Dynamics of bioluminescence potential and physical, bio-optical properties on the shelf and shelf-slope of the Delaware Bay.

Igor Shulman1, Bradley Penta2, Stephanie C Anderson2, Mark A Moline3, Matthew J Oliver4, Jonathan Cohen5, Katherine Hudson Gallagher4, Clark David Rowley6 and Ana E Rice2, (1)US Naval Research Laboratory, Washington, DC, United States, (2)US Naval Research Laboratory, Stennis Space Center, MS, United States, (3)University of Delaware, Lewes, DE, United States, (4)University of Delaware, Newark, DE, United States, (5)University of Delaware, School of Marine Science and Policy, Lewes, DE, United States, (6)US Naval Research Laboratory, Ocean Sciences Division, Washington, DC, United States
Dynamics of chlorophyll enhancement at the shelf-slope hydrographic front is investigated. On May 2nd of 2018, high chlorophyll (Chl) filament (enhancement) was observed by VIIRS ocean color imagery along the shelf-slope front (SSF) of the Delaware Bay area. The high Chl filament had weakened and disappeared in satellite imagery over next two days. Our observational and modeling studies demonstrated that the following processes affected the dynamics of the Chl enhancement at the SSF: a) wind reversal from down-welling to upwelling favorable, the observed wind reversal changed currents direction: from southward to offshore; b) offshore currents brought warmer and fresher Delaware Bay outflow waters (from estuary-slope system) to the shelf and shelf –slope areas; c) interaction of the warmer and fresher Delaware Bay outflow with colder and more saline water at SSF resulted in downwelling on the dense side of the front and a subduction of high CHL filament into the subsurface below 10-15m depth. Bioluminescence (BL) potential observations in combination with Chl and optical backscattering (bb) indicated the transition from an autotrophic bioluminescent community (before the wind reversal) to more heterotrophic bioluminescent community (after the wind reversal).