A pond is a good example of a self sufficient and self regulating complex system. The basic components are as follows.
Abiotic component: The chief substances are heat light pH value of water and the basic inorganic and organic compounds such as water itself carbon - dioxide oxygen calcium nitrogen phosphate amino acids humic acid etc. Some proportions of nutrients are in solution state but most of them are stored in particulate matter as well as in living organisms.
Biotic component: The various organisms constitute the biotic component are as follows:
Producers: These are autotrophic and green plants and some photosynthetic bacteria. The producers fix radiant energy and with the help of minerals derived from water and mud, they manufacture complex organic substances as carbohydrates proteins, lipids etc., and producers are of the following types.
a) Macrophytes: they are mainly large rooted plants which include partly or completely submerged floating and emergent hydrophytes . Ex. Trapa, Typha, Saggrtaria , Nymphaea, potamogeton, chara, Hydrilla, vallisneria, Utricultaria, Marselia, Nelumbo, etc.. Besides, them some free floating forms as Azolla, Salvinaia, Wolfia, Eichhomia and Lermna were also occur.
b) Phytoplankton: these are minute floating or suspended lower plants majority of them are filamentous algae such as Zygnema, ulothrix spirogyra, Ctadophora and Oedognonium. Besides them there are also present chlorococcades. Closterium, Eudorina, Pandorina Scendesmus, Volvox, Microcystics, Oscillatoria, Chalmydomonas, Spiirullina.
Consumers: They are heterotrophs which depend on the organic food manufactured by green plants for their nutrition. Most of the consumers are herbivores while a few insects and some large fish are carnivores. The consumers in a food ecosystem are distinguished as follows.
a) Primary consumers: these are herbivores feeding directly on living plants (producers) or plant remains. They may be large as well as minute in the size.
The herbivores are further differentiated as:
Benthos: These are herbivores feeding directly on living plants (producers) or plant remains lying at the bottom of pond. These are known as detritivores. Benthic populations include fish insect larvae beetles, mites, mollusks and crustaceans etc.
Zooplankton: These are chiefly the rotifers as Brachionus, Asplancha, Lecane etc, some protozoan as Euglena, Coleps.Dileptus, etc. and Crustaceans like Cyclops, Stcnocyupris etc. They feed chiefly on Phytoplankton.
b) Secondary Consumers: They are the carnivores which feed on the primary consumers herbivores. These are chiefly insects and fish which feed on zooplankton.
c) Tertiary consumers : Some large fish a" game fish feed on the smaller of fish and thus become the tertiary (top) consumers. In a pond a fish may occupy more than one trophic level. The small fish (herbivores) feed on Phytoplankton white some fish feed on zooplankton while some fish feed on zooplankton at carnivore level.
Decomposers: They are also known as micro consumers, since they absorb only a fraction of the decomposed organic matter.
They bring about the decomposition of complex dead organic matter of both plants and animals to simple forms. Thus they play an important role in recycling the mineral elements again to the medium of the pond. They are chiefly bacteria actinomycetes s and fungi, Aspergillus, Rhizopus. Penicillin etc are most common fungi in water and mud of the pond.
