Estuary Glossary

Estuary background image with color overlay


Abiotic factors (abiotic): non-living characteristics of a habitat or ecosystem that affect organisms' life processes.

Adaptation (adapt): a genetically-based body feature or behavior that allows an organism to be better suited to its environment.

Aerobic: with air, oxygen.

Algae: chlorophyll containing non-vascular organisms, plant or plant-like.

Anadromous: fish that live their adult lives in the ocean but move into freshwater streams to reproduce or spawn (for example: salmon).

Anerobic: without air, no oxygen.

Anoxic: without oxygen, anaerobic.

Anthropogenic: arising from human activity.

Aquatic organisms: organisms that live in or on the water.

Arthropod: any of a phylum (Arthropoda) of invertebrates (as insects, arachnids, and crustaceans) that have a segmented body and jointed appendages.

Autotrophs: an organism that makes its own food from light energy or chemical energy without eating. Most green plants, many protists and most bacteria are autotrophs. Autotrophs are the base of the food chain and can also be called producers.

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Back dune: area immediately behind fore dune; inhabited by mixture of grasses, beach heather and lichen.

Ballast water: water carried in ship's for stability. Water is pumped into a ship's hold to steady it; when the water is released in other oceans the organisms in it may become pests (or invasives).

Bar-built estuaries: areas where sandbars form parallel to the shore, partly enclosing the water behind them as the sandbars become islands.

Barrier beaches: spits of sand that form parallel to the shore.

Barrier islands: barrier beaches with a cross-section profile that often includes dunes, shrub thickets, maritime forests, and saltmarshes.

Beach/ocean interface: where waves meet beach.

Behavior: the way an animal acts, especially in response to something in its environment.

Benthic: relating to the ocean bottom.

Benthos: bottom-dwelling flora and fauna; from tiniest microbenthos (bacteria) to medium-sized meiobenthos (nematode worms) to the highly visible macrobenthos (clams, polychaete worms).

Biogeochemical cycle: natural processes that recycle nutrients in various forms from the environment, to organisms and then back to the environment. Also called nutrient cycle.

Bio-geographic region: is a geographic area with similar dominant plants, animals and prevailing climate.

Biotas: assemblages of living things.

Biotic factors (biotic): relationships among organisms that affect their survival.

BOD: biological oxygen demand. The amount of dissolved oxygen that will disappear from an enclosed water sample as aerobic bacteria decompose the organic material in the water.

Brackish: slightly salty water with a salinity between 0.5 ppt and 32 ppt.

Bycatch: unwanted fish or other animals caught in fishing nets by accident.

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Carnivores: animals that eat other animals as opposed to herbivores, which eat only plants.

Caudal fin: tail, provides forward mobility.

Chlorine: poisonous, gaseous substance.

Climate change: a regional change in temperature and weather patterns. Current science indicates a link between climate change over the last century and human activity, specifically the burning of fossil fuels.

Coastal plains estuary: estuary formed when rising sea level flooded existing river valley.

Coliform bacteria: bacteria commonly found in colon and used as an indicator of water contamination.

Commensalism: form of relationship in which one species gains from the interaction and the other is neither positively nor negatively affected.

Community: an association of interacting populations.

Commercial fishing: fishing for a commercial purpose, i.e. to sell the catch.

Competition: occurs between organisms using a finite resource, whether they are of the same or different species.

Condensation: the process in which water vapor changes into liquid water (such as dew, fog, or cloud droplets).

Conditions: characteristics of the environment that influence the survival of an organism but are not consumed by it (e.g., temperature, salinity).

Contamination: an undesirable element, impure or unclean, something that is not supposed to be there (such as oil or insecticides in water).

Conservation: careful preservation and protection of ecological processes and biodiversity of the environment.

Consumer: individual that eats other organisms to obtain energy rather than producing its food through photosynthesis or chemosynthesis.

Copepods: one of most common herbivorous zooplankton.

Countershading: coloration that features dark shading on the dorsal (top) side and light shading on the ventral (bottom) side, used as camouflage.

Crustaceans: anthropods having hard-shelled bodies and jointed ligaments such as crabs, shrimp and lobsters.

Currents: large-scale circulation of water caused by thermodynamics and winds.

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Decomposer: an organism that feeds on and breaks down dead plant or animal matter, thus making organic nutrients available to the ecosystem.

Delta: a low-lying sediment deposit found at the mouth of a river.

Density: the ratio of the mass of any substance to the volume occupied by it.

Desiccation: loss of water.

Detritus: newly dead or decaying organic matter coated with bacteria.

Diatoms: one of most common groups of phytoplankton; single-celled organism that reproduces asexually.

Diel: the daily cycle; a 24-hour period.

