A seasonally varying biotope at Signy Island, Antarctic: implications for meiofaunal structure

Under the typical high-latitude conditions of temperature, productivity and settlement of chlorophyll and phaeophytin to the sediment, many benthic or ganisms in the Antarctic show strong seasonal variation. Although meiofauna comprise an important component of the southpolar benthic ecosystem, our k nowledge of them is limited. The metazoan meiofauna and the surrounding sed iments were studied fortnightly for 18 mo in a shallow bay at Signy Island (Factory Cove, South Orkneys, Antarctica) to test whether and how the tempo ral variability of the environment influenced meiobenthos dynamics. By exam ination of the distribution of the abundance and biomass of the total commu nity, the density of higher taxonomic groups, and of individual dominant ne matode genera and feeding categories, we assessed changes in faunal structu re. Short-term variations were often effective, and several correlations we re observed between temperature and food availability (chlorophyll and its derivatives and bulk organic matter, C and N, in both sediment and water co lumn). However, complex temporal patterns characterised the otherwise fairl y predictable seasonal variations of the Antarctic ecosystem. The results s uggest that variations in meiobenthic population density and structure were primarily regulated by the input and availability of organic matter and le ss so by water temperature, which was constantly low. The virtual lack of a 'winter stop' also leads to the conclusion that food was not limiting in t he Antarctic coastal sediment.