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article imageClimate change to cause major loss of marine life by 2100

By Robert Myles     Dec 31, 2013 in Environment
Southampton - Using advanced climate modelling, new research predicts climate change will have a profound impact on deep-sea marine life. Even the most remote ecosystems in the ocean deeps are likely to be affected by climate change, says a new study.
In many cases, little is known about the ecosystems present in the deepest of ocean trenches, making it difficult to predict how changes in the environment for plants and animals inhabiting the ocean depths will affect other marine life.
An international team of researchers drawn from the UK’s National Oceanography Centre, the Memorial University of Newfoundland, Canada, the University of Tasmania, and the Laboratoire des Sciences du Climat et de l'Environnement in France predicted seafloor dwelling marine life will decline by up to 38 per cent in the North Atlantic and over five per cent globally over the next 100 years.
The impetus for the predicted changes comes from a reduction in the plants and animals that live at the surface of the oceans. Those same plants and animals provide sustenance for life in the ocean depths. A knock-on effect of the changes is likely to be a threat to fisheries on which many communities worldwide depend.
The study, led by the National Oceanography Centre (NOC), based at Southampton in the UK, used state-of-the-art climate models to predict changes in food supply throughout the world oceans. The team of scientists then correlated the relationship between the ocean’s food supplies and biomass — the total mass of all living organisms, in this case, in a given volume of water — calculated from a huge global database of marine life.
Changes in seafloor life is expected despite such plants and animals living, on average, four kilometers (2.5 miles) beneath the surface of the seas; the reason being that such deep sea communities depend for their food on the dead remains of near-surface dwelling marine life sinking to the ocean floor. Less ocean surface nutrients mean a less abundant supply of decomposing vegetation and carcasses reaching the ocean depths.
A dearth of the nutrients essential for sustaining deep-dwelling ocean life is the predicted result of climate changes. Such changes include a slowing of global ocean circulation and increased separation of water masses — a process known as 'stratification' — as a result of warmer and rainier weather. Stratification of the oceans has the effect of making oceans less homogeneous. It results in masses of water with different properties, be it salinity, temperature or oxygenation, forming layers. These ‘strata’ of water act as barriers to nutrients mixing between layers, effectively staunching the flow of food to lower levels.
Lead author of the study, Dr Daniel Jones, Senior Scientist at the NOC, commented, “There has been some speculation about climate change impacts on the seafloor, but we wanted to try and make numerical projections for these changes and estimate specifically where they would occur.”
Dr Jones added, “We were expecting some negative changes around the world, but the extent of changes, particularly in the North Atlantic, were staggering. Globally we are talking about losses of marine life weighing more than every person on the planet put together."
As Doctor Jones touches on, one of the striking features of the research was the asymmetric results predicted across the world’s oceans. But the results of the study did predict negative change in marine life, worldwide, with over 80 per cent of all identified key habitats – such as cold-water coral reefs, seamounts and canyons – predicted to suffer losses in total biomass.
Apart from the decline in overall biomass, another feature of the research was a prediction that animals, individually, would get smaller. As smaller animals tend to use energy less efficiently, this would also have an impact on seabed fisheries, compounding the effects of the overall decline in available food.
The NOC study, though focused on the effects of climate change on deep ocean life and ocean biomass, appeared to confirm the conclusions of wider based research by the scientists at the University of Hawaiʻi at Mānoa in October 2013 which described the full chain of events whereby ocean bio-geochemical changes triggered by man-made greenhouse gas emissions may cascade through marine habitats and organisms.
The NOC led research, entitled “Global reductions in seafloor biomass in response to climate change,” is published Dec. 31 in the scientific journal Global Change Biology.
More about marine biology, Oceanography, Climate change, Global warming, Marine life