Title:

Investigating trends of Organic Alkalinity in Estuaries of the Gulf of Maine

Increased concentrations of atmospheric Carbon dioxide (CO2) are driving the acidification of coastal ecosystems. The ability these aquatic systems have to buffer changes in acidity is called alkalinity. The total alkalinity of a system is comprised of both inorganic and organic species that work to neutralize a change in pH through chemical bonding. Estuaries exhibit a noticeably high organic alkalinity signature that diminishes towards the ocean where inorganic species dominate alkalinity. This shift in alkalinity from a low salinity to high salinity environment has not been sufficiently studied. The goal of this investigation is to better understand the role organic alkalinity plays in the buffering of coastal ecosystems. Ten estuaries that feed into the Gulf of Maine were selected for sampling ranging from Maine, U.S.A to New Brunswick, Canada. River endmember samples will be serially diluted with seawater to simulate river water mixing with the ocean. Analysis of these samples has been halted due to the COVID-19 pandemic. Total alkalinity, organic alkalinity and dissociation constants (pKas) will be determined through titration analysis. Understanding the contribution of organic alkalinity to the buffering ability of estuaries is essential to predict the future resilience these ecosystems. Acidification in estuaries threatens the habitat of many shellfish and fish species. This investigation will not only further develop the ability to estimate the total alkalinity of a coastal ecosystem, but can aid in analysis of estuary health and fisheries management.

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