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.
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