appears that xylans and mannans along with galactans are also immune to our digestive attack (Tiffany).
As far as alginic acid is concerned, it seems we are unable to handle this any better than we can cellulose because although alginic acid has a -COOH group where cellulose has a -CH2OH, it is the nature of the connecting bond between the monomer units which seems to determine ultimate digestibility. This link is the same for cellulose and alginic acid.
We come now to groups which are hybrid as regards type of linkage; in which beta-1:3 alternates with beta-1:4 (as in agar and its allies) or where there is a different ratio of beta-1:3 to beta-1:4 (as in the particular type of xylan called ‘dulsin ’ found
Rhodymenia palmata). Since human enzymes will not attack either of these linkages, we are unable to claim any of the photosynthetic prizes locked away in these polysaccharides. And the same would apply to fucoidin — found in some of the laminarians, Fucus, Chordaria and others. Bacteria from a sheep's rumen have been found capable of hydrolysing dulsin — but one would expect this since some of these bacterial types can split the beta-1:4 link in cellulose.
Thus it seems that seaweeds cannot be relied upon to provide a large proportion of usable carbohydrates. Tiffany has this to say — ‘About 65% of the dry weight of most edible algae is composed of complex carbohydrates with rather low digestibility. In fact Oshima places the digestibility of edible seaweeds of Japan at 67.7% which is lower than that of any carbohydrate of common foodstuffs.’ In 1906 Saiki wrote —‘Experiments with a variety of alga preparations (Irish moss, kombu, wakame, asakusanori, kanten (agar-agar)—H.W.J.) containing a large proportion of polysaccharide carbohydrates indicated that the latter were not readily transformed to sugar by carbohydrate-digesting enzymes of animal origin and scarcely more readily by vegetable enzymes or bacteria. Corresponding with this, the digestibility and availability of such products in the alimentary tract were found to be very imperfect in both man and animals.’ Anybody who has grown fungi and bacteria will know that not many organisms of these two classes will attack agar, although most would excrete carbohydrate-splitting enzymes of some kind into the growing medium. It looks then as if we can dismiss seaweeds as a high-class source of carbohydrates.
Kirby (1950) made a pertinent observation about the digestibility of seaweeds — ‘It is interesting to note that in Japan the weeds are often left until they have been attacked by fungi. These may help to break down the weeds so that they are more easily digested when eaten.’ Fungi are well-known for their ability to break down most things, and few of the algal polysaccharides are likely to withstand the onset of fungal attack. Some are even equipped with cellulases to break this intractible beta-1:4 linkage. One encounters more bacteria capable of breaking down agar than fungi; and because of this fact, maybe bacteria are just as important as fungi in this softening-up process. In many cases this predigestion would be necessary because some seaweeds appear to be rather indigestible. Ulva, for instance, has been described by one writer as something which would tax the digestive system of the mighty. There is a certain amount of conflicting evidence about the digestibility of seaweeds. If, in the experiments, the seaweeds were eaten fresh, the digestibility could quite easily be low; but if the seaweeds had been kept for sometime and thus were partially predigested by fungi and bacteria, the results would understandably
With ready access to fish and other delectable high-protein seafoods, people are not likely to rely on seaweeds for protein. Yet analyses show that some seaweeds contain respectable amounts of this form of nitrogen reserve. Miller investigated the nutritional value of two forms of limu (seaweed) of the indigenous Hawaiians. Analyses were made of Enteromorpha (‘limu eleele’) and Haliseria plagiogramma (‘limu lipoa’). When recalculated on a dry-weight basis these analyses appear as follows:
Here we see that Enteromorpha is almost 300% higher in protein than Haliseria. Again, Bersamin and others published analyses of several seaweeds eaten fresh in the Phillipines. Their figures for total protein recalculated on a dry-weight basis are thus:
Kirby (1950) quotes a protein figure of 32.9% for Porphyra laciniata growing on the Alaskan Coast; and the following short list sets out some analyses carried out on Brittany seaweeds (Citharel and Villeret).
