Benthic community shifts: A possible linkage to climate change?

RICARDO SAHADE; SOLEDAD TARANTELLI; MARCOS TATIÁN; GUILLERMO MERCURI

POLARFORSCHUNG

Año: 2008 vol. 571 p. 331 - 340

0032-2490

The Earth mean temperature has increased around 0,6º C in the last 50 years, however, there are critical areas such as the Antarctic Penninsula and the Arctic Ocean where the increase was up to 2,5 º C (Vaughan et al. 2003). As a consequence the majority of the glaciers at the Penninsula showed an important retreat (Cook et al. 2005). Ecological impacts of these processes are difficult to asses since several variables can be affected showing unpredictable responses, however, based on knowledge of community patterns and natural history of key species is possible to speculate about some of them. In the case of coastal marine ecosystems the most important effects are probably twofold. First, the increased input of terrigenous materials transported by melting glaciers. Since sediments besides affecting local primary production due to the reducing light penetration on the water column (Schloss et al. 2002), would affect shallow benthic ecosystems especially those dominated by filter-feeders by diluting the percentage of particulate organic matter, difficulting the filtration and even clogging the filtration apparatus of these organisms. Second, at least in the short term, a higher ice abrasion could be expected due to the increase of brush ice and growlers coming from retreating glaciers, this impact would have a great impact at the beginning of the process showing a decrease as the glaciers retreats and broke on land. On the other hand, another important factor would be the water temperature increase; however, not a clear signal of a steady water temperature increment was still detected in Antarctic waters (Barnes et al. 2006). But at small scale a slight trend could be measured at Potter Cove (Schloss et al. this volume). Macrobenthic communities structure patterns in a temporal scale has long be used as important tools assessing short- and long term changes in marine ecosystems for both, human induced and natural causal impacts (Ruhl and Smith 2004; Blanchet et al. 2005; Grebmeier et al. 2006 and many others). Besides that, it is clear that for properly analyze and interpret forcing factors and ecosystem processes is fundamental to observe and understand the patterns (Underwood et al. 2000).  Although much work has been done on Antarctic benthic communities patterns, both at shallow and shelf areas (see a comprehensive list at Clarke and Johnston 2003 and Gili et al. 2006), most of the work was devoted to spatial arrangements and studies dealing with benthic communities temporal dynamics are almost lacking except for that of Dayton (1989).  In the present study benthic communities patterns at Potter Cove in a time lapse of three years are analyzed and causal processes inferred in the frame of actual warming scenario.