Flushing time variability in a short, low-inflow estuary. (5th May 2023)

• Record Type: Journal Article
• Authors: Taherkhani, Mohsen; Vitousek, Sean; Walter, Ryan K.; O'Leary, Jennifer; Khodadoust, Amid P.
• Is Part Of: Estuarine, coastal and shelf science. Volume 284(2023)
• Publication Date: 2023-05-05
• Subjects: Estuarine oceanography -- Periodicals; Coasts -- Periodicals; Estuarine biology -- Periodicals; Seashore biology -- Periodicals; Coasts; Estuarine biology; Estuarine oceanography; Seashore biology; Periodicals; 551.461805
• DOI: 10.1016/j.ecss.2023.108277
• Languages: English
• ISSNs: 0272-7714

Abstract

Abstract: 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. Highlights: Low-inflow estuaries are more sensitive to natural and anthropogenic disturbances. Tidal range/phasing exerts the strongest control on estuarine flushing times. Sea-level rise and vegetation loss increase flushing rates in low-inflow estuaries. Low-inflow estuaries are likely susceptible to cyclical changes in biogenic habitats.