Zooplankton are small organisms that are generally carried with the
flow of water currents. The diversity within this group in Puget Sound
marine waters encompasses copepods, euphausiids (krill), cnidarians and
ctenophores (jellies), amphipods, larval stages of benthic invertebrates
such as crabs and oysters, larval fish, and more.
These diverse taxa play a variety of unique roles in the marine ecosystem.
Zooplankton are consumers of tiny plant-like organisms (phytoplankton)
that form the base of the marine food web, as well as other zooplankton.
In turn, zooplankton (particularly the larger species), are important prey for
juvenile salmon and small forage fish.
- The King County Field Science Unit using a bongo net to sample for zooplankton.
Photo credit: Richard Droker
Due to their diversity and key position in the marine food web, zooplankton
communities reflect the integration of many ecosystem characteristics over
seasonal and annual timescales. These ecosystem characteristics include
oceanographic and estuarine circulation, phytoplankton community composition
and productivity, physical and chemical conditions, and predation. For these
reasons, the zooplankton community composition data collected for this program
are a valuable measure of biological response to environmental change.
- Puget Sound copepod.
Photo credit: Gabriela Hannach
King County’s zooplankton monitoring program, which began in 2014, is a
collaboration with Dr. Julie Keister
at the University of Washington (UW) and contributes data to the
Salish Sea Marine Survival Project
(SSMSP) headed by Long Live the Kings. King County collects zooplankton samples
at four locations
in Puget Sound twice monthly February-November and once monthly December-January. Samples
for phytoplankton as well as water quality
parameters such as salinity, nutrients, chlorophyll, and dissolved oxygen are
collected at the same time as zooplankton samples.
King County samples for zooplankton using two types of nets, which each
capture different components of the zooplankton community. To capture smaller
zooplankton such as copepods, which typically dominate zooplankton biomass, a
fine-mesh (200 micrometers, μm) ring net is deployed to a maximum depth of 200
meters (m) and then raised to sample the entire water column. To capture larger
zooplankton, which may swim fast enough to escape the slower vertically-towed
net, a double “bongo” net with larger mesh (335 μm) is towed obliquely (at an
angle) down to a depth of 30 m and then back to the surface.
Samples undergo detailed analysis by expert taxonomists in Dr. Julie Keister’s
laboratory at UW. Zooplankton are identified to species and life-cycle stage where
possible and are measured for biomass estimates.
View a copy King County’s zooplankton monitoring program
sampling and analysis plan.
Data from the zooplankton monitoring program are available here. Please contact
with any questions about the program.