Seagrass may shield marine life from acidifying oceans

Photo by Jay Fleming / Corbis

Photo by Jay Fleming / Corbis

Rising carbon dioxide levels in the atmosphere are acidifying the world’s oceans and threatening the survival of shell-forming organisms like clams, oysters, crabs (pictured), and lobsters. As pH drops, the shells and skeletons of some marine life can literally dissolve away. However, results from a new study suggest that marine ecosystems, such as seagrass meadows, may help shell-forming organisms overcome the effects of future ocean acidification. The finding, published online ahead of print in the Journal of Experimental Marine Biology and Ecology, is among the first to study the effects of acidifying waters on a natural marine community made up of a diverse assemblage of multiple species. Researchers compared the number and diversity of shell-forming organisms at two seagrass sites—one with normal ocean water pH (pH 8.1) and one exposed to acidified waters (pH 7.8) from natural underwater carbon dioxide vents—over the course of 1 year.

The results were unexpected; the number of shell-forming organisms collected at the acidified site was almost double that of the site with normal ocean conditions. Moreover, shell-building organisms that were previously noted to be susceptible to acidified waters in laboratory experiments appeared to thrive. Seagrass density increased in response to a lower pH, so it’s possible that the plant is providing more food and protection from predators. Seagrasses also undergo a high rate of photosynthesis that may serve to buffer changes in ocean chemistry that affect shell-building organisms. Such ecosystems may therefore provide a unique refuge to protect shell-forming organisms from ocean acidification and prevent the collapse of these fragile marine communities, the authors say.

Jennifer Balmer, Science, 10 September 2014. Article.

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