I found this when browsing the web, it won't let me copy and paste so I'll type it.
I find it interesting and thought provoking, just how complex nature is and how even the smallest contributes to the whole.
What price does nature pay for mans overuse of chemicals?.

Life In A Pond
A pond ecosystem, a basic unit in ecology formed from the cohabitation of plants, animals, microorganisms, and a surrounding environment, refers to a community of freshwater organisms largely dependent on each of the surviving species to maintain a life cycle. A pond ecosystem consists of algae, fungi,microorganisms,, plants and various fish, which may fall into three distinct classifications, producer, consumer and decomposer. The ponds natural cycle begins with the producer and then to the consumers before ending with the decomposers.

A ponds ecosystem consists of abiotic environmental factors and biotic communities of organisms.
Abiotic environmental factors of a ponds ecosystem include temperature, flow and salinity. the percentage of dissolved oxygen levels in a body of water determines what kind of organisms will grow there. Fish need dissolved oxygen in order to survive, however, anaerobic bacteria will not thrive in an ecosystem pumped with dissolved oxygen. Salinity may also determine the different species present. Freshwater organisms will not thrive when exposed to salt. in fact, freshwater ecosystems often have plant species present which will absorb salts that are dangerous for freshwater organisms.

A ponds ecosystem consists of four habitats, including the shore, surface film, open water and bottom water. the shore, depending on it's rocky, sandy or muddy composition lures in various organisms. Rocky shores may not allow plants to grow, while muddy or sandy shores attract grasses, algae, earthworms, snails, protozoa, insects, small fish and microorganisms.
The ponds surface is an excellent place for water striders, free floating organisms and organisms that can walk on the water surface.
An open water habitat permits sizable fish, plankton, phytoplankton and zoo plankton to grow.
Phytoplankton includes a large variety of algae, while zooplankton refers to insect larvae, rotifers, small crustaceans and invertebrates.
A ponds ecosystem food chain has three basic levels. Producers prepare their own food with the energy from the sun by a process of photosynthesis.The second trophic level consists of herbivores, such as insects, crustaceans and invertebrates that inhabit the pond and consume the vegetable matter.
Third level comprise of carnivores, such as fish, which feed on both the plants and herbivores atop the first and second trophic levels. Saprotropic organisms, also known as decomposers located at the bottom of the food chain,help decompose dead organic matter which further breaks down into carbon dioxide and essential nutrients such as nitrogen, phosphorus and magnesium. These nutrients supply the necessary life force for the first trophic level organisms to produce the food for the second trophic level organisms which results in the perpetual flow of energy in the ponds ecosystem.

You can see that by damaging any one of those parts of the ecosystem can interrupt or break the cycle that is essential to a thriving water habitat.