SS3.15 Physical Forcing and Pelagic-Benthic Interactions in Aquatic Systems
Date: Thursday, June 13, 2002
Location: Poster Session - VCC
 
HarrisLE, Darling Marine Center, Walpole, USA, leslie.harris@umit.maine.edu
Shellito, S, M, Darling Marine Center, Walpole, USA, shellito@maine.edu
Jumars, P, A, Darling Marine Center, Walpole, USA, jumars@maine.edu
 
ACOUSTIC EXAMINATION OF ESTUARINE EMERGENCE PATTERNS IN RELATION TO TIDAL CURRENTS
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Emergence-trap sampling has shown that several species living primarily on or in the sediment emerge nightly into the water column. Vertical migration in an environment with strong tidal currents leads to horizontal transport, suggesting tidally modulated emergence is a mechanism enabling an organism to control its position within the estuary. A TRACOR acoustic profiler, TAPS, was mounted on the sea bottom, looking upwards in approximately 10 meters of water in the Damariscotta River Estuary, Walpole, Maine. TAPS emits high frequency (265-3000kHz) sonar pulses and each minute measures backscatter from 12.5-cm range bins in the water column. TAPS data showed a distinct increase in backscatter in the water column most evenings, beginning around or after dusk and terminating before dawn. The duration, intensity and initiation time of this emergence pattern varied. Size classes of organisms were resolved by applying inversion models to the backscatter data. Organisms of the largest size class appear to emerge in a different pattern than organisms in the smaller size classes, and we are comparing potential trajectories along with dependence on flow velocities.