A field study of the effects of CO2 ocean disposal on mobile deep-sea animals

Before the feasibility of ocean sequestration of anthropogenic carbon dioxide can be evaluated completely, there is a clear need to better understand the potential biological impacts of CO2-enriched (low pH and high pCO2) seawater in regions of proposed disposal. We describe here the first empirical study directly examining animal responses to dissolving CO2 hydrates on the deep-sea floor. Using a remotely operated vehicle (ROV) to conduct experiments within Monterey Canyon, CA, we found that several species (both invertebrate and vertebrate) did not avoid rapidly dissolving flocculent hydrates when attracted by the scent of food. Furthermore, while there were no apparent short-term effects of decreased pH, mobile animals appeared to suffer from respiratory distress due to increased pCO2 when in close proximity to hydrates. Losses of higher organisms as a result of CO2 disposal in the deep-sea may therefore be more extensive than previously predicted from toxicological models. However, the extent of changes to surrounding seawater chemistry, and thus biological impact, is largely dependent on CO2 release method or the type of hydrate formed.