If we compare the protein content of algae with that of the garden pea (Pisum sativum), we find that certain seaweeds contain more protein than do green peas — whose content is about 27% D.W. (Spector). While the seaweeds are not rich in protein when compared with animal sources, what is present in some would make a useful supplement to the diet. (Additional protein figures are quoted below).
Animal foods would also supply the fat requirements. People relying on seaweeds to provide this high-energy substrate would most certainly be misplacing their trust, since most analyses reveal very low fat contents: thus—
Green peas are quoted as having 1.58% D.W. (Spector). Other edible seaweeds which have fat figures similar to these can be dismissed as unimportant sources of this high-energy form of food.
The fatty acids are of the same type as those found in higher plants. Of the saturated-acid series, palmitic (C16) is found in highest concentration — followed by myristic (C14) and stearic (C18) in that order. Among the unsaturated acids, oleic (C18) is present to the greatest extent followed by palmitoleic (C16) and then gadoleic (C20) (Fogg). Humans are used to handling these molecules and what little fat is present could be easily assimilated.
Among the major elements we must feature sodium, potassium, magnesium, calcium, phosphorus and sulphur. The figures below give some indication of the content of these elements in some animal food-meals made from seaweeds:
Hendrick gave the following analyses for some of the more economically important British seaweeds:
Lastly, some figures are quoted by Kirby (1950) for Fucus and Laminaria used as fertiliser in Jersey:
These figures reveal the high potassium content of most of these seaweeds as well as high amounts of sulphur, sodium and chloride. In those cases given, calcium is quite high; but the phosphorus figure seems low when compared with that for garden peas (0.44% D.W.).
There is not a great deal of information available on the minor-element content of seaweeds. Black and Mitchell report some analyses for several brown algae gathered off the Scottish coast in early summer 1949. Except for ash, the other figures are expressed as parts per million (p.p.m.) on a dry-weight basis.
They also give a figure called the ‘concentration factor’: this is the ratio of minor-element content in the fresh seaweed to the content of the same minor-element in the sea-water.
(No Fe figure was given by them for the sea-water analyses).
Seaweeds vary in their contents of these elements. For instance, it seems that minor-elements, which may have some role in reproduction, are lower in quantity in sterile fronds than in sporulating ones. Then there is seasonal variation, as well as variation due to location, proximity to land drainage, type of shoreline rock. There is also the variation within the plant itself, for we see that the minor-element content is higher in Laminaria digitata stipe than in the frond.
Öy (quoted by Black and Mitchell) published some figures for minor-elements in the following algae — Ascophyllum nodosum, Laminaria sp., Fucus serratus and Fucus vesiculosus. Iron ranged from 120 to 1.330 p.p.m.: and boron, 100 p.p.m. Figures for copper were more explicitly allocated —
The presence of iodine has been known for a long time — seaweed was the first commercial source of this element. Arsenic has also been known to be present. Many other elements are found — such as nickel, lead, tin, vanadium, titanium, chromium, silver, strontium. The presence of the latter calls for some comment. The strontium figures given below are also taken from Black and Mitchell and represent analyses done on seaweeds collected in winter time.
Bowen showed that brown seaweeds concentrated strontium more heavily than did greens and reds — thus:
This differential concentration of strontium between groups may occur because brown algae contain alginic acid which can act like a cation exchange resin whereas the greens and reds do not contain this chemical.
The absorption of strontium by certain algae is highlighted in the following analysis of Macrocystis pyrifera — expressed in p.p.m. on a D.W. basis (Wilson and Fieldes).
In relation to metabolically required minor-elements it is interesting to see that iron is again high, with zinc next in order, followed by copper, manganese, molybdenum and cobalt.
We will now examine seaweeds as a source of vitamins — the last group of essential requirements for human nutrition to be considered. Beta-carotene is present in all seaweeds, and since it is the precursor of vitamin A, there should be no shortage of this vitamin in people who include seaweed in their diet. The beta-carotene of several algae investigated is not much affected after harvest: but in one, Rhodymenia palmata, there is a very quick enzymatic breakdown unless the enzymes are killed (Haug and Larsen).
