Ecological Engines: Finescale Hydrodynamic and Chemical Cues 
Affecting Zooplankton in Nearshore Marine Ecosystems

                Abstract

Nearshore marine ecosystems are highly heterogeneous and 
structured on fine temporal and spatial scales; hydrodynamic and 
chemical sensory cues contained in finescale, ephemeral patches 
are fundamental to the life success of plankton populations and 
thus the overall health and vitality of nearshore marine 
ecosystems. The coupling of local physics (tidal forcing, 
surface and internal wave action, turbulence, stratification 
dynamics, etc.) and biology (migrating/foraging/mating/grazing 
zooplankton, phytoplankton bloom dynamics, etc.)  at relevant 
scales leads to a highly dynamic and complex and patchy 
spatiotemporal distribution of productivity. Here, we have 
employed various tools from experimental fluid mechanics to 
recreate ecologically-relevant hydrodynamic and chemical 
conditions in a recirculating flume system for zooplankton 
behavioral assays; the end goal being to quantify and correlate 
changes in zooplankton behavior with coincident sensory cues. A 
laminar, planar free jet (the Bickley jet) is used to create 
finescale, free shear layers with targeted hydrodynamic 
characteristics as well as finescale, sharp-edged layers of both 
beneficial and toxic ("red tide") phytoplankton species. Planar 
particle image velocimetry (PIV) and laser-induced fluorescence 
(LIF)  are used to quantify the flow and concentration fields, 
respectively. Behavioral assays with a variety of crustacean 
zooplankton species including Antarctic krill (Euphausia 
superba), crab larvae (Panopeus herbstii), mysids (Neomysis 
americana) and copepods (Temora longicornis and Acartia tonsa), 
each unique in its ecology, morphology, and life history, show 
clear and statistically significant (ANOVA) behavioral responses 
to ecologically-relevant hydrodynamic and chemical cues. These 
changes in individual behavior are quickly extrapolated to the 
population level with profound implications for trophic 
interactions and productivity dynamics in nearshore ecosystems. 
Quantifying changes in zooplankton behavioral in response to 
ecologically-relevant sensory cues is a crucial step in modeling 
and managing sustainable marine fisheries (e.g.via 
biophysically-coupled Individual-based Ecosystem Models).