While nitrogen and sunlight can activate plankton populations and invigorate the food web, particularly in spring and summer, it turns out that not all plankton are equally beneficial, and some are considered harmful. Water conditions —including temperature, minerals, and salinity — play a role in determining which types of plankton will win in the Battle of the Species.
Spring phytoplankton growth in Puget Sound is normally dominated by diatoms, a stunningly beautiful variety of planktonic species with a cell wall made of silica, the raw material for glass. Diatoms are considered to be a foundation of the food web, providing energy-rich lipids for a variety of zooplankton — from tiny shrimplike crustaceans, such as krill and copepods, to the larval stages of fish, crabs and shellfish.
As spring turns to summer, Puget Sound sees a decline in river flows, the primary source of silica. Without silica, the diatom population can be overwhelmed by other phytoplankton, such as dinoflagellates that do not need silica and can thrive in the presence of excess nitrogen. Dinoflagellates, which include a variety of toxic species, are characterized by their tail-like flagella that help them move through the water.