Members of the B group of vitamins are present in seaweeds. Niacin was found to range from 1 microgram/g D.W. for Ceramium tenuicorne to 63 microgram/g for Alaria esculenta: pantothenic acid — from less than 0.2 microgram/g D.W. in several to 12.5 microgram/g in Chara tomentosa (Lundin and Ericson). They also state that the niacin (and vitamin C) content appears to be more or less the same in red, brown and green algae. An analysis of one seaweed meal made from Macrocystis pyrifera gave the following results (Kirby 1951):
With food seaweeds, the really interesting member of the B group is vitamin B12; and it would help now to recall the analytical figures and concentration factors quoted earlier for cobalt, since this element is the inorganic constituent of vitamin B12. Provasoli has summarized the figures for the vitamin B12 content of various seaweeds published by several groups of research workers. The following are high in this vitamin:
Apparently green seaweeds contain more than red, and both are higher than brown. It has been shown that some algae can accumulate cobalt to the remarkable extent of producing a concentration factor of 10,000 (Ericson). The origin of the B12 is bacterial — due either to the presence on the algae of epiphytic bacteria which synthesize this vitamin or to the occurrence of these bacteria in the surrounding sea-water. In either case the vitamin is taken up by the seaweed and accumulation occurs. ‘Bacteria from algae which were poor in vitamin B12, generally produce small amounts of B12, while bacteria from vitamin B12-rich algae formed larger quantities of the vitamin’ (Lundin and Ericson). These authors also suggested that red and green seaweeds may have higher B12 contents than brown because the former ‘often have greater surface areas per gram dry weight than the brown algae.’
Vitamin C is well represented. Ascorbic acid content of Fucus vesiculosus may reach 77mgs./100gms. wet weight — which is considerably higher than lemon juice at 31-57mgs./100gms. Vitamin C content also varies with season and depth (Mautner). Several browns compare favourably with many fruits and vegetables as sources of B1 and C (Mautner). Lundin and Ericson stated ‘it can be concluded that many marine algae are good sources of vitamins;’ and this would seem to be the case.
From a dietetic point of view, we lack a great deal of analytical information on the constituents of seaweeds. The little
The absence of insect pests to ravage this marine vegetable garden is rather interesting to ponder. Many land plants are poisonous, and their poisonous nature is thought by some to have been evolved through selection as a survival mechanism against predation by insects and other forms of animal life. But one never sees reference to poisonous seaweeds. Some algae are toxic — but these are planktonic and microscopic. Maybe it is too soon to state categorically ‘There are no poisonous seaweeds!,’ because future research may reveal examples. There are certain seaweeds, for example Desmarestia, which would not be toxic in the normally-accepted meaning of the word but might have to be considered hazardous because of the relatively high sulphuric acid content. At the moment no truly poisonous seaweeds appear to have been reported. Alkaloids are the toxic chemicals present in many terrestrial plants: for example nicotine, colchicine, coniine (from hemlock), ricinine (from castor oil seeds), atropine and hyoscyamine (from the Solanaceae), strychnine and brucine, curine and curarine (from Strychnos); and all the opium poppy alkaloids such as narcotine, morphine and codeine. It seems that alkaloidal compounds have not been found in seaweeds so far. Another often-found plant poison, oxalic acid, has not yet been reported although two of its non-poisonous cohorts — citric and malic — are known to occur.
This apparent lack of poisonous seaweeds is of some consequence since any seaweed — apart from those with a violently acid taste — could therefore be used as food by starving castaways. Looking
In what form are the seaweeds eaten? How are they prepared for the table? In Western European countries such as Scotland and Wales, Porphyra laciniata (popularly called ‘laver bread’) has been collected and eaten for centuries. It was harvested and washed free of extraneous materials and slime, shredded very finely and kneaded like dough into balls or rolls. These were eaten raw or fried with oatmeal and butter (Newton 1957). Or it was pickled and stored in stone jars. ‘It was then served cold with oil, vinegar, pepper and a dash of sugar —’ (Newton). One of the earlier delicacies was moor mutton with laver sauce. The sauce was made by boiling the cleaned weed ‘to a stiff green mush; two cupfuls of this were added to a knob of butter and the juice of half a lemon or Seville orange (not a sweet orange)’. This mixture was beaten and served hot (Hartley).
