Marine trophic networks in Terra Nova Bay during different ice extent: stable carbon and nitrogen isotopes for determination of trophic interactions affecting biodiversity and heavy metal bioconcentration.

Trophic interactions underlie coexistence mechanisms between species and affect biodiversity and heavy metal bioaccumulation processes. Sea ice dynamics, which at Terra Nova Bay is characterized by an extraordinary seasonality, drives interspecific interactions. Indeed, the activation of the primary production after sea-ice break up opens alternative trophic pathways for consumers. By means of C and N stable isotope analyses, the present project aims at (i) determining food web structure at Terra Nova Bay at different bathymetries and in opposite sea-ice cover conditions; (ii) evaluating heavy metal bioaccumulation in species along food chains, including fish of commercial interests, both in the presence and absence of photosynthetic primary producers. The hypothesis to be tested is if the activation of primary producers following sea-ice break up significantly modifies the food web structure and stability against species loss, as well as heavy metals concentration along food chains. Data on Antarctic food webs are scarce, and even scarcer is our knowledge on mechanisms of primary and secondary biodiversity loss and biomagnification processes in invertebrates and fish. The present research project will shed light on mechanisms underlying biodiversity maintenance in the Antarctic ecosystem and on risks for human health related to heavy metals accumulation in fish species currently or potentially exploited commercially, also in light of expected changes in the extension of sea ice cover. A valuable reference baseline will be established for future studies at the Italian Antarctic Station and for the Marine Protected Area in the Ross Sea.