Plankton are the building blocks on which any lake management program starts. Plankton is a term used for all microscopic and near microscopic living things that float in the water. Plankton includes both tiny aquatic plants called phytoplankton or algae, and animals called zooplankton. Planktonic algae serve as the base of the food chain in every lake, river, pond, and even in the ocean. Zooplankton and aquatic insects feed on algae, and they in turn are eaten by small fish.
Small fish are then eaten by larger fish. Directly or indirectly, algae provide almost all the basic food for the lake or pond except for a small quantity of insects and worms that fall or wash into the pond. As a result, managing planktonic algae is essential in providing the food to produce an abundant and healthy fish population.
Changes in lake water color can be related to planktonic algae concentrations, called “algae blooms,” or because of suspended sediments and organic matter. Water which is good for fish production is greenish. The green color comes from billions of suspended microscopic algae blue-green algae. Water color changes if these algae blooms die-off rapidly, turning the water brown, black, milky or clear.
When this happens, decomposition of the dead algae consumes oxygen, leading to possible stress, suffocation. or disease in fish. Algae die-offs are common in deep lakes or in fish ponds receiving too many nutrients. Mechanical aeration may be necessary after algae die-offs to keep fish alive.