Seaweed Responses to Ocean Acidification

Ocean acidification (OA) is the decline in seawater pH caused by the sustained absorption by the oceans of anthropogenically produced atmospheric CO2. The consequences of OA to seaweed-based coastal ecosystems range from organismal to community levels of biological organization. Organismal responses can be species specific, depending on their carbon physiology, mode of calcification, and morphology (functional form). At the community scale, changes in community structure and function can have severe consequences on trophic dynamics. Biologically driven fluctuations in seawater carbonate chemistry are observed from micro- (diffusion boundary layer, DBL) to mesoscales (e.g., within a kelp forest), and such fluctuations may be exacerbated by OA. The synergistic effects of elevated CO2 with other human-induced environmental stressors (e.g., warming, eutrophication, and UVR) could make the primary producers of coastal ecosystems vulnerable to global climate change; some species may perform better than others under “greenhouse” conditions, leading to community phase shifts.