US Army Corps of Engineers
Portland District Website Website


Charts showing various plankton populationsPlankton are small floating plants, animals, and microbes, which play a major role in the production and cycling of organic matter in the water column.


The figure at bottom left shows seasonal density of total zooplankton, upper estuary cladocerans, and mid and lower estuary copepods (Jones et al. 1990).


The figure at bottom right shows mean water-column chl a concentrations by sampling months and by regions along the main estuary axis (top) and in the shallows and tributary rivers (bottom) (Small et al. 1990)

Controlling factors that affect plankton:

Chart showing relative concentrations of chlorophyll in plankton in 1980 and 1981Ecosystem processes that are affected by emergent marsh:




Contact information

Ronald Thom, Ph.D

Marine Research Operations, PNNL
1529 W. Sequim Bay Rd.
Sequim, WA 98382