Glossary

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

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Accretion
Accumulation of sediments by deposition, as for a river delta or along a shoreline.

The clearing of forested wetland for crop production and plant nurseries

Algea Bloom
Population explosion of phytoplankton in response to changing environmental conditions, including nutrient over-enrichment from wastewater and non-point sources. Blooms can result in oxygen depletion and biological impacts.

Ambient
Prevailing environmental conditions, as opposed (for example) to measurement in a laboratory or waste stream. In an estuary, ambient conditions are receiving water conditions in the bay itself, representing an integration of the various sources of impact to the system.

Anaerobic
Lacking oxygen, for example submerged sediments below a narrow oxygenated layer. Also refers to metabolic function in the absence of oxygen, present in some microbe species.

Assimilative Capacity
The amount of pollution a water body can receive without degradation, as a result of the natural ability of the water and its associated chemical and biological systems to dilute or transform contaminants.

Atmospheric Deposition
The contribution of atmospheric pollutants or chemical constituents to land or water ecosystems. Deposition results from materials in rain or snowfall, combined with dry dust fallout. Increasingly, atmospheric sources are recognized as a significant source of nutrients and contaminants to coastal systems.

Autotrophic
A species or ecosystem sustained entirely by food created within, for example a green plant or an estuary which is a net exporter of organic matter. Contrasts with heterotrophic a species or ecosystem which imports energy (e.g. a predator or estuary which receives substantial organic matter from upstream).

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

Berm
An elongated ridge elevated above the surrounding area; could be natural (for example an underwater long shore bar created by currents) or man-made (a ridge of sediment disposed along a navigation channel or an upland feature constructed to manage runoff).

Biomass
Physical mass (weight) of living tissue. This is a biological measurement used to establish the importance of certain groups of living things in an ecosystem, as opposed to numbers of individuals. For example, the biomass of phytoplankton (standing crop) is an important measurement in describing an estuarine food chain.

Bioturbation
The disturbance of sediments due to displacement by living things. For example, bioturbation resulting from burrowing of organisms in the benthic habitat increases sediment aeration and influences contaminant equilibria with the overlying water.

Blue-Green Algae
Primitive algae with a bacteria-like cell structure, lacking a nucleus and other organelles. These species manufacture photosynthetic pigments but lack chloroplasts (the specialized photosynthetic organelles in higher plants). In some situations, an increase in blue-green algae can indicate an environmental stress such as pollution.

Blowouts
A shallow depression formed by wind erosion on loosely consolidated sediments and soils.  These depressions maybe in various shapes, such as a saucer, cup, or trough.   Blowouts are found on flats and slopes where there is little vegetation to hold the sand or sediment in place.

Bulkhead
A man-made vertical wall on the shoreline which replaces the natural gradual depth gradient. Bulkheads are normally constructed to stabilize shorelines and prevent wave damage to upland property.

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Channelization
The conversion of shallow coastal areas to deeper dredged navigation channels.

Contact Recreation
Human activity involving bodily contact with water, and therefore the potential for increased risk to health when contaminants or pathogens are present. In Galveston Bay, contact activities like wade-fishing and sail-boarding are more common than swimming, traditionally perceived as the principle form of contact recreation.

Cordgrass
Group of several wetland plant species common to both brackish and salt estuarine marshes. Smooth cordgrass, Spartina alterniflora, is the dominant plant species of the fringing salt marshes of the Gulf Coast.

Crustacean
Member of the aquatic class Crustacea of the phylum Arthropoda. A heterogeneous and important estuarine group including shrimp, crabs, barnacles, and others.

Cubic Feet Per Second (cfs)
Standard unit for measurement of stream flow or wastewater discharge.

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Decomposer
An organism which consumes dead organic matter. Decomposers are a major (perhaps dominant) component of the estuarine food chain.

Delta
The fan-shaped mass of sediments deposited where a river discharges to a larger, slower moving water body. Deltas are important for their wetland habitat values.

Denivellation
Wind forcing of water resulting in water depth changes. Denivellation in Texas estuaries can produce more extreme water level fluctuations than do tides.

Density Current
Currents resulting from salt water being heavier than fresh water. For example, seawater from the Gulf intrudes landward along the bottom of the Houston Ship Channel, displacing lighter, fresher waters seaward.

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

Diurnal Tide
Tide occurring on a cycle of once daily.

Diversity
A measure of the variety of living things in a community, based upon one of several mathematical formulae which account for both numbers of species and numbers of individuals within species. High diversity results from high numbers of species and an even distribution of numbers within species. Stressed environments generally have low diversity.

