Larval retention, entrainment, and accumulation in the lee of a small headland: Recruitment hotspots along windy coasts

Morgan, Steven G., Jennifer L. Fisher, and John L. Largier

Limnol. Oceanogr., 56(1), 2011, 161-178 | DOI: 10.4319/lo.2011.56.1.0161

ABSTRACT: We surveyed crustacean larvae in the plankton in the lee of Bodega Head, California, for 2 months during late spring and summer and cross-correlated the larval abundance and stage of development of 16 taxa with 8 indicators of upwelling-relaxation conditions. Larvae in all stages of development for 11 of these taxa were entrained and accumulated in a recirculation feature in Bodega Bay, found in the lee of this small headland as soon as upwelling-favorable winds began, and persisted until winds weakened. The remaining taxa were more prevalent during relaxation events when the recirculation feature dissipated and a poleward coastal current transported larvae into and through the bay. During upwelling conditions, a vertically sheared flow occurs in the lee of the headland that accounts for the accumulation of plankton. However, larval behavior did not have a substantial effect on density and persistence in the lee of the headland, regardless of whether taxa were more prevalent during upwelling or relaxation conditions or whether they developed entirely nearshore or migrated offshore later in development. Thus, larvae and postlarvae of many, diverse taxa are concentrated in the plankton in the lee of small headlands in upwelling areas, which is consistent with previously reported recruitment hot spots in small upwelling bays. These headland-related hot spots increase spatial structure in population density and community structure in recruitment-limited upwelling regions and other wind-driven coasts.

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