Phytoplankton are being used as indicators of environmental conditions within the Bay because their populations are especially sensitive to changes in nutrient levels and other water quality conditions. A good picture of the current conditions in the Bay can be derived by looking at phytoplankton indicators such as chlorophyll, primary production rates, biomass and species composition. Zooplankton Zooplankton are planktonic animals that range in size from microscopic rotifers to macroscopic jellyfish. Their distribution within the Chesapeake Bay is governed by salinity, temperature and food availability. The smallest zooplankton can be characterized as recyclers of water-column nutrients and often are closely tied to measures of nutrient enrichment.
Larger zooplankton are important food for forage fish species and larval stages of all fish.
The zooplankton community is composed of both primary consumers, which eat phytoplankton, and secondary consumers, which feed on other zooplankton. Zooplankton, like phytoplankton, make 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.