Ocean Acidification: Short Video


From Climate Change Summary essay, specifically the section on self-reinforcing feedback loops:

23. Ocean acidification leads to release of less dimethyl sulphide (DMS) by plankton. DMS shields Earth from radiation. (Nature Climate Change, online 25 August 2013). Plankton form the base of the marine food web, some populations have declined 40% since 1950 (e.g., article in the 29 July 2010 issue of Nature), and they are on the verge of disappearing completelyaccording to a paper in the 18 October 2013 issue of Global Change Biology. As with carbon dioxide, ocean acidification is occurring rapidlyaccording to a paper in the 26 March 2014 issue of Global Biogeochemical Cycles. Acidification is proceeding at a pace unparalleled during the last 300 million years, according to research published in the 2 March 2012 issue of Science. Over the past 10 years, the Atlantic Ocean has soaked up 50 percent more carbon dioxide than it did the decade before, measurably speeding up the acidification of the ocean, according to a paper published in the 30 January 2016 issue of Global Biogeochemical Cycles. Not surprisingly, the degradation of the base of the marine food web is reducing the ability of fish populations to reproduce and replenish themselves across the globe, as reported in the 14 December 2015 online edition of the Proceedings of the National Academy of Sciences.

Diatoms, one of the major groups of plankton, is declining globally at the rate of about one percent per year, according to a paper in the 23 September 2015 issue of Global Biogeochemical Cycles.

The Southern Ocean is acidifying at such a rate because of rising carbon dioxide emissions that large regions may be inhospitable for key organisms in the food chain to survive as soon as 2030, according to a paper in the 2 November 2015 online issue of Nature Climate Change.

A paper in the 26 November 2015 issue of Science Express indicates millennial-scale shifts in plankton in the subtropical North Pacific Ocean that are “unprecedented in the last millennium.” The ongoing shift “began in the industrial era and is supported by increasing N2-fixing cyanobacterial production. This picoplankton community shift may provide a negative feedback to rising atmospheric CO2.” One of the authors of the papers is quoted during an interview: “This picoplankton community shift may have provided a negative feedback to rising atmospheric carbon dioxide, during the last 100 years. However, we cannot expect this to be the case in the future.”

Further research on primary productivity in the ocean was published in paper in the 19 January 2016 issue of Geophysical Research Letters. Referring to the Indian Ocean, the abstract concludes, “future climate projections suggest that the Indian Ocean will continue to warm, driving this productive region into an ecological desert.”

For the first time, researchers have documented algae-related toxins in Arctic sea mammals. Specifically, toxins produced by harmful algal blooms are showing up in Alaska marine mammals as far north as the Arctic Ocean — much farther north than ever reported previously, according to a paper in the 11 February 2016 issue of Harmful Algae. The abstract indicates, “In this study, 905 marine mammals from 13 species were sampled including; humpback whales, bowhead whales, beluga whales, harbor porpoises, northern fur seals, Steller sea lions, harbor seals, ringed seals, bearded seals, spotted seals, ribbon seals, Pacific walruses, and northern sea otters. Domoic acid was detected in all 13 species examined and had the greatest prevalence in bowhead whales (68%) and harbor seals (67%). Saxitoxin was detected in 10 of the 13 species … These results provide evidence that … toxins are present throughout Alaska waters at levels high enough to be detected in marine mammals and have the potential to impact marine mammal health in the Arctic marine environment.”

54. From a paper in the 1 September 2015 issue of Nature Communications comes evidence that increased ocean acidification drives irreversible, large increases in nitrogen fixation and growth rates of a key group of ocean bacteria known as Trichodesmium. Trichodesmium is one of the few organisms in the ocean that can “fix” atmospheric nitrogen gas, making it available to other organisms. It is crucial because all life — from algae to whales — needs nitrogen to grow. Climate change could send Trichodesmium into overdrive, with no way to stop, thus reproducing faster and generating lots more nitrogen. Without the ability to slow down, however, the bacteria has the potential to gobble up all its available resources, which could trigger die-offs of the microorganism and the higher organisms that depend on it. The change is projected to be irreversible and large even after being moved back to lower carbon-dioxide levels for hundreds of generations. According to the abstract of the paper: “This represents an unprecedented microbial evolutionary response, as reproductive fitness increases acquired in the selection environment are maintained after returning to the ancestral environment.”

From Climate Change Summary section titled, Then See Where We’re Going (beginning with the 13th paragraph of this section):

Ocean acidification associated with increased atmospheric carbon dioxide is proceeding at an unprecedented rate — the fastest in 300 million years — leading to great simplification of ecosystems, and capable of triggering mass extinction by itself (as supported by this peer-reviewed paper). Already, half the Great Barrier Reef has died during the last three decades and the entire marine food web is threatened. As with many attributes, the Arctic Ocean leads the way in acidification. Similarly to the lag in temperature relative to increase greenhouse gas emissions, changes in ocean acidity lag behind alterations in atmospheric carbon dioxide, as reported in the 21 February 2014 issue of Environmental Research Letters. Further adding to the interactions involving ocean acidification comes from a paper in the 18 April 2016 issue of Nature Geoscience reporting that ocean acidification is an important consequence of the release of carbon dioxide into the atmosphere from fossil fuel burning. Specifically, when excess atmospheric CO2 reacts with seawater it forms carbonic acid, which, in turn, “acidifies” the ocean, causing dramatic changes to ocean ecosystems. The Arctic Ocean is particularly sensitive to such changes. This latest study proposes a novel mechanism for Arctic Ocean acidification involving release and subsequent breakdown of organic matter from thawing permafrost and carbon-rich river runoff in seawater. In other words, melting of permafrost on land leads to accelerating acidification of the ocean.

study published in the 18 April 2016 online issue of Nature Geoscience indicates a strong contribution of freshwater and terrestrial carbon to acidification of the East Siberian Arctic Shelf. The study includes Igor Semiletov and Natalia Shakhova as co-authors, and it indicates the interaction among the self-reinforcing feedback loops studied, freshwater melt, permafrost, and ocean acidification.

Observations made since 1999 indicate that in some locations, acidity has already surged past levels researchers didn’t expect to emerge until the year 2100, due in part to “extreme aragonite undersaturation.” Aragonite is a form of calcium carbonate that is pervasive in the ocean. It tilts ocean chemistry toward the base level of the pH scale. Carbon in the water tilts the pH scale toward the acid level. The degree to which the water is saturated with aragonite is a marker of overall calcium levels — and a marker of acidification caused by increasing loads of carbon in the water.

Even bacteria are negatively affected by ocean acidification. According to a paper in the 11 January 2016 issue of Nature Climate Changethese miniscule organisms function as the wastewater treatment plants of the ocean. At the same time, bacteria help release nutrients such as nitrogen and phosphorous, which are essential to the food chain.

A metaanalysis of 632 published experiments published in the 12 October 2015 online edition of the Proceedings of the National Academy of Sciences quantified the direction and magnitude of ecological change resulting from ocean acidification and warming and found simplication as the rule. According to the abstract: “Analysis of responses in short- and long-term experiments and of studies at natural CO2 vents reveals little evidence of acclimation to acidification or temperature changes, except for microbes. This conceptualization of change across whole communities and their trophic linkages forecast a reduction in diversity and abundances of various key species that underpin current functioning of marine ecosystems.”


From ocean acidification entry at brittanica.com


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