Marine zooplankton navigate a fluid world of physical and chemical stimuli which they must exploit for foraging, mating, and avoiding predation. Thin plankton layers are vertically-thin, persistent layers that are ubiquitous in marine ecosystems, featuring levels of biological productivity orders of magnitude higher than the surrounding water column. They have distinct biochemical and hydrodynamic signatures, most often occurring in the pycnocline, thermocline, and in layers of elevated fluid shear. They are oases of beneficial resources for zooplankton in the surrounding marine desert and are critical drivers of the health of nearshore marine ecosystems.
In this highly interdisciplinary project we applied tools from experimental fluid mechanics and biology to build a physical model of thin layers using a laminar slot jet flume, characterize hydrodynamic and chemical concentration fields using particle image velocimetry (PIV) and laser-induced fluorescence (LIF), respectively, and conduct behavioral assays with a variety crustacean zooplankton from copepods to Antarctic krill.
A custom 3-layer density stratification flume for replicating thin layers of toxic algal exudates. Adapted from Fig. 1 of True et. al, “Copepod avoidance of thin chemical layers of harmful algal compounds”, Limnology and Oceanography, 2018.
A hypothetical swimming trajectory in relation to the thin toxic algal exudate layer. Adapted from Fig. 2 of True et. al, “Copepod avoidance of thin chemical layers of harmful algal compounds”, Limnology and Oceanography, 2018.
Copepods modify swimming kinematics to strongly avoid and escape thin layers of toxic algal exudates. Adapted from Fig. 4 of True et. al, “Copepod avoidance of thin chemical layers of harmful algal compounds”, Limnology and Oceanography, 2018.
Swimming speeds and accelerations achieved during escape reactions at high toxic algal exudate concentrations are comparable to predatory escape reactions. Adapted from Fig. 5 of True et. al, “Copepod avoidance of thin chemical layers of harmful algal compounds”, Limnology and Oceanography, 2018.
Two reef-dwelling copepods species from the Gulf of Aqaba, Red Sea. Adapted from Fig. 3 of True et. al, “Patchiness and depth-keeping of copepods in response to simulated frontal flows”, Marine Ecology Progress Series, 2015.
Digitized copepod swimming trajectories around a downwelling fluid shear layer produced by a vertical laminar slot jet flow. Adapted from Fig. 4 of True et. al, “Patchiness and depth-keeping of copepods in response to simulated frontal flows”, Marine Ecology Progress Series, 2015.
PIV and analytical self-similar velocity profiles in the vertical laminar slot jet flow. Adapted from Fig. 2 of True et. al, “Patchiness and depth-keeping of copepods in response to simulated frontal flows”, Marine Ecology Progress Series, 2015.
Copepods modified swimming kinematics often to maintain depth, an important adaptation for optimizing fitness in coral reef ecosystems. Adapted from Fig. 7 of True et. al, “Patchiness and depth-keeping of copepods in response to simulated frontal flows”, Marine Ecology Progress Series, 2015.
III. Antarctic krill swimming kinematics near horizontal fluid shear layers
The antarctic krill Euphausia superba.
An antarctic krill swimming trajectory in a horizontal fluid shear layer.
IV. Fluid shear layer orientation & differential behavior of crab larvae
