Climate change is likely to have important consequences for spawning patterns and productivity cycles in the ocean, according to this report. Most international studies centred on change in the ocean take temperature increases into account. But other important variables that require consideration include changes to ocean chemistry (ie. acidification) impeding the ability of organisms to build shells; ocean circulation influencing population dynamics; and change in cloud cover and sea ice affecting light supply to the ocean surface.
Although Australia has an extensive coastline and one of the largest fishing zones in the world, its coastal and mid-depth waters are considered to be low in productivity and fisheries are reliant on processes such as upwelling to provide nutrients. Using computer simulations of possible change up to 2030, the authors considered changes in temperature, ocean currents, winds, nutrient supply, rainfall and ocean chemistry.
Changes to ocean circulation in the western Pacific Ocean and Tasman Sea and an upward trend in water temperatures have led to environmental modification in south east Australia as the East Australian Current pushes further south carrying sub-tropical species into temperate waters. This is a region where climate models indicate rapid warming and a 50-year observation program has shown a water temperature increase of two degrees Celsius; as a result, sub-tropical introductions to the Tasmanian east coast are already altering the habitat of a whole range of species, and introducing new species such as the sea urchin.
The report generated three core findings:
• While ocean temperature has a significant influence on observed changes in Australia’s marine flora and fauna, it is the combined effects of multiple climate and oceanographic factors that will shape Australia’s marine life in the future.
• The ecological effects of non-climate related stress factors such as fisheries, coastal run-off and pollution which may reduce ecosystem resilience to climate change.
• Programs to measure change and modelling of climate change impacts will be crucial components of a strategic national assessment of climate change impacts so that management strategies can be developed.
The report identifies six key questions that required addressing by future modelling and ocean and coastal monitoring programs.