Antarctic deep-sea food webs: Understanding Ecological and Environmental drivers using South Sandwich Islands and South Georgia regions as case-studies

• Main Author: Queirós, José Pedro Marques
• Format: Thesis
• Language: English
• Published: 2024
• Subjects: Antarc*; Antarctic; Scotia Sea; South Sandwich Islands; Southern Ocean
• Online Access: http://nora.nerc.ac.uk/id/eprint/537868/; https://nora.nerc.ac.uk/id/eprint/537868/1/Jose%20Marques%20Querios%202024.pdf; https://estudogeral.uc.pt/handle/10316/115253?mode=full

The Southern Ocean is a unique and extreme environment that is changing fast due to climate change, with shifts recorded from the surface to deep-sea ecosystems. By evolving in such a specific environment, Southern Ocean biodiversity generally shows low capacity to cope with this changing environment. Like climate change, toothfish fisheries also pressure this ecosystem, especially deep-sea demersal communities where they operate, with these two factors having reciprocal/accumulating impacts. The Southern Ocean deep sea presents a major role on the World’s Ocean circulation and its biodiversity presents high levels of endemism. Nonetheless, it remains inadequately sampled, with the biodiversity and the influence of environmental conditions in these communities being poorly understood. This is off particular concern because deep-sea species have low productive life cycles, e.g. long lifespan, slow growth, and late maturation, which make them more vulnerable to disturbance. The way communities respond to climate change and fisheries depends on the food-web structure, with the food chain length being a feature that largely influences the response to these stressors. However, a lack of knowledge persists regarding the food-web structure of the Southern Ocean deep sea, especially when considering the demersal communities and the benthopelagic coupling. Therefore, this thesis, using the South Sandwich Islands (SSI) and South Georgia (SG) (Scotia Sea) as study regions, aims to study: 1) potential impacts of toothfish fisheries in the deep-sea communities at SSI and how climate change can impact this fishery; 2) the biogeography of bathyal communities at SSI; 3) the interannual variability in the food-web structure at SSI; and 4) the structure of the food web in a latitudinal gradient at the Scotia Sea (from SSI to SG). Results show that toothfish fisheries are well managed and not substantially impacting the populations of target and non-target species at SSI. However, the influence of environmental conditions in the ...