Tidally phased emergence events in a strongly tidal estuary |
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| Authors: | Leslie H Taylor Shawn M Shellito Heather U Abello Peter A Jumars |
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| Institution: | (1) School of Integrative Biology, University of Queensland, Brisbane, QLD, 4072, Australia;(2) Department of Microbiology and Parasitology, University of Queensland, Brisbane, QLD, 4072, Australia; |
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| Abstract: | Acoustic backscatter from an active sonar system over a range of six frequencies between 265 kHz and 3 MHz in the tidally
dominated Damariscotta River estuary, Maine, United States, revealed that the major emergence event of the night commenced
on the first tidal deceleration after dark (3.5–4 h after local slack), irrespective of flow direction. Emergence traps identified
the mysid shrimp,Neomysis americana, as the dominant migrator. Water-column-integrated, acoustically estimated biovolume at our 10-m deep study location increased
by a factor of about 6 during these large events, entirely dominating the holoplanktonic contribution and likely being a major
component in benthic-pelagic coupling. Application of the same algorithm used to locate this nighttime emergence revealed
a parallel but considerably smaller daytime emergence event near the same phase of the tide. Daytime trap samples failed to
recover the organisms responsible, but transmissometry rejected the alternative hypothesis that we observed resuspension events.
We suspect, but have yet only weak evidence, that animals emerging in daylight are copepods rather than mysids. |
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