Meeting Abstract

13.3  Monday, Jan. 4  Turbulence over a coral reef interferes with zooplankton escape behavior ROBINSON, H.E.*; FINELLI, C.M.; BUSKEY, E.J.; University of California, Berkeley erobinson@berkeley.edu

Bottom-dwelling marine animals rely on water motion to deliver planktonic prey. As currents and waves interact with the ocean floor, variation in the fluid environment can alter predator-prey interactions. Some zooplankton can avoid predation by detecting hydrodynamic cues that are formed as fish predators lunge and open their mouths. Calanoid copepods exhibit rapid escape jumps in response to the flow fields generated by suction feeding fish. In structurally complex marine environments such as coral reefs, flow passing over corals can increase turbulence. Turbulence may interfere with copepod avoidance behavior by masking hydrodynamic signals of their predators. We tested the ability of Acartia tonsa to detect and evade predation in laboratory flumes that produced both unidirectional and wavy flow conditions similar to those measured over coral reefs. Turbulent flow regimes over smooth vs. rough substrata were compared. A fixed siphon simulated a suction predator flow-field; copepod detection of the hydrodynamic stimuli was measured as the reaction distance from the siphon. Escape jumps were initiated closer to the siphon in faster currents and in rough turbulence, indicating copepods were less able to detect predators in these flow regimes. While the capture rates of non-evasive Artemia nauplii did not vary with flume conditions, adult copepods were captured significantly more with increases in current speeds, wave motion, and in rough flow. The effect of turbulence on escape behavior may account for increases in predation in hydrodynamically complex environments.