Just last week an excellent article appeared in Science that reported new estimates of past sea-level rise; estimates that help forecast what we might expect in the not-too-distant future. In a separate article from the same issue, there are also new projections of rapid ocean acidification in the California Current system. The main article describes the development of ocean acidification in the region as projected by a computer simulation, or model. The California Current is susceptible to acidification due to the already low carbonate saturation state of seawater*. Using two established emissions scenarios, the authors project that by 2050 much of the near-shore shallow waters and seafloor will be chronically undersaturated with the carbonate ions required for calcification for most of the year, threatening the viability of marine ecosystems.
The California Current supports a rich and diverse range of marine organisms, and along with the intrinsic importance of marine biodiversity these regional waters also support the livelihoods of many through extensive fisheries and aquaculture. In a commentary accompanying the main article, the findings are cleverly discussed in the context of an oceanographer from the region who also makes his living farming oysters.
The piece begins with the oyster farmer cursing the warm summer breeze that delights most holiday makers. These offshore warm winds favour upwelling and as the surface waters are replenished with CO2 rich deep water, the pH drops. As the pH lowers (increased acidity) so does the saturation state of seawater, and it becomes increasingly difficult for calcifying organisms to produce their shells. Previous studies demonstrated that ocean acidification is already affecting larval development in oyster hatcheries. In 2007 and 2008, oyster farmers believed that an infestation of marine bacteria was effecting larvae development and was responsible for the financially catastrophic years. However, after dumping the contents and sterilizing their tanks the problem returned. It was later discovered that massive swings in pH were responsible for the die-off rather than any bacterial contamination.
The latest studies only highlight how these issues are likely to become more prevalent due to anthropogenic activity. The commentary was particularly effective as it places the scientific theory into the context of a regional economy and the livelihood of a community. This kind of approach highlights the danger of a business-as-usual emissions target – business as usual presently tops 35 billion tons a year. The carbon tax was not popular but a carbon price is absolutely necessary is we are going to afford the infrastructure required to manage the climate change we have already committed to. And that includes sea level rise and ocean acidification.
To access the full article you will need a subscription to Science, but the abstract to the article can be found here, and the associated commentary here. The latter also has a thorough explanation of the fundamental science behind ocean acidification.