In South-East Asia and the Pacific, seaweeds are prepared for eating in many ways. Some are preserved by salting, e.g. Cladosiphon decipiens (Japan), Caulerpa and Codium spp. (Japan), Mesogloea crassa (Japan), Porphyra atropurpurea (Hawaii). In the Molucca Islands Sargassum polycystum is smoked and dried: but generally most are merely dried without smoking. Species of Porphyra, Laminaria, Undaria, Gracilaria, Gloiopeltis, Grateloupia, Gelidium and Heterochordaria abietina are preserved in this way in Japan. Many after cleaning are eaten raw in salads; e.g.
Some are eaten as dessert: Caulerpa racemosa var. clavifera is quite often eaten as a dessert after a rice meal. Padina australis is made into a gelatine-like sweetmeat in Indonesia; and in the Phillipines, Agardhiella is made into a sweetmeat by boiling with sugar and spices. Ulva lactuca is made into a soup or is used in a garnish for other dishes. Others are prepared in various ways, such as —
Chaetomorpha javanica with coconut milk or vinegar — Sargassum granuliferum—Moluccas as a vegetable — Sargassum siliquosum — Phillipines with coconut milk — Turbinaria ornata — Moluccas as a vegetable — Gracilaria eucheumoides — Phillipines.
And if some of these accounts have not activated your salivary glands, you might like to tantalise them with either of these two recipes. In Burma Catenilla nipae is eaten raw (or boiled) mixed with oil of Sesamum indicum, salt, powdered fruit of Capsicum annuum, fried rhizome of ginger (Zingiber officinale), onion and garlic. On the island of Bali, Hypnea cervicornis is collected, dried and bleached on the beach for 3 or 4 days. It is then boiled, filtered and cooled; the resulting jelly is eaten with palm sugar and grated coconut.
Because of their agar content, a number are used for making jellies. Notable amongst these are Corallopsis salicornia; Eucheuma edule, E. gelatinae, E. horridum, E. muricatum; Gelidium amansii, G. rigidum, G. latifolium; Gigartina spp; Gracilaria confervoides, G. lichenoides, G. taeniodes; Hypnea divaricata, H. museiformis.
Japan ranks very high as a user of seaweeds; and for this reason we will now consider in some detail how the Japanese prepare and use some of their seaweeds. Most are eaten raw after having been thoroughly washed. These include Porphyra, Nemalion vermiculare, Undaria pinnatifida, Cladosiphon decipiens, Mesogloea crassa, Grateloupia flabella — and many more. Others are blanched by boiling just enough to change their colour: this treatment is accorded to Gracelaria confervoides, G. compressa, young shoots of Codium, and Meristotheca papulosa. All of these may be eaten as side dishes to the regular meal or may be taken with saké. Others such as Laminaria, Undaria, Cladosiphon, Porphyra, Gloiopeltis, are used in soups. Many are eaten with boiled rice — for instance Laminaria, Eisenia, Ecklonia spp., Undaria spp., Porphyra (mainly tenera), Enteromorpha; but they require some form of pre-treatment. Laminaria, Undaria, Porphyra and Enteromorpha are sun-dried before use, while Eisenia and Ecklonia are boiled first to remove an astringency before being sun-dried.
Okamura states that of all the seaweeds eaten in Japan the most important are Porphyra, Laminaria and Gelidium. Some Porphyra is eaten fresh but most is sun-dried and preserved in thin sheets. The following passages referring to Porphyra and Laminaria are taken from his article.
‘These dried Porphyra sheets are extensively used in Japanese cooking, and are the special delight of children. The sheets, almost black, are gently heated over the fire until the colour changes to green, when they also become quite crisp. Used with soy the taste is much improved. Porphyra sheets are an essential article in the
Porphyra sheet. It is then rolled up and cut transversely into smaller cylinders. The Porphyra being fairly tough, holds the rice and the ingredients together, acting the part of a sausage skin. Porphyra is also cooked with soy and made into a paste called ‘norino - tsukudani.’ This condiment, which is greatly relished, is an expensive luxury, with the result that cheaper substitutes are made from Monostroma, Enteromorpha and Ulva.'
