Sutherland, DavidMarin Jarrin, Maria Jose2022-02-182022-02-182022-02-18https://hdl.handle.net/1794/27068The Coos Estuary, is the second largest estuary in Oregon in terms of area and volume, after the Columbia River Estuary, with extensive tidal flats and subsidiary sloughs. Estuaries, like the Coos, are utilized for habitat and refuge by many organisms, such as oysters, crabs, fish, and phytoplankton. Despite its importance, it had been highly understudied, and its characteristics had been defined based on general definitions of estuaries. The estuary is shaped like an inverted-U, due to a 4-km long bend centered around 15 km from the mouth. This torturous geometry is common among estuaries in the Pacific Northwest, and complicates circulation. In Chapter 2 I describe the influence of winds on the subtidal flow in the main estuarine channel. Velocity time series show that during high and moderate discharge, the exchange flow deepens and strengthens in the classical sense: seaward flow at the surface and landward flow at depth. However, we find reversals where landward flow occurs for periods of more than a day during neap tides and downwelling-favorable northward winds. I further explored in situ data in combination with idealized numerical simulations to quantify the effect of winds, tides, river discharge and coastal currents on the observed flow. In Chapter 3 I describe the impact of the combination of drought, El Niño and marine heatwaves in 2014- 2016, in the water temperature of the estuary. This warming was observed in stations inside the estuary, with higher anomalies at the shallower stations, where an extensive decline of eelgrass (Zostera marina) has been observed. Water temperature increased landward, suggesting that river input and atmospheric heat flux may be important contributors to the anomalous conditions observed. In Chapter 4 I used a numerical model to explore the variability of timescales within the Coos Estuary. Timescales in the estuary vary in space and time, hence whole-volume approaches may be over/underrepresenting these scales. I also explored the influence of connectivity between different areas due to its impact on the transport and availability of Olympia oyster (Ostrea lurida) larvae in the Coos Estuary. This dissertation includes previously both previously published/unpublished and co-authored material.en-USAll Rights Reserved.EelgrassEstuaryOlympia oyster larvaeResidence timeTemperatureWindElectronic Thesis or Dissertation