How climate change and pollution affect ocean chemistry

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Washington, June 20 (ANI): In a new study, researchers have evaluated the total impact of climate change, carbon dioxide, pollution and other human-related phenomena on the world's oceans.

The study, led by a marine geochemist at the Woods Hole Oceanographic Institution (WHOI), has also predicted what the future might hold for oceans.

"What we do on land-agriculture, fossil fuel combustion and pollution-can have a profound impact on the chemistry of the sea. A whole range of these factors have been studied in isolation but have not been put in a single venue," said Scott C. Doney, a senior scientist at WHOI.

The study represents a meticulous compilation of the work of others as well as his own research in this area, which includes ocean acidification, climate change, and the global carbon cycle.

He concluded that climate change, rising atmospheric carbon dioxide, excess nutrient inputs, and the many forms of pollution are "altering fundamentally the...ocean, often on a global scale and, in some cases, at rates greatly exceeding those in the historical and recent geological record."

The research documents several major trends, which include a shift in the acid-based chemistry of seawater, reduced subsurface oxygen, both in coastal waters and the open ocean, rising coastal nitrogen levels, and a widespread increase in mercury and other pollutants.

"Human impacts are not isolated to coastal waters," said Doney.

They "are seen around the globe," he added.

Moreover, he said: "Many of these changes in climate and ocean chemistry can compound each other, making the problem considerably worse for marine life."

For example, warming and nutrient runoff both can trigger a decline in oxygen levels off the coast, said Doney, and acidification may exacerbate coral bleaching.

He found that global ocean pH and chemical saturation states are changing at an "unprecedented" rate, 30 to 100 times faster than temporal changes in the recent geological past, "and the perturbations will last many centuries to millennia."

"Ocean acidification will likely reduce shell and skeleton growth by many marine calcifying species, including corals and molluscs," said Doney.

"Ocean acidification may also reduce the tolerance of some species to thermal stress...Polar ecosystems may be particularly susceptible..." he added.

Fertilizer runoff and nitrogen from fossil fuels are increasing the severity and duration of coastal hypoxia, or decreased oxygen.

In the study, Doney called for "a deeper understanding of human impacts on ocean biogeochemistry...Although some progress has been made on a nascent ocean observing system for CO2, the marine environment remains woefully undersampled for most compounds. The oceanographic community needs to develop a coordinated observational plan..."

The study is published in the latest issue of the journal Science. (ANI)

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