Provided by the NOAA Arctic
Research Office
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RUSCALA
A Census of Arctic
Zooplankton Communities
Russell R. Hopcroft, Institute of Marine Science, University of
Alaska Fairbanks
Ksenia Kosobokova, PP Shirshov Institute of Oceanology, Russian
Academy of Sciences
 |
Ksenia Kosobokova,
Photo: B. Holladay |
Our knowledge of abundance, composition and distribution of zooplankton
communities in the Arctic Ocean is poor compared to most other northern regions.
The Chukchi Sea represents a key oceanographic gateway
into the Arctic, but our ability to understand its complex dynamics have been
hampered by the political border that has prevented critically needed synoptic
surveys. We have undertaken a comprehensive
survey and census of zooplankton species in the Bering Strait through central
Chukchi Sea at 33 stations to understand the transport patterns of
Pacific zooplankton
into the Arctic and serve as a baseline for future studies on ecosystem change
in this climatically sensitive region.
The
census has been conducted using plankton nets of 150 and 53 µm mesh with analysis
to involve a
combination of traditional taxonomic enumeration and identification, along with
comprehensive molecular sequencing to be undertaken by Ann Bucklin (University
of New Hampshire). Photographic
documentation has been completed for a number the species encountered. To determine why zooplankton biomass remains
low despite the incredibly high primary production in much of this region, egg
production experiments have been conducted at 22 stations with several of the
dominant copepod species in this region (i.e. primarily Pseudocalanus spp., with variable contributions by Metridia pacifica, Eucalanus bungii, and Calanus
marshallae). These rates are
expected to be very sensitive to modification by climate change.
 |
| Ksenia Kosobokova
and Russ Hopcroft. Photo: K. Crane |
The
differences in zooplankton communities encountered on the transect lines has
been striking, with communities on the eastern side having an “estuarine”
community structure characteristic of Alaska Coastal water (i.e. Acartia longiremis, Eurytemora affinis, Centropages
abdominalis, Pseudocalanus spp.,
Podon leuckarti, Evadne nordmanni). Moving westward, communities characteristic
of Bering shelf water, with large population of the larvacean Oikopleura vanhoeffeni, and overwhelming
numbers of barnacle nauplii and cyriped larvae were found suspended in a soup
of phytoplankton. Along the Russian coastline, phytoplankton biomass remained
high, and zooplankton again shifted toward more coastal forms, but differed
in the relative composition of species as compared to the Alaska coast. On the more northern transects, a pronounced
change in community composition was also evident, with communities on the
western and central waters very similar to the Bering Shelf communities encountered
to the south, while water on the eastern side was lower in phytoplankton and
zooplankton and had a more coastal character.
Egg production experiments were conducted most consistently with Pseudocalanus species, and they suggest
that reproduction occurs throughout the region but is significantly enhanced
in Bering shelf waters compared to coastal waters. A fuller characterization
of the communities and their reproductive rates will require more detailed
analysis of the samples.
This
work will represent an extension of work begun in the Canada Basin under the
Ocean Exploration Office, provide geographic coverage of the zooplankton
community to compliment the concurrent Shelf-Basin Interactions program, and
ties into the Arctic Ocean Biodiversity project by the Census of Marine Life.
All of these efforts share common methods that will allow for the first
comprehensive broad-scale mapping of zooplankton communities and processes
throughout the Western Arctic Ocean.