Large zooplankton were collected with 1m2 square MOCNESS with 500 mm mesh. Samples collected in 20 m

1
Distribution and abundance of zooplankton on the
northern Gulf of Alaska shelf relative to water
masses Kenneth O. Coyle School of Fisheries and
Ocean Science, University of Alaska, Fairbanks
Alaska
Introduction Zooplankton abundance and
distribution on the northern Gulf of Alaska shelf
are tightly linked to physical processes
influencing production and advection of water on
and off the shelf. A primary goal of the LTOP
project was to document the cross shelf
distribution and abundance of major zooplankton
taxa relative to water mass movements and to
elucidate processes leading to interannual
differences is abundance. This poster
illustrates cross shelf distribution of major
zooplankton species relative to their depth
distribution and water mass movements. Contrary
to expectation, the abundance of Neocalanus
flemingeri, an oceanic species, is negatively
correlated to salinity. The abundance-salinity
correlation and interannual differences in
Neocalanus abundance are related to physical
processes, potentially influencing
production. Acknowledgments This research was
conducted on the R. V. Alpha Helix. Technical
support was provided by the captain, crew and
ships technicians (Steve Hartz, Brian Rowe, Dave
Aldridge and Dan Mahalck). Aid in sample
processing and data entry was provided by Chris
Stark, Janet Ballek and Elizabeth Stockmar. The
research was multidisciplinary, involving the
cooperation of a number of researchers and
institutions. They include Tom Royer, Old
Dominion University Amy Childers, Tom
Weingartner, Seth Daniels, Steve Okkonen, Dean
Stockwell and Terry Whitledge, University of
Alaska Fairbanks. We thank all of the above for
their participation in this research effort. The
Long Term Observation Program was funded by US
GLOBEC award number NA67RJ0147AMD7
Interannual Differences in Abundance of
Neocalanus flemingeri
Cross Shelf Distribution of Major Zooplankton
Species Relative to Depth Distribution (bar graph
insets)
Neocalanus, an oceanic species, was more abundant
in 1998 and 2002 than in 2000 and 2001 (error bar
are 95 confidence intervals)

• Large zooplankton were collected with 1-m2 square
  MOCNESS with 500 mm mesh. Samples collected in
  20 m depth increments from 100 m to the surface
  at night.
• Small zooplankton were collected with a 25 cm
  diameter CalVET net with 150 mm mesh. Vertical
  tows from 100 m to surface during the day.
• Water column profiles were collected with a
  Seabird model 911 plus CTD and fluorometer.
• Samples were collected during years and months
  listed below

Methods

• Collection Sites
• 13 Stations along Seward Line (labeled GAK)
• 5 Stations in Prince William Sound (PWS box)
• 4 Stations at Hinchinbrook Entrance (HE)

Hypothesis The most likely explanation for the
observations is that horizontal mixing between
high-nutrient, low-iron oceanic water and
high-iron, low-nutrient ACC water promotes
elevated primary production in the mixing zone,
leading to elevated production of zooplankton
grazers.