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Variability of carbonate chemistry in association with land use in a Tillamook Bay tributary: Tracing acidification from the river to the bay
Citation:
Ernest-Beck, A., C. Brown, AND H. Stecher. Variability of carbonate chemistry in association with land use in a Tillamook Bay tributary: Tracing acidification from the river to the bay. SETAC, Vancouver, WA, April 04 - 06, 2019.
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:
Acidification from rising atmospheric carbon dioxide can be exacerbated by local factors such as land inputs of inorganic carbon. In Tillamook Bay, OR, there is oyster aquaculture in the bay and large amounts of agriculture in the bay’s watershed, which makes acidification from inputs of inorganic carbon a concern. The US EPA has monitored water conditions in Tillamook Bay tributaries from 2017 to 2018, and preliminary findings show increased dissolved inorganic carbon (DIC) downstream of agricultural areas. To determine the causes of elevated DIC, changes attributed to land-based inputs must be distinguished from temporal variability and in-stream processing. To measure temporal variability, three day-long time series of DIC and pH were measured at locations upstream and downstream of agricultural areas along the Trask River. Time series data show that DIC is lower and decreases more throughout the day in the upstream location. To account for in-stream processing (photosynthesis and respiration of periphyton), stream rocks were placed in sealed containers for 7 hours. Initial and final conditions (dissolved oxygen (DO) and DIC) in each container were compared to the conditions in the stream. In containers, the ΔDIC : ΔDO ratio is consistent with photosynthesis-respiration stoichiometry at both sites, while in streamwater, the ΔDIC : ΔDO ratio is much lower downstream. In-stream processing can therefore account for most of the changes in DIC in the containers, but not in the streamwater, suggesting that elevated DIC levels can be attributed to inputs of inorganic carbon from land-based sources.