ANTARCTIC BENTHOS UNDER INCREASING SEDIMENTATION, A BALANCE BETWEEN SENSITIVITY AND STRATEGY

ALURRALDE, GASTÓN; SAHADE, RICARDO; ABELE, DORIS; TORRE, LUCIANA; SCHLOSS, IRENE

Punta Arenas

Congreso; IX Congreso Latinoamericano de Ciencia Antártica 2017; 2017

Instituto Nacional Antartico Chileno (INACH)

As a consequence of glacier retreat, there is an increasing interest trying to understand the effect of sedimentation up on Antarctic coastal marine systems that are generally dominated by suspension feeders. In Potter Cove (South Shetland Island, Antarctic Peninsula), as a consequence of increasing sedimentation, changes in benthic assemblage have been revealed, being ascidians the most affected group. Experimental studies show that sedimentation increases metabolic rates and diminishes food absorption efficiency, leading to a carbon bugged imbalance. These results, together with the observed changes in this benthic assemblage point out sedimentation as the key forcing factor of change, as species abundance diminishes and depth limits distribution retreats in accordance with their sensitivity. Nevertheless, in a new ice-free island recently described subjected to high sedimentation regimes, Molgula pedunculata and Cnemidocarpa verrucosa are dominating over other considered less sensitive as Corella antarctica or Ascidia challengeri. This entails the questing how the most sensitive species are able, to not only to survive at high sediment concentration but to dominate over the others. In order to answer these questions we performed a sampling study were we collect specimens of M. pedunculata and C. antarctica under different natural sedimentation regimes to study their in situ physiological state. We analyzed gut content quality, muscle glycogen concentration (as energy reservoir) and MDA branchial concentration as oxidative stress marker. The %OM in gut contents increases with the distance to the glacier in both species (ANOVA F= 87.82 p < 0.0001; F = 10.97 p = 0.0004 for M. pedunculata and C. antarctica, respectively). It is also significantly different between species at all stations (ANOVA F= 31.16 p < 0.0001). The glycogen content was significantly different only for C. antarctica (K-W H=6.95 p=0.031) increasing as expected with the distance to the glacier. The MDA content of the branchial sacs of M. pedunculata and C. antarctica has no statistical significant differences between stations but, as expected, it seems to have less accumulation for C. antarctica far from glacier influence. Finally, we evaluate carbon balance for both species considering metabolic rate and food quality intake under increasing sedimentation. Contrary to expected, M. pedunculata dominates not only at low but also at very high TPSM concentrations. These results suggest that even when sedimentation affect carbon balance of this species, their pioneer traits make M. pedunculata a better competitor even in a supposed disadvantage condition.