Dinoflagellates: common type of phytoplankton, most abundant in fall; responsible for “red tides” as well as bioluminescence.

Disturbance: any event that opens up space for colonization, such as the falling of a tree in a forest or removal of marsh grass by storm waves.

Diverse: of different kinds, types, or species.

Dorsal fin: fin(s) on dorsal or back side of a fish.

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Ebb: the falling tide when the water moves out to the sea and the water level lowers.

Ecosystem: the biotic community and its abiotic environment.

Eco-tourism: travel undertaken to witness sites or regions of unique natural or ecologic quality. Often it is environmentally responsible travel that benefits nature and local communities.

Epibenthos: organisms that live on the bottom, rather than burrowed into, of an aquatic system.

Elasmobranchs: approximately 400 species of fish, including sharks and rays that have skeletons made of cartilage.

Erode (erosion): the wearing away of the land by the action of water, ice or wind.

Estuarine: of or relating to an estuary.

Estuarine habitat: habitats associated with estuaries.

Estuary: a semi-enclosed body of water which has a free connection to the open sea and within which seawater is measurably diluted by fresh water derived from land drainage. Some unique Great Lakes coastal wetlands are referred to as freshwater estuaries. They occur where rivers and Great Lakes water mix in shallow wetlands located near the mouth of a river.

Euryhaline: able to live at a variety of salinities.

Eutrophication: process by which large additions of nutrients causes an overgrowth of algae and subsequent depletion of oxygen.

Evaporate: to change from liquid to vapor.

Exoskeleton: a hard outer covering.

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False-color map: an image that uses colors to represent differences in measured values, rather than true appearances.

Fjords: a glacial trough valley now flooded with seawater to create a steep-walled inlet.

Food chain: a representation of the flow of energy between producers, consumers, and decomposers.

Food web: a representation of the linkages between food chains in a community.

Foreshore: the area between mean low water and mean high water.

Frontal dune: the dune closest to the water's edge.

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Gastropod: one of a class of mollusks that includes the snails and nudibranchs.

Geologic time: the total time involved since formation of the earth to the present time. It spans millions or billions of years in the past.

Gill arch: the bone structure in the throat of fish that contains the gill rakers and filaments.

Gill raker: bony, finger-like projection in the throat of fish, used for food retention in some species.

Gills: respiration organs that absorb oxygen from the water.

Gravity: the force of attraction between all masses in the universe; especially the attraction of the earth's mass for bodies near its surface.

Groundwater: water contained below ground in soil and rock.

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Habitat: the place where an organism lives.

Haul-out: an area on the shore where marine mammals rest.

Herbivore: an animal that eats plants.

High marsh: the area of the marsh flooded infrequently by the high tides associated with new and full moon.

Human impact: impacts arising from human activity; often referring to negative impacts on the environment.

Hypothesis: a scientific idea about how something works, before the idea has been tested. Scientists do experiments to test a hypothesis and see if the hypothesis is correct.

Hypoxia (hypoxic): very low oxygen levels.

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Infauna: organisms living between the grains of sand or mud.

Isopods: aquatic crustaceans with flat, oval body and seven pairs of legs.

Intertidal: estuary habitat flooded by high tide waters only.

Invasive species: non-native species of plants or animals that out-compete native species in a specific habitat.

Invertebrate: an animal that does not have a backbone; such as snails, worms, and insects.

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Lateral Line: canal running along the sides of a fish that is used by the fish to sense movement and vibration in the water.

Light: energy source used by plants to form carbohydrates, an important abiotic factor.

Low marsh: the area of marsh flooded twice daily by tides and dominated by Spartina alterniflora in Gulf of Maine region.

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Macroalgae: large multicellular algae (green red and brown varieties).

Mangrove: tree species that grow in non-freezing estuaries. There are about 12 species though the black, red, and white are most common.

Maritime forest: forest dominated by pitch pine and located on the mainland side of a barrier beach or island.

Marshes: soft wet land usually characterized by grasses.

Mesohaline: intermediate levels of salinity, about 15ppt.

Metadata: the reference information about how the data is collected.

Migration (migratory): the movement of living organisms from one biome to another, commonly with changing seasons.

Mobile epibenthos: bottom-dwelling animals that move on top of sediments: crabs, shrimp, snails, amphipods, isopods.

Mollusks: soft bodied, shelled animals such as clams, oysters, nudibraches and octopi (the latter two have either small remnant shell within their bodies or an embryonic shell).

Monitoring (environmental monitoring): sampling of environment (air, water, soil, vegetation, animals) that is compared with baseline samples to see if any changes have occurred.

Monitoring station: an instrument that makes in situ measurements in the environment.

Mudflat: part of benthic (bottom) zone exposed at low tide and comprised of extremely fine sediments.

