Glacial melt could change chemistry and food web in world’s oceans

Along with increasing sea levels, melting glaciers are putting something else into the world’s oceans — a huge load of organic carbon that has the potential to change marine chemistry and ecosystems, says a newly published study by a team of mostly Alaska scientists. (…)

The accelerated melt of glaciers gets attention because of its contribution to sea-level rise, but the “real take-home message” of the new study is that there will be “not just changes to the level of the ocean but changes to the chemistry and the food web,” Hood said.

Organic carbon is eaten by microbes and is at the base of the food web, he said. But it can also break down into inorganic carbon, which changes marine chemistry in other ways, he said. (…)

One expected chemical effect of glacial melt is the accelerated acidification in the Gulf of Alaska and similar nearshore waters close to such tidewater ice.

Scientists from the National Oceanic and Atmospheric Administration’s Pacific Marine Environmental Laboratory reported this week on preliminary results from a project that measured water chemistry throughout the summer in Prince William Sound.

The project used three remotely operated “gliders” — small watercraft similar in appearance to surfboards – and a local cruise ship to ferry measuring equipment around the glacier-fed sound.

The latest news from the project was presented by Wiley Evans, a PMEL research associate, at the Alaska Marine Science Symposium held this week in Anchorage.

The project is the most comprehensive effort ever to track the corrosive characteristics of water at different sites in the sound and the nearby northern Gulf, Evans said. Up to now, the scientists studying ocean acidification in the Gulf region have had to rely on relatively short-term water-sampling cruises conducted at the beginning and end of the summer, he said. But this project was collecting data daily for four months, he said.

While glacial runoff is not acidification in itself, it can exacerbate the change in pH by mixing fresh water with low calcium content into calcium-containing salt water, according to the researchers. In addition, meltwater from glaciers is known to quickly absorb carbon dioxide from the atmosphere, adding to the forces behind acidification, the researchers said.

Evans said data from the summer’s project is still being analyzed, but that already some interesting results have emerged. One striking result, he said, was the discovery of hotspots near glaciers where calcium and associated pH levels were particularly low.

“I was pretty shocked at the lower values that were observed near the glacier and the extent of the chronic effect,” he said.

Yereth Rosen, Alaska Dispatch News, 24 January 2015. Article.

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