Ocean acidification is a decrease in the pH (increased acidity) of marine waters associated with rising carbon dioxide concentrations in seawater. Calcifying organisms, including crustaceans, are particularly vulnerable to this increase in carbon dioxide and changing ocean chemistry because a lower pH causes an increase in the dissolution rates of calcium carbonate. Calcium carbonate is essential component of the calcification process for crab species whereby their shells harden after molting. In other words, the more acidic the sea, the harder crab species have to work expending energy to build and maintain their exoskeletons. In addition, embryos and larvae exposed to increased acidity in seawater exhibit lower survival rates, lower growth rates, and increased rates of malformation.
King and Tanner crab experimental studies have been conducted by leading scientists and researchers at the Alaska Fisheries Science Center's Kodiak Laboratory (http://www.afsc.noaa.gov/kodiak/). The effects of increased carbon dioxide on the survival, condition, and growth of king and Tanner crab species were investigated from 2009 to 2011. At that same time, infrastructure was developed to support a multi-year program capable of assessing both direct and indirect effects of ocean acidification on shell building in commercial crab species in Alaska. The results of this research program will not only provide empirical data specific to the physiological response of crabs to increasingly acidic condition, but they will also support modeling efforts on the indirect impacts of ocean acidification associated with food webs and fisheries interactions. More information on this research into the effects of ocean acidification on Alaska marine resources can be found at http://www.afsc.noaa.gov/Quarterly/jas2012/JAS12-Feature2.pdf.
The issue of ocean acidification and its effects upon living marine resources and dependent-industries is gaining increased publicity and attention, including this recent multi-part Seattle Times article http://apps.seattletimes.com/reports/sea-change/2013/sep/11/pacific-ocean-perilous-turn-overview/. More information on the broader topic of ocean acidification, including research and monitoring investments that will improve our understanding of ocean acidification, its potential impacts on marine species and ecosystems, and adaptation and mitigation strategies can be found at http://oceanacidification.noaa.gov/IWGOA.aspx.