In hot water: the future of Australia's coastal and marine ecosystems

Full text: Full text: Marine ecosystems are extremely important economically and ecologically to Australia in terms of tourism, coastal defence, resources, and ecosystem services such as nutrient cycling and waste disposal. Australia is also a globally important repository of biodiversity. Here we describe the observed and potential future impacts of climate change on Australia's marine diversity. Climate simulations project oceanic warming, an increase in stratification, a strengthening of the Eastern Australian Current, increased ocean acidification, a rise in sea level, and altered storm and rainfall regimes, which taken collectively will fundamentally change marine ecosystems. There has already been widespread bleaching of tropical corals, poleward shifts of temperate fish and plankton populations, and a decline in cold-water giant kelp off Tasmania. Future changes are likely to be even more dramatic and have considerable economic and ecological consequences, especially in 'hot spots' of climate change such as theTasman Sea and the Great Barrier Reef area. Corals are likely to bleach more frequently and decline in abundance in response to both warming and ocean acidification. Planktonic animals with calcium carbonate shells, such as winged pteropod snails and coccolithophorid phytoplankton, are likely to decline as increased ocean acidification impairs their ability to maintain carbonate body structures. The projected high warming off south-east Australia is of particular concern. Marine ecosystems in this region are already stressed by high metal concentrations, sewage pollution, and overfishing, and climate models project that this region will warm more than anywhere else in the Southern Hemisphere this century because of enhanced southerly penetration of the East Australian Current. Venomous jellyfish and harmful algal blooms, which are major threats to human health, will potentially extend further south and occur more frequently. Temperate species inhabiting south-east Australia may find no suitable habitat to retreat to as waters warm, as the continental shelf does not extend far south of Australia. The relatively productive cool-temperate south-east may become a much less productive warm water regime, having considerable economic impacts on fisheries. Finally, we argue that the lack of baseline data for key marine biota and systems is hampering Australia's efforts to tackle climate change. Unless this is redressed through a greater commitment to monitoring and research program, Australia will: be unaware of how its marine ecosystems will change in the future; not have the baseline data for understanding this change, and have no way of assessing mitigation or adaptation strategies