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Glossary of Coral Reef Terminology - U


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u - a common replacement for the Greek letter µ as a symbol for the micron or micrometer. The correct symbol for this unit is µm

U.S. Coral Reef Task Force (USCRTF) - established by President Clinton in June, 1998, through Executive Order 13089 on Coral Reef Protection, to lead the U.S. response to this growing global environmental crisis. Chaired by the Secretary of the Interior and the Secretary of Commerce, the USCRTF is composed of the heads of 11 federal agencies and the Governors of 7 states, territories or commonwealths with responsibilities for coral reefs. The USCRTF is responsible for overseeing implementation of the Executive Order, and developing and implementing coordinated efforts to: map and monitor U.S. coral reefs; research the causes and solutions to coral reef degradation; reduce and mitigate coral reef degradation from pollution, overfishing and other causes; and implement strategies to promote conservation and sustainable use of coral reefs internationally

U.S. Pacific Remote Insular Area (PRIAs) - PRIAs consist of the following islands and coral reefs appurtenant to such island, reef or atoll, as applicable: Baker Island, Howland Island, Jarvis Island, Johnston Atoll, Kingman Reef, Wake Island, and Palmyra Atoll

ubiquitous - having a worldwide distribution; common to abundant in a given area

ultimate - last or farthest

ultramarine - deep blue color

ultrasonic - sound waves that have frequencies higher than what humans can hear, usually greater than 20,000 Hz. Some animals such as bats, a species of cave bird, and cetaceans use these high frequency ultrasonic sounds for communication and navigation

Ultraviolet-A (UV-A) - UV with wavelengths 315 - 400 nm

Ultraviolet-B (UV-B) - UV with wavelengths 280 - 315 nm

Ultraviolet-C (UV-C) - UV with wavelengths less than 280 nm

Image of bivalve shell

A bivalve shell: 1 = umbo; 2 = periostracum (the pigmented outermost layer of the shell). (Photo: Rick Gillis, Ph.D., Biology Dept., University of Wisconsin-La Crosse)


umbo - the earliest part of a bivalve or brachiopod shell; in bivalves, it is the most dorsal section of the shell, while in brachyopods, it is the most posterior

umbraculiform - umbrella-shaped

Image of jellyfish

The transparent umbrella of this jellyfish makes it less obvious to predators.


umbrella - describes the body of a jellyfish or medusa

umbrella species - in conservation biology, species with large area requirements. Conservation of these species should automatically conserve a host of other species

unaltered fossil - a fossil which retains much or all of its original chemical and structural composition

unavailable name - in taxonomy, a name which does not meet all mandatory provisions of the International Code of Zoological Nomenclature and thus has no status in nomenclature. Unavailable names include: nomen oblitum, nomen negatum, nomen nudum, nomen nullum, nomen vetitum

uncinate - hooked at the tip

undercurrent - a current below another current, or beneath the surface

underwater dB - the unit used to measure the intensity of an underwater sound. Underwater dB refers to "decibels referenced to 1 microPascal," which is abbreviated as "dB re 1 µPa." Sound intensity given in underwater dB is not directly comparable to sound intensity give

undulating - moving in waves

unincorporated territory - a United States insular area in which the United States Congress has determined that only selected parts of the United States Constitution apply

uniplanar - occurring in one plane

uniramous appendage - a type of appendage that is characteristic of insects and other members of the arthropod subphylum Uniramia. It consists of an unbranched series of segments

unite - in taxonomy, to combine or join two or more taxa

United States Insular Area - United States territory that is neither a part of one of the fifty states or the District of Columbia. Insular area is the current generic term used by the U.S. State department to refer to any commonwealth, freely associated state, possession or territory controlled by the US government. Several islands in the Pacific Ocean and Caribbean Sea are considered insular areas of the United States. Palmyra Atoll is an incorporated, uninhabited island, owned by the Nature Conservancy but administered by the Office of Insular Affairs. Unincorporated and inhabited U.S. possessions are Puerto Rico, U.S. Virgin Islands, American Samoa, Guam, and the Commonwealth of the Northern Mariana Islands. Uninhabited areas are the United States Minor Outlying Islands, which are: Baker Island, Howland Island, Jarvis Island, Johnston Atoll, Kingman Reef, Midway Islands, Wake Island, Palmyra Atoll, and Navassa Island (disputed with Haiti)

United States territory - any extent of region under the jurisdiction of the federal government of the United States, including all waters (around islands or continental tracts). The United States has traditionally proclaimed the sovereign rights for exploring, exploiting, conserving, and managing its territory

Universal Time (UT or Z) - the correct name for the time system previously called Greenwich Mean Time (GMT). The symbol Z is often pronounced "Zulu," the name of the letter Z in the international radio alphabet

unorganized territory - an unincorporated United States insular area for which the United States Congress has not enacted an organic act

unpublished name - in taxonomy, any name which has not been printed and circulated to meet the criteria of publication as stated by the International Code of Zoological Nomenclature

unused name - in taxonomy, an available senior synonym that is not known to have been used as a valid name in the past 50 years

unzip - a method for uncompressing files on a PC after downloading them from the Internet. Many files are stored on servers in a compressed format, making them take up less disk space, and reducing the time it takes to download them. These files must be decompressed to make them usable by your computer. WinZip and pkunzip are popular free software programs that will uncompress files

upload - transferring data (usually a file) from the computer you are using to another computer. The opposite of "download"

upstream - toward the source or upper part of a stream or current; against the current

uptake - the entry of a substance into the body, into an organ, into a tissue, into a cell, or an organism's body fluids by passage through a membrane or by other means

upwelling - the process by which warm, less-dense surface water is drawn away from a shore by offshore currents and replaced by cold, denser water brought up from the subsurface

Diagram of uracil

Diagram of the chemical structure of uracil, one of the four nitrogenous bases in RNA.


uracil - one of the four bases in RNA. The others are adenine, guanine, and cytosine. Uracil replaces thymine, which is the fourth base in DNA. Like thymine, uracil always pairs with adenine

urban area   - an area in which a majority of the people are not directly dependent on natural resource-based occupations

urea - a waste product of metabolism eliminated via the kidneys. In elasmobranchs (sharks, rays, skates), urea is found in the blood where it helps to maintain osmotic balance

uridine - the nucleoside having uracil as its base. Uracil is attached to a ribose ring

URL (Universal Resource Locator) - a website address, such as: www.coris.noaa.gov

Image of orange tunicate

Orange colonial tunicates (Urochordata) at Gray's Reef National Marine Sanctuary.


Urochordata (Tunicata) - a subphylum of the animal phylum Chordata that contains the ascideans (sea squirts). Most adults are sessile and bear little resemblance to the other chordates. They are common inhabitants of coral reefs and mangrove roots

Image of ventral side of crayfish

Ventral view of crayfish. (Photo: Copyright LTTM 2003)


uropod - fan-shaped, paired posterior abdominal appendage in certain crustaceans, e.g., lobsters or shrimp, that are used for swimming

UV (ultraviolet) radiation - the region of the electromagnetic spectrum consisting of wavelengths from 1 to 400 nm

uvelloid - resembling a small cluster of grapes

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