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Puget Sound phytoplankton. Counterclockwise from top left:
Thalassionema sp.,
Stephanopyxis palmeriana,
Actinoptychus senarius, and
Chaetoceros debilis
Photo credit: Gabriela Hannach
Phytoplankton are a group of microscopic organisms consisting of
single-celled or colonial algae. They form the base of marine food
webs as the dominant photosynthetic producers (similar to plants on
land) and influence water chemistry and nutrient dynamics. Major
groups of phytoplankton in marine waters include diatoms, dinoflagellates,
and nanoflagellates. Diatoms are relatively large and are adapted
to high-nutrient environments. They can multiply rapidly at certain
times of the year, such as in early spring in Puget Sound. Diatoms
are a major food source for a wide variety of zooplankton, including
larger species that are important prey for fish. Dinoflagellates and
nanoflagellates, in contrast, generally flourish under lower nutrient
conditions and are generally too small to be a good food source for
the larger zooplankton. The progression from diatom-dominated communities
in the spring to more diverse communities of smaller, motile (flagellated)
types of phytoplankton in the summer is a general pattern that is frequently
observed in coastal marine waters.
The diversity in responses to environmental conditions and unique roles
played by different types of phytoplankton mean that the composition of
the phytoplankton community, not just how much phytoplankton is growing,
is key information for understanding marine food webs. King County’s
phytoplankton monitoring program aims to collect such community composition
data throughout the year in the Central Basin of Puget Sound, alongside
the commonly measured metric of phytoplankton growth, chlorophyll.
 - Adding water sample to FlowCAM® particle analyzer
Photo credit: Gabriela Hannach
King County’s phytoplankton monitoring program began in 2008 with a
semi-quantitative microscopy method of analysis, which assessed the
relative abundance of different types of phytoplankton. In 2014, sample
analysis with a particle imaging analyzer (FlowCAM®) was added to the
program. This method partially automates identification and quantifies
both abundance and size of all phytoplankton present in a sample. The
semi-quantitative method was retired at the end of 2014 and superseded
by qualitative microscopy. This method provides higher resolution
identification to complement the FlowCAM’s quantitative method. For a
history of the sampling program view the following table.
King County collects phytoplankton samples offshore at eight sites
in Puget Sound, twice monthly from Feb-Nov and once monthly from Dec-Jan.
These locations are also sampled for water quality parameters such as
salinity, temperature, nutrients, chlorophyll, and dissolved oxygen, as
well as zooplankton at three sites
(see summary here).
Data from the phytoplankton monitoring program are not currently available
online. Please contact
Wendy Eash-Loucks
with any data requests. Phytoplankton images are available here, and
publications and presentations are available
here.
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