The ecology (including physiological aspects) of selected Antarctic marine invertebrates associated with inshore macrophytes

Abstract

Benthic surveys of Borge Bay, Signy Island, South Orkney Islands indicated that the biomass of macrophytes per area, in shallow; antarctic waters, was less than in temperate seas. This decrease was mainly attributed to the shading and mechanical attrition of sea ice. The habitat provided by macroalgae was important as a source of food and shelter to a wide variety of benthic and demersal species. Feeding relationships within the habitat were complex. Many species relied heavily on phytoplankton or detritus (often phytoplankton 'fall-out') as the main source of food. The biology of two contrasting invertebrates, commonly associated with the fronds of the brown alga Desmarestia anceps was investigated. The species chosen were the amphipod Pontogeneia antarctica and the bivalve Lissarca miliaris. The mollusc remained in the benthos throughout the year, whilst the crustacean exhibited a major migration to the under surf ace of the fast ice during the winter. Despite such obvious ecological differences, some fundamental similarities were apparent in the reproductive biology of these animals. In addition, the growth rates of both species were relatively slow. Studies on metabolism and feeding of P.antarctica indicated that the rate of respiration was higher than expected for the constant low ambient temperature. It is considered that the phenomena of slow growth, increased parentalism and decreased fecundity present in these, and many polar species, can be partly attributed to such elevated metabolism and to the highly fluctuating primary production of antarctic waters which subsequently affects the overall amounts of energy which can be ingested during the year. Breeding in both animals was synchronised to the period of optimum food supply during early spring or summer.