<descriptor thcode="62"><thesaurus thcode="62" name="Coastal and Marine Ecological Classification Standard" scope="Categories of ecosystems for coastal, estuarine, and marine environments." creator="FGDC" rights="public domain" date="2017-05-10" codetype="alpha" prefix="cmecs" uri="https://www2.usgs.gov/science/CMECS" tblname="cmecs" root_code="root" contact="pschweitzer"><category><term thcode="25" code="16" name="hierarchical" parent="11" scope="Substantive broader-narrower relationships exist among the terms."/><term thcode="25" code="16" name="hierarchical" parent="11" scope="Substantive broader-narrower relationships exist among the terms."/></category><altlabel><altlabel>CMECS</altlabel><altlabel>CMECS</altlabel><altlabel>Coastal and Marine Ecological Classification Standard (CMECS)</altlabel><altlabel>Coastal and Marine Ecological Classification Standard (CMECS)</altlabel></altlabel></thesaurus><term thcode="62" code="WC-C015" name="Biogeochemical Feature" parent="WC-C001"/><bt><term thcode="62" code="WC-C001" name="Water Column" parent="root"/><term thcode="62" code="root" name="CMECS" scope="Coastal and Marine Ecological Classification Standard: Category terms encompassing waters from the head of tide or inland incursion of ocean salinity to the splash zone of the coasts to the deepest portions of the oceans and the deep waters of the Great Lakes."/></bt><nt><term thcode="62" code="WC-1327" name="Benthic Boundary Layer" parent="WC-C015" scope="Biogeochemical Feature: The layer formed at the interface between the lower water column and the benthic substrate."/><term thcode="62" code="WC-1328" name="Boundary Layer" parent="WC-C015" scope="Biogeochemical Feature: Layer formed at the interface between water and another water mass (or solid interface) where frictional shear forces on water motion cause exponential damping of movement with proximity to the interface."/><term thcode="62" code="WC-1329" name="Chlorophyll Maximum" parent="WC-C015" scope="Biogeochemical Feature: A feature in deeper water columns (often in the ocean), where phytoplankton production is locally high at depths along a surface of nutrient (nitrate) entrainment from lower-water layers."/><term thcode="62" code="WC-1330" name="Chlorophyll Minimum" parent="WC-C015" scope="Biogeochemical Feature: A layer of low chlorophyll?and hence phytoplankton?concentration (relative to adjacent waters) due to highly concentrated grazing activity."/><term thcode="62" code="WC-1331" name="Drifting Fine Woody Debris" parent="WC-C015" scope="Biogeochemical Feature: Aggregations of floating or suspended fine woody material such as small tree branches, husks or fibrous seeds, with a median particle size &lt; 64 millimeters."/><term thcode="62" code="WC-1332" name="Drifting Herbaceous Debris" parent="WC-C015" scope="Biogeochemical Feature: Floating or suspended detached, decaying herbaceous plant matter such as leaves, forbs or grasses, including deciduous leaves or needles, palm leaves, seagrass debris, Spartina debris."/><term thcode="62" code="WC-1333" name="Drifting Trees" parent="WC-C015" scope="Biogeochemical Feature: Floating or suspended large dead trees or very large branches, with a median particle size of greater than 4,096 millimeters."/><term thcode="62" code="WC-1334" name="Drifting Woody Debris" parent="WC-C015" scope="Biogeochemical Feature: Floating or suspended detached large branches with a median particle size of 64 millimeters to &lt; 256 millimeters such as Mangrove branches, coconut rafts."/><term thcode="62" code="WC-1335" name="Euphotic Zone" parent="WC-C015" scope="Biogeochemical Feature: The zone of the water column that is sufficiently illuminated for photosynthesis to occur."/><term thcode="62" code="WC-1336" name="Halocline" parent="WC-C015" scope="Biogeochemical Feature: The zone of rapid salinity change with depth in the water column, often separating two layers of different, homogeneous salinity. ..."/><term thcode="62" code="WC-1337" name="Lens" parent="WC-C015" scope="Biogeochemical Feature: A homogeneous parcel of water that?by composition?maintains coherence within water of different properties. Often a freshwater lens will sit perched atop saline ocean waters for long periods."