Loop Current Spin-off Eddies, Slope Currents and Dispersal of Reef Fish Larvae from The Flower Gardens National Marine Sanctuary and The Florida Middle Grounds

Abstract

Large energetic spin—off eddies from Loop Current intrusions into the Gulf of Mexico play a major role in water exchange between the continental shelf and the deep basin in the northern Gulf. Reef fish larvae, spawned on the outer shelf and planktonic during their early life history, are broadly dispersed by this mechanism, but may be lost to the cohort by transport away from suitable settlement habitat. In this study, satellite altimeter data—assimilative ocean model currents (HYCOM) from 2003—2015 are used to calculate kinetic energy of the mixed layer over the upper continental slope (200 m —1000 m) due to eddy interactions with the shelf and to track the dispersal of larvae spawned during core summer (June—August) season. Over the 13 year model period, dispersal into the deep basin from the Flower Gardens National Marine Sanctuary averaged 63.5%, with a high of 90.8% and a low of 34.6%. Dispersal from the Florida Middle Grounds averaged 9.5%, with a high of 23.1% and a low of 0.6%. Temporal dispersal of larvae was associated with trends in turbulent kinetic energy and mean kinetic energy over the continental slope, and varied with the North Atlantic Oscillation Index. Between 2010 and 2011, mean kinetic energy replaced turbulent kinetic energy as the dominant dispersal mechanism.