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Ecological Niche
The way a species' makes its living'; where it lives, what it consumes, and how it avoids consumption by predators or displacement by other species.

Ecosystem
A natural system including the sum total of all living things, the non-living environment and its physical forces, and the relationships among these, including processes such as predation, competition, energy flow, and nutrient cycling. An estuary is an ecosystem.

Ecotourism
Tourism supported by natural ecological attributes of an area, for example bird-watching.

Effluent Waste
Water discharged to a receiving water.

Embayment
Portions of open water or marsh defined by natural topographical features such as points or islands, or by human structures such as dikes or channels.

Emergent Wetlands
Marshes in which vegetation is rooted underwater and the tops exposed (as contrasted with submerged vegetation or upland habitats).

Environmental Protection Agency
Develops and interprets environmental criteria used in evaluating permit applications determines scope of geographic jurisdiction approves and oversees State assumption identifies activities that are exempt reviews/comments on individual permit applications has authority to veto the Corps' permit decisions (Section 404[c]) can elevate specific cases (Section 404[q]) enforces Section 404 provisions. (www.epa.gov)

Epifauna
Organisms living on a surface, for example the bay bottom or submerged leaves of a rooted aquatic plant.

Epiphytic
Organisms growing on, and supported in part by a plant, for example epiphytic algae growing on the surface of submerged aquatic vascular plants.

Estuary
A semi-enclosed body of water having a free connection with the open sea and within which seawater is diluted measurably by fresh water from land drainage.

Estuarine Debris
Trash in a bay or along its shoreline. Debris consists of tires, construction wastes, household trash, and above all, plastic. Debris degrades aesthetic values and represents a hazard to wildlife (e.g. entanglement or mistaken consumption as food).

Eutrophication
A process of nutrient over-enrichment of a water body, resulting in overgrowth of algae, frequently followed by algae die-offs and oxygen depletion.

Evapotranspiration
Uptake of water by living plants, transport to leaf surfaces, and evaporation to the atmosphere.

Exotic Species
Species not native to an ecosystem, often established purposefully or inadvertently by human activity. Some exotic species have fewer natural population controls in their new environment, becoming a pest or nuisance species.

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Fecal Coliform Bacteria
Enteric bacteria which ferment lactose with gas and acid formation at a temperature typical of warm-blooded animals. In water, fecal coliforms are commonly used as an indicator of contamination, and are normally measured using filtration and culture on disk media (also refer to Most Probable Number).

Flushing
The natural process of water replacement in an estuary; for example Galveston Bay is flushed four to five times per year by river water and other runoff.

Freshet
An influx of fresh water inflow, for example following seasonally high precipitation.

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Geographic Information System (GIS)
A computer system which links geographic reference data to attribute data sets, with the capability to display features and analytical outcomes on maps. GIS tools are increasingly being applied to ecosystem, watershed, and landscape studies, both in ecological research and for environmental management planning.

Green Algae
A common algae type in estuaries, with nucleated cells and photosynthetic pigments contained in organelles called chloroplasts.

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Habitat
The environment chosen by a species to live in, providing life requisites such as food and shelter.

Hydrologic Cycle
The continuous cycle of water in the biosphere as solid, liquid, and gas. Marked by evaporation from oceans to the atmosphere, precipitation to the earth's surface, replenishment of groundwater, runoff, uptake by plants, and storage in oceans and ice caps.

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Impervious Cover
Land surfaces with a low capacity for soil infiltration, for example paving, roofs, roadways, or other human structures. The presence of impervious cover increases runoff and affects the quantity and composition of nonpoint source.

Indicator Species
A species which, through its population size or condition, mirrors environmental conditions within an ecosystem. For example, eastern oysters are a good indicator species in estuaries by virtue of their wide distribution, inability to move about, and sensitivity to conditions of interest like salinity and contaminant concentrations.

Infauna
Animals living within submerged sediments.

Inflow
The water feeding an estuary, generally referring to river sources.

Intertidal
The portion of shoreline between low and high tide lines, intermittently submerged.

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Loading
The rate of introduction of a constituent (e.g. contaminant) to a receiving water, for example in pounds per day. Loading is significant in relation to the volume and circulation of the receiving water; problems occur when high loadings occur into receiving waters with limited assimilative capacity.

Longshore Drift
The movement of water and suspended and dissolved materials along and parallel to a shoreline as a result of tidal, wind-driven, or other currents.

