Effects Of Low pH Water On European Green Crabs (Carcinus maenas): An Assessment Of Survival And Post-Ecdysis Cuticle Properties

Abstract

Excess of carbon emissions drives not only global warming but also ocean acidification (OA). In addition to that, it has been established that OA negatively affects a variety of organisms that depend on calcium carbonate to build their shells. However, the effects of low pH water on crustaceans is not well understood. These marine organisms do not rely exclusively on calcium carbonate to build their carapaces, which are also composed of a wide range of organic and inorganic compounds. In this study, the effects of low pH water on the carapaces of European green crabs (Carcinus maenas) as well as on their survival were assessed. Twenty-two adult males between approximately 50mm and 60mm in length were included. Twelve were exposed to an initial decrease in pH from 8.0 to 7.8 over 50 days and then to a pH of 7.8 for 106 days, while the other ten were kept at a pH of 8.0 for the duration of the study (156 days). The thickness of the endocuticle and exocuticle was determined, and their quality assessed. Although the thickness appears to have been unaffected by the experimental conditions, the quality of the outer cuticle may have been compromised. In particular, structures such as tubercles and bristles were highly impacted. Survival analysis also suggests that drops in pH might lead to an increase in death that is not necessarily related to the process of ecdysis, a period in which the crabs are highly vulnerable. Negative impacts of OA on crustaceans could shed new insights on how this environmental problem indeed can impact not only calcifiers but possibly all marine life. A better understanding of the consequences of OA might lead to new initiatives on how to reduce carbon emissions.