A | B | C | D | E | F | G | H | I | J | K | L | M
N | O | P | Q | R | S | T | U | V | W | X | Y | Z


Salinity– A measure of salt concentration in marine waters, ranging from zero to about 33 parts per thousand (ppt) in estuaries.

Salt Marsh– A type of wetland found in high salinity (30-35 ppt) areas along protected estuary shorelines. Prevalent plant species include Spartina alterniflora (smooth cordgrass), Batis maritima (saltwort), Distichlis spicata (saltgrass), and Salicornia sp. (glasswort).

Sanitary Sewer– Underground pipes that carry off only domestic (household, human) or industrial waste, not storm water.

Sanitary Sewer Overflow– Discharge of untreated sewage directly to streams and the bay from wastewater collection systems typically due to heavy rainfall events where the capacity of the system is exceeded or due system malfunctions.

Seafood Advisory– Warning issued by a public health authority recommending avoidance or reduced intake of certain species of seafood that may pose health risks to consumers.

Seafood Risk Assessment– Qualitative and quantitative evaluation of the risk posed to human health and/or the environment by the actual or potential presence and/or use of specific pollutants in seafood.

Seagrass– Rooted, submerged marine or estuarine macrophytes of several species. Habitats created by seagrass meadows are among the most diverse and productive estuarine environments. Loss of seagrass has become a marine conservation issue Gulf?wide.

Secondary Consumer– Predator that derives its energy from eating plant?eaters (primary consumers).

Sediment– Soil, sand, clay, silt and plant matter washed from land into water, usually after rain. They pile up in reservoirs, rivers and harbors, destroying fish and wildlife habitat, and clouding the water so that sunlight cannot reach aquatic plants. Careless farming, mining, and construction activities will expose sediment materials, allowing them to wash off the land after rainfall.

Sewage– Sanitary wastewater or wastewater generated by commercial or industrial operations but does not include storm water.

Sewage Bypass– Discharge of untreated sewage directly to streams and the bay from wastewater treatment facilities typically due to heavy rainfall events where the capacity of the system is exceeded or due system malfunctions.

Shellfish– An aquatic invertebrate animal with a shell such as mollusks or crustaceans, e.g. shrimp and crabs.

Shoreline Erosion– Loss of the shoreline and associated vegetation due to natural causes such as wave action, storms, relative sea level rise, and bluff failure. Erosion can be exacerbated by man-made causes such as boat wakes, dredging, accelerated subsidence and shoreline modification. Results in the conversion of vegetated fringing wetlands to open water.

Shoreline Modification– Modification, often detrimental, of shorelines by dredging, channelization and the placement of rip rap, bulkheads, seawalls and groins.

Spat– An oyster life cycle term; oysters during early growth on a hard substrate. The spat set is the process of settling and attachment of planktonic larvae and onset of shell growth, establishing new recruitment on a reef.

Species– A reproductively isolated aggregate of interbreeding organisms having common attributes and usually designated by a common name; an organism belonging to belonging to such a category.

Stakeholder– An individual or organization with a “stake” in a natural resource or other issue by virtue of livelihood or simple personal interest.

Storm Sewer– A system of pipes (separate from sanitary sewers) that carries water runoff from buildings and land surfaces.

Storm Water Management Program– A program comprising six elements that, when implemented in concert, are expected to result in significant reductions of non-point source pollutants discharged into receiving water bodies. The six elements are: (1) public education and outreach, (2) public involvement, (3) illicit discharge detection and elimination, (4) construction site runoff control, (5) post-construction runoff control and (6) pollution prevention.

Submerged Aquatic Vegetation (SAV)– Rooted, submerged macrophytes, including seagrasses and freshwater rooted macrophytes; contrasts with emergent species such as smooth cordgrass.

Subsidence– The loss of land elevation due to groundwater or petroleum withdrawal and natural settling. Groundwater withdrawal has been the most important contributor to subsidence for up to nine feet in the Galveston Bay region.

Subtidal– Below the low tide line, submerged virtually continuously; contrasts with intertidal, which is the area intermittently submerged.

Subwatershed– A subdivision of a watershed based on hydrology, generally corresponding to the area drained by a small tributary or bayou, as opposed to a major river.

Suspension Feeder– An organism that feeds on materials in water suspension, for example oysters which filter plankton.

Swamp– A type of freshwater wetland consisting of woodland or forested areas with saturated soils, which are inundated by water much of the year. Plant species include Taxodium distichum (baldcypress) and Nyssa aquatica (water tupelo).


Terrestrial– Refers to land, as opposed to the aquatic or marine environment.

Threatened Species– Threatened means a species is likely to become endangered within the foreseeable future. Requirements for declaring a species endangered are contained in the Endangered Species Act.

Total Maximum Daily Load (TMDL)– The total amount of a pollutant a water body can accumulate and still meet state water quality standards.

Toxic– Capable of causing death, disease, or birth defects in organisms.

Toxicant– An element or compound with a negative effect on physiology or behavior of an organism.

Texas Pollutant Discharge Elimination System (TPDES)– Texas’ state water quality program administered by the TNRCC; authorized by the USEPA in September 1998; it has federal regulatory authority over discharges of pollutants to Texas surface waters.

Tributary– A surface water drainage such as a stream, creek, bayou or river within the estuary watershed.

Trophic Level The position in the food chain relative to eating and being eaten; including primary producers, primary consumers, and higher consumers.

Turbidity– The relative lack of clarity (cloudiness) of water, caused by suspended material (e.g. sediments), colored materials in solution, and plankton. Turbidity correlates (inversely) with available light for photosynthesis; can be measured with a transmissometer.


Upland– ground elevated above wetlands and open water.

Upper Galveston Bay Watershed– Galveston Bay actually has two large “upper watersheds,” consisting of 2,828 square miles upstream of Lake Houston on the San Jacinto River and 26,000 square miles upstream of Lake Livingston on the Trinity River.


Vibrio– Genus of bacteria containing 11 naturally?occurring species, some of which have the potential to cause rapid and sometimes life?threatening infections in humans. Vibrio vulnificus, an estuarine species, favors warm saline conditions in Texas bays.

Viral– caused by a virus, a submicroscopic infectious agent that is regarded as either an extremely simple microorganism or a very complex molecule.


Wastewater Collection System– The system of pipes and pumping stations (lift stations) used to collect and carry wastewater from individual sources wastewater treatment facility.

Water Column The portion of an aquatic or marine environment extending from the water surface to the bottom.

Water Exchange– The transport of waters into and out of the bay; exchange of waters of the bay with that of the Gulf of Mexico and tributaries through the forces of tide and freshwater inflow.

Watershed The land area drained by a river or stream. The watershed is the natural hydrologic unit associated with numerous ecological and physical processes involving water. Increasingly, the watershed is being accepted as the most appropriate geographic unit for management of water quality.

Wetland An area where saturation with water is the dominant influence on characteristics of the soil and on composition of the plant community.


Zooplankton– Animals that are suspended in and move within the water column.