Integrating high-resolution coastal acidification monitoring data across seven United States estuaries


Beginning in 2015, the United States Environmental Protection Agency’s (EPA’s) National Estuary Program (NEP) started a collaboration with partners in seven estuaries along the East Coast (Barnegat Bay; Casco Bay), West Coast (Santa Monica Bay; San Francisco Bay; Tillamook Bay), and the Gulf of Mexico (GOM) Coast (Tampa Bay; Mission-Aransas Estuary) of the United States to expand the use of autonomous monitoring of partial pressure of carbon dioxide (pCO2) and pH. Analysis of high-frequency (hourly to sub-hourly) coastal acidification data including pCO2, pH, temperature, salinity, and dissolved oxygen (DO) indicate that the sensors effectively captured key parameter measurements under challenging environmental conditions, allowing for an initial characterization of daily to seasonal trends in carbonate chemistry across a range of estuarine settings. Multi-year monitoring showed that across all water bodies temperature and pCO2 covaried, suggesting that pCO2 variability was governed, in part, by seasonal temperature changes with average pCO2 being lower in cooler, winter months and higher in warmer, summer months. Furthermore, the timing of seasonal shifts towards increasing (or decreasing) pCO2 varied by location and appears to be related to regional climate conditions. Specifically, pCO2 increases began earlier in the year in warmer water, lower latitude water bodies in the GOM (Tampa Bay; Mission-Aransas Estuary) as compared with cooler water, higher latitude water bodies in the northeast (Barnegat Bay; Casco Bay), and upwelling-influenced West Coast water bodies (Tillamook Bay; Santa Monica Bay; San Francisco Bay). Results suggest that both thermal and non-thermal influences are important drivers of pCO2 in Tampa Bay and Mission-Aransas Estuary. Conversely, non-thermal processes, most notably the biogeochemical structure of coastal upwelling, appear to be largely responsible for the observed pCO2 values in West Coast water bodies. The co-occurrence of high salinity, high pCO2, low DO, and low temperature water in Santa Monica Bay and San Francisco Bay characterize the coastal upwelling paradigm that is also evident in Tillamook Bay when upwelling dominates freshwater runoff and local processes. These data demonstrate that high-quality carbonate chemistry observations can be recorded from estuarine environments using autonomous sensors originally designed for open-ocean settings.



coastal acidification, ocean acidfication, estuary, autonomous sensors, carbon dioxide, ph, dissolved oxygen, national estuary program


This publication was developed in part under Assistance Agreement No. 83588701 awarded by U.S. Environmental Protection Agency (US EPA) to the American Association for the Advancement of Science (AAAS). Monitoring in Tillamook Bay was funded through US EPA Regional Applied Research Effort (RARE) and Office of Research and Development funding. In Mission-Aransas Estuary, funding for autonomous sensors and sensor deployment was provided by the US EPA’s National Estuary Program via the Coastal Bend Bays and Estuaries Program Contract No. 1605. Funding in Tampa Bay was provided by the Tampa Bay Estuary Program (TBEP; 2017 Tampa Bay Environmental Restoration Fund) and US EPA Section 320 Grants through multiple TBEP Workplans. Funding in Barnegat Bay was provided by US EPA under cooperative agreement CE98212312 to Ocean County College and Barnegat Bay Partnership. Funding in Casco Bay was provided by the EPA National Estuary Program to the Casco Bay Estuary Partnership at the University of Southern Maine through multiple cooperative agreements (CE96185501, CE96190301, CE 00A00063, CE 00A00299, and CE 00A00319) beginning in 2014, and subcontracted to the University of New Hampshire. Partial funding in San Francisco Bay was from the Central and Northern California Ocean Observing System (CeNCOOS), EPA Region 9 Section 320 (Grant No. 00T74501 - some equipment), and complementary funding was from San Francisco State University and University of California, Davis.


Attribution 4.0 International


Rosenau, N.A., Galavotti, H., Yates, K.K., Bohlen, C.C., Hunt, C.W., Liebman, M., Brown, C.A., Pacella, S.R., Largier, J.L., Nielsen, K.J. and Hu, X., 2021. Integrating High-Resolution Coastal Acidification Monitoring Data Across Seven United States Estuaries. Frontiers in Marine Science, p.1066.