A new report has made dire predictions about ocean ecosystems. Has it gone too far?by Philip Ball / July 20, 2011 / Leave a comment
Published in August 2011 issue of Prospect Magazine
Ocean scene: the light blue-green spots are caused by microscopic marine plants known as phytoplankton—some of which are toxic
The global oceans are in a very bad way, according to scientists at an April meeting of the International Programme on the State of the Ocean (IPSO). When a summary report from the meeting was released in June, it spawned disaster-movie headlines. The future of the ocean’s ecosystem looks “far worse than we had realised,” said Alex Rogers, director of IPSO and a professor in conservation biology at Oxford. “If the ocean goes down, it’s game over.”
Are things really so bad? According to Hugh Ducklow, director of the Ecosystems Centre at Woods Hole, Massachusetts (one of the US’s most prestigious marine biology laboratories), IPSO isn’t exaggerating. “If anything,” says Ducklow, who is not a part of IPSO, “the true state of the ocean is probably worse than the report indicates.”
The IPSO meeting addressed threats to ocean ecosystems including over-exploitation of fish stocks, acidification (caused by rising levels of atmospheric carbon dioxide), vanishing coral reefs and—unglamorously but crucially—changes to plankton growth, on which the entire food chain depends.
Phytoplankton are microscopic plants that bloom in the upper ocean and dictate the cycling of carbon between the ocean and atmosphere. Some phytoplankton are toxic, and when growth is artificially stimulated by nutrients in fertilisers and sewage (eutrophication), they poison their environment. Worse, bacteria feeding on decaying phytoplankton consume oxygen in the water, turning it into a dead zone. Oxygen depletion (hypoxia or, if total, anoxia) is also caused in deep water over much longer timescales by warming of the upper ocean, which suppresses the circulation of oxygen-rich surface water to the depths.
Also discussed at the meeting was the faster-than-expected melting of Arctic sea ice: summer at the North Pole co…