The Northern Gulf of Alaska (NGA) marine environment is highly variable, both in space and time, presenting technical challenges for describing its zooplankton communities. Abundances and distributions can be poorly resolved by plankton net sampling due to patchiness, a problem that is further compounded by the damage inflicted on fragile soft-bodied organisms during collection. High resolution data is limited by practical constraints on both sample collection and taxonomic analysis. To resolve these challenges, we have deployed an In Situ Ichthyoplankton Imaging System Deep-Focus Particle Imager (ISIIS-DPI) to describe zooplankton community structure in the NGA. The ISIIS-DPI is an undulating towed vehicle with a wide array of mounted instrumentation, and an imaging system of 3 line-scan cameras that images ~250 liters/second while conserving the scale of particles and plankton. Deployments are illuminating the substantial variability occurring within most components of the epipelagic zooplankton community. In particular, here we will describe the fine-scale vertical and horizontal aggregative patterns of gelatinous zooplankton abundance and distribution in the NGA, and relate them to biophysical drivers. For example, we show that abundances are elevated around frontal features, as well as concentrated near the pycnocline.  Furthermore, we will demonstrate the prominence of the most fragile members of the gelatinous zooplankton - ctenophores - within the NGA that are virtually missed by traditional sampling methods.

Primary Presenter: Hannah Kepner, University of Alaska Fairbanks (hekepner@alaska.edu)

Authors:

Thomas Kelly, University of Alaska Fairbanks  (tbkelly@alaska.edu)

Russell Hopcroft, University of Alaska Fairbanks  (rrhopcroft@alaska.edu)