The effects of sill-circulation on zooplankton patchiness

Senior thesis written for Oceanography 445

[author abstract] Fine scale zooplankton patchiness is an important component of similarly scaled trophic interactions. There are biological and physical drivers of patchiness--this study focused on the physical component, specifically the circulation patterns formed around sills. During a research cruise to Nootka Sound, British Colombia, 200 kHz sonar was used to collect data from zooplankton backscatterers including copepods and euphausiids. Raw sonar data was binned and a variance:mean ratio was calculated to assess zooplankton patchiness. Transects of patchiness over sills and flat bathymetry were compared, revealing higher peak patchiness over sills and more vertically stratified patchiness in flat sections. Subsampling from zooplankton layers revealed that patchiness was higher in proximity to sills when compared to flat-bathymetry sites.

University of Washington School of Oceanography