Florida Current frontal eddies and the settlement of coral reef fishes

Abstract

We deployed three replicate larval light traps off the upper Florida Keys from June-September 2001 to measure the delivery of settlement-stage fish larvae to the coral reefs. Nightly measures of larval abundance were compared to water temperatures measured across the outer reef, nearby wind records, and the alongshore and cross-shelf components of the currents measured at the seaward edge of the reef. These time series, together with satellitederived sea surface temperature and color fields indicate that a very large multi-taxa larval pulse on 20 July was directly associated with the passage of a Florida Current (FC) sub-mesoscale frontal eddy embedded within the elongated remnant of a mesoscale eddy. A second large pulse of larvae occurred when a similar mesoscale eddy passed the upper Keys in mid-June. Periods of increased tidal bore activity occurred with the passage of these eddies. Semidiurnal internal tides caused near-bottom onshore intrusions of cooler slope waters during periods of onshore meanders of the FC front when the downstream baroclinic flow and stratification increased at the reef margin. The high abundance and similarity in larval ages within taxa on 20 July indicate a Keys shelf origin, although the temporal and spatial scales of entrainment cannot be resolved. The passage of a third mesoscale eddy in September did not result in a larval pulse, possibly because of a mismatch between biological and physical criteria, several of which must be met for larval…