Sustained glider observations of acoustic scattering suggest zooplankton patches are driven by vertical migration and surface advective features in Palmer Canyon, Antarctica

Oliver, Matthew J.Antarctic zooplankton and micronekton link the highly productive waters of the Southern Ocean to upper trophic levels. The distribution of zooplankton and micronekton is highly patchy both vertically and horizontally, suggesting that both behavior and oceanographic advection are important for understanding their distributions. A Slocum glider was deployed with an acoustic Doppler current profiler within a surface current field measured by HF-Radar in Palmer Canyon, Antarctica, during austral summer. I used this data to investigate the relative importance of surface currents and vertical migration behavior on the presence of zooplankton and micronekton in the mixed layer. I show that zooplankton and micronekton are more likely to be found shallower than the mixed layer during night-time hours, indicating diel vertical migration is a driver of their vertical distribution. I also found both Eulerian and Lagrangian characterizations of surface physical features to be important in predicting the presence of zooplankton and micronekton shallower than the mixed layer. While I found that both diel vertical migration (DVM) and surface currents were significant predictors of zooplankton and micronekton presence above the mixed layer, the strongest predictor of zooplankton and micronekton presence were surface currents represented as repelling Lagrangian Coherent Structures (LCS). This indicates that in this region during summer, horizontal advection and behavior plays a critical component in structuring zooplankton and micronekton distributions.University of Delaware, School of Marine Science and PolicyM.S