Influence of sea-ice cover changes on the food web structure and key species in the Ross Sea “MPA” in a context of climatic change

In Antarctica, biodiversity architecture is closely linked to the dynamics of sea ice cover and uncovering, which, due to climate change, is expected to undergo major changes. This could have unexpected consequences for two main reasons such as an increase in primary productivity and water acidification, with consequent effects on calcifying organisms, and a potential shift in trophic preferences at the base of the food chain from detritus (animal and plant) to grazing. In addition, such changes could promote the invasion of sub-Antarctic species with significant effects on trophic structure and its functioning. These aspects could significantly affect the robustness of the trophic network to biodiversity loss and the functioning and efficiency of trophic transfer, including bioaccumulation and biomagnification of organic and inorganic pollutants along food chains. To this end, an unequivocal determination of the trophic and functional role of taxa based on multiple methods is needed to understand and anticipate the effect of climate change on the functioning of sub- and meta-food webs in the Ross Sea MPA.

In line with SCAR's (Scientific Committee on Antarctic Research) "next generation SRPs," and specifically the themes "Ecosystem Resilience and Adaptation (AnT-ERA)" (ecosystem functioning and services) and "State of the Antarctic Ecosystem (AntEco)," the project aims for a detailed description of trophic linkages between species and ecosystem compartments, including key species and trophic pathways that support key predators. This research will help fill these gaps by shedding light on the ecological mechanisms underlying biodiversity conservation and management processes and ecosystem functioning in the Ross Sea even under a scenario of changes in sea ice dynamics associated with climate change.

The main objectives of the project are: 1) determine the isotopic signals of carbon, nitrogen and sulfur, trace metals, and PAH (Polycyclic Aromatic Hydrocarbons) concentrations in benthos, plankton, sympagic algae, necton, birds (carcasses and guano), and seals (droppings and carcasses) in areas characterized by different seasonal dynamics of sea ice cover; 2) reconstruct sub- and meta food webs by a multiple (three isotopes) approach for unambiguous identification of the functional role of species; 3) identify key species and critical pathways for nutrient and pollutant transfer between benthic, sympatric, and pelagic compartments; 4) describe the spatial and temporal variability of trophic network structure and robustness to secondary biodiversity loss along sea ice cover gradients. Based on this, it will be possible to assess the structural and functional fragilities of the trophic network to disturbance as a result of potential changes in sea ice dynamics. In addition, the biomagnification of pollutants in species actually or potentially targeted by commercial fisheries will be investigated. Knowledge about the structure and tropho-functional composition of the trophic network obtained through the methodology proposed with this project will elucidate the organization of the biodiversity architecture and its vulnerability to primary and secondary species loss, providing a sound basis for biodiversity management of the Ross Sea MPA in a context of climate change.