Marine ecosystem change
Sea ice algae provides food for krill and other planktonic organisms.
Photo: Wendy Pyper
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Southern Ocean ecosystems are threatened by:
- global warming;
- ocean circulation changes;
- ocean acidification (due to increasing carbon dioxide from the atmosphere dissolving in the ocean);
- sea ice retreat;
- invasive species; and
- increased exploitation by humans.
We are seeing changes in the phytoplankton and zooplankton communities, with some species becoming more dominant; the movement of temperate species south and a contraction in the range of polar species; and changes in the ability of some organisms to form shells, due to ocean acidification. The current recovery of many higher predators (whales and seals) from historic over-exploitation will impose further change on Southern Ocean ecosystems.
Sea ice provides important habitat for many Antarctic and Southern Ocean organisms including these Weddell seals.
Photo: Diana Calder
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In the future, a predicted reduction in sea ice will cause a loss of habitat for ice-associated organisms, from microbes to seals. It will also change the amount of light penetrating the ocean surface and surface water stratification (water layers of different salinity and temperature). These changes may reduce the extent of the ice edge algal bloom that is crucial to the productivity in the Southern Ocean and that supports the specialised food chain linked to krill.
This research stream will:
- identify the ecological responses and resilience of Southern Ocean ecosystems to the impacts of global change; and
- develop cost-effective monitoring approaches to track the impacts of global change and the effectiveness of conservation measures on ecosystems.
The key questions being investigated are:
- How have Southern Ocean ecosystems responded to environmental change in the past?
- What are the potential ecosystem impacts of observed and predicted physical change (e.g. ocean currents and sea ice) and chemical change (e.g. ocean acidification and salinity) in the Southern Ocean?
- What evidence is there that the biodiversity and structure of Southern Ocean ecosystems off eastern Antarctica is changing, and how much of this can be attributed to global change or past exploitation?
- How might these changes affect the productivity and sustainability of species and ecosystems?
- Which key pelagic (open ocean) species and communities are most vulnerable to the effects of ocean acidification, and how does ocean acidification affect them?
20 years of data on the distribution, diversity and abundance of plankton, captured with this continuous plankton recorder, is contributing to scientists' understanding of changes in Southern Ocean ecosystems.
Photo: Sandy Zicus
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The ability to detect and understand ecological changes in the Southern Ocean requires a carefully designed program of observations, experiments, monitoring and modelling. In terms of observation and monitoring, existing initiatives such as the CCAMLR Ecosystem Monitoring Program (CEMP), Australia’s Integrated Marine Observing System (IMOS), our marine microbial ecology program and the emerging Southern Ocean Observing System (SOOS) and Southern Ocean Sentinel program, provide a useful foundation.
Synthesis and modelling is being coordinated with and guided by the Antarctic Climate and Ecosystems Cooperative Research Centre (ACE CRC) Antarctic Marine Ecosystems program and the Integrating Climate and Ecosystem Dynamics (ICED) program (based in the UK).
Products from the research will include spatially explicit biophysical ecosystem models that will inform conservation and management strategies in the Southern Ocean.
Stream leaders: Dr Jan Strugnell and Professor Andrew McMinn
Stream Implementation Plan: Stream 3.1 Marine ecosystem change
This research feeds into:
