Plankton pelagic photosynthesis trophic photic zone micron .
Plankton are tiny open-water plants, animals or bacteria.
These organisms range in size from microscopic bacteria and plants to larger animals, such as jellyfish. Plankton generally have limited or no swimming ability and are transported through the water by currents and tides. In the Chesapeake Bay, plankton communities serve as a base for the food chain that supports the commercial fisheries. Phytoplankton are useful indicators of high nutrient conditions due to their propensity to multiply rapidly in the right conditions. Zooplankton are useful indicators of future fisheries health because they are a food source for organisms at higher trophic levels, such as finfish.