Water Cycle: Circulation of water among various ecological systems, in various states, on, above, and below the surface of the earth.Fresh Water: Water containing no significant amounts of salts, such as water from RIVERS and LAKES.Lakes: Inland bodies of still or slowly moving FRESH WATER or salt water, larger than a pond, and supplied by RIVERS and streams.Rivers: Large natural streams of FRESH WATER formed by converging tributaries and which empty into a body of water (lake or ocean).Water: A clear, odorless, tasteless liquid that is essential for most animal and plant life and is an excellent solvent for many substances. The chemical formula is hydrogen oxide (H2O). (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Water Supply: Means or process of supplying water (as for a community) usually including reservoirs, tunnels, and pipelines and often the watershed from which the water is ultimately drawn. (Webster, 3d ed)Seawater: The salinated water of OCEANS AND SEAS that provides habitat for marine organisms.Gills: Paired respiratory organs of fishes and some amphibians that are analogous to lungs. They are richly supplied with blood vessels by which oxygen and carbon dioxide are exchanged directly with the environment.Tilapia: A freshwater fish used as an experimental organism and for food. This genus of the family Cichlidae (CICHLIDS) inhabits Central and South America (one species extends north into Texas), West Indies, Africa, Madagascar, Syria, and coastal India.Body Water: Fluids composed mainly of water found within the body.Wetlands: Environments or habitats at the interface between truly terrestrial ecosystems and truly aquatic systems making them different from each yet highly dependent on both. Adaptations to low soil oxygen characterize many wetland species.Salinity: Degree of saltiness, which is largely the OSMOLAR CONCENTRATION of SODIUM CHLORIDE plus any other SALTS present. It is an ecological factor of considerable importance, influencing the types of organisms that live in an ENVIRONMENT.Water Microbiology: The presence of bacteria, viruses, and fungi in water. This term is not restricted to pathogenic organisms.Water Pollutants, Chemical: Chemical compounds which pollute the water of rivers, streams, lakes, the sea, reservoirs, or other bodies of water.Fishes: A group of cold-blooded, aquatic vertebrates having gills, fins, a cartilaginous or bony endoskeleton, and elongated bodies covered with scales.Water Pollution: Contamination of bodies of water (such as LAKES; RIVERS; SEAS; and GROUNDWATER.)Water Purification: Any of several processes in which undesirable impurities in water are removed or neutralized; for example, chlorination, filtration, primary treatment, ion exchange, and distillation. It includes treatment of WASTE WATER to provide potable and hygienic water in a controlled or closed environment as well as provision of public drinking water supplies.AnguillaWater Quality: A rating of a body of water based on measurable physical, chemical, and biological characteristics.Salmonidae: A family of anadromous fish comprising SALMON; TROUT; whitefish; and graylings. They are the most important food and game fishes. Their habitat is the northern Atlantic and Pacific, both marine and inland, and the Great Lakes. (Nelson: Fishes of the World, 1976, p97)Water-Electrolyte Balance: The balance of fluid in the BODY FLUID COMPARTMENTS; total BODY WATER; BLOOD VOLUME; EXTRACELLULAR SPACE; INTRACELLULAR SPACE, maintained by processes in the body that regulate the intake and excretion of WATER and ELECTROLYTES, particularly SODIUM and POTASSIUM.Ecosystem: A functional system which includes the organisms of a natural community together with their environment. (McGraw Hill Dictionary of Scientific and Technical Terms, 4th ed)Tropical Climate: A climate which is typical of equatorial and tropical regions, i.e., one with continually high temperatures with considerable precipitation, at least during part of the year. