time, and “adaptation” which in the evolutionary sense involves genetic changes. The potential for acclimatization may be critical in conferring short-term tolerance to ocean acidification during a species’ lifetime (e.g., during diurnal or seasonal fluctuations in pH found in tide pools and kelp forests). Likewise, acclimatization to factors such as temperature and oxygen content that may co-vary with pH may be critically important. However, the ultimate success of a species in coping with ocean acidification over longer multigenerational time scales may demand genetic adaptation. Species with shorter generation times are likely to have greater abilities to evolve adaptive changes than species with long generation times, assuming adequate genetic variation exists. Related to the latter, currently little is known about differences between species or among populations of a single species in tolerance of reduced pH; this area of research merits vigorous study to identify the potential adaptive capacities of different marine species in the face of ocean acidification.

The analysis in Theme 2 would benefit from a broader consideration of the types of nonbiological chemical effects relevant to biogeochemical cycles and ecosystem function. Although the FOARAM Act’s mandate for Theme 2 is focused chiefly on organismal and ecological effects of ocean acidification, many of these effects are closely coupled with the influences of ocean acidification on nonliving processes. Thus, one notable gap within this Theme is the lack of attention given to the chemical effects of acidification. Besides a discussion of the influence on element availability to phytoplankton, there is very little presented in Theme 2 about how acidification might affect chemical properties of detrital particles, or processes like sorption or flocculation, which are very important in coastal and open-ocean waters. Sorption of many elements and compounds on natural particles is greatly affected by pH (Millero, 2009). Trace metal speciation, bioavailability and toxicity are influenced by pH. These effects of ocean acidification, which remain poorly understood, could influence the physiologies of individual organisms and the broader ecological responses to falling pH. Thus, the analysis needs to also include the types of chemical effects mentioned above, that is, the characteristics of detrital material important in nutrient cycling and diets (especially of species associated with the detrital particles), the physical processes of flocculation/disaggregation and their effects on marine particle dynamics.

The IWGOA is commended for its recommendations to include paleo-studies and data synthesis. Theme 2 notes that paleo-studies can yield important insights about conditions that caused ocean acidification in the geologic past, and the associated marine biological responses. This section could benefit from a brief mention of past ocean acidification events and their causes, with references to the key publications. It should also mention the value of Earth system modeling in understanding past ocean



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