Award: OCE-1061268

The major activities of this project included laboratory-scale tests of turbulence effects on Mnemiopsis, a voracious predator with significant trophic impacts; real-time measurements of prey capture; and development of technologies for field measurements of the salient biophysical processes. The specific objective of the laboratory studies was to determine the behavioral response of Mnemiopsis to increasing levels of turbulence. This was accomplished with a new turbulence generator designed for this project. The turbulence generator created a spatial gradient of turbulence, with maximum levels at the top of the tank and lower levels at depth. This provided a more realistic refuge from turbulenence as compared to previous studies which did not facilitate refuge behaviors. A specific objective of the field studies was to develop a new technology to enable daytime particle image velocimetry measurements of the animal-fluid interactions. This was accomplished using a novel optical filtering technique to enhance a recently developed self-contained underwater velocimetry apparatus (SCUVA). We observed behavioral responses of Mnemiopsis to realistic turbulence in the lab for the first time. Companion measurements of clearance rates linked those behaviors to the trophic impact. In particular, the animals are found to adjust their swimming pattern to compensate for prey loss due to turbulence. We also successfully demonstrated the daytime SCUVA technology on deployments at the Marine Biological Labs in Woods Hole, MA. The key outcomes of this project are the elucidation of the mechanism whereby this invasive predator is able to adjust to environmental factors such as turbulence to affect the populations of its prey. The observed limits to the ability to Mnemiopsis to make such adjustments suggests corresponding limits on its environmental impact. The development of the daytime SCUVA technology will feed into ongoing efforts to develop lab-in-the-ocean technologies to observe a broad range of processes relevant to biological oceanography. Last Modified: 03/03/2015 Submitted by: John O Dabiri