Climate change, glacier retreat and a new ice-free island offer new insights on Antarctic benthic responses

LAGGER C.; NIME, M; TORRE L; SERVETTO N; TATIÁN M; SAHADE R

ECOGRAPHY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2017 vol. 40 p. 1 - 12

0906-7590

Th e Antarctic Peninsula is among the places on Earth that registered major warming in the last 60 yr. Massive ice losses,represented by glacier retreat, ice-shelf collapses and sea-ice reduction are among the main impacts of this regionalwarming. Th e loss of sea-bed ice coverage, on the one hand has been aff ecting benthic assemblages, but on the other it isopening up new areas for benthic colonisation. Potter Cove (South Shetland Islands) off ered the opportunity of assessingboth processes. We recently reported a sudden shift of benthic assemblages related to increased sedimentation rates causedby glacier retreat. Th is glacier retreat also uncovered a new island that presents a natural experiment to study Antarcticbenthic colonisation and succession. We sampled the new island by photo-transects taken up to 30 m depth. Here, wereport an unexpected benthic assemblage characterised by high species richness, diversity and structural complexity with awell-developed three-dimensional structure and epibiotic relationships. Filter feeders comprised the largest trophic groupat all depths, mainly ascidians, sponges and bryozoans. Densities were also surprising, recording only six ascidian specieswith a mean of ∼ 310 ind. m ? 2 . Th ese values are at least an order of magnitude higher than previous Antarctic reportson early colonisation. Th is fi nding challenges the extended idea of a slow and continuous recruitment in Antarctica.However, it also opens the question of whether these complex assemblages could have been present under the glacier inice-free refuges that are now exposed to open sea conditions. Under the current scenario of climate change, these resultsacquire high relevance as they suggest a two-fold eff ect of the Antarctic Peninsula warming: the environmental shiftsthat threaten coastal ecosystems, and also the opening up of new areas for colonisation that may occur at a previouslyunimagined speed.