Terry M. Bella
Although it seems bleak for oceanic creatures, particularly because of the possible catastrophic impact ocean acidification may have on phytoplankton, the base of the food web, there has been research that shows the resilience of many species and the potential for adaptation. Unfortunately though, this must be tempered with the fact that the ocean is an unimaginably complex ecosystem and whole ecosystem studies have not been conducted and likely cannot be done so easily (14). Below is a discussion of just one of the many research projects that have been conducted concerning ocean acidification and deals with the response of different marine calcifiers.
This research presents some interesting findings about the organisms involved. The methods of the experiment involved four conditions, current levels of CO
2
(409ppm), ~2, 3, and 10 times that of the preindustrial world where in the concentration of atmospheric CO
2
was approximately 280ppm. Recall that the IPCC continually increasing carbon dioxide scenario, their least conservative model, for 2100 is an atmosphere with a CO
2
concentration of 788ppm (10). Organisms were exposed to a concentration of 2856ppm and thrived, a level only used to elicit results in a reasonable time and mimic worst case scenario. Of the 18 organisms, ten experienced reduced calcification as CO
2
increased, and six of these ten had a net loss of calcified product at the highest level. Four of the 18 had an increased calcification rate through the 3 times preindustrial level scenario (~903ppm CO
2
) which exceeds the IPCC estimate. These same four organisms exhibited decreased calcification when in the highest CO
2
condition. Three of the 18 demonstrated increased calcification rates right through the highest scenario, these were the crabs, shrimp, and lobsters (crustaceans). Lastly, one organism, the blue mussel, did not exhibit any change in calcification rates throughout the 3 experimental scenarios (12).
The positive response of some of the organisms is believed to be attributed to the organism’s maintenance of an increased pH at the site of calcification. This supports the existence of carbonate ions to be used in aragonite construction. Recall that carbonate ions favor a higher pH. Secondly, the existence of an organic layer, albeit varying among organisms, seems critical to the success of the organism in an acidic ocean environment. The organic layer protects the shell from dissolution in the surrounding seawater. As the percentage of shell covered by an organic layer increased, the instance of increased calcification increased. Organisms, such as lobsters, that cover their entire shell with a protective organic layer did not experience the deleterious effects to calcification that other less-covered organisms did.