Understanding the Seasonal Dynamics of Chemical and Biological Processes in a Bay of the Central Coast of California

Nearshore regions provide a unique opportunity to study how local and large regional-scale processes interact to structure the chemical and biological environment. In this study, we couple inorganic carbonate chemistry with metrics assessing the biological community (e.g., chlorophyll a concentration and phytoplankton community structure via high throughput sequencing) to understand their seasonal variability in the coastal waters of San Luis Bay, CA. Seawater samples were collected monthly for approximately 1.5 years from the end of the California Polytechnic State University Pier in San Luis Bay using a CTD and sampling rosette. While carbonate chemistry is controlled broadly by large-scale ocean mixing and seasonal wind-driven coastal upwelling which bring low pH and low oxygen seawater into the bay, we also observe the impact of local physical (e.g., tides, local freshwater inputs) and biological (e.g., photosynthesis, respiration and bloom events) processes on the inorganic carbon dynamics. These processes can cause extreme variability and vertical stratification in this 10-m deep semi-enclosed bay. Given the importance of nearshore regions on global ocean dynamics, these results are significant for characterizing natural ecosystem variability, predicting future changes, and integrating coastal areas in our understanding of ocean biogeochemical cycling.