conclude that other unanticipated effects of acidification will be revealed as scientific research on this topic continues.

Whereas much remains to be learned about the scope and magnitude of the consequences of ocean acidification, existing data support a growing consensus in the research community that most documented responses to acidification reflect impairment of physiological capacity or performance. Certain physiological processes in some species may benefit from ocean acidification (e.g., enhancement of photosynthesis in sea grasses and some algae by increased levels of CO2 [Kroeker et al., 2010]). However, the beneficial effects on some species may directly lead to negative effects on other species in the same marine community (Kroeker et al., 2010).

Although our knowledge about the biological effects of ocean acidification is expanding quite rapidly, most of this research has either involved studies of single species under closely controlled laboratory conditions, or mesocosm-studies in which communities of organisms are confined under controlled conditions. Much remains to be learned about the effects of ocean acidification on natural ecosystems, but moving from laboratory and mesocosm experiments toward assessments and projections of the in situ, long-term responses of ecosystems presents not only scientific challenges, but logistical and financial ones as well. Simply extrapolating information on impacts from laboratory-derived species’ responses or short-term in situ observations (Gattuso and Riebesell, 2011) is hampered by the variability in the responses across species, and even within some single species. Lastly, as mentioned earlier, projecting long-term changes in marine ecosystems is complicated by the interactions of impacts due to ocean acidification with those resulting from alterations in water temperature and oxygen concentration or from other human activities (e.g., from agricultural run-off and extractive activities).

Socioeconomic impacts of ocean acidification are likely to be substantial, based, for example, on the dependence of humans on protein from marine species (approximately 6.5% of dietary protein in 2009) (FAO, 2012). However, projecting socioeconomic impacts of ocean acidification is currently challenging because of a dearth of research in this domain. Nonetheless, economically important natural resources may already be affected by ocean acidification resulting from upwelling events and, to a lesser extent, from increases in dissolved atmospheric CO2. For example, the Pacific Northwest Aquaculture industry, which is estimated to contribute approximately 270 million dollars per year and 3,200 jobs to local coastal communities, has recently experienced major failures in its oyster hatcheries due to effects of upwelling of low pH seawater on oyster larvae (Washington State Blue Ribbon Panel, 2012). In addition, complex ecological effects of low pH on coral reefs have been documented, notably

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