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Calanoid copepods are ubiquitous in marine ecosystems and play a major role in the plankton community. These small organisms reside in a constantly flowing environment. They are known to respond actively to large-scale flow motion such as tidal currents but information on their small-scale response to turbulence remains scarce. Given the fundamental role of behavior in their ecology, it is especially relevant to know whether these animals can overcome local advection imposed by turbulent flow motion. By means of three-dimensional particle tracking velocimetry, we tracked the motion of hundreds of adult Eurytemora affinis swimming freely and simultaneously under realistic intensities of homogeneous turbulence. By comparing the dynamics of dead and living animals, we demonstrate that copepods can overcome relatively energetic levels of turbulence, such as the ones found in their environment, even when the velocity fluctuations are higher than their tpyical swimming speed. We show that the response is adaptive and that changes in behavior result in a substantial increase in swimming speed and acceleration. We also demonstrate that males outplay background turbulence better than females, which is consistent with their more active role in other aspects of their behavior such as in mating.
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