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 organisms in the Antarctic show strong seasonal variation. Although meiofauna comprise an important component of the southpolar benthic ecosystem, our knowledge of them is limited. The metazoan meiofauna and the surrounding sediments were studied fortnightly for 18 mo in a shallow bay at Signy Island (Factory Cove, South Orkneys, Antarctica) to test whether and how the temporal variability of the environment influenced meiobenthos dynamics. By examination of the distribution of the abundance and biomass of the total community, the density of higher taxonomic groups, and of individual dominant nematode genera and feeding categories, we assessed changes in faunal structure. Short-term variations were often effective, and several correlations were observed between temperature and food availability (chlorophyll and its derivatives and bulk organic matter, C and N, in both sediment and water column). However, complex temporal patterns characterised the otherwise fairly predictable seasonal variations of the Antarctic ecosystem. The results suggest that variations in meiobenthic population density and structure were primarily regulated by the input and availability of organic matter and less 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 the Antarctic coastal sediment.