Glossary of Seagrass Terms



Aerobic  Living or occurring only in the presence of oxygen
Algae  Non-vascular plants that grow submerged in marine or freshwater environments. 
Algal bloom The sudden growth of algae in an aquatic ecosystem. They can occur naturally in spring or summer when production exceeds consumption by aquatic herbivores, or can be the result of nutrient enrichment of waters due to pollution. Algal blooms are a characteristic symptom of eutrophication.
Ambient  Pertaining to the status of the surrounding environment at the moment.
Amphipod  A small crustacean such as the beach flea, having a laterally compressed body with no carapace.
Anaerobic  A descriptive term for a process, such as fermentation, that can proceed only in the absence of oxygen, or a living thing that can survive only in the absence of oxygen.
Anoxic  Without oxygen.
Anthropogenic  Derived from or associated with human activity, often used to describe environmental contamination  or disruption resulting from human activities.


Benthic  Of or relating to the sea bottom.
Biodiversity  A description of the variety, abundance and distribution of living organisms within a defined ecosystem or habitat.
Bivalves  The class of mollusks that are laterally compressed and covered with two shells, or valves; clams, mussels, scallops.
Blade The leaf of grasses or similar plants; the broad flat part of a leaf.


Clone To reproduce or propagate asexually; a group of genetically identical plants all produced by vegetative propagation from a single parent.
Community A group of interdependent organisms inhabiting the same region and interacting with each other.
Crustaceans  Any of various predominantly aquatic arthropods including lobsters, crabs, shrimps, and barnacles, characteristically having a segmented body, a chitinous exoskeleton, and paired, jointed limbs.
Cyclic Happening or appearing at regular intervals.


Desiccation  Dryness resulting from the removal of water.
Detrivore  An organism that feeds on detritus, or decomposing plant and animal material.
Diatoms  Any of various microscopic one-celled or colonial algae of having cell walls of silica consisting of two interlocking symmetrical valves.
Dinoflagellate  Any of numerous minute, chiefly marine protozoans characteristically having two flagella and a cellulose covering and forming one of the chief constituents of plankton. They include bioluminescent forms and forms that produce red tide.
Distribution The geographic occurrence or range of an organism.
Disturbance A temporary change in average environmental conditions that causes a pronounced change in ecosystem structure that lasts longer than the change in the environment. Disturbances may be natural or anthropogenic.


Echinoderms  Any of numerous marine invertebrates of the phylum Echinodermata. Characteristics include being radially symmetrical, having an internal calcareous skeleton and often covered with spines. They include the starfishes, sea urchins, sand dollars, and brittle stars.
Ecology The scientific study of the relationships between plants, animals, and their environment.
Ecosystem An ecological community together with its environment, functioning as a unit.
Eelgrass  The temperate seagrass Zostera marina which is the dominant seagrass from Canada to the Carolinas, northern latitudes on the eastern Atlantic coast of Europe and the  Pacific ocean.
Epibenthic  Relating to the area on top of the sea floor. Epibenthic organisms may be freely moving or sessile (permanently attached to a surface).
Epiphytes  Organisms that live on the surface of plants and seaweeds.
Erosion The group of natural processes, including weathering, dissolution, abrasion, corrosion, and transportation, by which material is worn away from the earth's surface. The principal agents are gravity, running water, near-shore waves, ice (mostly glaciers), and wind.
Estuary A partially enclosed coastal body of water, having an open connection with the ocean, where freshwater from inland is mixed with saltwater from the sea.
Euphotic The photic zone; the uppermost layer of a body of water that receives sufficient light for photosynthesis and the growth of green plants.
Eutrophication  An environmental condition where excess nutrients, in the form of nitrogen or phosphorus, are introduced into a water body leading to increase growth of micro- and macroalgae. 


Food chain A succession of organisms in an ecological community that constitutes a continuation of food energy from one organism to another as each consumes a lower member and in turn is preyed upon by a higher member.
Food web A community of organisms where there are several interrelated food chains.
Forage The act of looking or searching for food.


