Despite COVID-19, over 700 coastal sites were sampled for Total Alkalinity in 2020 as part of EPA’s National Coastal Condition Assessment
Some coastal and estuarine areas are experiencing declines in pH that are more rapid than in the open ocean and are believed to be driven in part by local factors such as nutrient inputs. To better assess vulnerability of coastal waters to acidification, EPA incorporated total alkalinity (TA) as a pilot indicator in the 2020 National Coastal Condition Assessment (NCCA), a statistically based water quality survey conducted by the EPA’s Office of Water and Office of Research and Development, in partnership with coastal states in the contiguous U.S. Despite the challenges associated with COVID-19 and wildfires, field crews collected and filtered water samples for TA at 720 estuarine sites in 20 coastal states (Fig. 1). To avoid preserving samples with mercuric chloride in the field, all samples were preserved at a central processing laboratory and then shipped to US EPA facilities in Newport, Oregon and Narragansett, Rhode Island, where they were analyzed on Apollo SciTech Total Alkalinity titrators. In 2021, US EPA will sample alongside state partners to collect additional pH measurements using either Sunburst Sensors’ iSAMIs or Durafet pH probes to assess the quality of total alkalinity measurements and the feasibility of incorporating pH measurements into future surveys. Alkalinity correlates well with salinity in the open ocean, but the relationship is not as strong in coastal waters. We will use these data to identify covariates (e.g., nutrients, chlorophyll a) that improve the prediction of alkalinity from salinity in nearshore waters.