File Name: coral reefs under rapid climate change and ocean acidification .zip
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Under conditions expected in the 21st century, global warming and ocean acidification will compromise carbonate accretion, with corals becoming increasingly rare on reef systems. The result will be less diverse reef communities and carbonate reef structures that fail to be maintained. Climate change also exacerbates local stresses from declining water quality and overexploitation of key species, driving reefs increasingly toward the tipping point for functional collapse. This review presents future scenarios for coral reefs that predict increasingly serious consequences for reef-associated fisheries, tourism, coastal protection, and people. As the International Year of the Reef begins, scaled-up management intervention and decisive action on global emissions are required if the loss of coral-dominated ecosystems is to be avoided.
Ocean warming and acidification from increasing levels of atmospheric CO 2 represent major global threats to coral reefs, and are in many regions exacerbated by local-scale disturbances such as overfishing and nutrient enrichment. Our understanding of global threats and local-scale disturbances on reefs is growing, but their relative contribution to reef resilience and vulnerability in the future is unclear. Here, we analyse quantitatively how different combinations of CO 2 and fishing pressure on herbivores will affect the ecological resilience of a simplified benthic reef community, as defined by its capacity to maintain and recover to coral-dominated states. We use a dynamic community model integrated with the growth and mortality responses for branching corals Acropora and fleshy macroalgae Lobophora. We operationalize the resilience framework by parameterizing the response function for coral growth calcification by ocean acidification and warming, coral bleaching and mortality by warming, macroalgal mortality by herbivore grazing and macroalgal growth via nutrient loading. The model was run for changes in sea surface temperature and water chemistry predicted by the rise in atmospheric CO 2 projected from the IPCC's fossil-fuel intensive A1FI scenario during this century.
Climate: Weather expected at given location and time of year, based on observations over at least 30 years, including average values and range of variability. Greenhouse gas: Constituent of atmosphere that absorbs and emits thermal infrared radiation. Greenhouse effect: Trapping by atmospheric greenhouse gases of thermal infrared radiation, which otherwise would be lost to space, within climate system. Climate change is not new. Global and regional climate has varied and changed in the past on a range of time scales due to a variety of internal and external causes IPCC, a , Chap.
The density and width of the annual growth bands in coral skeletons decline in response to ocean acidification, resulting in slower growth. Rising levels of atmospheric carbon dioxide from fossil fuel combustion and deforestation is gradually altering the chemistry of the oceans, making seawater more acidic. The increased acidity has profound implications for all life on Earth, through its likely impacts on plankton, which is the basis of almost all marine food webs. It may also significantly affect the future of the Great Barrier Reef and other coral reefs. Ocean acidification and global warming are two very different, but equally important, spin-off effects of increasing atmospheric carbon dioxide concentrations. Mean concentration of atmospheric carbon dioxide has ranged between and parts per million over the past , years and possibly over as much as 20 million years; Raven et al. However, it has now risen to ppm within about years, predominantly due to the burning of fossil fuels and land clearing Orr et al.
Climate change is impacting coral reefs now. Recent pan-tropical bleaching events driven by unprecedented global heat waves have shifted the playing field for coral reef management and policy. While best-practice conventional management remains essential, it may no longer be enough to sustain coral reefs under continued climate change. Nor will climate change mitigation be sufficient on its own. Committed warming and projected reef decline means solutions must involve a portfolio of mitigation, best-practice conventional management and coordinated restoration and adaptation measures involving new and perhaps radical interventions, including local and regional cooling and shading, assisted coral evolution, assisted gene flow, and measures to support and enhance coral recruitment.
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Published in Science on December 14, Atmospheric carbon dioxide concentration is expected to exceed parts per million and global temperatures to rise by at least 2 degrees C by to , values that significantly exceed those of at least the past , years during which most extant marine organisms evolved. Under conditions expected in the 21st century, global warming and ocean acidification will compromise carbonate accretion, with corals becoming increasingly rare on reef systems.
Effects of climate change across ocean regions View all 11 Articles. Coral reefs are found in a wide range of environments, where they provide food and habitat to a large range of organisms as well as providing many other ecological goods and services. Warm-water coral reefs, for example, occupy shallow sunlit, warm, and alkaline waters in order to grow and calcify at the high rates necessary to build and maintain their calcium carbonate structures. Despite their importance, coral reefs are facing significant challenges from human activities including pollution, over-harvesting, physical destruction, and climate change. Cold-water corals are also threatened by warming temperatures and ocean acidification although evidence of the direct effect of climate change is less clear. Evidence that coral reefs can adapt at rates which are sufficient for them to keep up with rapid ocean warming and acidification is minimal, especially given that corals are long-lived and hence have slow rates of evolution.
Under conditions expected in the 21st century, global warming and ocean acidification will compromise carbonate accretion, with corals.
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