/><term thcode="62" code="WC-1338" name="Lysocline" parent="WC-C015" scope="Biogeochemical Feature: The depth in the ocean at which calcium dissolution increases due to increased pressure. ..."/><term thcode="62" code="WC-1339" name="Marine Snow Aggregation" parent="WC-C015" scope="Biogeochemical Feature: A concentration of organic material in the ocean water column. ..."/><term thcode="62" code="WC-1340" name="Microlayer" parent="WC-C015" scope="Biogeochemical Feature: Any extremely thin layer of material, nutrients, organisms or specific properties that exists on or in the water column. The microlayer can be a surface film or at depth and often refers to a microbial film."/><term thcode="62" code="WC-1341" name="Nepheloid Layer" parent="WC-C015" scope="Biogeochemical Feature: Layer of water that contains a high concentration of silt and sediment?usually at the benthic-water column interface. ..."/><term thcode="62" code="WC-1342" name="Neustonic Layer" parent="WC-C015" scope="Biogeochemical Feature: Layer of biota that lives at the surface of the water. ..."/><term thcode="62" code="WC-1345" name="Nutricline" parent="WC-C015" scope="Biogeochemical Feature: The zone of rapid nutrient change with depth in the water column, often as a result of entrainment of water from a lower depth that is higher in concentration of a particular nutrient. ..."/><term thcode="62" code="WC-1343" name="Nutrient Maximum" parent="WC-C015" scope="Biogeochemical Feature: A layer or region in the water column that has high concentrations of a particular nutrient or nutrients due either to biological transformation or to abiotic factors such as advection or entrainment from adjacent water masses."/><term thcode="62" code="WC-1344" name="Nutrient Minimum" parent="WC-C015" scope="Biogeochemical Feature: A layer in the ocean where net nutrient accumulation is at a minimum, often due to a locus of high biological activity drawing down nutrient stocks."/><term thcode="62" code="WC-1348" name="Oxycline" parent="WC-C015" scope="Biogeochemical Feature: Zone in the water column where oxygen concentration changes rapidly with depth, often as a result of biological or abiotic processes that consume oxygen. ..."/><term thcode="62" code="WC-1346" name="Oxygen Maximum" parent="WC-C015" scope="Biogeochemical Feature: A layer in the ocean where oxygen concentration is at a minimum, often due to a locus of high respiratory activity, notably microbial."/><term thcode="62" code="WC-1347" name="Oxygen Minimum" parent="WC-C015" scope="Biogeochemical Feature: Region in the water column where oxygen is reduced (relative to surrounding waters) due to high respiration rates, usually associated with high concentrations of organic matter."/><term thcode="62" code="WC-1349" name="Sea Foam" parent="WC-C015" scope="Biogeochemical Feature: Sea foam is produced by turbulent mixing and agitation of surface waters, enhanced by high concentrations of dissolved organic matter (DOM)."/><term thcode="62" code="WC-1350" name="Seep" parent="WC-C015" scope="Biogeochemical Feature: Area on the ocean bottom where fluid slowly emerges. ..."/><term thcode="62" code="WC-1351" name="Surface Film" parent="WC-C015" scope="Biogeochemical Feature: Thin layer of materials and biota that exist on the surface of the water, often only a few microns thick. ..."/><term thcode="62" code="WC-1352" name="Surface Mixed Layer" parent="WC-C015" scope="Biogeochemical Feature: The layer of water at the ocean surface that is mixed by wind. ..."/><term thcode="62" code="WC-1353" name="Thermocline" parent="WC-C015" scope="Biogeochemical Feature: The zone of rapid temperature change with depth in the water column, often separating two layers of different, homogeneous temperature. ..."/><term thcode="62" code="WC-1354" name="Turbidity Maximum" parent="WC-C015" scope="Biogeochemical Feature: Region in an estuary where turbidity is high, due to concentration of particulates in the water column. ..."/></nt></descriptor>