Citation:

Pacella, S., C. Brown, Jim Kaldy, J. Stecher, TChris MochonCollura, R. Labiosa, B. Hales, AND G. Waldbusser. Oceanic and watershed controls of coastal acidification in a small, agriculturally developed California Current estuary. ASLO 2019 Meeting, San Juan, Puerto Rico, February 23 - March 02, 2019.

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 due to eutrophication-enhanced coastal acidification have been studied in a variety of coastal systems, including the Chesapeake Bay, the Gulf of Mexico, and the northeast coast of the United States, but relatively little work has been done to understand the dynamics of this process in west coast estuaries. This is despite the large documented impacts of coastal acidification on the productivity of the west coast shellfish aquaculture industry, where over half of surveyed industry stakeholders have expressed that coastal acidification is negatively affecting their business. Therefore, there is a need to understand the role of watershed delivery of nitrogen and co-pollutants in current coastal acidification in west coast estuaries. This project estimates the contributions of human-driven changes in ocean and watershed chemistry to quantify the magnitude and timing of changes in estuary pH in Tillamook Estuary, OR. Tillamook Estuary has been identified as an estuary of national significance as part of the US EPA’s National Estuary Program, and is home to extensive shellfish aquaculture and agricultural industries. Our estimates of the watershed’s role in altering estuary pH will help inform the effectiveness of potential nutrient and co-pollutant management strategies on improving water quality in the estuary.

Description:

This study sought to characterize the seasonal CO2 system dynamics of Tillamook Estuary, OR (USA), a small open-coast estuary in the northern California Current Large Marine Ecosystem subject to coastal upwelling and river discharge from an agriculturally-developed watershed. From July 2017 through July 2018, we conducted a series of sampling cruises to characterize the CO2 biogeochemistry of the estuary, including the coastal ocean and watershed end-members. We quantified the roles of allochthonous input of oceanic and riverine dissolved inorganic carbon (DIC), as well as internal bay carbon cycling, in controlling the seasonal pH, CaCO3 saturation state, and pCO2 dynamics of the estuary. Seasonal variability in the ocean and watershed end-members was the primary control on CO2 chemistry of the estuary, with internal bay processes acting as a seasonally variable sink and source of DIC. Observed watershed DIC enrichments in areas of agricultural activity were hypothesized to be driven by human land use change. These watershed DIC enrichments were combined with published estimates of oceanic anthropogenic carbon burdens to estimate the magnitude and timing of human changes to present-day CO2 chemistry in the estuary. We estimate that most of the human-caused perturbation in estuarine chemistry during our study period was due to ocean acidification-driven changes in the coastal ocean. We discuss how attribution of changes in CO2 chemistry to ocean, bay, and watershed drivers informs the potential efficacy of management actions operating at local versus global scales.

Record Details: