An aquatic ecosystem is a group of interacting organisms dependent on one another and their water environment for nutrients (e.g., nitrogen and phosphorus) and shelter. Aquatic ecosystems include lakes and rivers, but aquatic ecosystems also include areas such as floodplains and wetlands, which are flooded with water for all or only parts of the year.

Characteristic features:

• Aquatic ecosystems usually contain a wide variety of life forms including bacteria, fungi, and protozoans; bottom-dwelling organisms such as insect larvae, snails, and worms; free-floating microscopic plants and animals known as plankton; large plants such as cattails, bulrushes, grasses, and reeds; and also fish, amphibians, reptiles, and birds.

• Aquatic ecosystems depend on their abiotic features or the physical features including salinity, clarity, oxygen content and rate of flow of water.

• Aquatic ecosystems maybe fresh water or saline, moving water or stagnant water.

Functions of Aquatic ecosystems:

• Viruses and micro organisms in the aquatic ecosystem play an important role in the nutrient and energy cycles.

• Sustaining biodiversity is essential to the health of our environment and the quality of human life. We depend on aquatic plants and animals, and their ecological functions, for our survival.

• Aquatic animals break down harmful toxins that we release into water bodies from industries and domestic areas.

• Aquatic biodiversity are sources of medicine, food, energy, shelter and the raw materials that we use and need.

• Aquatic organisms also add oxygen and reduce the carbon and ozone levels in the atmosphere. They also provide food for the growing human population.

• They help us discover and provide new drugs. Hence we should make and exceptional effort to conserve the aquatic biodiversity.