Pond ecosystem

Pond Ecosystem

A pond ecosystem refers to the freshwater ecosystem where there are communities of organism dependent on each other with the prevailing water environment for their nutrients and survival. Ponds are shallow water bodies with a depth of 12-15 feet in which the sun rays can penetrate to the bottom permitting the growth of plants there.

Light zonation of pond

On the basis of the depth of water, penetration of light and the types of plants and animals in the pond, the pond is divided into different zones. They are:

Littoral

It is a peripheral shallow water zone in which light can reach up to the bottom. It contains warm and oxygen rich circulating water. So, this zone includes abundant rooted vegetations and different types of consumers.

Limnetic

The limnetic zone is a central part of a pond up to where there is penetration of effective light. The associated organisms are small crustaceans, rotifers, insects and their larvae and algae. The water level, oxygen content, and temperature in this zone varies time to time. Decomposers are almost absent here.

Profundal

This is the deep-water region where there is no effective light penetration. There the microscopic plants and decomposers are present. So it is called Hypolimnion.

Role of temperature in stratification, biological oxygen demand, and dissolved oxygen:

The thermal stratification of ponds refers to a change in the temperature at different depth in the pond and it is due to change in water's density with temperature. Thermal variation influences the aquatic life and leads to the stratification of the pond. There are three different regions in the pond which are epilimnion, thermocline, and hypolimnion. Epilimnion is the zone of gradually decreasing temperature from the surface, thermocline of rapidly falling temperature and hypolimnion is a bottom zone where no temperature gradient evident.

Biological oxygen demand ( BOD )

It is the amount of oxygen required by bacteria in the pond in a unit volume of water at a specified time.

Dissolved oxygen

Dissolved oxygen refers to the level of free, non-compound oxygen dissolved or present in water or any other liquid. BOD and DO govern the kind of organisms present in water.

Structure of pond ecosystem

It contains two main components i.e. abiotic and biotic.

Abiotic components

The abiotic substances of Pond ecosystem are formed as a result of the mixture of some organic and inorganic materials. They have directly or indirectly effect in aquatic organisms of the pond. These includes:

• Light
• Temperature
• Dissolved oxygen
• Carbon dioxide
• Other gases
• P_H of water
• Turbidity
• Dissolved minerals

Biotic components

The biotic components of Pond ecosystem are the living components which consist of:

Producers

The producers are the aquatic green plants, which may be divided into two groups.

• Microphytes (phytoplanktons): They are microscopic autotrophs, which fix solar energy. Eg. Spirogyra, Zygnema, Volvox, Oedogonium.
• Macrophytes: They are large plants, which manufacture complex food. Eg; Pistea, Hydrilla etc.

Consumers

The consumers are those heterotrophic organisms, which consume producers as food. Their types are:

Primary consumer:

These herbivorous animals depend on autotrophic organisms such as microscopic plant eaters or zooplanktons, Mollusks, Beetles, Cyclops, and Daphnia etc.

Secondary consumer:

These are primary carnivores, which depend on herbivorous animals for food. Eg: Insects, fishes, frogs, crab etc.

Tertiary consumer:

These are the second grade of carnivores. They feed upon plants or animals (secondary consumer) therefore are called omnivores. Eg: Large fishes and frogs.

Decomposer

Most of the decomposers of Pond ecosystem are saprophytes but some parasites are also found. Bacteria, fungi like Aspergillus Cladosporium Rhizopus, Alternaria, Fusarium, Saprolegnia etc. are decomposers. Generally, the decomposers either live in the soil layer beneath water or in the mud. They act on dead and decayed organic matter of plants and animals and supply raw materials to the producers.

Functional aspect of pond ecosystem

Interactions: They are the food chains and food web formed by biotic communities. The food chain is of two types which are given below:

1. Predatory food chain:In a predatory food chain, food chain starts with aquatic green plants (autotrophs) whose source of energy is the sun and this autotroph becomes the source of energy for herbivorous which are the source of energy for primary carnivorous and then the secondary carnivorous.
2. Detritus (saprophytic) food chain:Here organic matter (i.e. dead plants and animals) are first converted into detritus food by microorganisms like bacteria and fungi which is then consumed by the consumer as a source of energy. There is no predatory and parasitic form.

Food Web

Food chains of pond ecosystem which are interconnected with one another in different ways forming a network is called food web.

Ecological pyramid

The distinct trophic levels in each type of food chain in pond ecosystem which shows a food relationship between one another in terms of energy, biomass, and the number is known as the ecological pyramid. There are three kinds of the ecological pyramid in pond namely- Pyramid of number, the pyramid of biomass, and the pyramid of energy. Here, a pyramid of the number shows that the population density relationship between the trophic level, which goes on decreasing at each successive trophic level due to predation. In the pyramid of biomass and energy, there is a progressive loss of biomass and energy in successive trophic levels. Pyramid of biomass and pyramid of number is inverted in the parasitic type of food chain.