<descriptor thcode="2"><thesaurus thcode="2" name="USGS Thesaurus" scope="Topics and methods of scientific study carried out by USGS, with product types, scientific disciplines, geologic time, and types of institutional structure and activities.  Broad and shallow, used to help people find scientific information." creator="U.S. Geological Survey" rights="Public domain" edition="2.0" date="2020-01-09" codetype="number" prefix="topic" uri="https://www2.usgs.gov/science/USGSThesaurus" tblname="term" nonpref="nonpref" relterm="relterm" root_code="1" contact="pschweitzer"><category><term thcode="25" code="29" name="distinct labels" parent="26" scope="Preferred labels (descriptor texts) are distinct within the thesaurus. A concept can be specified either by its unique identifier (code) or by the text of its descriptor."/><term thcode="25" code="16" name="hierarchical" parent="11" scope="Substantive broader-narrower relationships exist among the terms."/><term thcode="25" code="13" name="transitive" parent="12" scope="Narrower terms have an &quot;is a&quot; relationship with their broader terms, and generally can be described as part-of, type-of, or instance-of the broader term."/><term thcode="25" code="21" name="disciplines" parent="2" scope="Broad categories of human inquiry or activity, such as scientific disciplines."/><term thcode="25" code="20" name="methods" parent="2" scope="Actions taken to obtain or analyze information"/><term thcode="25" code="19" name="organizational functions" parent="2" scope="Things that organizations do, typically including various types of programs, projects, and services."/><term thcode="25" code="7" name="temporal" parent="2" scope="Terms indicate periods of time, such as chronostratigraphic units, named historical periods or intervals surrounding known historical events, or seasons."/><term thcode="25" code="5" name="theme" parent="2" scope="Terms indicate domains of human concern, such as scientific discipline, societal problems, or characteristics of earth, space, oceans, and living things."/><term thcode="25" code="29" name="distinct labels" parent="26" scope="Preferred labels (descriptor texts) are distinct within the thesaurus. A concept can be specified either by its unique identifier (code) or by the text of its descriptor."/><term thcode="25" code="16" name="hierarchical" parent="11" scope="Substantive broader-narrower relationships exist among the terms."/><term thcode="25" code="13" name="transitive" parent="12" scope="Narrower terms have an &quot;is a&quot; relationship with their broader terms, and generally can be described as part-of, type-of, or instance-of the broader term."/><term thcode="25" code="21" name="disciplines" parent="2" scope="Broad categories of human inquiry or activity, such as scientific disciplines."/><term thcode="25" code="20" name="methods" parent="2" scope="Actions taken to obtain or analyze information"/><term thcode="25" code="19" name="organizational functions" parent="2" scope="Things that organizations do, typically including various types of programs, projects, and services."/><term thcode="25" code="7" name="temporal" parent="2" scope="Terms indicate periods of time, such as chronostratigraphic units, named historical periods or intervals surrounding known historical events, or seasons."/><term thcode="25" code="5" name="theme" parent="2" scope="Terms indicate domains of human concern, such as scientific discipline, societal problems, or characteristics of earth, space, oceans, and living things."/></category><altlabel><altlabel>USGSThesaurus</altlabel><altlabel>USGSThesaurus</altlabel></altlabel></thesaurus><term thcode="2" code="53" name="aquatic biology" parent="650" scope="The scientific study of organisms living in or near water.  This term is to be used for the science of 'aquatic biology' and for  biological studies in fresh and brackish water. For marine biological studies, use 'marine biology'."/><bt><term thcode="2" code="650" name="life sciences" parent="1019" scope="Branches of science that study living and fossil organisms."/><term thcode="2" code="1019" name="sciences" parent="1" scope="Major educational fields, fields of study, and professional groupings within USGS."/><term thcode="2" code="1" name="Categories" scope="Thematic terms for categorizing information resources.  This thesaurus is intended to support finding and understanding scientific information."/></bt><rt><term thcode="2" code="54" name="aquatic ecosystems" parent="319" scope="Communities of interdependent organisms living primarily in or on water."/><term thcode="2" code="85" name="benthic ecosystems" parent="54" scope="Biologic communities and habitats at the bottom of lakes, streams, or oceans."/><term thcode="2" code="185" name="commercial fishery resources" parent="391" scope="Stocks of fish and other seafood used for marketing purposes."/><term thcode="2" code="311" name="ecology" parent="650" scope="Study of the relations between living plants and animals and their environment."/><term thcode="2" code="358" name="estuarine ecosystems" parent="54" scope="Biological communities and habitats within sea inlets or the zones where rivers meet the seas which are subject to tidal effects and the mixture of fresh and saltwater."/><term thcode="2" code="391" name="fishery resources" parent="777" scope="The stock of anadromous, marine, and freshwater fish in fishing areas of commercial, subsistence, and recreational value."/><term thcode="2" code="419" name="freshwater ecosystems" parent="54" scope="Biological communities and habitats that exist in lakes, rivers, ponds, and other bodies of water that are not salty."/><term thcode="2" code="589" name="inland fishery resources" parent="391" scope="Stocks of fish available to be taken in lakes, streams, ponds, rivers, and other inland bodies of water."/><term thcode="2" code="673" name="macroinvertebrates" parent="841" scope="Invertebrate animals large enough to be studied without a microscope."/><term thcode="2" code="702" name="marine biology" parent="650" scope="Branch of biology concerned with the organisms and habitats of the seas and oceans."/><term thcode="2" code="704" name="marine ecosystems" parent="54" scope="Biological communities composed of plants and animals living primarily in or on seawater."/><term thcode="2" code="705" name="marine fishery resources" parent="391" scope="The stock of fisheries located in seas and oceans."/><term thcode="2" code="744" name="migratory species" parent="841" scope="Species that have a pattern of moving from one geographical area to another, primarily according to the seasons, and usually traveling long distances along established routes."/><term thcode="2" code="903" name="plankton" parent="841" scope="Floating aquatic plants (phytoplankton) and animals (zooplankton) which are often microscopic and drift with the current in lakes, rivers, and oceans."/><term thcode="2" code="968" name="recreational fishery resources" parent="391" scope="The stock of fish and other seafood resources in areas used for recreational fishing."/><term thcode="2" code="1056" name="shellfish" parent="841" scope="Aquatic invertebrates with shells, usually mollusks and crustaceans. Includes clams, lobsters, and oysters."/><term thcode="2" code="1306" name="water quality" parent="1174" scope="The chemical, physical, and biological characteristics of water, usually in respect to its suitability for a particular purpose."/><term thcode="2" code="1326" name="wetland ecosystems" parent="319" scope="Ecosystems whose soil is saturated for long periods seasonally or continuously, including marshes, swamps, and ephemeral ponds.  More detailed terms for wetlands can be selected from the FGDC Wetland Classification &lt;http://fgdc.gov/standards/status/sub3_4.html&gt;."/></rt></descriptor>