Integrating high-resolution coastal acidification monitoring data across seven United States estuaries
Citation:
Rosenau, N., H. Galavotti, K. Yates, C. Bohlen, C. Hunt, M. Liebman, Cheryl A. Brown, S. Pacella, J. Largier, K. Nelson, X. Hu, M. McCutcheon, J. Vasslides, M. Poach, T. Ford, K. Johnston, AND A. Steele. Integrating high-resolution coastal acidification monitoring data across seven United States estuaries. Frontiers in Marine Science. Frontiers, Lausanne, Switzerland, 19:679913, (2021). https://doi.org/10.3389/fmars.2021.679913
Impact/Purpose:
Coastal acidification is broadly defined as the lowering of pH in coastal ocean and estuarine waters as a result of human activities, including fossil fuel combustion, land use change, and eutrophication. Water quality impacts from these drivers of coastal acidification can impair the fitness of coastal organisms and has negatively impacted commercial fisheries in the United States. EPA Office of Water, EPA Office of Research and Development, and their partners have worked to establish coastal acidification monitoring stations in National Estuary Program sites around the Unites States in order to better understand the dynamics and drivers of estuarine acidification. This manuscript presents a first synthesis and analysis of this coastal acidification monitoring in seven National Estuary Program sites across the United States. We compare and contrast patterns in estuarine acidification dynamics and drivers, including seasonal patterns of pH and CO2 and the relative importance of oceanic, freshwater, thermal, and biological drivers in controlling these patterns. This represents an important step in the coordinated monitoring of coastal acidification across the nation.
Description:
Beginning in 2015, the U.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 partial pressure of carbon dioxide (pCO2) and pH sensors to evaluate carbonate chemistry in the estuarine environment. 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 and allowed for an initial characterization of daily to seasonal trends in carbonate chemistry across a range of estuarine settings. Results of year to multiyear monitoring across all water bodies show that temperature and pCO2 covaried and were lower in cooler, winter months and higher in warmer, summer months, suggesting that part of the annual change in pCO2 was governed by seasonal temperature changes. 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 in the GOM water bodies (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). Temperature controlled pCO2 and non-temperature (i.e., biological/hydrologic) controlled pCO2 reveal 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 (Santa Monica Bay, San Francisco Bay, and Tillamook Bay). The co-occurrence of high salinity, high pCO2, low DO, and low temperature 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 records can be obtained from estuarine environments using autonomous sensors originally designed for open-ocean settings. A better understanding of the relative influence of the various drivers of acidification in these dynamic systems will be facilitated by the continued collection of high-resolution, multi-parameter datasets.
URLs/Downloads:
DOI: Integrating high-resolution coastal acidification monitoring data across seven United States estuaries