Ocean Acidification in the Gulf of Maine

Ann Tarrant (WHOI) Gareth Lawson (WHOI)

Dissolution of excess anthropogenic CO2 into the ocean is causing the marine environment to decrease in pH. This "ocean acidification" is predicted to threaten a broad variety of marine organisms, particularly calcifying animals such as the thecosome (i.e., shelled) pteropods. These pelagic gastropods form an aragonite shell, are prey for a number of commercially important fish, and are significant contributors to carbon biogeochemistry. Their ecosystem importance, abundance, and sensitivity to dissolution position them as an important group for investigating the impacts of acidification. Limacina retroversa is a particularly abundant thecosome pteropod in the North Atlantic, where it is prey for a number of fisheries species and other top predators. This species is also the most common pteropod in the Gulf of Maine (GoM) where it is present year round. L. retroversa thus offers the prospect of a useful model pteropod species, given both its ecological importance and its abundance in readily accessible waters. Currently we are in the middle of a project designed to seasonally sample L. retroversa from local waters of the GoM near Cape Cod. The carbonate chemistry of the GoM fluctuates seasonally, proving an opportunity to assess the response of wild caught pteropods to natural changes in CO2. By characterizing the carbonate chemistry of the water column and measuring the metabolic rate, shell quality, and gene expression of pteropods throughout the year, this will allow us to create time series of pteropod sensitivity to CO2 in situ. At the same time, using experimental manipulations the investigators will explore the effect of seasonal acclimation on pteropod response to short- and medium-term exposure to enhanced CO2. Finally, taking advantage of the fact that pteropods frequently lay eggs in captivity, we are documenting the natural development of L. retroversa and exploring the effect of CO2 on embryonic and larval stages. This work is funded by an NSF Ocean Acidification grant (1316040)

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