‘‘Kombu’ is a general term for several species of Laminaria, chiefly L. japonica and L. ochotensis, both widely consumed for food in Japan. ‘Kombu’ is prepared in a dozen or more ways. The most important form in which it is manufactured is shredded, greendyed ‘kombu.’ This is prepared by dyeing the dried Laminaria green in a large kettle containing a boiling solution of malachite green. The dyed kelp is drained and partially dried. After partially drying, the fronds are flattened out and arranged in wooden frames in piles. Each pile is then tightly compressed and held by four transverse cords. When the frame is completely filled with the evenly-arranged pieces, the whole mass is compressed by means of ropes, wedges, and levers. One of the sides of the frame is then removed and the ‘kombu’ is shredded by means of a hand plane The shredded ‘kombu’ is spread out on boards or on mats and dried in the open air. When the surface of the shreds has become dry, it is packed for shipment.’
‘Other forms are manufactured by scraping the epidermis, the remaining green covering, and the thick white cores of the fronds, etc. These scrapings take the form of exceedingly thin and delicate filmy sheets and strips.’
‘Dried ‘kombu’ is used by itself as confectionery and also in the candied state. It is also ground into fine powder to be used in sauces and soups and to be sprinkled on boiled rice like curry powder or to be mixed with other ingredients for making cakes, etc. When boiling water is poured on a quantity of the finely chopped ‘kombu’ a sort of substitute for tea is obtained.’
‘‘Kombu’ is used directly in various ways, not only by itself, but with other ingredients in the preparation of stocks. Bean-curd prepared with this stock is much appreciated by ‘saké’ drinkers. ‘Kombu’ is also cooked in soy and salt and used as a pickle. It is also used as a pickle for putting into ‘miso’ (salted bean-paste, ‘saké,’ or ‘mirin’-lees, and rice-bran mash (‘nukamiso’). ‘Kanten’ made from Chondrus elatus, is also used in this way in Chiba Prefecture.’
Gelidium, Ceramium (Campylaephora) hypnaeoides, C. boydenii and various species of Gracelaria are used in the manufacture of agar
Because of our ready access to good soil and our ability to use this to cultivate vegetables, we never think of the possibility of using a stretch of rocky coastline as a site for cultivating plants. However, this idea has become a reality and has been practised for centuries especially by the Japanese, and also by the Filopinos in the North of the Phillipines, by the Chinese at Lienyunkang and possibly by the Koreans. (This reference to seaweed culture by the Chinese is the only one known to the writer, and no further detail can be given. Knowledge of this comes solely from a photograph in a book entitled ‘People's Communes,’ edited by the Ministry of Agriculture, People's Republic of China). Porphyra tenera (amanori) is a favourite seafood in Japan and demand has always exceeded supply. For this reason a technique has been developed for the cultivation and harvesting of this red seaweed. To understand the mechanics of the process, it is necessary to be familiar with certain features of the life-cycle — which is as follows.
There are two different generations in this life-cycle — a leafy thalloid plant which is the main macroscopic plant called Porphyra; and a filamentous microscopic phase referred to generally as Conchocelis (for reasons which need not concern us in this article). In tracing this life-cycle let us start with the leafy thallus. In the early spring with the approach of long days, this phase begins to senesce and the plant body forms carpospores; with increasing senescence the tissues begin to disintegrate and finally the carpospores are released into the open water. These germinate in the late-spring to early-summer to form the filamentous Conchocelis phase which needs the long days of summer to mature. With the shortening days of the late-summer, this phase forms monospores which when released germinate to form the leafy Porphyra. This grows throughout the short days of autumn and winter and with the onset of the lengthening days of spring begins to form carpospores and degenerate. And so the cycle carries on. The edible phase is the leafy Porphyra which grows over the autumn and winter.
Now let's see how the practice fits the theory. In late summer fishermen plant out bundles of twigs and bamboo shoots by embedding them very securely in holes which they make in the mud. This is done at low tide. These close rows of brush intercept and form a place of attachment for the monospores released from the Conchocelis
Conchocelis phase — which grows during the summer on stones, gravel and other bottom detritus. During the summer the fishermen remove the old brush and set out new material — in time to intercept during late-summer the released monospores from the Conchocelis phase which has received its reproductive cue from the shortening days. Fig 1 sets out the cycle in a diagrammatic form — which shows more clearly the coincidence of practice and theory. The only point to remember about the coincidence is that the practice was worked out centuries before the theory was known!
