Trophic ecology of Southern Ocean sea stars: Influence of environmental drivers on trophic diversity

• Main Author: Le Bourg, Baptiste
• Format: Text
• Language: French
• Published: Université de LIège 2020
• Subjects: geo; envir; Antarctic; Antarctic Peninsula; Austral; Southern Ocean; The Antarctic; Antarc*; Sea ice
• Online Access: https://archimer.ifremer.fr/doc/00633/74468/74296.pdf; https://archimer.ifremer.fr/doc/00633/74468/

Like in the rest of the world, climate change impacts the Southern Ocean, but not in the same way in all regions of this ocean. Changes in sea ice cover around the Antarctic continent are one of the most visible manifestations. For example, sea ice cover has decreased significantly in the Western Antarctic Peninsula while it tends to increase slightly on the rest of the coastline of the continent. These changes in environmental conditions influence the functioning of the ecosystems of this ocean. In particular, the disappearance or persistence of sea ice in a region where it was seasonally present may prevent the appearance of summer phytoplankton blooms, thus impacting the dynamics of krill populations and their predators in the pelagic environment. The benthic environment will also be disturbed by environmental modifications resulting from climate change, as organic matter fluxes toward this compartment will be affected. Sea stars (Echinodermata: Asteroidea) are a key component of Southern Ocean benthos, with 12% of the known sea star species living there. In temperate environments, this taxon may play an important role in the functioning of ecosystems with its trophic interactions controlling the populations of other organisms, which themselves have a large effect on the ecosystems. This group is considered to be quite resistant to changes of seawater temperature in the Antarctic environment. However, it will likely be affected by changes of environmental conditions and functioning of food webs. Indeed, a reduction in the abundance or disappearance of common prey can lead to an increased competition in sea star assemblages. In order to determine the ecological role of sea stars in the Southern Ocean and to understand how they might be impacted by climate change, a study of their trophic ecology and of the factors controlling it is necessary. Therefore, the objectives of this PhD thesis were to determine the trophic role of sea stars in the Southern Ocean, and how environmental factors such as turbidity, depth ...