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Published: Wednesday 04 September, 2013

isabel marant shop online uk isabel marant shop online uk ´╗┐Dangerous shifts in ocean ecosystem functionquest



1Global Change Institute, University of Queensland, St Lucia, Queensland, AustraliaOne of the unique characteristics of our planet is that 71 of its surface is covered by water. This lifenurturing ocean has an overridingly important role in dete isabel marant shop online uk rmining the physical, chemical and biological characteristics of Earth and is, in many ways, the and lungs of our planet. Damaging the ocean will place Earth and our future in jeopardy and hence must be avoided. Although there is considerable uncertainty about how key planetary services provided by the ocean will change in the future, there are growing signs that conditions in the worlds oceans have shifted significantly away from where they have been for millions isabel marant shop online uk of years. Evidence is also mounting that these changes are having profound impacts on the marine ecosystems with potentially serious consequences for all life on our planet. Given this, reducing human emissions of greenhouse gases to zero must be our number one International priority over the next few decades.Top of pageUnprecedented physical and chemical changeThe ocean has a disproportionately large role in Earths climate. The ocean has consequently reduced the impact of human emissions on Earths atmosphere and t isabel marant shop online uk errestrial ecosystems. The added energy and carbon dioxide has, however, caused fundamental changes in the physical and chemical properties of the ocean. The average temperature of the upper layers of the ocean has increased by 0.6 over the past century and average pH has decreased by 0.1 units Doney et al., 2009. Changes in temperature have been 2 times greater in polar regions, leading to the rapid loss of Arctic sea ice and an accelerated melting of landlocked ice sheets in Greenland and western Antarctica.Human activities have already pushed the conditions of the ocean outside the limits of where they have been for millions of years Bindoff et al., 2007; HoeghGuldberg and Bruno, 2010. Although change has been a characteristic of Earth throughout its history, recent anthropogenically driven climate change has been extremely rapid and is comparable in scale and rate to that associated with four out of five mass extinction events Ward, 2007. As seen in periods of slower change for example, the ice age transitions biological systems trail the current rate of physical and chemical change, with little or no evidence that they are adapting sufficiently to the current rapid shift in conditions. Consequently, ocean ecosystems are beginning to change fundamentally, putting crucial ecosystem goods and services at risk and ultimately threatening the food and livelihoods of hundreds of millions of people.Top of pageMarine ecosystems are now in uncharted watersWarming of the upper layers of the ocean has led to an increased stratification of the water column, which has implications for nutrient cycles and consequently the productivity of marine ecosystems from the polar to tropical regions. Nutrientpoor deserts have increased in the Pacific and Atlantic Oceans by 6.6 million km2 over the past decade, primarily due to the heatgenerated stratification of the water column and loss of nutrients in the upper layers of the ocean in these regions Polovina et al., 2008. These changes have contributed to the 6 decline in ocean productivity reported since the 1980s Gregg et al., 2003. Observations increasingly support the notion that ocean ecosystems will become less productive as we warm the atmosphere and ocean Behrenfeld et al., 2006. Changes in ocean circulation are also linked to decreasing oxygen concentrations as well as an alarming increase in the spread of deepwater anoxia and zones across the world Diaz and Rosenberg, 2008.Changes in temperature are also influencing the ratio of photosynthesis to respiration, and consequently net primary productivity. The photosynthetic activities of microbes within the plankton respond more slowly to temperature than do respiratory rates, leading to reduced net primary productivity. Increasing temperatures are also influencing other components of the plankton. Invertebrate larvae, for example, develop faster at higher temperatures HoeghGuldberg and Pearse, 1995. These changes have the potential to produce mismatches between the timing the appearance of larvae in the water column and their food sources such as phytoplankton. Increased developmental rates and decreased larval periods will also reduced connectivity between marine populations with consequences for the replenishment of marine populations and ecosystems, and ultimately human resources such as fisheries.Rapid changes in conditions are also affecting habitat complexity from polar to tropical regions. Key habitatcreating organisms such as corals, sea grasses and mangroves face enormous pressure from both global and local stresses. In the case of reefbuilding corals, increasing temperatures are causing increasingly frequency and severity of mass coral bleaching and mortality, while steadily acidifying ocean waters are decreasing the ability of corals to build their calcareous skeletons and consequently maintain reef structures HoeghGuldberg et al., 2007. These impacts on corals and other marine calcifiers are putting at risk hundreds of thousands of species that use coral reefs for their habitat. Impacts of climate change and ocean acidification on habitat creating species are not restricted to tropical waters. Similar issues are appearing along temperate coastlines where the contraction of kelp forests is also reducing the availability of habitats for thousands of dependent species. Similarly, the rapid decrease in the extent of summer sea ice in the Arctic is putting pressure on associated biodiversity from ice algae to polar bears Wegner et al., 2010.Marine microbial systems provide approximately 50 of Earths net primary production Field et al., 1998 and are critically important to global nutrient cycles Arrigo, 2005. These systems also underpin globally important processes such as the biological that transports massive amounts of carbon from the sunlit surface to the oceans interior. Despite their importance, however, our current understanding of how climate change and ocean acidification will affect marine microbial processes is relatively undeveloped. Improving our knowledge and understanding of these changes and their potential impacts will become increasingly important if not vital as we navigate the uncharted waters of rapid anthropogenic climate change.Planetary emergency: a compelling case for deep and immediate action on emissionsIt may seem farfetched to some that human activities are causing such largescale and fundamental changes to the worlds oceans. However, the rapidly accumulating evidence and understanding of these changes is largely irrefutable Bindoff et al., 2007; HoeghGuldberg and Bruno, 2010 and should be of serious concern given the ramifications of these changes for the wellbeing of humans everywhere. In acknowledging the problem, however, we have no other choice but to mitigate the source of the problem that is, reduce greenhouse gas emissions and adapt to the consequences of climate change that are already the pipeline Mitigation of the problem relies heavily on identifying safe levels of CO2 and other greenhouse gases in the atmosphere. While it may seem an enormous and ambitious task, inaction is not an option given the scale and seriousness of the planetary scale risks involved. Current estimates of the cost of achieving this target are not excessive and involve the sacrifice of a few percent of global GDP growth over the next 3 decades IPCC, 2007. Given the scale and rapidity of the changes, however, time is fast running out. This will produce major challenges for human communities as they struggle to understand and manage ocean conditions that are completely novel and which are changing in rapid and unpredictable ways. Given their central role in how this future will unfold, there is an urgent need to increase our understanding of the response of marine microbial ecosystems to climate change. Given the strong evidence, however, that we are fundamentally changing Earths and lungs there is no longer any excuse for international community not to pursue deep and rapid cuts in the use of fossil fuels and other greenhouse gas emitting sources. If we continue to ignore this evidence, we will place our planet, and the future of ourselves and our children, in extreme jeopardy. isabel marant shop online uk

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