Abstract
We tested the sensitivity of early life stages and
the potential for geoduck clams to display acclimatization to ocean
acidification through a series of repeat exposure experiments. First, we exposed larval
geoducks to ambient (~8.0) and low pH (~7.4) for 10 days and found that larval
mortality is decreased and shell size increased in low pH conditions. Second, we
exposed juvenile geoduck to ambient (~8.0), low (~7.4) and lower (~7.0) pH for
23 days, placed them in ambient common garden for several months, then re-exposed
them to ambient (~8.0) pH and low pH (~7.4) for another 23 days. In geoduck
juveniles there was a size benefit of preconditioning to low pH. Juvenile
growth initially declined at pH ~7.4 and 7.0 in the first exposure, but when
replaced in the ambient conditions, the initial exposure to low pH resulted in
compensatory growth, such that the juveniles grew larger. Growth in the pre-exposed
juveniles was also more resistant to low pH in the second exposure. The role of DNA methylation as a mechanism of environmental memory was tested using reduced representation bisulfite sequencing. This
suggests that acclimatization to OA can result in benefits to geoduck growth,
with exposure memory that is potentially linked to epigenetic mechanisms such
as DNA methylation.