The harvesting of amanori is carried out in mid-winter by women and girls. It appears that Japanese women, like their European counterparts, can tolerate more cold than the men: conceivably, this is why the harvesting is a female occupation. One other interesting point is that in mild winters trouble is experienced with a marine fungus attacking the amanori thallus — a marine example this time of the troubles which beset those who engage in intensive and close cultivation of one particular plant. It seems axiomatic that no matter where one indulges in a monoculture — either on land or in the sea — the ogre of parasitism will surely appear.
When harvested, the amanori fronds are washed in tubs of fresh water to remove sand and other adhering matter. The plants are sorted for quality, chopped finely and spread out uniformly on bamboo-mats to dry in the air. These sheets are then baled and sold. In this form they are sold under the name of ‘asakusanori.’ Before being eaten, the asakusanori is crisped over a fire in which process it changes colour from dark brown to green. It is rubbed between the hand and dropped into soups or sauces to which it imparts a pleasant flavour.
‘The old order changeth yielding place to the new …’; and even the time-honoured practices of the Orient succumb to the new ideas of modern times. We now find that coconut palm or
A diagram showing how the life-cycle of
Porphyra is related to the seasons of the year and the practice of the fishermen.
‘The field work of nori-culture begins in the autumn when nets are hung on racks at ground level just as the spores emerge into the water. Since the harvest of the season depends greatly upon the abundance of the spore attachment, the relationship between the occurrence of the spores and hydrographical as well as meteorological conditions has been studied over a period of many years. Attempts have also recently been made to make quantitative determinations of the spores in sea-water. To give growers the maximum benefit from those various researches, the local experimental stations often announce over the radio the best time for collection.’
‘Artificial seeding of the nori spores is carried out to obtain spores for the season from the carpospores cultured since the preceding winter. The result of this research, however, still remains to be seen. Another method of artificial seeding recently found is connected with a species of laver, Porphyra yezoensis, whose distribution is limited to the northern part of Japan. The monospore formed on the summer plantlet of this laver is made to attach and grow on the collecting net.’
‘The height of the spore collector on the racks is adjusted in accordance with the growing stages of the laver and the seasonal fluctuation of the current and water temperatures so that the growth of the laver may be promoted, avoiding as much as possible any damage by disease. Fertilisers are also used in the growing areas alongside the spore collector.’
Earlier, it was mentioned that Porphyra can be attacked by a fungus in warm winters. The only treatment known so far for combating this disease is to move the racks to higher ground so that the seaweed will remain out of the water for about three hours each day. This is so simple but so ingenious, since the seaweed can stand a limited amount of exposure to air because of its mucilaginous covering, but the fungus (presumably, like most of its class) lacks this covering and its cells are desiccated and therefore killed.
In what other way could this fungus be controlled? Ordinary methods of using fungicides as practiced on land are just not applicable in the sea because of the physical nature of the
Porphyra were exposed at low tide, presumably a spray could be applied then before the tide came in; but would the chemical adhere to the algal surface when the tide did come in? Would sea-water inactivate our present fungicidal compounds? Under the circumstances, the locals have evolved by far the best form of control and possibly the only one for a problem such as this.
Species of other seaweeds are also cultured and the following list sets out a few but does no claim to be all-inclusive:
A rougher type of cultivation was practised by the Irish for cultivating Fucus vesiculosus, which they collected and used as a fertiliser (Newton 1951).
