Introduction to Coastal Management Journal Special Issue on Ocean Acidification

Anthropogenic carbon emissions are increasing atmospheric carbon concentrations. Global oceans absorb about one-fourth of these emissions each year (Friedlingstein et al., 2020). Seawater’s carbon absorption initiates several chemical reactions, including the production of carbonic acid, reduction in the availability of calcium carbonate ion, and declining pH (Doney et al. 2009). This process of chemical changes is called ocean acidification (OA). Models predict that under a “business as usual” greenhouse gas emissions scenario (RCP 8.5), the ocean may become 150% more acidified by 2100 (Phillips et al. 2018 and references therein). As with many climate change impacts, OA is occurring and interacting with many other stressors including ocean warming and deoxygenation, and non-climate-related stressors like development, habitat degradation and pollution (IPCC 2019). In coastal systems, processes including upwelling, nutrient loading (magnified by wastewater), pollutions and freshwater inputs can further exacerbate conditions (Duarte et al. 2013 and references therein). Increasing OA, combined with these multiple stressors, threatens marine species and ecosystems that are essential for sustaining jobs and supporting coastal economies (Jewett et al. 2020). Oyster larvae are particularly vulnerable to corrosive conditions and were among the earliest indicators of increasing acidification (Barton et al. 2012; 2015). Studies across the world are examining acidification’s full lifecycle impacts on shellfish including oysters, lobster, crab, shrimp and mussels. Additionally, simulated acidified conditions cause olfactory and behavioral changes in juvenile salmon (Williams et al. 2019) suggesting that OA could impact finfish. Pteropods, one of the building blocks of marine food webs, show significant signs of shell dissolution under acidified conditions (Bednaršek et al. 2018). And in 2020, studies confirmed existing impacts to wild populations of economically valuable crustaceans, finding that OA was causing carapace dissolution and damage to sensory organs in West Coast Dungeness crabs (Bednaršek et al. 2020). In the U.S., NOAA has increasingly focused attention and funding on regional vulnerability assessments looking at impacts to oysters, scallops and human communities that reply on species that are most at risk from ocean change (NOAA 2017). Many communities in the U.S. and worldwide rely on coastal resources for food, nutrients that sustain health, economic stability, and practicing of cultural and indigenous traditions. Increasingly acidified waters threaten species of cultural importance and may impact Tribal Treaty Rights of Tribal and First Nation communities (Crosman et al. 2019). One study estimates that OA may contribute to billions of dollars in losses to communities in the U.S. from the North Pacific to the Caribbean (Jewett et al. 2020). The shellfish industry in the Pacific Northwest contributes an estimated $270