Biogeography and ecology in antarctica

BOOK

REVIEWS

Biogeography and Ecology in Antarctica. 1965. Edited by J. VAN MIEGHEM and P. VAN OYE. Monographiae Biologicae, Volume XV, pp. xxviii and 762, 146 figs, 24 pls. W. Junk, The Hague, 115 Dutch Guilders, $31.95. THIS book is the third in a series concerned with biogeographical and ecological research in the Southern Hemisphere. (Australia was covered in vol. VIII and South Africa in vol. XIV o f the Monographiae Biologicae). The present Antarctic volume is not comprehensive. But, as explained in the preface, certain important groups, such as the marine Algae, Protozoa, Porifera, Echinodermata, Polychaeta, Rotifera, Nematoda, Tunicata, Pinnipedia and Cetacea " . . . h a d to be omitted because otherwise the publication would have been delayed for too long a time and also because biological research on the Antarctic has really only just started." The aspects covered are: Geology and Morphology, H. J. Harrington; Climatology, Morton J. Rubin; Oceanography, Feodor Ostapoff; Freshwater Algae, Minoru Hirano; Lichens, Carroll W. Dodge; Vascular Plants, N. M. Wace; Microbiology, John McNeill Sieburth, Chaetognatha, P. M. David; Decapod Crustacea, J. C. Yaldwyn; Mollusca, A. W. B. Powell; Free-living marine Copepoda, W. Vervoort; Bryozoa, Mary D. Rogick; Acarology, Per Datenius; Land Arthropods, J. L. Gressitt; Fishes, A. P. Andriashev; Penguins, J. Prevost and J. SapinJaioustre; Birds, K. H. Voous; Human Adaptation, Ove Wilson. These chapters are summarized and reviewed by the Associate Editor, J. Schnell, who also gives a short history of Antarctic Expeditions. Like other authorities, the editors o f this book have taken the Polar Front or Antarctic Convergence as the northern limit of antarctic regions. This boundary is quite sharp and it is relatively stable in time and space. Such aspects are stressed by Ostapoff. At the convergence there is a change in surface temperatures and a sinking o f northerly moving antarctic water. The latter process is not only revealed by temperature profiles, but also by the axis of minimum salinity and oxygen distribution (percentage o f saturation) at a suitable (200-m) subsurface level. Biologically, the Antarctic Convergence separates polar and sub-polar faunas, which may be seen in the reviews of Bryozoa, decapod crustaceans, and fishes in this volume. But Powell concludes that it is difficult to draw a hard and fast line between antarctic and sub-antarctic faunas of molluscs. The convergence, as the Discovery investigations revealed so well, also divides antarctic from more northerly, and closely related species, of animals. In the Pacific sector, at least, Andriashev has evidence that the lantern-fish, Electrona antarctica meets its subantarctic relative, E. subaspera. At the convergence there may also be a marked fall in population densities, such as David describes for the chaetognath, Sagitta gazellae, which is most abundant in subantarctic waters. Like Powell, David finds it essential to consider his group in relation to the entire Southern Ocean. As David observes : " F r o m the distribution of chaetognaths it will be seen that the surface boundary o f the Subtropical Convergence is the most important hydrographic feature, followed closely by the Antarctic Convergence." There is certainly more to be learned of the profound influence of the latter front, as is admirably shown in a recent paper by HAYS (1965) who studied radiolarian skeletons in cores of the sediments. Somewhat north o f the mean position o f the Antarctic Convergence is a mixed zone of radiolarian species in the sediments, which separates a limited Antarctic fauna from more diverse warm water species, most o f which are cosmopolitan. Further important generalizations emerge from reviews of the marine groups. For instance, antarctic waters, in sharp contrast to those of subantarctic regions, support a very poor fauna of benthic decapod crustaceans. As well as providing a detailed survey of the molluscan fauna, Powell considers such problems as the age and bi-polarity of the fauna. South America and the Scotia Arc are seen as a main, and persisting, pathway for the colonization of the Antarctic by diverse molluscs. For species associated with algae the West Wind Drift is the main means of dispersal. Vervoort pays special attention to the effects of northerly currents in transporting free-living copepods, away from antarctic waters. Adaptive life history patterns, whereby eggs and larvae, particularly of surfacedwelling species, are continually returned to waters undergoing depletion must presumably prevail. 135

