Plankton Plankton Mainly unseen by the naked eye, a community made up of predominantly microscopic organisms also fuels the Bay ecosystem. These tiny plants and animals, called plankton, drift at the mercy of the currents and tides. Some of the tiny creatures move up and down in the water column to take advantage of light. Others will drop below the pycnocline, an intermediate layer where the increase in salinity is more pronounced, to avoid being washed out to the ocean.
Phytoplankton are tiny single-celled plants.
Like higher plants, phytoplankton require light to live and reproduce. Therefore, the largest concentrations occur near the surface. Salinity affects phytoplankton distribution with the largest number of species preferring the saltier waters near the mouth of the Bay. The amount of nutrients in the water is a major determinant to the abundance of these plants. The largest concentrations of phytoplankton in the Bay occur during the spring when nutrients are replenished by freshwater runoff from the watershed.