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A pond as a whole serves as a good example of an aquatic as well as freshwater ecosystem. It has the following components:

1. Abiotic or Non-living Components:

The abiotic component comprises of:

  • Chief non-living substances: Light, heat, pH of water
  • Inorganic and organic compounds: Water, carbon dioxide, oxygen, calcium, nitrogen, phosphates, amino-acids, humic acid etc.
  • Inorganic salts: Occur in the form of nitrates, phosphates and chlorides of calcium, potassium and sodium.

2. Biotic or Living Components:

It includes various organisms which are classified into the following types:

  1. Producers: These include the photoautotrophic green plants and photosynthetic bacteria. The producers convert the solar energy into chemical energy with the help of organic substances such as enzymes and inorganic substances such as water and carbon dioxide by means of a process called photosynthesis.
    Producers of the pond are of the following types:
    1. Macrophytes: ​These mainly include the rooted large-sized plants which comprises of partly or completely submerged, floating and emergent hydrophytes. The common species of plants are Hydrilla, Chara, Typha, Vallisneria, Nymphaea, Marsilea, Utricularia, etc.
      Besides these plants, some free-floating forms are also seen in the pond ecosystem. These include Eichhornia, Wolffia, Azolla, Salvinia etc.
    2. Phytoplanktons: These include minute, microscopic, floating or suspended lower plants (algae), distributed throughout the water but mainly found in the photic zone.
      These include Anabaena, Volvox, Diatoms, Chlorella, Microcystis, Spirulina, Oscillatoria, Chlamydomonas, Ulothrix, Spirogyra, Cladophora etc. and some flagellates.
  2. Macroconsumers: They are phagotrophic heterotrophs which depend on green plants (producers) for their food.
    They are of three types:
    1. Herbivores (Primary Consumers): These animals directly feed on green plants or plant remains. These include fishes, beetles, insect larvae, mites, molluscs, Euglena and crustaceans such as Cyclops are present in the pond.
    2. Carnivores 1st order (Secondary Consumers): These carnivores feed on herbivores. They include fishes, insects, frogs, water beetles etc.
    3. Carnivores 2nd  order (Tertiary Consumers): These include some large fishes which feed on the smaller fishes.
  3. Decomposers: Also called as microconsumers. They breakdown the complex dead organic matter of both producers (plants) and macroconsumers (animals) to simple forms. They help in returning the mineral elements again to the pond system, thereby making them available for the green plants. Bacteria, Actinomycetes and fungi constitute the decomposers of the pond ecosystem.
    The species of Penicillium, Aspergillus, Rhizopus, Alternaria, Cephalosporium, Trichoderms etc. are the most common fungi (decomposers) present in the water and mud of the pond.