Rising levels of acidity in the oceans is worrisome and “potentially catastrophic”

The Guardian reports, 25th August 2013: “Rapidly rising carbon dioxide levels in the atmosphere are causing a potential catastrophe in our oceans as they become more acidic, scientists have warned.

Hans Poertner, professor of marine biology at the Alfred Wegener Institute in Germany, and co-author of a new study of the phenomenon, told the Guardian: “The current rate of change is likely to be more than 10 times faster than it has been in any of the evolutionary crises in the earth’s history.”

Seawater is naturally slightly alkaline, but as oceans absorb CO2 from the air, their pH level falls gradually. Under the rapid escalation of greenhouse gas emissions, ocean acidification is gathering pace and many forms of marine life — especially species that build calcium-based shells — are under threat. Poertner said that if emissions continue to rise at “business as usual” rates, this would be potentially catastrophic for some species. Acidification is just one of a broader range of the problems facing the oceans and the combination of different effects is increasing the threat. Poertner said: “We are already seeing warm water coral reefs on a down-slide due to a combination of various stressors, including [rising] temperature. Ocean acidification is still early in the process [but] it will exacerbate these effects as it develops and we will see more calcifying species suffering.”

The new study, entitled Inhospitable Oceans, published in the peer-review journal Nature Climate Change, was based on examinations of five key components of ocean ecosystems: corals, echinodermsechinoderms Spiny-skinned animals which live in the sea, their bodies generally displaying radial symmetry e.g. starfish, sea-urchins, brittlestars, sea-cucumbers. These animals have a "water vascular system" which communicates with the surrounding sea water and operates, by means of hydrostatic pressure, rows of radially arranged suckers. These suckers are known as "tube-feet"., molluscs, crustaceans and fish. All were found to be adversely affected by acidification: crustaceans were more resilient, while corals, molluscs and echinoderms were worst affected. The direct effects on fish were less clear.

Astrid Wittmann, co-author of the paper, said species with low resilience could be out-competed by those that were less vulnerable to acidification, and that further studies were needed, particularly on plants and planktonplankton Plankton is a generic term for a wide variety of the smallest yet most important organisms form that drift in our oceans. They can exist in larger forms of more than 20cm as the larval forms of jellyfish, squid, starfish, sea urchins, etc. and can be algae, bacterial or even viral down to as small as 0.2µm. They are nutrient and light dependent, and form the essential foodchain baseline for larger dependent aquatic lifeforms. Fish species rely on the density and distribution of zooplankton to coincide with first-feeding larvae for good survival of their larvae, which can otherwise starve. Man-made impacts such as dredging, dams on rivers, waste dumping, etc can severely affect zooplankton density and distribution, which can in turn strongly affect larval survival and thus breeding success and stock strength of fish species and the entire ecosystem. They also form the essential basis of CO2 take up in our seas ecosystem, hence Global Warming., which were left out of this research.

Source: The Guardian, 25th August 2013. For the full text see www.theguardian.com/environment/2013/aug/25/rising-acid-levels-seas-endanger-marine-poertner

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