Glossary

Airshed - The area from which most airborne particles emanate. The Chesapeake Bay's airshed extends west as far as Ohio.

Algae - A group of non-vascular aquatic plants, most of which have chlorophyll; often referred to interchangeably as phytoplankton.

Anoxia - A complete depletion of oxygen in the aquatic environment. Anoxia occurs in the Bay's deepest waters, especially during summer.

Anthropogenic - Referring to the influence of human beings on the environment.

Atrazine - An organic herbicide, used widely in the cultivation of corn and sorghum, that can have deleterious effects on some species of underwater grasses.

Benthic organisms - Refers to organisms that live in or on the bottom of the aquatic environment (e.g., bacteria, rooted grasses, worms, oysters, clams). Referred to collectively as members of the benthos.

Bioavailibility - Describes whether a contaminant is available for uptake by living organisms.

CBEEC - Chesapeake Bay Environmental Effects Committee, the committee which oversees the Toxics Research Program, funded by the National Oceanic and Atmospheric Administration (NOAA).

CCA - A compound containing copper, chromium and arsenic (chromated copper arsenate) that is used to treat wood, including wooden bulkheads.

Chlordane - A powerful pesticide once used to treat termites and other insects, but now banned. Highly resistant to degradation.

Complexation - The joining of elements (e.g., chemical contaminants) with other elements or compounds, generally rendering them less available for uptake by living organisms.

Copepods - A small planktonic crustacean vital to the food web in the Chesapeake.

DDT - Dichlorodiphenyltrichloroethane, a polychlorinated pesticide banned in the U.S. since 1972.

DEN - Also called DENA, n-nitrosodiethylamine is a well known mammalian carcinogen; it has been shown to increase an oyster's susceptibility to Dermo disease (Perkinsus marinus).

Dermo - A parasitic disease agent, Perkinsus marinus, that has caused extensive mortality on Chesapeake Bay oyster reefs and elsewhere.

Diagenesis - A term for characterizing the physical and chemical processes that alter sediments during the interval between deposition and final lithification.

Diffuse sources - Sources of contaminants to an aquatic environment that are not derived from a single, discrete (point) source, but are derived from multiple sources such as storm drains, groundwater seepage and septic tanks.

Dimilin - An organic pesticide, diflubenzuron, that acts as a growth inhibitor. Dimilin is used in parts of the Chesapeake region to control the Gypsy moth and adversely affects crustaceans (e.g., copepods, amphipods, shrimps, crabs).

Ecotoxin - Toxicants that adversely impact ecosystems.

EH - Redox potential. See oxygen reduction.

EPA - Environmental Protection Agency

Eutrophication - The process of nutrient overenrichment in aquatic ecosystems. In the Chesapeake, eutrophication and a resulting increase of phytoplankton biomass has contributed to oxygen depletion.

Flocculation - The physical process whereby particles such as sediments are joined together.

Food web - Refers to the flow of energy through an ecosystem via successive steps or trophic levels.

HOCs - Halogenated organic compounds.

Hydrolysis - Occurs when a compound reacts with water, essentially the chemical breakdown by the addition of water to replace a covalent bond.

Hypoxia - The presence of very low dissolved oxygen in the aquatic environment, usually considered to be dissolved oxygen concentrations ranging between 2 to 0 mgO2 L-1.

Kepone - A potent pesticide, well known because of a large spill by the Allied Chemical Company into the James River.

NOAA - National Oceanic and Atmospheric Administration.

Oxygen reduction - Often referred to as "redox potential." This is a measure of reducing or oxidizing capacity of sediments, etc.

PAHs - Polycyclic aromatic hydrocarbons, a large class of chemicals generated by the burning of fuels such as coal, gas, wood, charcoal, gasoline and diesel.

PCBs - Polychlorinated biphenyls, a type of complex chlorinated hydrocarbon which is very stable and highly persistent in the environment; although now outlawed they are widely distributed and were extensively used in manufacturing industries.

Pelagic organisms - Organisms that live within the water column of aquatic environments (e.g., phytoplankton, zooplankton, fish) in contrast to those live on the bottom (benthic).

Penta-chlorophenol - A chemical used as a wood preservative. A halogenated ring structure that like of PCBs, PPT and Chlordane, it is highly resistant to degradation.

Petrogenic - A contaminant produced from unburned petroleum products.

pH - A measure of acid or base, as determined by the hydrogen ion concentration.

Plankton (phytoplankton and zooplankton) - A diverse group of minute animals (zooplankton) and plants (phytoplankton) that freely drift in the water.

Point source - A single direct source of a contaminant such as an oil spill or sewage outfall. Contrasts with diffuse source.

Pyrogenic - A contaminant produced from the combustion of fossil fuels.

Redox (or redox potential) - See oxygen reduction.

Regions of Concern - Areas in the Chesapeake Bay with acute toxic contamination such as the Baltimore Harbor, Elizabeth River and Anacostia River.

SAV - Submerged aquatic vegetation, important but badly degraded bottom habitat in the Chesapeake Bay and its tributaries.

Simazine -Like Atrazine, one of the s-triazine herbicides used in agriculture; its mechanism of toxicity is based on photosynthesis inhibition.

Speciation - The form or "species" taken by a metal. Metals such as copper can appear in numerous forms in the Chesapeake Bay, some far more toxic than others.

TBT - Tributyltin, a potent anti-fouling paint largely banned because of its toxicity, but with some exemptions (e.g., for military vessels).

TRI - Toxics Release Inventory, a list of 650 chemicals used by industry and an annual accounting of their releases into the environment; created in 1986 as part of the Community Right To Know Act.

Watershed - The drainage basin of a creek, stream, river or bay. The watershed of the Chesapeake Bay covers 64,000 square miles in six states.

For more information, report problems or provide comments, please contact: webmaster@mdsg.umd.edu