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m

meter

mangrove

Ecologically, mangroves are defined as an assemblage of tropical trees and shrubs that inhabit the coastal intertidal zone. A mangrove community is composed of plant species specially adapted to survive the variable flooding and salinity stress conditions of the coastal environment. Mangroves provide protected habitat for many land and marine animals. The many species of mangroves are found in about 20 plant families.

Marine Safety Unit (MSU)

In the U.S. Coast Guard, a subordinate office to a Sector office. For example, MSU Valdez reports directly to Sector Anchorage.

Marine Science Technician (MST)

U.S. Coast Guard Marine Science Technicians (MSTs) conduct marine-safety activities, such as investigating pollution incidents, monitoring pollution cleanups, conducting foreign-vessel boardings to enforce pollution and navigation safety laws, conducting harbor patrols for port safety and security, inspecting waterfront facilities and supervising the loading of explosives on vessels. They may be assigned to the National Strike Force for oil and hazardous-material response. MSTs are also the Coast Guard's safety and environmental health experts ashore.

mass

Mass is a physical property related to weight. Mass is a measure of the amount of a substance that occupies a given space. While the weight of a given amount of a substance is a measure of the force by which it is attracted by gravity (and is less on the moon than on the earth), the substance's mass is independent of gravity.

Material Safety Data Sheet (MSDS)

Product data sheet prepared under 29 CFR § 1910.1200 by the manufacturer or marketer of a hazardous material; describes product, its hazards, and safe handling and response procedures.

mechanical removal

Includes the use of pumps, skimmers, booms, earth-moving equipment, and other mechanical devices to contain the discharge of oil and to recover the discharge from the water or adjoining shorelines.

melting point

Also freezing point. The temperature at which the solid and liquid phases of a substance exist in equilibrium. Depends on chemical composition and applied pressure.

miscible

Completely soluble.

mitigate

To create, restore, or enhance a natural system, such as an estuary or wetland, to maintain the functional characteristics and processes of that system.

mitigation

A coastal management concept requiring developers to replace developed areas with equivalent natural areas or to reengineer other areas to resemble areas prior to development.

mixture

A uniform or nonuniform blend of two or more substances. Examples include blood, milk, petroleum products, and alloys.

MMS

Minerals Management Service. The U.S. federal agency that manages the nation's natural gas, oil and other mineral resources on the outer continental shelf, and collects, accounts for, and disburses revenues from federal mineral leases (onshore and offshore) on federal and Indian lands.

molecular weight

The sum of the weights of all the atoms in a molecule.

molecule

A chemical entity composed of one or more elements in the form of atoms.

monomer

One of the molecules that link together to make a polymer. For example, the monomer of natural rubber is isoprene. Monomers may be naturally occurring or synthetic. See also polymerization.

mousse

A water-in-oil emulsion that resembles chocolate mousse in color and texture. These emulsions are often very stable, and often have a pudding-like consistency. Typically, a mousse forms when relatively fresh oil is exposed to strong wave action. Mousse colors can range from orange or tan to dark brown. A mousse may contain up to 75 percent water, and may have a volume up to four times that of the original oil. See also emulsion.

MSDS

See Material Safety Data Sheet.

MSO

U.S. Coast Guard Marine Safety Office. As of the mid-2000s, nearly all MSOs have been combined with groups and other units to form Sectors.

MST

See Marine Science Technician.

MSU

See Marine Safety Unit.

mutagen

A chemical or radiation source that alters an organism's DNA, affecting transmission of inherited characteristics from one generation to the next.

mystery spill

An oil or chemical spill for which no source or responsible party (RP) has been identified.