One further curious point that emerges from this study of seaweeds as food is that people in different parts of the world have picked on one particular genus of seaweed to eat — namely Porphyra. Maoris in New Zealand gather and relish it. The Chinese in New Zealand collect it and send it home to China as do the Chinese in California. The Chinese in southeastern Alaska collected and ate Porphyra laciniata. The Japanese, as we have seen, farm several species of Porphyra. The Koreans eat it, and it is farmed in North Luzon in the Phillipines. It was eaten by people around the western European coasts, in England and Wales, and also in Chile. Apart from any appeal to the palate, all the members of this genus may be like Porphyra laciniata which, as we have seen earlier, has such a high total nitrogen figure. It is an interesting thought that these different peoples, without the aid of analytical chemists to tell them what is good for them to eat, should have selected in each case the local species of a genus that possibly is the most nutritious seaweed available, because of its high nitrogen content and its stock of major and minor elements. Funny how empirically-determined practice is so often substantiated by research! And yet we are all too often inclined to denigrate it because it was evolved by a non-academic society.
Earlier, we saw that China scarcely figures at all in Table I either as a user of seaweeds for food or as a substrate for their occurrence. This situation contrasts strongly with that of her near neighbours, Japan and Korea; and the disparity merits closer investigation.
The earliest extant writings reveal the importance and esteem with which seaweeds were regarded by the ancients of China, who have eaten these plants since time immemorial. It has been said that the Japanese acquired the habit of using seaweed as food from the Chinese — in much the same way as they learnt the techniques of flower-arranging, development of ming trees, and other things cultural as well as horticultural. In those early days ‘the term for algae was also used in a complimentary sense, as in praise of the thinking of a learned man, to signify that his thoughts were ordered as systematically as the parts of an alga’ (Kirby 1950). In a book by Sze Ten in about 600 B.C. it is written that ‘some algae are a delicacy fit for the most honourable guest, even for the king himself.’ The Chinese attitude to seaweeds differs completely from that of the ancients of Rome who regarded these plants as the most loathsome and useless of the biological world. In fact the Romans used the term ‘seaweed’ as a synonym for the nadir on their scale of what was useful and useless or obnoxious. Hence the reference by Vergil in his Eclogues VII, line 42: ‘horridior rusco, proiecta vilior alga’ — prickly as butcher's broom and useless as seaweed which has been cast up. Horace in his Fifth Satire reckons that family and virtue, without wealth, are as worthless as seaweed; and in his Ode to Aelius he speaks of ‘inutilis alga’ — worthless seaweed (Brook).
In view of the esteem bestowed by the Chinese on seaweeds, it is surprising that an industry centred around the latter's cultivation and harvesting was never developed to the extent of achieving mention in the history books. One imagines that the early knowledge of seaweeds’ delectability and their use as effective herbal medicines would surely have led the inhabitants to ensure a good supply to meet this type of luxury demand; and yet no indications of this are found. This enigma becomes more complex when we come to look for present-day references to the marine algal flora of China. There are very few. In Table IV those seaweeds that are eaten and sold in the markets are listed (Kirby 1950). But when we come to look for a source of these seaweeds in China, we find an unbelievable paucity of indigenous marine algae along her coast. This is all the more intriguing when we realise that the country possesses about 5,000 miles of coastline. Of course we are not entitled to believe that the last word has been written on the incidence of seaweeds around the China coast.
Locations for various of these seaweeds are also given in Table IV. Reference to a map for locating the sites mentioned will bring into focus the point that these occur within fairly restricted areas; and
References: Cotton, Gepp, Grubb, Kirby (1950), Tseng and Tang.
before considering the oddities of distribution, we must become acquainted with certain physical features of the coastal land-form and sea-water characteristics because these two things seem to explain much that is puzzling.
