Benthic ecosystem responses to glacier retreatment process: different approaches to understand observed patterns.

SAHADE RICARDO; DORIS ABELE; ACOSTA SOLEDAD; DE ARANZAMENDI MARÍA CARLA; DEMARCHI M,; HELD CHRISTOPH; LAGGER C; SERVETTO N; TARANTELLI S; TATIÁN MARCOS; WIERNES P

Buenos Aires

Workshop; Forth IMCOAST Workshop; 2012

Glacier retreatment registered consistently along the Antarctic Peninsula, caused by its rapid warming, can impact coastal ecosystems in two folds. On one hand by affecting established communities by increased ice calving, sedimentation rates and fresh water input. On the other hand, this process is also opening new ice free areas available for colonization and establishment of benthic organisms. In Potter Cove both effects, marked by shifts in established benthic communities structure and newly ice free areas densely colonized, have been observed. These findings are not only surprising but also challenge some established ideas of Antarctic ecosystem dynamics, i.e. the stability of Antarctic benthic communities, the velocity of colonization processes and growth rates of some Antarctic organisms or the suitability of under ice habitats for the development of benthic assemblages, depending whether the observed communities in newly ice free areas are the result of a rapid colonization process or were already inhabiting in ice refugia under the glacier. We assess these topics using different approaches aiming to improve our current understanding of the ongoing processes and prediction capacity. Benthic communities and food web structure are the basis to analyze interspecific relationships and ecosystem functioning. Then potential forcing factors driving the observed shifts in benthic assemblages were inferred on the basis of environmental data and available knowledge of the natural history of more affected species. Increased sedimentation rates appear as a good candidate for explaining observed processes, and two approaches are used to test this hypothesis. From eco‐physiology perspective, sedimentation effects were analyzed in targeted species and mathematical models simulating different scenarios are under development to verify the potentiality of sedimentation as forcing variable or to reveal more factors able to produce similar patterns. The colonization of newly ice free areas entails a major challenge to be addressed from different perspectives as well. If colonization took place once the ice opened the areas or if these assemblages were established under the glacier is a major question to focus on. In the first case colonization and growth rates should be much faster the previously supposed, in the second case environmental conditions and food supply in such refugia or how extended or unique can this be along the Antarctic Peninsula are important questions as well. To analyze colonization and growth rates succession panels and cleaned areas were set up. While genetic tools as fast evolving molecular markers will be crucial to assess the antiquity and origin of these populations, analyzing genetic diversity we will be able to detect a founder effect in case of new colonization, as well as the connectivity of these and surrounding populations. In this project we use an interdisciplinary approach to tackle our main questions; however, our disciplines are fundamentally biological/bio‐chemical and will be important to strength the correlation with environmental disciplines like geology and sedimentology. For instance, we are working on an increasing sedimentation rates assumption but a sedimentation event could also explain observed shifts. Although biologically we can observe the same result the implications and involved processes can be completely different.