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Temporal and spatial variability of carbonate chemistry in a Tillamook Bay tributary: Tracing acidification from rivers to the bay
Citation:
Ernest-Beck, A., C. Brown, AND J. Stecher. Temporal and spatial variability of carbonate chemistry in a Tillamook Bay tributary: Tracing acidification from rivers to the bay. Western Society of Naturalists Conference, Tacoma, WA, November 08 - 11, 2018.
Impact/Purpose:
Coastal acidification is causing impacts on shellfish production in Pacific Northwest estuaries. Local land-based factors can exacerbate acidification in estuaries. A Sea Grant Summer Scholar working with EPA's Western Ecology Division scientists examined spatial and temporal variability in carbonate chemistry in a tributary of Tillamook Estuary. Dissolved inorganic carbon (DIC) was elevated at downstream sites and these changes in DIC could not be explained by in situ production/respiration, suggesting additional inputs of DIC from land-based sources.
Description:
Coastal acidification from rising atmospheric CO2 can be exacerbated by additional factors such as land inputs of inorganic carbon and nutrients. In Tillamook Bay, OR, inputs of inorganic carbon are a concern due to oyster aquaculture in the bay and large amounts of agriculture above it. The US EPA has been monitoring water conditions in Tillamook Bay tributaries for 1 year, and preliminary findings show increased total dissolved inorganic carbon (TCO2) downstream of agricultural areas. To determine the causes of elevated TCO2, changes attributed to land-based inputs must be distinguished from temporal variability and in-stream processing. To measure temporal variability, a day-long time series of TCO2 and partial pressure of CO2 (pCO2) was measured at locations upstream and downstream of agricultural areas along the Trask River. To account for in-stream processing (periphyton photosynthesis and respiration), stream rocks were placed in sealed containers for 7 hours. Initial and final concentrations (Dissolved oxygen (O2), TCO2, and pCO2) in each container were compared to the conditions in the stream. Times series data show that TCO2 is lower and decreases more throughout the day upstream. In containers, the ΔTCO2 : ΔO2 ratio is consistent with photosynthesis-respiration stoichiometry at both sites, while in stream-water, the ΔTCO2 : ΔO2 ratio is much lower downstream. In-stream processing can account for most of the changes in TCO2 in the containers, but not in the stream-water, suggesting that there are inputs of inorganic carbon from land-based sources.