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For some species, seasonal changes in vertical distribution, linked to a returning pattern of circulation, must play an important part, though some surface-living copepods do not seem to undergo seasonal submergence. But the life histories of most of the chaetognaths, which are known in some detail, involve such submergence of adult and breeding stocks. For the fishes, Andriashev gives a full and well balanced review of their systematics, distribution and general biology. Concerning their physiological adaptations, we still do not know how their body fluids remain fluid at freezing temperatures. Experiments, such as those undertaken for arctic species, ought to be rewarding. The chapter on Antarctic climatology forms a background to the treatment of land-dwelling and freshwater biota. The low precipitation and humidity make the Antarctic a " w h i t e desert." But lichens, as Dodge shows, have structural and physiological adaptations that enable them to flourish in the freezing, dessicating conditions of antarctic lands. Hirano's comprehensive review of the freshwater algae contains a list of antarctic and subantarctic species, In the Antarctic blue-green algae are decidedly dominant, and their success is seen to be due to such factors as their simple, asexual means o f reproduction, their means of assimilating free nitrogen, and the existence of favourable microclimates. The full treatment of vascular plants by Wace includes some account of Antarctic fossil floras. The present vegetation zones are divided into cold, temperate, subantarctic, low antarctic and high antarctic, which are compared and contrasted with the zonation o f marine animal groups. In a concluding section, Wace summarizes present knowledge and outlines problems for future research. In his chapter on microbiology, Sieburth emphasises the low bacterial content of all habitats: air, snow, ice, soil, ponds, cryptogams and, curiously, the sea. After listing the species of antarctic and subantarctic acarines, Dalenius contrasts the poor land fauna with the more diverse one in the sea. Terrestrial mites feed on algae, mosses or lichens, which in turn get much of their nutrients from the excreta of sea birds. In the Antarctic the food chains are very short: nutrients--bacteria--lichens and mosses--springtails and mites feeding on vegetation ~ a r n i v o r o u s mites. In his comprehensive review of the land arthropods, Gressitt also deals with mites. Acarines and insects, both represented by five orders, a few freshwater crustaceans, and tardigrades are the only known land-based animals on the continent. Gressitt also stresses the adaptation to stringent conditions by way of simple food chains, loss of wings, by certain insects, and by physiological means. In dealing with penguin ecology, Pr6vost and Sapin-Jaloustre pay most attention to the Adelie and the Emperor. The breeding of the latter in winter is correlated with a relatively stow development of the young. The authors conclude : " U s e of very special areas with natural micro-climates and open water throughout the year, four-month fasting period, social thermo-regulation in common made possible by non-territorial organisation and very low intra-specific aggressivity, all serve to explain the survival of the species in the worst conditions on earth." The general chapter on antarctic birds by Voous emphasises their dependence on the sea and their northward migrations to escape the antarctic winter. The series ends with Wilson's treatment of human adaptation to life in Antarctica. But there is no convincing evidence of physiological acclimatization: man brings his own micro-climates. This is a valuable series of reviews, which also have some originality. Here and there one finds oversights and misprints. For instance, on page 272 there is this statement: " T h e sinking of the Antarctic and the enforced additional year of the Swedish Expedition gave Ekelof an opportunity to continue his studies on the soil microflora of Snow Hill Island." Inverted commas or some such indication that the Antarctic was a ship are needed. The editors could have done more to integrate the reviews of their contributors. But perhaps they are awaiting studies of the biota that could not be included in this book. Eventually too, biologists must take account of the remarkable geological history of Antarctica, which is well surveyed by Harrington in the opening chapter. N. B. MARSHALL HAYS J. D. (1965) Radiolaria and Late Tertiary and Quaternary history of Antarctic Seas. Biology of the Antarctic Seas H V o L 5. Antarctic Res. Ser. Am. Geophys. Un. Publ. No. 1297.

Elements of Physical Oceanography. HUGH J. McLELLAN, Pergamon Press, 150 pp. £3 3s. 1965. THIS book is described as suitable for an introductory course in Physical Oceanography to students of varied background such as chemists, geologists, biologists, physicists and mathematicians. There