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| 08/20/15

Ocean acidification studies not rigorous enough


Carbon dioxide pumped into the atmosphere isn’t just leading to a warming planet; much of the CO2 that we release is absorbed by bodies of water—a phenomenon that alters the chemistry of the world’s oceans. But one of the difficulties of investigating ocean acidification is the sheer complexity of an environment’s direct and indirect effects on species. While laboratory experiments have shown negative effects from acidification on the behaviour and survival of sea-dwelling organisms, the lack of real-world—or ‘in situ’—studies, hampers our understanding, limits the predictive power of our research, and ultimately restricts our ability as a society to respond to this potential threat to ecosystem services that benefit humans.

Such concerns came to the fore in a July commentary in Nature that focused on experimental protocols used by the community of scientists who study ocean acidification. A survey of some 465 ocean acidification papers published over the course of two decades found that few researchers have been designing experiments that are rigorous enough to mimic well real-world conditions. Most attempts at predicting the effects of changes in pH (a measure of acid content) are conducted in tanks in which seawater chemistry is manipulated, and the survey found that many experimenters employed methodologies with insufficient randomisation to prevent bias in the results. Some failed to pay sufficient attention to the effects of adding acid to a tank, rather than carbon dioxide. In just 27 of the 465 studies did the authors find appropriate experimental design. They pin the blame on the logistical complexity and cost of such studies, and recommend that researchers do a better job of reporting their experimental methods, noting that improved understanding and prediction of the effects of ocean acidification will rely on “continuing to improve best practices” in experimental design.

A better understanding of the effects of acidification on different marine species is of particular importance for British Columbia due to the province’s fish and shellfish industries. Earlier this year, Rob Saunders, the head of Qualicum Beach firm Island Scallops told the media: “It’s full-scale panic mode” for his sector. The company has suffered a 95 percent increase in scallop death rates since 2010, causing millions of dollars in losses and dozens of lay-offs. Oyster, shrimp and sea urchins have been similarly affected, with the primary culprit held to be acidification of BC’s coastal waters. Production has declined 12 percent since 2003, according to the BC Shellfish Growers’ Association.

But while acidity is a probable factor, other causes may contribute to increased mortality, including increased ocean temperatures, which encourage the growth of more bacteria and parasites, and run-off from industrial and agricultural activities.

UBC marine virologist Curtis Suttle told The Province newspaper in February: “We don’t have a great understanding of what is going on.” He and his colleagues want to see if there are varieties of shellfish that are resilient in more acidic waters so that the industry can thrive again.

Meanwhile in February, a group of marine scientists and aquaculture industry leaders from Canada, the USA, and Europe convened in Victoria to develop a deeper understanding of ocean acidification and better strategies for adapting to the phenomenon. They concluded that both the federal and provincial government need to update policies to take the threat into account, boost funding for research into this young field, and launch education programmes directed at affected coastal communities.

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