Mutualism: form of relationship in which both species involved gain from the interaction (example: lichen).

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National Estuarine Research Reserve System: network of 28 protected areas established for long-term research, education and coastal stewardship authorized as part of the Coastal Zone Management (CZM) Act of 1972, which called for the establishment of a network of estuaries that represent different biogeographical regions of the United States.

Natural selection: the differential survival and/or reproduction of individuals within a population based on hereditary characteristics.

Neap tides: average tides that occur between full and new moons.

Nekton: all aquatic animals that can swim through the water against currents: marine mammals, fish, squid and some crustaceans.

Niche: the role of a species within a community.

No-take zones: aquatic or coastal areas in which all extractive activities (such as fishing) are prohibited.

Non-point source pollution: water pollution arising from indistinct sources such as petroleum products from roadways or pesticides from farmland.

Nursery: term used colloquially to refer to estuaries. Many fish species are dependent on estuaries for part of their lives.

Nutrients: substances required by organisms in order to grow and survive such as nitrogen and phosphorus.

Nutrient cycle: natural processes that recycle nutrients in various forms from the environment, to organisms and then back to the environment. Also called biogeochemical cycle.

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Oligohaline: low salinity areas, 0-15 ppt.

Omnivores: animals that feed at several levels of food web; diet includes a mix of living and/or dead plants and animals.

Organic matter: materials and debris that originated as living plants or animals.

Organism: a living thing, such as animal, plant or micro-organism, that is capable of reproduction, growth and maintenance.

Oxygen: used in respiration, the process in which organisms release stored chemical energy.

Oxygen content: often referring to the oxygen content of water. The amount of oxygen dissolved in a given volume of water at a particular temperature and pressure.

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Panne: small pond or pool in the salt marsh.

Parameter: the thing that is being measured.

Parasitism: similar to predation in that one species benefits from the relationship and the other is harmed; differs from predation in that parasitism generally not fatal to adversely affected organism.

Peat: soil in marsh composed of partially decayed moisture-absorbing plant matter.

Pectoral fins: fins originating near the gills from the pectoral muscle area that stabilize and steer.

Pelagic: of or in the open ocean or open water; in the water column.

Petroleum derivatives: toxic pollutants from crude oil products; mixture of hydrocarbons, which are organic solvents.

Photosynthesis: process of using energy in sunlight to convert water and carbon dioxide into carbohydrates and oxygen.

Phytoplankton: floating plants or plant-like photosynthetic single cellular organisms.

Pioneer species: plant species that first invades unvegetated area.

Plankton: free-floating organisms drifting in water, unable to swim against currents.

Point source pollution: pollution from a clearly defined, localized source such as a sewage outfall.

Pollution: contamination of natural environment.

Polyhaline: high salinity about 30-335 ppt.

Polyps: often refered to as coral polyps. A small individual coral animal with a tube-shaped body and a mouth surrounded by tentacles.

Population: all the individuals of a particular species within a defined area.

Precipitation: rain, snow, sleet, freezing rain, mist.

Predation (predatory): the killing and/or consumption of living organisms by other living organisms.

Prey: an animal that is hunted, killed and eaten by other animals.

Primary dune: foredune; dune closest to water's edge.

Producer: autotroph; organism that creates energy-rich compounds from sunlight (through photosynthesis) or certain chemicals (through chemosynthesis); first level in any food web; in estuarine systems, most abundant producers are phytoplankton.

Productive ecosystem: a biological system that efficiently converts energy into growth and production.

Protists: often unicellular but they can be multi-cellular or colonial the organisms in this Kingdom have characteristics of plants, animals and fungi and contains most algae.

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Recreational fishing: any fishing for which the primary motive is leisure rather than profit; fishing for pleasure.

Reef: chain or string of coral, oysters, rocks or other hard substrate.

Research: systematic investigation to establish facts.

Resource: entity (e.g., food, light, water, space) that an organism uses or consumes during its lifetime.

Respiration: process that, using oxygen, releases stored chemical energy to power an organism’s life processes; opposite reaction of photosynthesis.

Response: ecological responses are behavioral and physical changes that happen during the lifetime of a single organism and increase individual’s chance of survival as opposed to evolutionary adaptation, which takes place over multiple generations and is a result of a change in the species genetic makeup.

Restoration: make physical changes in a destroyed or impaired habitat that returns a site to the type of habitat it was prior to human made impacts.

Riparian zone: the land and vegetation bordering flowing or standing water such as streams, rivers, lakes and ponds.

Rock cycle: also called the geologic cycle, the rock cycle is a fundamental concept in geology that describes the dynamic transitions through geologic time among the three main rock types: sedimentary, metamorphic, and igneous.

Runoff: precipitation that drains into a water body from the surface of the surrounding land.