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National Pollution Discharge Elimination System (NPDES)
A regulatory program created under the Water Quality Act and administered by the EPA. The NPDES was originally enacted to eliminate all point source pollution by the mid-1980s through a process of wastewater permitting and regulation. The program, while not successful in eliminating point source pollution, has done much to improve water quality in the U.S.

Nonpoint Source (NPS)
Constituents in water (including pollutants) originating from diffuse, land-based sources, and generally transported in runoff from precipitation. This contrasts with point sources, or 'end of the pipe' constituents generally transported in wastewater from a discrete source. The regulatory definition of nonpoint source is 'anything not a point source'.

Nutrient Cycle
Chemical transformation of nitrogen, phosphorus and silica compounds in continuous cycles of organic and inorganic phases in an ecosystem.

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Outfall
The discharge point for a wastewater stream, for example from a sewage treatment plant or refinery.

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Palustrine
Relating to a freshwater environment, for example a fresh marsh.

Photic zone
The upper portion of the water column admitting sufficient light for photosynthesis. The photic zone is reduced with increased turbidity, and in Texas estuaries, rarely reaches the bottom in open bays.

Photosynthesis
The incorporation of solar energy into carbon compounds by green plants, chemically combining atmospheric carbon dioxide and water. The chemical opposite of respiration (the 'burning' of carbon compounds to power metabolism), ultimately powering the vast majority of life on earth.

Phytoplankton
Green plants (for example algae) inhabiting waters, unattached and drifting with the currents.

Primary Producer
Green plants capable of photosynthesis; the base of the food chain.

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Red Tide
Algae bloom involving dinoflagellate phytoplankton species which naturally manufacture biotoxins. Depending upon species, red tides can cause fish kills and several types of shellfish poisoning in human consumers.

Residence Time
The period of time water is retained in a reservoir, bay, or other system, based upon flow rates into and out of the system. Also refer to flushing.

Resuspension
Incorporation of non-soluble matter into water by physical forces, for example sediments resuspended by currents or dredging activity.

Return
Flow Wastewater discharged to an aquatic or marine environment. Return flows can alter hydrology and fresh water inflow when the original source of the water was not the receiving water (for example groundwater discharge to an estuary as wastewater).

Riparian
Associated with the bank of a watercourse, for example the riparian woodlands bordering a river.

Riprap
Rock, concrete, or other material used as a hard, artificial shoreline facing to reduce erosion.

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Salinity
Salt concentration in marine waters, ranging from zero to about 33 parts per thousand (ppt) in estuaries. Salinity originated as an oceanographic term and does not have a precise chemical definition, since the proportions of various ions vary in the different waters of the world.

Salinity Gradient
A spatial salinity transition, for example from a fresh river mouth to ocean inlet. 'Steep' gradients can occur between adjacent water masses of differing salinity, as occurs in a density current.

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 seagrasses have become a marine conservation issue Gulf-wide.

Shoaling
Decrease in water depth due to sediments deposited by currents, for example at an inlet.

Siltation
The accumulation of sediments transported by water. Siltation is an ongoing process of one to three feet accumulation per century in Galveston Bay.

Spat
Young 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.

Storm Surge
The increase in water depth caused by a Hurricane, due to a combination of low atmospheric pressure (which creates a 'bulge' in surface waters) and wind-piling of water. Serious damage can result after a storm surge moves onshore, as waters rush back to their source.

Stratification
Vertical separation of water masses into layers with different characteristics. For example, dense salt water intruding under fresher water in a navigation channel can establish salinity stratification.

Stress Proteins
Proteins synthesized by aquatic organisms as a physiological response to environmental stress. Tissue analysis for stress proteins can be combined with other more traditional measurements to indicate the presence of environmental contamination.

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 of 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.

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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.

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Washover Fan
The fan-shaped deposits of sediment resulting from deposition by water currents, for example when a storm surge breaches a barrier island.

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.

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Sources for Glossary:

Smith, M. F. Jr., ed. 1984. Ecological characterization atlas of coastal Alabama: map narrative. U.S. Fish Wildlife Service. FWS/OBS-82/46; Mineral Management Service. MMS 84-0052. 182 pp. + 30 maps.

Environmental Protection Agency. Available: http://www.epa.gov/OWOW/wetlands/wet10.html

Galveston Bay National Wetland Program - Available: http://ricenfo.rice.edu/armadillo/Galveston/Glossary/glossary.html

Glossary Available: http://ricenfo.rice.edu/armadillo/Galveston/Glossary/glossary.html