A. Habitats In the Pond Community
The place where an organisms live is considered its habitat. Four distinctive habitats can be found within the pond community. These four habitats are the surface film habitat, open water habitat, bottom habitat and the shore habitat.
The surface film habitat is located on the top (surface) of the pond water. It is the habitat of air-breathing floating animals (insects) such as marsh treaders, broad-shouldered water striders, and animals that have special devices that allow them to walk on the surface of water without breaking through such as water striders. Some insects and free-floating animals are adapted to live only on the upper side of the surface film. The animals that dwells on the surface usually feed on the floating plans, insects and other animals that may have been killed or drown and floated to the surface. The surface dwelling animals may even feed on one another. Other animals, along with the larvae of some beetles and flies spend much of their life on the underside of the film beneath the floating plants.
The open-water area mainly consist of the water surrounded by plant life. It ends where vegetation is dense and rooted into the soil. The open water habitat is composed of large, free-swimming organism such as fish, and small microscopic plants and animals called plankton that drift suspended in the water. Phytoplankton (small suspended plants), mostly consisting of algae, are the basic food in lakes. Small suspended animals such as tiny crustaceans, insect larvae, rotifers, and other invertebrates called zooplankton also live in the open-water habitat and are basic food for pond animals. The availability of plankton vary from season to season, but are most abundant during the spring.
Other animals such as turtles, birds and larger fish comes to the open-water area for food. Some insects, insect larvae, and crustaceans migrate from the bottom towards the surface, but return to the bottom as daylight appears.
Life in the bottom habitat of a pond depends upon the type of bottom a pond may have. For example, if the pond is shallow and has a sandy bottom it could be inhabited by sponges, earthworms, snails and insects. The bottom of quiet, standing water ponds are characterized as muddy or silty, and life represented in these types of ponds are crayfish, and the nymphs of mayflies, dragonflies, and microorganisms. These animals usually burrow into the bottom muds.
If the water in the pond is turbid, conditions at the bottom of the sea is extremely different from that in the opened waters because light does not penetrate to the bottom and plants cannot grow. Due to the lack of vegetation, the availability of shelter for animals is almost null. The amount of dissolved oxygen will be low, and the concentration of carbon dioxide will be high. Despite all of the previously mentioned conditions, animals such as earthworms, small clams, and fly larvae such as bloodworms and phantoms can survive in the deep bottom zone. There is usually a large amount of bacteria in this zone because they can survive off of dead organic matter.
The littoral habitat extends from the waters edge outward as far as rooted plants grow. This is the richest area in the pond community because of the plant life that exist in this area. The observer will find unlimited amounts of biotic life. Typically, there are three distinct borders of flowering plants that makes up the littoral habitat: the emergent plant zone; floating plant zone; and submersed plant zone. If the shore is rocky, plants may not grow in this area. Therefore, some ponds may have two distinct borders of flowering plants.
The emergent plant zone is closest to the shore. The observer will find plants that are rooted to the bottom. Their stems and leaves appear above the surface. The emergent zone should be bountiful with grasses, sedges, rushes, and algae. Along with the plant life, the observer will find animals such as protozoans, worms, insects, snails, and small fishes.
The floating-leaf plant zone is made up of broad, flat-leaved water lilies, water ferns, and duckweed. If the observer picks up one of the leaves, animals such as snails, bugs, and mayflies, larvae and eggs may be located underneath them. A variety of algae can be found in this zone. Most water animals use this area for breeding and nesting.
The submersed plant zone is the area of vegetation that surrounds the center of the pond. The plants in this area all have leaves that are long and slender, or bushy and branched leaves. Pondweed, waterweeds, and hornwarts are some of the flowering plants found in this zone. The flowers of these plants are pollinated above the water surface. The seeds of these plants germinate and the plants develop underneath the water.
B. Food Webs and Chains
As ecosystems have living and nonliving parts. The living, or biotic part, of an ecosystem is known as the ecological community. Living things interact with each other by feeding on one another. Therefore, energy, compounds, and chemical elements are transferred from creature to creature along the food chains.
Food chains group organisms into trophic levels. A trophic level include all the organisms in a food chain that are the same number of steps away from the original source of energy. Therefore, green plants are in the first trophic level and plant eating animals (herbivores) are placed in the second level. The third trophic level consists of carnivores (meat eating animals) that feed on herbivores. The fourth trophic level consists of carnivores that feed on the animals from the third trophic level, etc.
For example, trophic levels that exist within the pond community could be diagrammed as follows:
(1) First Trophic Level—green plants such as phytoplankton, algae, microscopic plants, pond lilies, etc. which manufactures food through photosynthesis.
(2) Second Trophic Level—herbivores such as mayflies, small crustaceans, nymphs, and certain types of beetles that feed on the plants in level one.
(3) Third Trophic Level—carnivores such as fish who consume plants and animals from the first and second trophic levels.
C. The Ecological Makeup Of A Pond
The components of a pond ecosystems are very diverse, but it can be divided into several basic units: (1) abiotic substances; (2) producer organisms; (3) macroconsumer organisms; and (4) saprotrophic organisms.
The abiotic substances that make up the pond includes basic inorganic and organic substances such as water, carbon dioxide, oxygen, phosphorus salts, amino acids and nitrogen. Small portions of the necessary nutrients that organisms need in order to survive in the water is always available. The rate at which these nutrients are released into the water are regulated by the temperature cycle (seasons), the amount and availability of sunlight, and the climatic regimes.
There are two different kinds of producer organisms that make up a pond: (1) small minute and/or microscopic floating plants call phytoplankton. The word phytoplankton comes from the prefix “phyto” which means plant and the suffix “plankton” which means floating. If the pond produces a large amount of algae, the water will have a green coloration. This can be hazardous to the pond community. Phytoplankton can be found all over the pond, as long as there is sunlight to sustain its life. Algae are a good example of phytoplankton. The second type of producer organism are the rooted or large floating plants which are found growing in the shallow water area.
Fish, crustaceans, and insect larvae is are examples of the macroconsumer organisms that can be found in a pond. The primary macroconsumers consist of zooplankton and benthos. They are herbivores that feeds directly on living plants and the remains of those plants. The secondary consumers consist of carnivores (insects and game fish) which feeds on the primary consumers.
Saprotrophic organisms are the aquatic bacteria, fungi, and flagellates which are widely distributed throughout the pond. Large numbers of these organisms can be found in the mud at the bottom of the pond where dead plants and animals accumulate. Under the correct climatic conditions, decomposition of the dead matter occurs rapidly. Some saprotrophic organisms are pathogenic because they have the ability to cause diseases in other living organisms. However, most of these organisms only feed on dead organic matter.