Spatial Heterogeneity of Artificial Reefs Functioning according to Wind-Induced Lagrangian Circulation.
Résumé
In the scope of the program "Récifs Prado" for artificial reef immersion in the Bay of Marseilles (southern France), we adapted the fine resolution (100 m) of the 3D numerical model POM (Princeton Ocean Model) to compute the typical patterns of the wind induced circulation within the bay. In addition, we derived from those results the lagrangian trajectories of planktonic particles drifting over periods of 3 days, both from natural habitats to colonize the reefs, and inversely from the reefs to enrich peripheral ecosystems. Results emphasized the high spatial heterogeneity of the reefs functioning at short scales. First, reefs were submitted to a general southward particle flux, being colonized from the northern bay and then impacting the southern bay 50% and 40% of the time, respectively. Second, adjacent reefs frequently showed contrasted impacts, with fluxes simultaneously oriented offshore or inshore, in opposite directions. Third, at the top of reefs particles were released both southward and northward 32% and 8.6% of the time, respectively, when at the bottom of reefs particles were only released southward 40% of the time.
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