About Puget Sound and Plankton Movement
Puget Sound and adjoining waters to the north are located on the Pacific northwest coast of North America between the Cascade and Olympic mountains. Within this area are many islands that have small channels of water running between them. This water movement can affect the vertical mixing of the water. In some channels the currents are very fast and turbulent, which leads to thoroughly mixed water. In bays, on the other hand, there is little mixing of the water layers. There are two unequal pairs of tides per day in Puget Sound, and the lower of the low tides usually succeeds the lower of the high tides. The difference in water level between low and high tides in a given day is from 0.9 m to +3 m, with these extremes usually occurring during May and June.

Animals that make up the plankton typically migrate vertically on the order of 400 to 1,000 meters per day. The plankton is found deep in the water during the day and toward the surface at night. Factors that influence this migration behavior are thought to be:

grazing plankton can feed more effectively on phytoplankton, which are near the surface for photosynthesis;

plankton can escape from visually-oriented predators that are near the surface during the day;

planktonic animals can decrease their metabolic activity when they are in deeper and colder waters;

planktonic animals may have better geographic dispersal through deep water movement.

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