The Chemical and Biological Effect of a Gulf Stream Intrusion off St. Augustine, Florida

During a 3-day anchor station in shelf waters off St. Augustine, Florida we observed the effect of an intruding mass of deeper Gulf Stream water. The shelf waters were relatively low in nutrients and salinity while the Gulf Stream waters were high in salinity and nutrients. Onshore currents correlated with increases in nitrate and chlorophyll concentrations.

The advection of higher nutrient Gulf Stream water coincided with high chlorophyll (∼ mg chl a m⁻³) concentrations and dense populations of Phaeocystis pouchetii (up to 3.12 × 10°1⁻¹). Zooplankton sampling was impossible in the bottom layer because of the dense Phaeocystis bloom. The dominant zooplankton in the upper layer was the doliolid Dolioletta gegenbauri f. tritonis. Concentrations reached 1561 m⁻³.