Spatial and temporal variations in the macroalgal community of Potter Cove (Antarctica) over two decades

DOLORES DEREGIBUS; GABRIELA LAURA CAMPANA; FERNANDO ROBERTO MOMO; KATHARINA ZACHER; MARIA LILIANA QUARTINO

Leuven

Congreso; XIIth SCAR Biology Symposium; 2017

Scientific committee of antarctic research

Climate warming has been associated to retreating of ice fronts and increased melt water run-off in the Western Antarctic Peninsula (Cook et al. 2005). One effect of glacial retreat along the WAP is the opening of newly ice-free areas (NIFAs, Rückamp et al. 2011). Furthermore, it increases the sediment inflow and diminishes the light penetration into the water column (Schloss et al. 2012). At Potter Cove (62º 14? S, 58º 38? W), a big fjord at King George Island/Isla 25 de Mayo a deeper knowledge of the macroalgal community spatial and temporal variation has been achieved during the last two decades. Video surveys of macroalgal extension within the cove were repeatedly performed in 1993/4, 2008 and 2013. In 1994 the sublittoral macroalgal vegetation was restricted to the outer part of the cove whereas the inner cove was devoid of macroalgae (Klöser et al. 1996). The extension of macroalgal occurrence into the inner part could be proofed during the last two surveys (Quartino et al. 2013). The increase of macroalgal extension into the inner cove is related to the NIFAs, with new hard substrate for benthic colonization. Furthermore, at sites more distant to the retreating glacier more complex communities were identified, whereas less mature communities (lower richness and lower presence of perennial species) occurred in sites with the highest sediment inflow (closer to the glacial run-off). Macroalgal communities in the NIFAs did not significantly change in structure and spatial distribution between 2008 and 2013. The expansion of the macroalgal community into the inner Potter Cove could lead to higher macroalgae primary production. On the other hand, increased turbidity is leading to a narrowing of the vertical distribution of the macroalgae (Deregibus et al. 2016, Jerosch et al. 2017). Certainly, the benthic communities have undergone profound changes within the last decades with multiple factors interacting in synergistic or antagonistic ways. Repeated surveys are necessary to follow the changes and to validate and improve the models.