Fine-scale hydrodynamics around St. John, U.S. Virgin Islands. Part II: variability in residence time in coastal bays
Coastal currents can vary dramatically in space and time, influencing advection and residence time of larvae, nutrients and contaminants in coastal environments. However, spatial and temporal variabilities of the residence time of these materials in coastal environments, such as coastal bays, are ra...
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Frontiers Media S.A.
2025-06-01
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| Series: | Frontiers in Marine Science |
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| Online Access: | https://www.frontiersin.org/articles/10.3389/fmars.2024.1464645/full |
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| author | Yan Jia Weifeng (Gordon) Zhang Amy Apprill T. Aran Mooney |
| author_facet | Yan Jia Weifeng (Gordon) Zhang Amy Apprill T. Aran Mooney |
| author_sort | Yan Jia |
| collection | DOAJ |
| description | Coastal currents can vary dramatically in space and time, influencing advection and residence time of larvae, nutrients and contaminants in coastal environments. However, spatial and temporal variabilities of the residence time of these materials in coastal environments, such as coastal bays, are rarely quantified in ecological applications. Here, we use a particle tracking model built on top of the high-resolution hydrodynamic model described in Part 1 to simulate the dispersal of particles released in coastal bays around a key and model island study site, St. John, USVI without considering the impact of surface waves. Motivated to provide information for future coral and fish larval dispersal and contaminant spreading studies, this first step of the study toward understanding fine-scale dispersal variability in coastal bays aimed to characterize the cross-bay variability of particle residence time in the bays. Both three-dimensionally distributed (3D) and surface-trapped (surface) particles are considered. Model simulations show pronounced influences of winds, intruding river plumes, and bay orientation on the residence time. The residence times of 3D particles in many of the bays exhibit a clear seasonality, correlating with water column stratification and patterns of the bay-shelf exchange flow. When the water column is well-mixed, the exchange flow is laterally sheared, allowing a significant portion of exported 3D particles to re-enter the bays, resulting in high residence times. During stratified seasons, due to wind forcing or intruding river plumes, the exchange flows are vertically sheared, reducing the chance of 3D particles returning to the bays and their residence time in the bays. For a westward-facing bay with the axis aligned the wind, persistent wind-driven surface flows carry surface particles out of the bays quickly, resulting in a low residence time in the bay; when the bay axis is misaligned with the wind, winds can trap surface particles on the west coast in the bay and dramatically increase their residence time. The strong temporal and inter-bay variation in the duration of particles staying in the bays, and their likely role in larval and contaminant dispersal, highlights the importance of considering fine-scale variability in the coastal circulation when studying coastal ecosystems and managing coastal resources. |
| format | Article |
| id | doaj-art-74cf0b29d0b54f09a2a48b9a7e1ef9b3 |
| institution | Kabale University |
| issn | 2296-7745 |
| language | English |
| publishDate | 2025-06-01 |
| publisher | Frontiers Media S.A. |
| record_format | Article |
| series | Frontiers in Marine Science |
| spelling | doaj-art-74cf0b29d0b54f09a2a48b9a7e1ef9b32025-08-20T03:45:14ZengFrontiers Media S.A.Frontiers in Marine Science2296-77452025-06-011110.3389/fmars.2024.14646451464645Fine-scale hydrodynamics around St. John, U.S. Virgin Islands. Part II: variability in residence time in coastal baysYan Jia0Weifeng (Gordon) Zhang1Amy Apprill2T. Aran Mooney3Applied Ocean Physics and Engineering Department, Woods Hole Oceanographic Institution, Woods Hole, MA, United StatesApplied Ocean Physics and Engineering Department, Woods Hole Oceanographic Institution, Woods Hole, MA, United StatesMarine Chemistry and Geochemistry Department, Woods Hole Oceanographic Institution, Woods Hole, MA, United StatesBiology Department, Woods Hole Oceanographic Institution, Woods Hole, MA, United StatesCoastal currents can vary dramatically in space and time, influencing advection and residence time of larvae, nutrients and contaminants in coastal environments. However, spatial and temporal variabilities of the residence time of these materials in coastal environments, such as coastal bays, are rarely quantified in ecological applications. Here, we use a particle tracking model built on top of the high-resolution hydrodynamic model described in Part 1 to simulate the dispersal of particles released in coastal bays around a key and model island study site, St. John, USVI without considering the impact of surface waves. Motivated to provide information for future coral and fish larval dispersal and contaminant spreading studies, this first step of the study toward understanding fine-scale dispersal variability in coastal bays aimed to characterize the cross-bay variability of particle residence time in the bays. Both three-dimensionally distributed (3D) and surface-trapped (surface) particles are considered. Model simulations show pronounced influences of winds, intruding river plumes, and bay orientation on the residence time. The residence times of 3D particles in many of the bays exhibit a clear seasonality, correlating with water column stratification and patterns of the bay-shelf exchange flow. When the water column is well-mixed, the exchange flow is laterally sheared, allowing a significant portion of exported 3D particles to re-enter the bays, resulting in high residence times. During stratified seasons, due to wind forcing or intruding river plumes, the exchange flows are vertically sheared, reducing the chance of 3D particles returning to the bays and their residence time in the bays. For a westward-facing bay with the axis aligned the wind, persistent wind-driven surface flows carry surface particles out of the bays quickly, resulting in a low residence time in the bay; when the bay axis is misaligned with the wind, winds can trap surface particles on the west coast in the bay and dramatically increase their residence time. The strong temporal and inter-bay variation in the duration of particles staying in the bays, and their likely role in larval and contaminant dispersal, highlights the importance of considering fine-scale variability in the coastal circulation when studying coastal ecosystems and managing coastal resources.https://www.frontiersin.org/articles/10.3389/fmars.2024.1464645/fullU.S. Virgin IslandsSt. Johnparticle trackingflushing timetidal exchangewind forcing |
| spellingShingle | Yan Jia Weifeng (Gordon) Zhang Amy Apprill T. Aran Mooney Fine-scale hydrodynamics around St. John, U.S. Virgin Islands. Part II: variability in residence time in coastal bays Frontiers in Marine Science U.S. Virgin Islands St. John particle tracking flushing time tidal exchange wind forcing |
| title | Fine-scale hydrodynamics around St. John, U.S. Virgin Islands. Part II: variability in residence time in coastal bays |
| title_full | Fine-scale hydrodynamics around St. John, U.S. Virgin Islands. Part II: variability in residence time in coastal bays |
| title_fullStr | Fine-scale hydrodynamics around St. John, U.S. Virgin Islands. Part II: variability in residence time in coastal bays |
| title_full_unstemmed | Fine-scale hydrodynamics around St. John, U.S. Virgin Islands. Part II: variability in residence time in coastal bays |
| title_short | Fine-scale hydrodynamics around St. John, U.S. Virgin Islands. Part II: variability in residence time in coastal bays |
| title_sort | fine scale hydrodynamics around st john u s virgin islands part ii variability in residence time in coastal bays |
| topic | U.S. Virgin Islands St. John particle tracking flushing time tidal exchange wind forcing |
| url | https://www.frontiersin.org/articles/10.3389/fmars.2024.1464645/full |
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