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Abstract The Antarctic environment has special characteristics that influence the local marine life. The benthic organisms, adapted to these extreme conditions of life, are subject nowadays to effects of climate change. Recently, the consequences of glacier retreat on these assemblages have been observed in many West Antarctic Peninsula (WAP) regions, including King George Island (KGI). This study described the spatial variation of the benthic macrofauna in different areas of the Martel Inlet (Admiralty Bay - KGI), at depths around 25-30 m. Sampling was done in January 2001 at ten stations classified in localities according to their proximity to ice-margin/coastline in marine-terminating glacier (MTG), terrestrial-terminating glacier (TTG) and ice-free area (IFA). The total density and the abundance of annelids, nematodes, peracarid crustaceans and bivalves were higher at IFA stations. The locality discrimination by taxa and species was independent of available environmental/sedimentary conditions or was the result of unmeasured variables or species life history processes not assessed herein. Considering that our findings were obtained 21 years ago, they will be especially useful for comparing future studies of benthic assemblage responses to the influence of climate change and continuous glacier retreats in the WAP region.

A variação espacial e temporal da densidade e biomassa da meiofauna, em nível de grupos taxonômicos superiores, foi analisada e relacionada com as características do sedimento e as massas de água no Canal de São Sebastião. As coletas foram realizadas em dez estações, em fevereiro (verão) e agosto (inverno) de 1994. No verão, a densidade média foi de 605 ± 442 ind x 4,9 cm-2 e no inverno, 213 ± 181 ind x 4,9 cm-2. A biomassa média total variou de 184,7 ± 156,8 ¼g x 4,9 cm-2, no verão, diminuindo para 66,6 ± 48,9 ¼g x 4,9 cm-2, no inverno, mostrando padrão semelhante ao da densidade. Nematoda foi o grupo dominante em quase todas as estações, seguido de copepoda, em função do sedimento predominante. As características gerais da meiofauna na Canal de São Sebastião refletiram tanto a heterogeneidade espacial da distribuição dos sedimentos ao longo do canal, como também a sua variação temporal.Spatial and seasonal variation of the density and biomass of meiofauna at higher taxonomic group levels were studied and related to sediment characteristics and water masses in São Sebastião Channel. The sampling was done at ten stations in the channel in February (summer) and August (winter) 1994. In the summer, the mean density was 605 ± 442 individuals per 4.9 cm², and in the winter, the mean density decreased to 213 ± 181 individuals per 4.9 cm². Total mean biomass ranged from 184.7 ± 156.8 ¼g x 4.9 cm-2 to 66.6 ± 48.9 ¼g x 4.9 cm-2, showing similar pattern as the density. Nematoda was the main group at most stations followed by Copepoda, as function of sediment type. Meiofauna characteristics at São Sebastião Channel reflected both the heterogeneous spatial distribution of the sediment along the channel and its seasonal variation, as well.

In this study, the meiofauna associated with Sargassum cymosum was qualitatively and quantitatively analyzed between December 1990 and July 1991. Sampling was carried out on a moderately exposed shore at Lázaro Beach, Ubatuba (32°S - 45°W). Each alga was washed in a formaldehyde solution and the fauna in suspension was washed through a series of 500, 250, 120 and 60 µm mesh sieves. The biomass of each taxonomic group was estimated as ash-free dry weight (AFDW) according to size categories. Algae volume and dry weight were determined, incIuding epiphytes. Densities of epifauna ranged from 502.9 to 2706.6 ind.20 ml-1 as algae volume. The biomass values (326.6 to 1214.4 µg.20 ml-1 AFDW) represented a low standing stock. Harpacticoid copepods and their nauplii were the dominant group and also showed the highest biomass values, being represented by larger individuaIs (250 to 120 µm). Higher values were observed between the end of the summer and the beginning of the fali (March and April), decreasing until winter (July). This variation may be explained by habitat complexity changes, or reproduction of some taxa, as higher meiofaunal densities were found on the 60 µm mesh sieve, incIuding high percentages of nauplii.Este trabalho avalia qualitativa e quantitativamente a meiofauna associada a Sargassum cymosum estimando-se a densidade e biomassa da fauna, assim como uma possível variação temporal. As coletas foram realizadas à nordeste da Praia do Lázaro, Ubatuba (23°S - 45°W), de dez/90 a jul/91. As frondes foram mergulhadas em solução de água e formaldeído, e os organismos em suspensão retidos em uma série de malhas (500,250, 120 e 60 µm). Para cada grupo taxonômico foi estimada a biomassa em µg de peso seco livre de cinzas. Como medida de substrato foi determinado o volume e a biomassa em peso seco de alga, incluindo-se as algas epífitas. Os valores de densidade da meiofauna variaram entre 502,9 a 2706,6 ind.20 mrl de alga. A biomassa estimada por sua vez apresentou valores baixos, entre 326,6 a 1214,41-µg.20 ml-1 peso seco livre de cinzas. Copepoda Harpacticoida e seus náuplios foram dominantes numericamente e em relação à biomassa. Os valores de densidade e biomassa da meiofauna foram altos no final do verão (março) e início do outono (abril), e diminuíram gradativamente até o início do inverno (julho). Esta variação pode ser explicada por mudanças na complexidade do habitat ou, ainda, devido ao período reprodutivo de alguns táxons, já que a maior quantidade de meiofauna ocorreu na malha de 60 µm (náuplios).