ORIGINAL PAPER C. A. Echeverrı´a Æ P. C. Paiva Macrofaunal shallow benthic communities along a discontinuous annual cycle at Admiralty Bay, King George Island, Antarctica Received: 14 July 2004 / Revised: 7 July 2005 / Accepted: 12 July 2005 / Published online: 2 September 2005 Ó Springer-Verlag 2005 Abstract Temporal variations in composition and density of the benthic macrofauna at two stations (12 and 25 m depth) were studied in Admiralty Bay, King George Is- land, Antarctica. Samples where carried out using an van Veen sampler between March and December 1999 (win- ter) and December 2000 and March 2001 (summer), comprising a discontinuous annual cycle. Sediment or- ganic matter showed a marked seasonal cycle, with lowest values at middle winter. Communities showed little vari- ations in density and composition. Temporal variations were not detected at 25 m depth. Variations at 12 m were related to one iceberg impact and to wind generated hy- drodinamism, as a function of wind direction, intensity and fetch. As winter scarcity of primary production did not seem to affect macrofaunal community densities, nutrient availability for the benthos in winter can be re- lated to the remineralization of sediment organic matter by bacterial activity. Introduction Researches on benthic communities in Antarctica were carried out mostly on summer surveys (Platt 1979; Oliver and Slattery 1985; Wa¨gele and Schminke 1986; Wa¨gele and Britto 1990; Arnaud 1985, 1998; Arnaud et al. 1986, 1998; Gambi et al.1994, 2000). Studies including year-round sampling or winter-summer com- parisons are scarce; they report a high standing crop with low temporal variability in community densities and compositions (Lowry 1975; Kauffman 1977; Tucker 1988; Mu¨ hlenhardt-Siegel 1989; Battershill 1990). However, Zhang et al. (1986, p. 141), reported that ‘‘population density showed obvious seasonal variations’’. The responses of shallow benthic commu- nities to seasonal variations on primary production in Antarctica are still not well established but primary production is known to influence the shallow benthos mainly through winter resource limitations (Grebmeier and Barry 1991; Nedwell et al. 1993, 1995; Arntz et al. 1994; Clarke 1996a, b, Gambi et al. 2000). Composition of Antarctic fauna is comparatively well known (Retamal et al. 1982; Parulekar et al. 1983; Arnaud et al. 1986). Communities seem to be composed by long-lived individuals (Arntz et al. 1994; Clarke 1996), and hence recovery of benthic communities after impacts can take years (Arntz et al. 1994). On the other hand, Peck et al. (1999) found that after an iceberg im- pact, species return time, via locomotion from adjacent areas, is about 10 days. Hydrodynamism can be con- sidered a factor contributing to the temporal variability of shallow communities due to substratum instability (Wu et al. 1992a, b). Hence, year-round studies are necessary in order to assess response modes of benthic communities to seasonal variation in Antartica, mainly in the highly physically impacted shallow environments. The main goal of this study is to evaluate if density and composition of shallow benthic communities are affected by: (1) winter resource limitations, (2) iceberg impacts, and (3) hidrodinamism generated by storms. For these purposes we studied the temporal variation of the shallow benthic macrofauna at two stations (12 and 25 m) in Admiralty Bay (King George Island, Antarc- tica) from March to December 1999 (winter) and from December 2000 to March 2001 (summer). Materials and methods Abiotic factors Wind speed, wind direction, air temperature and surface solar radiance were measured continuously using a C. A. Echeverrı´a (&) Æ P. C. Paiva Laborato´rio de Polychaeta, Depto. de Zoologia, Universidade Federal do Rio de Janeiro, CCS, bloco A, sala A0-104, subsolo. Av. Brigadeiro Trompowsky, S/N, Cidade Universita´ria, Ilha do Funda˜o, Rio de Janeiro, CEP: 21949-900 Brasil E-mail: caecheve@acd.ufrj.br Polar Biol (2006) 29: 263–269 DOI 10.1007/s00300-005-0049-6