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Salinity: the concentration of salts dissolved in salt water.

Salts: most commonly NaCl or table salt but includes other salts such as MgCl2.

Salt marsh: wetland flooded regularly by tidal, brackish water.

Saltwater intrusion: the invasion of freshwater bodies by denser salt water.

Sandflat: area of bottom of aquatic system that is exposed by low tides and composed of sand - particles of sediment larger than those of mud.

Scientific method: the steps necessary for scientific investigation including 1) identify a problem you would like to solve, 2) formulate a hypothesis, 3) test the hypothesis, 4) collect and analyze the data, 5) make conclusions.

Sea level rise: long-term increases in mean sea level. The expression is popularly applied to anticipated sea level changes due to the greenhouse effect and associated global warming.

Sea Surface Temperature: the average temperatures at the uppermost layer of the ocean –only a few millimeters deep. Sea Surface Temperature, often referred to as SST, can be globally monitored through satellite remote sensing.

Sediment: particles deposited by wind or water.

Sedimentary rock: rock that is formed by the consolidation of sediment particles or of the remains of plants and animals.

Sessile: permanently attached or fixed; not free-moving.

Space: resource needed by all organisms; most pronounced need by organisms that require substrate.

Spawn: to deposit sperm or eggs into the water (fish reproduction).

Speciation: formation of new species through natural selection; occurs when selective force is intense; accounts for diversity of living things on planet today.

Species: a classification of related organisms that can freely interbreed.

Spring tides: extreme high and low tides that occur about twice a month, with the full and new moons.

Stenohaline: unable to tolerate a range of salinities.

Sublittoral zone: portion of rocky shore always submerged.

Substrate: the surface on which an organism grows.

Subtidal: area usually flooded near edge of tidal waters.

Succession: progressive replacement of populations in a habitat.

Supratidal: occaisionally flooded by very high or storm tides.

Surface water: water in streams, brooks, rivers, ponds and lakes, etc.

Swash zone: part of foreshore washed by waves.

Synthetic compounds: manufactured compounds.

System-Wide Monitoring Program (SWMP): pronounced "swamp". The monitoring program of the ational Estuarine Research Reserve System which tracks short-term variability and long-term changes in estuarine waters to understand how human activities and natural events can change ecosystems. This program measures physical and chemical water quality indicators, nutrients and the impacts of weather on estuaries. As the program expands, plans include adding a biological monitoring component and tracking changes in land use through remote sensing.

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Tectonic estuaries: land flooded by sea due to subsidence, not sea-level rise.

Temperature: important abiotic factor affecting distribution and abundance of organisms; influences metabolic rate and affects rates of growth and reproduction.

Tidal height: difference between water level at high tide and mean sea level, the average height of the ocean.

Tidal range: difference between high and low tide.

Tides: periodic rise and fall of ocean waters due to gravitational pull of sun and moon, and rotation of earth.

Tolerant: capable of withstanding effects. Often refered to as the ability of speicies to withstand variabilities of their environment.

Trophic level (trophic): level in a food chain, e.g., producer, primary consumer, secondary consumer, tertiary consumer.

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Uplands: lands lying above the reaches of the highest high tides.

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Vertebrate: animal having a backbone.

Vertical stratification: laying of fresh water on top of salt water, also known as “salt wedge” effect; occurs when the fresh and salt water is not vigorously mixed together by turbulence.

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Water: a molecule-composed compound of hydrogen and oxygen.

Water column: the area of water from the seafloor up to the water surface. The water column contains free swimming, or pelagic, organisms and plankton (tiny drifting and floating organisms). The water column is a part of all bays, sloughs, lagoons and coastal areas; and is therefore part of an estuary.

Water cycle: the recycling of water between the earth and the atmosphere.

Watersheds: area of land drained by a river or river system, lake or estuary.

Weathering: the process of physical disintegration and chemical decomposition whereby earth and rock materials are changed in color, texture, composition, firmness, or form upon exposure to the atmosphere.

Wetland: “ areas inundated or saturated by surface or ground water at a frequency and duration sufficient to support , and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions.” (US Army Corp of Engineers for Section 404 support of the 1977 Clean Water Act Amendments)

Wrack line: a string of debris stranded by last high tide; cast ashore seaweeds, isolated sources of food and shade support an important community of isopods and amphipods as well as providing food for birds.

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Zonation (zonal habitats): distribution of plants or animals arranged in zones or bands, caused by gradations of abiotic and/or biotic factors.

Zooplankton: animal or animal-like protists, small or microscopic, that drift with the currents, may be either herbivores or carnivores.

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*Some of the defintions above were adapted from the Estuary-Net Curriculum, Estuarine Ecology Section, National Estuarine Research Reserves.