Award: OCE-1061353

We used laboratory as well as in situ particle image velocimetry (PIV) to quantify flows around animals both in the laboratory and under natural mixing conditions.  We also measured ingestion rates in both condtions and measured how turbulence affected behaviro and feeding by Mnemiopsis.  this involved extensive development of new laboratory (e.g. Dabiri et al. 2014) and field approaches (e.g. Sutherland et al. 2014) for  flow quantification.  Our results included :

1. Quantification of in situ feeding currents
2. Quantification of in situ feeding patterns in low and high ambient turbulent flows
3. Evaluation of small scale turbulent effects on feeding currents and animal behaviors
4. Description of the mechanical basis of turbulent effets on trophic exchange patterns

Most significantly, we found that high levels of turbulence erode the predator's feeding current and limit  prey detection (Sutherland et al. 2014).  However, in most situations, the animal's behavioral response allows them to avoid high turbulence by moving to regions of lower turbulence.  Importantly, turbulent mixing attenuates extremely rapidly with depth and distance from surfaces winds, so that relatively short vertical excursions (meters) by the ctenophores can diminish the turbulent mixing they experience by several orders of magnitude.  Additionally, the ctenophores are capable of compensationg for decreased prey encounter rates accompanying feeding current erosion by increased swimming rates so that prey flux rates to capture surfaces can be maintained at the relativlely low turbulence levels selected by the ctenophores (Sutherland et al. 2014).  Even at higher turbulence levels, elevated swimming and strong sensory scanning capabilities enable high (~80%) capture efficiencies of Mnemiopsis on crustacean prey (Colin et al. 2014).  These results help explain field distribution patterns and trophic impacts of Mnemiopsis in a variety of field conditions.

the techniques that we have developed demonstrate that in situ PIV can be used to understand in situ animal-fluid interactions.  Although we have studied feeding and swimming behaivors, the methods that we have developed have wide applicability to other areas such as organism propulsion in in unsteady flows.

Last Modified: 03/06/2015
Modified by: John H Costello