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Eels: Common name for an order (Anguilliformes) of voracious, elongate, snakelike teleost fishes.Water Pollutants: Substances or organisms which pollute the water or bodies of water. Use for water pollutants in general or those for which there is no specific heading.Phylogeny: The relationships of groups of organisms as reflected by their genetic makeup.Elapidae: A family of extremely venomous snakes, comprising coral snakes, cobras, mambas, kraits, and sea snakes. They are widely distributed, being found in the southern United States, South America, Africa, southern Asia, Australia, and the Pacific Islands. The elapids include three subfamilies: Elapinae, Hydrophiinae, and Lauticaudinae. Like the viperids, they have venom fangs in the front part of the upper jaw. The mambas of Africa are the most dangerous of all snakes by virtue of their size, speed, and highly toxic venom. (Goin, Goin, and Zug, Introduction to Herpetology, 3d ed, p329-33)Acidic Glycosphingolipids: A subclass of GLYCOSPHINGOLIPIDS containing large polar heads made up of several sugar units. One or more of their terminal sugar units are bound to a negatively charged molecule at pH 7. Members of this class include: GANGLIOSIDES, uronoglycosphingolipids, SULFOGLYCOSPHINGOLIPIDS, phosphoglycosphingolipids, and phosphonoglycosphingolipids.Queensland: A state in northeastern Australia. Its capital is Brisbane. Its coast was first visited by Captain Cook in 1770 and its first settlement (penal) was located on Moreton Bay in 1824. The name Cooksland was first proposed but honor to Queen Victoria prevailed. (From Webster's New Geographical Dictionary, 1988, p996 & Room, Brewer's Dictionary of Names, 1992, p441)Trout: Various fish of the family SALMONIDAE, usually smaller than salmon. They are mostly restricted to cool clear freshwater. Some are anadromous. They are highly regarded for their handsome colors, rich well-flavored flesh, and gameness as an angling fish. The genera Salvelinus, Salmo, and ONCORHYNCHUS have been introduced virtually throughout the world.Sodium Chloride: A ubiquitous sodium salt that is commonly used to season food.Estuaries: A partially enclosed body of water, and its surrounding coastal habitats, where saltwater from the ocean mixes with fresh water from rivers or streams. The resulting mixture of seawater and fresh water is called brackish water and its salinity can range from 0.5 to 35 ppt. (accessed http://oceanservice.noaa.gov/education/kits/estuaries/estuaries01_whatis.html)Crustacea: A large subphylum of mostly marine ARTHROPODS containing over 42,000 species. They include familiar arthropods such as lobsters (NEPHROPIDAE), crabs (BRACHYURA), shrimp (PENAEIDAE), and barnacles (THORACICA).Conservation of Natural Resources: The protection, preservation, restoration, and rational use of all resources in the total environment.RNA, Ribosomal, 16S: Constituent of 30S subunit prokaryotic ribosomes containing 1600 nucleotides and 21 proteins. 16S rRNA is involved in initiation of polypeptide synthesis.Water Deprivation: The withholding of water in a structured experimental situation.Trematode Infections: Infections caused by infestation with worms of the class Trematoda.Atriplex: A plant genus in the CHENOPODIACEAE family.Biodiversity: The variety of all native living organisms and their various forms and interrelationships.Adaptation, Physiological: The non-genetic biological changes of an organism in response to challenges in its ENVIRONMENT.Trematoda: Class of parasitic flukes consisting of three subclasses, Monogenea, Aspidogastrea, and Digenea. The digenetic trematodes are the only ones found in man. They are endoparasites and require two hosts to complete their life cycle.Northwestern United States: The geographic area of the northwestern region of the United States. The states usually included in this region are Idaho, Montana, Oregon, Washington, and Wyoming.Water Movements: The flow of water in enviromental bodies of water such as rivers, oceans, water supplies, aquariums, etc. It includes currents, tides, and waves.Environmental Monitoring: The monitoring of the level of toxins, chemical pollutants, microbial contaminants, or other harmful substances in the environment (soil, air, and water), workplace, or in the bodies of people and animals present in that environment.Species Specificity: The restriction of a characteristic behavior, anatomical structure or physical system, such as immune response; metabolic response, or gene or gene variant to the members of one species. It refers to that property which differentiates one species from another but it is also used for phylogenetic levels higher or lower than the species.Water SofteningBathing Beaches: Beaches, both natural and man-made, used for bathing and other activities.Climate: The longterm manifestations of WEATHER. