Dr Roshni Subramaniam1, Dr James Smith, Dr Cathy Bulman1, Dr Hayden Schilling2, Dr Jess Melbourne-Thomas1, Dr Martina Doblin2, Dr Iain Suthers2
1CSIRO Oceans & Atmosphere, Hobart, Australia, 2Sydney Institute of Marine Science, Mosman, Australia
The temperate reefs in south-east Australia are dominated by habitat-forming macroalgae and form part of the Great Southern Reef. These reefs support a wealth of biodiverse benthic invertebrates and fish assemblages and human activities (such as fishing), which contributes to a socio-economic value of over 10 billion AUD per annum for coastal economies. Warming coastal waters, accelerated by the strengthening East Australian Current (EAC), are impacting the ecosystem. The influx of tropical herbivorous fishes (i.e. tropicalisation) and overgrazing by sea urchins are driving declines in habitat-forming macroalgae. Further, the strengthening of the EAC may potentially transport phytoplankton production poleward and displace the chlorophyll-rich waters of the Tasman Sea. These impacts can propagate through the food web to impact ecosystem structure and function. Forage fish have also responded negatively to tropicalisation, raising further questions around the potential to increase fishing for forage fish. While aspects of the ecosystem have been studied (for example, fish assemblages), the ecosystem-level impacts of these changes are relatively unknown. Using a model ensemble approach, we develop a qualitative and a quantitative ecosystem model to understand coastal ecosystem dynamics in New South Wales. We explore ecosystem-level responses to environmentally driven scenarios of ecosystem change: declining macroalgae, declining phytoplankton production and declining planktivorous fish. We show through food web-mediated change, that seals, pelagic sharks, coastal pelagic piscivorous fish, shelf demersal fish and sharks and filter feeders may be early indicators of environmentally driven changes to ecosystem structure and function in coastal New South Wales.
Biography:
Roshni Subramaniam is a CERC Postdoctoral Fellow at CSIRO. She has a strong interest in understanding the dynamics of marine socio-ecological systems and has sought to understand how human pressure and environmental change are impacting Antarctic and temperate marine ecosystems. She has applied qualitative and quantitative models to detect, manage and predict spatio-temporal changes in ecosystem structure and function.
At CSIRO she is investigating the resilience and sustainability of Australia’s seafood supply chains. As disruptions, or shocks, become more frequent across social, economic and ecological domains, building resilient and sustainable systems to better respond to these disruptions is critical.
