Preliminary observations on macrolagal communities developing in the ice-free areas in Potter Cove, South Shetland Islands, Antarctica

DOLORES DEREGIBUS; GABRIELA LAURA CAMPANA; MARIA LILIANA QUARTINO; GUSTAVO EDGAR JUAN LATORRE

Varsovia

Workshop; IMCOAST (Impact of climate induced glacial melting on marine coastal systems in the Western Antarctic peninsula region) Workshop; 2009

IMCOAST (Impact of climate induced glacial melting on marine coastal systems in the Western Antarctic peninsula region) Workshop

Climate warming has especially been related to glacial retreat along the Western Antarctic Peninsula. Consequently, new ice-free areas have become available for benthic colonization but also an alteration of the water column (due to an increase of sediment input and salinity changes) and on the ice disturbance patterns are expected for coastal areas. One notorious example of this situation is observed at Potter Cove (Isla 25 de Mayo/ King George Island), where the benthic macroalgal communities have been studied regularly over the last 18 years. In 1993-1994 the sublittoral vegetation was documented by subaquatic video transects, providing information of the vertical macroalgal distribution. The soft bottom of the inner cove was completely devoid of macroalgae and only rare exceptions were found on few boulders and stones of moraine deposits, which occurred in front of the glacier cliffs. Over the last years a visible melting of Fourcade glacier has exposed ice-free areas, providing a substrate for macroalgal colonization. The aim of this study is to report the vertical and spatial distribution of the macroalgal communities in this new ice-free scenario. From December 2007 to August 2008, fourteen underwater video transects were performed at six identified new ice-free areas, from the waterline down to 12-15 m. The areas closer to the mouth of the cove (areas 1-2) showed more complex macroalgal communities than those located in the most disturbed site (area 5), where Palmaria decipiens was the only conspicuous species colonizing hard substrata of different size. A significant observation is the presence of large Desmarestiales (e.g Himantothallus grandifolius) at shallower depths. These preliminary results can be attributed to a decrease in light penetration caused by sediment input, which might shift the lower distribution limit of macroalgae from deep to shallower waters.