A pond ecosystem as a whole serves as a Good example of a freshwater ecosystem. A pond is an excellent example of self-sustaining and self-sufficient ecosystem i.e. both the abiotic and biotic components of this ecosystem exist in equilibrium and survive without the assistance of any member external to the pond ecosystem. In pond, ecosystem exists both at a micro level and macro level. Now to examine the Microorganisms in the plant a bottle of pond water is taken and examined. However, to study the ecosystem at a macro level, we have to take, in consideration, the entire pond. Hence to avoid confusion we segregate the pond ecosystem into the following categories for organized analysis.
The primary substances are heated, Light, the pH value of water and the basic organic and inorganic components of water. Now to understand the various organic and inorganic components of water we have to understand a simple mechanism. Due to highly energized particles like photons penetrating deep into the surface of the water, water breaks up into Ions in the form H+ and OH- ions. These H+ ions dissolved in water combines with the carbon dioxide also in dissolved in water to form a bicarbonate ion. This Bicarbonate Ion serves as a basic component of all the complex organic structure we find in the pond ecosystem. Dissolved minerals essential for the survival of living organisms like dissolved oxygen are also present in a solution state in water. Besides water also comprises of Colloidal suspensions, phosphate and nitrogen contents. For analysis, the amount of sunlight penetrating to a particular depth in water is determined by a Luxphotometer. Turbidity Index of water at different levels are measured by a Secchi Disc.
This level in pond ecosystem is mainly composed of autotrophic green plants as well as some photosynthetic bacteria which is exclusive of the pond ecosystem. The producers fix radiant energy with the help of minerals derived from water and mud to produce complex organic substances like carbohydrate, protein, lipids, etc. One of the most important producers are the macrophytes. Now, these macrophytes are mainly rooted larger plants that include partly or completely submerged floating and emergent hydrophytes. The common plants include Trapa, Eleocharis, Sagittaria, Nymphaea, etc. macrophytes may be sampled by quadrat method in a unit volume of water.
Biomass is estimated as the weight of standing crop per unit area or volume. The biomass of vegetation increases from the center of the pond to its periphery. Each biological organism has some energy stored in them. This energy can be calculated by using an Oxygen Bomb Calorimeter. However like biomass, Energy also decreases from periphery to center. Thus, we can say that for both biomass and energy of producers we have identical ecological pyramids being produced.
Now we come to the section of [producers that act as primary food components of all aquatic animals, the phytoplankton. These are minute floating or suspended lower plants. The majority of them are however filamentous algae that float in water, e.g., Closterium, Cosmarium, Audrina, etc. Phytoplankton sampling Takes place however in a Collection glass bottle. The biomass is expressed as average biomass per unit volume of water.
They are heterotrophs that depend on the producers for their food. The energy that the producers obtain by converting inorganic and organic substances into food is hence transferred to the consumers. However, the entire energy of the producers is not transferred to the consumers, which is the next trophic level in the ecological pyramid. The consumers can use only 10% of the energy that is being stored by the producers. The consumer level in pond ecosystem include Benthos, which feed upon plants at the base of the pond like small fish, insect larvae, mollusks, mites etc., and Zooplanktons which feed on phytoplankton closer to the surface of water like Brachionus, A plancha etc. act as primary consumers, i.e. they consume plants directly to obtain their energy.
The next sub-level under consumers after primary consumers are the secondary consumers. This category mainly includes fish, insects, and water beetles that feed on the Zooplanktons Now the name of this sub trophic level originates from the fact that secondary consumers are however not directly dependent on food for plants or rather to be more specific phytoplankton.
Next, in the consumer list comes to the tertiary consumers who meet their demands of energy by feeding on the secondary consumers and hence in the consumer family they are the sub level receiving a minimum amount of energy. This sublevel mainly includes large game fishes that feed on the small fishes. Confusions may arise about the presence of fish in both secondary and tertiary consumer level, but We need to realize there are a variety of fishes in a pond ecosystem, and hence it is not abnormal that different subspecies of fish occupy different sublevels under the category of consumers. Tiny fish feed on phytoplankton basically and also on plants lying at the bottom. While the category of fish larger than the tiny species feeds on the zooplanktons and hence occupies the secondary consumer level. Besides as mentioned earlier, large game fish feed on the smaller fishes to occupy the highest level of tertiary consumers in the Consumer pyramid.
These are termed as micro consumers and forms the most important part of any ecosystem as the abiotic components that the biotic components absorb from the surroundings for their survival are returned to the ecosystem in the form of raw materials by these decomposers and hence they help to carry on a stable cycle in any ecosystem. They bring about the decomposition of complex dead organic matter of both plants and animals to simple forms, and thus they play an indispensable role in the ecosystem in the return of minerals again to the pond such that they can be used by the producers for initiation, continuation, and persistence of the ecological cycle. These include species of Aspergillus, Cephalosporium, Cladosporium, Pythium, Rhizophora, etc
Thus, as illustrated in the picture above, pond ecosystem is one of the most stable ecosystems where one can find almost all components of environmental ecology. Study and observation of this ecosystem help us to get an idea of how the various ecological cycles are occurring in nature However we have to keep in mind that a pond ecosystem or rather to be more specific any ecosystem is very stable till all its components are working in perfect harmony. As in pond ecosystem, excess water pollution often results in a decrease of phytoplankton thus causing an imbalance to the whole ecological stability in the aquatic system.