Incze, L. S. Bigelow Laboratory for Ocean Sciences,
Hebert, D. S. Graduate School of Oceanography, Univ. of Rhode Island,
Wolff, N. Bigelow Laboratory for Ocean Sciences,
Oakey, N. Bedford Institute of Oceanography,
Dye, F. Bigelow Laboratory for Ocean Sciences,

We examined changes in the vertical distribution of Calanus finmarchicus, Pseudocalanus spp., Oithona spp. and Temora spp. copepodites and nauplii before, during and after a moderate wind event (max. sustained wind speed = 10.5 m/s) in early June on Georges Bank. Pump sampling for zooplankton (retention on 40 um mesh) and microstructure profiling (Epsonde) was conducted at an anchor station on the stratified southern flank of the bank in approximately 84 m of water. During calm conditions before and after the wind event, copepodites and nauplii had maximum concentrations in the upper 10-15 m of the water column. The wind event led to an increase in near-surface turbulent dissipation rates (Epsilon) from 10^-8 W/kg (before) to 10^-7 W/kg at 15 m and >10^-6 W/kg at shallower depths. Copepodites of all four taxa responded by descending below the turbulent surface layer to form new maxima below 20 m where water column turbulence was at a minimum (Epsilon = 10^-8 W/kg). Response time appeared to be rapid. For nauplii, responses lagged behind copepodites but were of similar pattern except for Temora, which remained near the surface. Therefore, moderate surface turbulence caused a major reorganization of vertical patterns and a >4x increase in concentration at depth for most copepod stages. All stages appeared to reestablish the prior, shallow distributions soon after turbulent mixing declined to about 10^-7.5 W/kg. We consider these changes in the context of springtime climatology, the interpretation of zooplankton vertical distribution data (for example, interpreting the spatial overlap with a sub- surface chlorophyll maximum or the pycnocline), and the various ways that turbulence may impact larval fish feeding rates.
Day: Tuesday, Feb. 2
Time: 03:30 - 03:45pm
Location: Hilton of Santa Fe
Code: SS01TU0330H