The seas in the immediate vicinity of the Chinese coastline are dominated by the huge outflow of fresh water from the major rivers — especially the Yangtze Kiang and the Hwang Ho whose anglicised name (Yellow River) has been applied to the sea surrounding its mouth (the Yellow Sea). The southern end of the Yellow Sea also receives silt and fresh water in even greater quantity from the Yangtze, which emerges close to Shanghai. Immediate effects of all this fresh water are that the salinity of the sea is altered, as well as its transparency and the nature of its floor. Thus, much of the coast of Northern China is unfavourable for a good seaweed flora due to decreased salinity and transparency of the water, and also to the lack of a suitable substratum. Cotton remarked that the Gulf of Chihli (the upper part of the Yellow Sea) is for the most part muddy. The coastline of this Gulf round to the Shantung Peninsula and south of this peninsula down to the mouth of the Yangtze is deltaic in origin, having been built up from silt brought down by these rivers. Shantung however is a rocky promontory. Little wonder that not many algae grow
The second feature to consider is the geological nature of this shoreline. Most of the coast bordering the Yellow Sea is composed of alluvium — except for the Shantung peninsula. Grubb, describing the substrate near the Pei-tai-ho, said that the ‘coast is alluvial, with a few jutting out reefs of rocks. The strata in this district appear to be of quaternary or tertiary origin, and the rocks are a hard coarsely-grained granite. They do not offer any very satisfactory foothold for algae, and the flora, even in rock-pools, is confined almost wholly to species of Corallina, Hypnea, and Gelidium.’ Gepp quoted a letter from a surgeon of the Royal Navy who collected some seaweeds on an island close to Wei-hai-wei: ‘the rocks are metamorphic, consisting of beds of quartzite, gneiss, crystallite, and limestone cut across by dykes of volcanic rock and granite. Mica abounds everywhere. Where the seaweeds were found, the rocks were mainly granite and gneiss.’
The third feature contributing to this paucity of seaweeds is water temperature. At its western extremity the Pacific North Equatorial current turns north along the eastern side of the Phillipines and becomes the Kuro Siwo, the ‘Black Current’ or Japan stream. This forks, and one part comes up on the eastern side of Formosa and Japan as far as the heel of Honshu, then turns east across the North Pacific (Grubb). The other arm of the Kuro Siwo flows on the western side of Formosa and bathes the coast of China. As one would expect, this is a warm current having a mean temperature of 80° F.— which is about 5°-15° warmer than the surrounding water (Grubb). This temperature therefore effectively excludes the cool-water seaweeds of the Fucales and Laminariales.
It will now be appeciated how the interplay of these ecological factors helps to reduce the size of the Chinese seaweed flora. When we refer again to Table IV we find a number of algae sold in the markets which are not found anywhere on the China coast as far as the present records show us. These include Ecklonia cava, Laminaria spp., Chondrus elatus, Eucheuma papulosa and E. spinosum. It is obvious these must have been imported — more than likely from
Embassy exchanges between China and Japan have been recorded for almost two thousand years (Reischauer), and it is known that the establishment of trade relations has always been one of the aims of the Japanese embassies since the first mission went to China in 57 A.D.. Over the period 838-847 A.D. a diary was kept by a Japanese Buddhist monk who accompanied one of these embassies. In this he mentioned that Kombu was taken to China as one of the articles for which the Japanese hoped to develop a market. It could be that trade in seaweeds between these two countries has been occurring for well over a thousand years. When we couple production for Japan's home market with that needed to provide such a large export quantity (assuming present day exports to be about the same as previously!. we are forced to realise how large the seaweed industry in Japan must be. However, this is getting more into economics; and although it is intended to look at the economic aspect of seaweeds, this must be delayed a while.
So we will close this section now, leaving you with the thought that people should not be like the Romans and regard seaweeds as utterly useless: on the contrary, these plants can supply all the minerals and most if not all the vitamins needed by the human body. Spinach cannot do any more than this! Having the population explosion in mind, one need not romance too wildly to envisage the use of small factory-ships to collect the cold-water seaweeds and process them as food additives.
And here is a special thought for those to whom the use of artificial fertilisers, hormone weedkillers and pest-control chemicals is an anathema. The eating of seaweeds would provide a never-ending supply of ‘pure and wholesome food’ — unsullied by pesticidal members of the Periodic Table, uncontaminated by chlorinated hydrocarbons and unpolluted by organo-phosphorus compounds. Being plants, the seaweeds do not ingest food that has already been elaborated; they start from the ground floor up, so to speak, and build their own complex molecules from simple chemicals obtained from the surrounding sea. They therefore do not come into contact with such compounds as DDT through being a link in a food
12by some Marine Algae. Chem & Ind. 1952: 829-30.
Tegula funebralis.Jour. Exptl. Zoo. 140: 415-440.
Eisenia bicyclis.Sci. Repts. Rokyo Kyoiku Bunrika Daigahu Sech. B3 289-301.
Macrocystis pyrifera). N. Z. Jour. Sci. Tech. 23B: 47-48.