Marine benthic populations in Antarctica: Patterns and processes

Abstract

Sampling difficulties have meant that there have been more studies of population patterns than of processes in Antarctic benthos, but a number of generalizations can be made. Benthic marine invenebrates in Antarctica have species/abundance relationships similar to those found in temperate or tropical regions but, several striking examples of gigantism notwithstanding. most species are small. Diversity is generally high, particularly in comparison with the Arctic, although some taxa (for example molluscs) are low in diversity when compared with temperate or tropicaJ faunas. Most species produce larger eggs than related non-polar species, and embryonic development is typically slow. Although the Southern Ocean contains fewer taxa reproducing by feeding pelagic larvae than elsewhere, such larvae are by no means absent. Somewhat paradoxically, these larvae are often released in winter. Post-juvenile growth rates are typically slow, and recruitment rates are slow and episodic. The low temperature slows many biological processes, but other factors are also involved. Ice is an irnponant factor in many biological processes, and the recently described sub-decadal variability in the e"tent of winter sea-ice is likely to e"ert a profound influence on benthic ceo10gica1 processes in Antarctica. I, INTRODUCTIONIt has long been traditional in ecology to draw a distinction between the study of pattern and process. These two complementary approaches provide different infonnation, and require different techniques. In particular studies of ecological processes require time, and in Antarctica, where many ecological processes take place slowly, such studies are necessarily long-tenn. The particular difficulties of ecological research in Antarctica mean that most studies have been directed at understanding ecological patterns; studies of ecological processes have been less common, although a few generalizations can be made.Aspects of the biology of Antarctic benthic organisms have been reviewed regularly during the past twenty years [Hedgpeth, 1971;Dell, 1972;Clarke, 1983;White, 1984;Dayton, 1990; Arntz et 01., 1994, in press] _ In this review I shall therefore concentrate on selected features of panicular interest to the Antarctic Peninsula area. Distributional patterns are discussed elsewhere [Clarke, this volume]; in this chapter I shall concentrate on species/abundance patterns and diversity. For ecological processes I shall discuss reproductive ecology, settlement, growth rate and the influences of temperature and sea-ice.

Growth and seasonal energetics of the Antarctic bivalve Laternula elliptica from King George Island, Antarctica

“…These organisms are expected to have developed strategies to deal with this problem. In fact, many Antarctic benthic marine herbivores show distinct seasonality in growth and reproduction (Clarke 1988, Urban & Mercuri 1998, Peck et al 2000, Brockington et al 2001, which may be related to the overall seasonality of their environment, particularly food availability (Clarke 1988(Clarke , 1996. However, experimental or field studies to support this hypothesis are lacking.…”

Antarctic macro-zoobenthic communities: a review and an ecological classification

“…Similarly, in temperate seas one usually discriminates between hard and soft bottom communities. The application of such a traditional classification to the Antarctic macrobenthos has been attempted, for example, by Richardson & Hedgpeth (1977), Dayton (1990), Dayton et al (1994), Clarke (1996), Cattaneo-Vietti et al (2000a) and Barnes & Conlan (2007). However, the difficulties of this approach, due to physical and biological peculiarities (poorly sorted glacio-marine sediments and adaptation to "unusual" sediments), has already been recognized for the Antarctic by Gallardo (1987) and in an experimental approach by Wu & Shin (1997).…”

“…In contrast to the concept of splitting the Antarctic benthos into distinct sub-systems, there are also good reasons to categorize the Antarctic benthos as a relatively homogenous biological unit: in general, many species share the same evolutionary constraints (Clarke 1990, Clarke & Crame 1992, Crame 1994 and some large-scale ecological conditions are similar around most parts of the continent, e.g. low and relatively stable temperature, a short phase of primary production, as well as low terrigenous input (Bullivant 1959, Clarke 1996. In addition, there is the presence of a circumpolar coastal current that transports food particles and supports the dispersal of juveniles (Underwood & Fairweather 1989.…”

Amphipod crustacean size spectra: new insights in the relationship between size and oxygen

“…In a recent review about Antarctic benthic biodiversity in a latitudinal context, Gray (2001) expressed the need for worldwide size spectra (size‐frequency plots) to elucidate the, still contested, size gradient hypothesis (Thorson 1957, Barnard 1962, Brey and Clarke 1993, Clarke 1996, Brey and Gerdes 1997). However, following the first systematic study on that subject (De Broyer 1977), it was precisely by establishing such size spectra that the existence of larger amphipod species in polar regions and in Lake Baikal was confirmed (Chapelle and Peck 1999).…”