ABSTRACT
For all practical purposes, water pollution is the addition by humans of something to the water that alters its chemical composition, temperature, or microbial composition to such an extent that harm occurs to resident organisms or to humans. In locations where there is agricultural runoff or non-biodegradable detergents being added to the water, the growth of phytoplankton is stimulated due to excess amounts of plant nutrients. The conditions producing a low dissolved oxygen concentration and toxic chemicals are the most important types of water pollution that affect fish. An important problem when working with metals in water is that they tend to complex with organic and inorganic chemicals and this may reduce their bioavailability to resident organisms. Toxic chemicals in the environment tend to accumulate in particular organs but the organs most affected by that chemical are not necessarily the ones with the highest concentration.
