dead zones: areas of low-oxygen water in the aquatic environment, often caused by decomposition of vast algal blooms.
decomposers: organisms such as bacteria, fungi, earthworms and vultures that feed on dead animals and plants, as well as other organic wastes and cause them to break down physically and chemically.
detergents: a product designed to render, for example, oils and greases soluble in water, usually made from synthetics that lower the surface tension of a solvent (usually water).
detritus: parts of dead organisms and cast-off fragments and wastes of living organisms.
developed country: a country with a relatively high per capita income, where most people have a higher standard of living with access to more goods and services than most people in developing countries.
developing country: a country with a relatively low per capita income, where most people have a lower standard of living with access to fewer goods and services than most people in developed countries. Also known as a third-world country.
diarrhea: frequent, loose bowel movements.
dissolved oxygen: a measure of the amount of oxygen available for biochemical activity in a body of water. The amount of dissolved oxygen can serve as an indicator for water quality.
drinking water standards: standards set under the authority of the Safe Drinking Water Act by the Environmental Protection Agency for approximately 90 contaminants in drinking water.
dysentery: an infection of the intestines marked by fever and severe diarrhea, often accompanied by blood and mucus.