Glossary of Aquatic Vegetation Terms

Conditions that result from human activities. "Anthropo-" meaning human and "-genic" meaning produced from.

A small, sedentary, marine invertebrate (chordate) having a saclike body and a siphon through which water enters and leaves; commonly known as sea squirts.

Not contaminated by or associated with any other living organisms. Usually used in reference to pure cultures of microorganisms that are completely free of the presence of other organisms.

Suspension-feeding organism that belong to the Phylum Bryozoa. These animals usually live in branching colonies and obtain food by using tentacles to collect particles suspended in the water column. Bryozoans can use seagrasses for support and in turn provide habitat for juvenile fish and various invertebrates.

A class of invertebrates including shrimps, crabs, barnacles, and lobsters that usually live in water and breathe through gills. They have hard outer shells and jointed appendages and bodies.

Dead or decaying animal or plant matter.

The process where solids, liquids, or gases are transported (sometimes through a membrane) from a region of higher concentration to an area of lower concentration.

Dragging something along the ocean bottom, inadvertently or intentionally removing and redistributing the sediment and other materials found there. There are several specific definitions for dredges:

1. To deepen waters to form channels or improve navigation, boats or barges with dredges attached remove sediment from the bottom of the area.
2. To collect shellfish, an implement consisting of a net on a frame, called a dredge, is used.
3. When a boat drags its propeller through seagrass beds or other bottom types, it is called prop dredging.

Any animal belonging to the phylum Echinodermata, which features radially symmetrical (radiating from a common center) bodies; this includes starfishes, sea urchins, sea cucumbers, etc.

When studying seagrasses, scientists use the term “epiphyte” to refer to any non-parasitic organism living on seagrasses. This can include filamentous and calcareous microalgae, single-celled algae such as diatoms, foraminifera, and invertebrates such as colonial bryozoans, spirorbids, Corophium, mussels, sponges, and barnacles.  

A change in the rate of flow. In reference to seagrasses, the term refers to the rate of nutrient exchange between the sea floor sediments and the overlying water column.

Single cellular eukaryotic organisms, of ancient origin, with a hard shell or test; may be benthic or planktonic. 

GIS is a sophisticated computer-based tool that allows users to produce simple maps from complex spatial data. Researchers can overlay multiple data layers to perform a variety of tasks, including generating a detailed view of the ecosystem, determining changes over time, and predicting various scenarios in the future. See the GIS and Mapping section for more information.

A state of higher-than-normal temperatures.

A Latin term meaning, "in its original position." In biology, it refers to experiments or observations gathered in the natural habitat, as opposed to those gathered in a laboratory.

Organisms that live in the substrate of a body of water and obtain their nutrients through digestion of ingested detritus or by filtering particles out of the surrounding water. Common examples include species such as clams, crabs, shrimp, sea cucumbers, and polychaete worms.

Describes how light intensity decreases with distance from the water surface. As water depth increases, less light is available to organisms living on the ocean bottom. Light attenuation increases with increased amounts of phytoplankton, dissolved organic matter, and macroalgae and epiphytic microalgae.

Algae species that can be seen without a microscope. In the marine environment, this usually refers to seaweed.

A specialized area within a plant where rapid cell division occurs. Apical meristems allow for vertical growth.

Algae species that cannot be seen without a microscope (phytoplankton).

Use of tissue culturing methods to grow large numbers of plants from very small pieces of plants, often single cells. 

A shallow bottom area of shifting mud.

An organism that can cause diseases in other organisms.

The formation of carbohydrates in plants from water and carbon dioxide-caused by the action of sunlight on the chlorophyll pigments.

Microscopic plants that float in water and are transported by the currents; often used as a food source by marine animals

An event in which the density of phytoplankton in the water drastically increases.

The rate of production of biomass (which is the amount of living matter in an area); primary productivity refers to the biomass produced by the photosynthesizing plant components of an ecosystem.

Increasing the number of plants through cuttings, seeds, or divisions.

An underground stem that can grow horizontally or vertically and from which roots grow to provide anchorage for seagrasses. A vertical rhizome is sometimes referred to as a short shoot; horizontal rhizomes have longer internodes, or rhizome fragments. For more details, see illustration in Seagrasses and Land Plants.

The flow of water, usually from precipitation, which is not absorbed into the ground. It flows across the land and eventually runs into stream channels, lakes, oceans, and depressions or lowpoints in the Earth's surface. Runoff can pick up pollutants from the air and land, carrying them into the water body and affecting the species that live there.

The ability of water to flow through sediment. The degree of water movement through sediment depends on sediment characteristics such as type, grain size, and degree of compaction.

The remixing of sediment particles and pollutants back into the water by storms, currents, organisms, and human activities such as dredging or shipping.

Aquatic animals with shells, such as oysters and clams.

An exchange of molecules (and their kinetic energy and momentum) across the boundary between adjacent layers of a fluid or across cell membranes.

In water bodies, the condition of having suspended particles that reduce the ability of light to penetrate beneath the surface. Soil erosion, runoff, and phytoplankton blooms can increase turbidity.