Posts Tagged ‘dead zones’

Sea Sick: The Global Ocean in Crisis by Alanna Mitchell. McClelland & Stewart, 2009.

Overfishing isn’t the only problem facing the world ocean. Alanna Mitchell spent two and a half years travelling the globe as an investigative journalist in a quest to examine the state of the seas. Sea Sick is an account of her journey as she discovers first hand what scientists are learning. Each of the ten chapters in Sea Sick takes Mitchell to a different part of the globe, where she joins scientists on the front lines as they study how the ocean is changing.

In Australia, she snorkels over the Great Barrier Reef and talks to Katharina Fabricius on Magnetic Island about reefs and their future. Climate change has three direct effects on corals. First, the high concentration of carbon dioxide in the atmosphere warms the ocean to the point that the coral’s symbiotic algae die and result in coral bleaching. Second, climate change will potentially raise sea levels, depressing the ability of coral algae to photosynthesize and, in effect, drowning the corals. Third, the acidification of the ocean that results from increasing carbon dioxide levels inhibits the availability of calcium, which in turn depresses the ability of coral to build structures. If acidity levels climb high enough, coral structures will be corroded by the acidic water. Coral reefs are often compared to the rainforests of the sea. They are centers of diversity. And they are dying.

In the Gulf of Mexico, Mitchell joins a ten-day expedition with scientists investigating the 17,000 square kilometre dead zone that forms at the delta of the Mississippi River. The dead zone is an area of low or no oxygen where virtually nothing can survive. The Gulf dead zone is related to the runoff of agricultural chemicals from land all along the mighty Mississippi River. Plankton gobble up the phosphorus and nitrogen that the river dumps into the Gulf, reproduce rapidly and then die and fall to the bottom of the Gulf. Bacteria then eat the plankton and decompose, using up all the oxygen in the water. The ability of the Gulf waters to handle all the extra phosphorus and nitrogen that pores into it with the river has failed. The dead zone is a result. The Gulf dead zone is one of 407 around the world. The number of dead zones has doubled each decade since 1960.

In other chapters, Mitchell takes the reader with her to Puerto Rico, Plymouth, England, Panama, Halifax, Spain, China and Zanzibar as she pursues the latest in ocean research. In an interview on CBC’s Last Chapter, Mitchell talks about her experience. As a result of her investigation, Mitchell fell into a clinical depression and was bedridden for a month.

It’s not a happy picture, but it is vitally important that we understand that carbon emissions and global warming effect more than the continents. The very oceans, unimaginably huge, are being changed by our actions. We are running out of time if we wish to salvage the oceans, and indeed the planet, for future generations.

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