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Algae– Simple rootless plants that grow in sunlit waters in proportion to the amount of available nutrients. They can affect water quality adversely by lowering the dissolved oxygen in the water. They are food for fish and small aquatic animals.

Algal Bloom– Population explosion of phytoplankton in response to optimal growth conditions, including nutrient over?enrichment from wastewater and nonpoint sources. Blooms can result in oxygen depletion and biological impacts; see also eutrophication.

Atmospheric Deposition– The contribution of atmospheric pollutants or chemical constituents to land or water ecosystems. Deposition can occur as a result of human activities (e.g. fossil fuel combustion, industrial processes and transportation) or natural processes (e.g. volcanic activity).


Bacteria– Microscopic living organisms that can aid in pollution control by metabolizing organic matter in sewage, oil spills or other pollutants. However, bacteria in soil, water or air can also cause human, animal and plant health problems.

Base Flow– The volume of flow in a stream or river during dry conditions (as opposed to conditions influenced by storm runoff).

Benthic Organism– An organism living primarily in or on bottom sediments.

Benthos– term for the organisms living in or on the bottom of a body of water.

Bioaccumulate The accumulation of a contaminant in the tissues of a living organism due to uptake from the environment.

Biochemical Oxygen Demand (BOD)– A measure of the amount of oxygen consumed by natural, biological and chemical processes that break down organic matter. High levels of oxygen-demanding wastes in waters deplete dissolved oxygen (DO) thereby endangering aquatic life.

Biological Productivity– The ability of a water body to support life such as plants, fish, and wildlife. Defined scientifically as the rate at which organic matter is produced.

Bivalve A mollusk with two hinged shells belonging to the class, Bivalvia (e.g. oysters, clams and scallops).

Brackish– Water with a salinity lower than that of seawater; seawater and freshwater mixed; typical of estuarine environments.

Brackish Marsh– A type of wetland found in the transitional zone between salt marsh and fresh marsh and is affected by a wide range of water levels and salinities (0.5-29 ppt). Usually dominated by Spartina patens (marshhay cordgrass) and Distichlis spicata (saltgrass).

Bulkhead– A man?made vertical wall constructed to stabilize shorelines and prevent wave damage to upland property.
By-catch– The incidental catch of one species during pursuit of another, the term is often applied to species of fish and shellfish captured incidentally by commercial fishing and shrimping operations.


Channelization– The conversion of a naturally flowing river or stream to a dredged drainage or navigation channel, often lined with concrete; channelization increases flow velocity, but negatively impacts stream ecology.

Clean Water Act– The Federal Water Pollution Control Act Amendments of 1972, as amended in 1977. The Act established the basic structure for regulating discharges of pollutants into the waters of the United States. It gave EPA the authority to implement pollution control programs such as setting wastewater standards for industry. The Clean Water Act also continued requirements to set water quality standards for all contaminants in surface waters. The Act made it unlawful for any person to discharge any pollutant from a point source into navigable waters, unless a permit was obtained under its provisions. It also funded the construction of sewage treatment plants under the construction grants program and recognized the need for planning to address the critical problems posed by non-point source pollution.

Colonial Waterbird– Birds, such as herons, egrets, gulls, terns, and ibises that nest in dense colonies.

Contact Recreation– Human activity involving bodily contact with water, e.g. wade fishing and swimming; increases the risk to health when contaminants or pathogens are present in the water.

Cordgrass– Any member of the genus, Spartina; a partially submerged wetland plant common to brackish and salt marshes of the Gulf Coast.

Crustacean– Any member of the Arthropod class, Crustacea, which includes shrimp, crabs, barnacles, and lobsters.


Dermo– A disease of oysters caused by the parasitic protozoan Perkinsus marinus; outbreaks are most severe during drought periods in high salinity estuarine waters.

Detritivore– An organism that derives nutrients and energy by consuming decaying organic matter.

Detritus– Decaying organic material.

Dioxin– Any of a family of compounds known chemically as dibenzo-p-dioxins. Concern about them arises from their potential toxicity as contaminants in commercial products. Tests on laboratory animals indicate that it is one of the more toxic anthropogenic (man-made) compounds.

Dissolved Oxygen (DO)– The oxygen freely available in water, vital to fish and other aquatic life and for the prevention of odors. DO levels are considered a most important indicator of a water body’s ability to support desirable aquatic life. Secondary and advanced waste treatment are generally designed to ensure adequate DO in waste-receiving waters.

Dredge-and-Fill Activity– Removal and subsequent discharge of dredged materials such as mud and sediments from the bottom of water bodies, including wetlands. This can disturb the ecosystem and causes silting that can kill aquatic life. Additionally, dredging of contaminated muds and sediments can expose living organisms to heavy metals and other toxicants. Dredge-and-fill activities may be subject to regulation under Section 404 of the Clean Water Act.