Zooplankton

Zooplanktons are planktonic animals that range in size from microscopic rotifers to macroscopic jellyfish. The distribution of zooplankton is governed by salinity, temperature and food availability in the environment. The smallest zooplankton can

be characterized as recyclers of water-column nutrients and often are closely tied to measures of nutrient enrichment.

Larger Zooplanktons are important food for forage fish species and larval stages of all fish. They also link the primary producers (phytoplankton) with larger or higher trophic-level organisms. The zooplankton community is composed of both primary consumers, which eat phytoplankton, and secondary consumers, which feed on other zooplankton.

Zooplankton can be classified into three size classes:

• Microzooplankton–(protozoans and rotifers) are usually less than 200 microns in size.

• Mesozooplankton-(including copepods and invertebrate larvae) are between 200 microns and 2 millimeters in size.

• Macrozooplankton-(including amphipods, shrimp, fish larvae and gelatinous zooplankton or jelly fish) are greater than 2 millimeters in size.

Zooplankton, like phytoplankton, makes excellent indicators of environmental conditions within the Bay, because they are sensitive to changes in water quality. They respond to low dissolved oxygen, high nutrient levels, toxic contaminants,

poor food quality or abundance and predation. A good picture of the current conditions in the Bay can be derived by looking at zooplankton indicators such as their biomass, abundance and species diversity.