Their movement depends largely on tides, currents, and winds, because they are too small or weak to swim against the currents. That component of the plankton comprising bacteria and microscopic algae and fungi is called the phytoplankton. Important algal groups in the phytoplankton include diatoms, golden algae, green algae, and blue-green algae. The other component of the plankton, the zooplankton, is comprised of protozoa, small crustaceans, jellyfish, worms, and mollusks, together with the eggs and larvae of the many animal species inhabiting marine and fresh waters. Important protozoan groups in the zooplankton are dinoflagellates and foraminifera.
Phytoplankton are tiny single-celled plants that require light to live and reproduce.
The largest concentrations of plankton occur near the surface. The amount of nutrients in the water is a major factor in the abundance of these plants. The largest concentrations of phytoplankton in the Bay occur during the spring when nutrients are replenished by the fresh water runoff. Changes in chemical conditions can cause an increase in growth of algae. Even after they die they cause problems.