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Drinking: The consumption of liquids.Fisheries: Places for cultivation and harvesting of fish, particularly in sea waters. (from McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Molecular Sequence Data: Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.Sequence Analysis, DNA: A multistage process that includes cloning, physical mapping, subcloning, determination of the DNA SEQUENCE, and information analysis.Chlorophyta: A phylum of photosynthetic EUKARYOTA bearing double membrane-bound plastids containing chlorophyll a and b. They comprise the classical green algae, and represent over 7000 species that live in a variety of primarily aquatic habitats. Only about ten percent are marine species, most live in freshwater.Necatoriasis: Infection of humans or animals with hookworms of the genus NECATOR. The resulting anemia from this condition is less severe than that from ANCYLOSTOMIASIS.Fish Diseases: Diseases of freshwater, marine, hatchery or aquarium fish. This term includes diseases of both teleosts (true fish) and elasmobranchs (sharks, rays and skates).Sodium: A member of the alkali group of metals. It has the atomic symbol Na, atomic number 11, and atomic weight 23.Chlorides: Inorganic compounds derived from hydrochloric acid that contain the Cl- ion.Weather: The state of the ATMOSPHERE over minutes to months.Oceans and Seas: A great expanse of continuous bodies of salt water which together cover more than 70 percent of the earth's surface. Seas may be partially or entirely enclosed by land, and are smaller than the five oceans (Atlantic, Pacific, Indian, Arctic, and Antarctic).Soil: The unconsolidated mineral or organic matter on the surface of the earth that serves as a natural medium for the growth of land plants.Geography: The science dealing with the earth and its life, especially the description of land, sea, and air and the distribution of plant and animal life, including humanity and human industries with reference to the mutual relations of these elements. (From Webster, 3d ed)Bacteria: One of the three domains of life (the others being Eukarya and ARCHAEA), also called Eubacteria. They are unicellular prokaryotic microorganisms which generally possess rigid cell walls, multiply by cell division, and exhibit three principal forms: round or coccal, rodlike or bacillary, and spiral or spirochetal. Bacteria can be classified by their response to OXYGEN: aerobic, anaerobic, or facultatively anaerobic; by the mode by which they obtain their energy: chemotrophy (via chemical reaction) or PHOTOTROPHY (via light reaction); for chemotrophs by their source of chemical energy: CHEMOLITHOTROPHY (from inorganic compounds) or chemoorganotrophy (from organic compounds); and by their source for CARBON; NITROGEN; etc.; HETEROTROPHY (from organic sources) or AUTOTROPHY (from CARBON DIOXIDE). They can also be classified by whether or not they stain (based on the structure of their CELL WALLS) with CRYSTAL VIOLET dye: gram-negative or gram-positive.Topography, Medical: The systematic surveying, mapping, charting, and description of specific geographical sites, with reference to the physical features that were presumed to influence health and disease. Medical topography should be differentiated from EPIDEMIOLOGY in that the former emphasizes geography whereas the latter emphasizes disease outbreaks.Base Composition: The relative amounts of the PURINES and PYRIMIDINES in a nucleic acid.Trees: Woody, usually tall, perennial higher plants (Angiosperms, Gymnosperms, and some Pterophyta) having usually a main stem and numerous branches.Rain: Water particles that fall from the ATMOSPHERE.Aquaporins: A class of porins that allow the passage of WATER and other small molecules across CELL MEMBRANES.Larva: Wormlike or grublike stage, following the egg in the life cycle of insects, worms, and other metamorphosing animals.Seasons: Divisions of the year according to some regularly recurrent phenomena usually astronomical or climatic. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Genes, rRNA: Genes, found in both prokaryotes and eukaryotes, which are transcribed to produce the RNA which is incorporated into RIBOSOMES. Prokaryotic rRNA genes are usually found in OPERONS dispersed throughout the GENOME, whereas eukaryotic rRNA genes are clustered, multicistronic transcriptional units.DNA, Ribosomal: DNA sequences encoding RIBOSOMAL RNA and the segments of DNA separating the individual ribosomal RNA genes, referred to as RIBOSOMAL SPACER DNA.Necator americanus: A common parasite of humans in the moist tropics and subtropics. These organisms attach to villi in the small intestine and suck blood causing diarrhea, anorexia, and anemia.Time Factors: Elements of limited time intervals, contributing to particular results or situations.