Gastropods  The class of mollusks that includes snails, nudibranchs, and slugs.
Gene pool The collective genetic information contained within a population of sexually reproducing organisms.
Genetic diversity  The variety of genetic materials within a single species of organism that permit the organism to adapt to changes in the environment.
Genotype The genetic makeup of an organism or a set of organisms.
Geomorphology The study of the shape and form of the landscape, and how the nature of landforms relates to their origin, development, and change over time.
Global warming An increase in the average temperature of the earth's atmosphere, believed by most scientists to be the result of an enhancement of the greenhouse effect caused by air pollution.
Greenhouse effect The natural phenomenon in which gases such as carbon dioxide, water vapor, and methane in the earth's atmosphere trap solar radiation. Most scientists believe that the greenhouse effect has been enhanced due to air pollution, resulting in global climate change.


Herbivore  An animal that feeds primarily on plants.
Holdfast  A structure in seaweeds or other algae that anchors the thallus to a substrate (e.g. rocks, other plants, shells). The holdfast may be root-like or discoid and sucker-like.
Hypothesis A tentative explanation for an observation, phenomenon, or scientific problem that can be tested by further investigation.
Hypoxic  The amount of dissolved oxygen in the water is reduced to a level significantly lower than its theoretical maximum resulting in induced stress in aquatic organisms due to lack of oxygen for normal metabolism.


Infauna Those aquatic organisms that exist buried in the sediment as opposed to those that live at the sediment surface or in the water column.
Inflorescence A flowering structure that consists of more than a single flower; the time and process of budding and unfolding of blossoms.
Intertidal The area between high tide and low tide lines; littoral zone.
Introduced species Species that have been inadvertently or intentionally brought into a new region by the activities of humans. An introduced species may not be considered invasive.
Invasive species An introduced species that has spread widely throughout the new location and causes harm by altering ecological relationships among native species. Common invasive species traits include fast growth, rapid reproduction, high dispersal ability, phenotypic plasticity, tolerance of a wide range of environmental conditions, ability to live off of a wide range of food types, single parent reproduction (especially in plants), and, commonly, association with humans.


Littoral  The region or zone between the limits of high and low tides; intertidal.


Macroalgae  A classification of algae that are defined according to the size of the plant where the body of the plant is large enough to be observable to the eye.
Meadow A tract of land where grass or grass-like vegetation grows and is the dominant form of plant life.
Microalgae  A classification of algae that are defined according to the size of the plant where the body of the plant is small enough that it requires magnification to observe.
Mollusk Any of numerous chiefly marine invertebrates of the phylum Mollusca, typically having a soft unsegmented body, a mantle, and a protective calcareous shell, including snails (gastropods), clams (bivalves), squid and octopus (cephalopods).


Native species A species that has a long history of living in a particular region.
Nursery grounds Habitats used by juveniles for food and protection from predators and physical stresses.


Omnivore An animal whose normal diet includes both plants and animals.


Pelagic In the water column; the open water above the sea floor.
Phenotype The observable physical or biochemical characteristics of an organism, as determined by both genetic makeup and environmental influences.
Phenotypic plasticity The ability to alter one’s growth form to suit current conditions; the ability of a genotype to change its phenotype in response to changes in the environment.
Photosynthesis The process in which green plants and certain other organisms utilize the energy of sunlight to manufacture carbohydrates from carbon dioxide and water in the presence of chlorophyll, usually producing oxygen as a byproduct.
Phylogeny  A pattern of evolutionary relationships among organisms.
Physical stresses  Abiotic (heat, water loss, wave impacts) as opposed to biotic (competition, predation) stresses.
Phytoplankton  Single-celled microalgae that are found suspended in the water column and provide the first step most marine food chains.
Plankton  The collection of small or microscopic organisms, including algae and protozoans, that float or drift in great numbers in fresh or salt water, especially at or near the surface, and serve as food for fish and other larger organisms.
Plasticity  Expression of a trait that is not fixed and varies with the environment.
Pollination  The transfer of pollen (male sex cells) from the anther (male) to the stigma (female) of a plant for fertilization.
Population a group of organisms of the same species populating a given area.
Predator An organism that lives by preying on other organisms.
Primary production The production of biological organic compounds from inorganic materials through photosynthesis or chemosynthesis; the fixing of inorganic carbon from an outside energy source, usually solar energy.
Propagule  Generic term for the seeds, spores, and larvae used by plants, algae and animals to reproduce themselves. Usually produced sexually.


