Flushing time variability in a short, low-inflow estuary

Estuarine, Coastal and Shelf Science
By: , and 



Flushing time, the time scale for exchange and mixing between embayed and oceanic waters in an estuary, plays an integral role in determining water quality and aquatic ecosystem health. Here, we investigated the spatiotemporal variability of flushing times throughout Morro Bay, a short, low-inflow estuary (LIE) on the California coast, using a calibrated and validated hydrodynamic model (Delft3D). Morro Bay has historically supported an extensive eelgrass (Zostera marina) habitat, which declined substantially from 139 to 5.4 ha during 2007–2017. Eelgrass decline motivated the current research into the role of changing bed roughness and oceanic drivers (i.e., tide and sea-level rise) on estuarine hydrodynamics and flushing times. We found that tidal variability exerts the strongest control on flushing times compared to other effects, i.e., bed roughness or sea-level rise. Additionally, we found that increasing sea level and decreasing bed roughness (associated with declining seagrass coverage) yielded higher rates of mixing (lower flushing times). We detected a strong correspondence between areas having shorter flushing times (e.g., near the estuary mouth) and areas occupied by resilient eelgrass populations in Morro Bay. Our findings further indicated that flushing times in short LIEs are particularly sensitive to several factors (e.g., bed roughness, sea level) that are susceptible to anthropogenic disturbance and future climate change.

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Publication type Article
Publication Subtype Journal Article
Title Flushing time variability in a short, low-inflow estuary
Series title Estuarine, Coastal and Shelf Science
DOI 10.1016/j.ecss.2023.108277
Volume 284
Year Published 2023
Language English
Publisher Elsevier
Contributing office(s) Pacific Coastal and Marine Science Center
Description 108277, 16 p.
Country United States
State California
Other Geospatial Morro Bay
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