Quadrat  Any of a group of small rectangular plots arranged for close study of the distribution of plants or animals in that area. We use this term when referring to our PVC frames which we use for monitoring purposes in our eelgrass beds to determine the shoot density and algal percent cover of a given area (ex. 0.25m2).


Rhizome  A horizontal, usually underground stem that often sends out roots and shoots from its nodes.
Roots  The usually underground portion of a plant that lacks buds, leaves, or nodes and serves as support, draws minerals and water from the surrounding soil, and sometimes stores food.


Salinity  A measurement of the amount of salt that is dissolved in water and is normally reported in parts per thousand (ppt).  Normal seawater has a salinity of 30-35 ppt.
Scavengers Animals that consume already dead organic life-forms. Scavengers are useful to the ecosystem by feeding on and therefore breaking down dead animal and plant remains.
Seagrasses Rooted vascular plants of terrestrial origin that have adapted to life submerged in the sea. Seagrasses provide coastal zones with a number of ecological goods and ecological services, for instance fishing grounds, wave protection, oxygen production and protection against coastal erosion.
Sediment  Any material having a geological origin and comprised of small particles.  The size of the individual particles determines the description of the sediment and it can range from fine clay to coarse gravel. 
Sedimentation  The accumulation or deposition of sediment. In a seagrass bed, sedimentation occurs due to the ability of seagrasses to dampen wave energy causing particulates from the water column to settle as well as sediments moving across the sea floor to become trapped. The opposite of erosion.
Seed bank  The supply of propagules that are present and will germinate if an opportunity to do so occurs.
Seedling  A young plant that is grown from a seed.
Sheath  In plants, the protective covering at the base of a blade or stalk that covers the stem; an enveloping structure or covering enclosing an animal or plant organ or part.
Shellfish A common term for clams, mussels, scallops, shrimps, lobsters; commercially harvested marine organisms other than fishes.
Shoot One of two primary sections of a plant; the other is the root. The shoot refers to what is generally the upper portion of a plant, and consists of stems, leaves, flowers, and fruits.
Spadix An inflorescence with small flowers crowded on a thickened, fleshy axis.
Spathe A conspicuous bract surrounding or subtending a spadix or other inflorescence.
Species A fundamental category of taxonomic classification, ranking below a genus or subgenus and consisting of related organisms capable of interbreeding and sharing unique characteristics.
Stipe A supportive structure in seaweeds that may be stem-like. This structure is particularly common in brown algae such as kelp.
Stress/stressor A perturbation applied to a system (a) which is foreign to that system or (b) is natural to that system but applied at an excessive level. In marine ecosystems, stressors are often anthropogenic, resulting from coastal development (e.g. excess nutrients/contaminants like nitrogen and phosphorus, overfishing, invasive species, increased temperature, etc. When multiple stressors occur, they can interact and intensify, altering predictability within that system, and therefore resulting in difficulty for restoration and management strategies.
Sublittoral The subtidal zone below the low tide line; permanently immersed. The sublittoral zone extends to the point where the continental shelf drops.
Submerged aquatic vegetation (SAV): Any of a group of plants that can live and grow under water. Local examples of submerged aquatic vegetation include eelgrass (Zostra marina) and widgeon grass (Ruppia maritima), as well as macroalgae.
Supralittoral The zone extending from the high-tide line toward dry land, only underwater during unusually high tides or storms. Also known as the "spray zone".


Taxonomy The classification of organisms in an ordered system that indicates natural relationships.
Thallus  A primitive type of vegetative plant body undifferentiated into stem, root, or leaf. The term is mainly used in non-vascular plants e.g. algae.
Tolerance The power or capacity of an organism to survive unfavorable environmental conditions.
Tunicates  Sea squirts; a phylum of filter-feeding organisms that are common fouling organisms, and larvae show characteristic chordate features also found in the embryos of vertebrates.
Turbidity A cloudiness or haziness of water caused by sediment or foreign particles being stirred up or suspended.


Vegetative reproduction  The ability of plants to reproduce without sexual reproduction, by producing new plants from existing vegetative structures; Asexual reproduction.


Water column  The water mass lying above the benthic (seafloor) habitat; the open water where planktonic and pelagic organisms live.
Wrack  Floating plant material (often containing seeds) that is carried away by winds and currents onto shorelines.


Zooplankton  Plankton that consists of animals, including small crustaceans, fish larvae, corals, rotifers, sea anemones,  and jellyfish.



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