Home | Search/Browse

Layer Subcomponent (WC)


Unit name Description
Estuarine Coastal Surface Layer Estuarine waters between the shore and the 4 meter depth contour at the surface of the water column to a depth of a few centimeters.
Estuarine Coastal Upper Water Column Estuarine waters above the pycnocline (or the mid-depth) between the shore and the 4 meter depth contour.
Estuarine Coastal Pycnocline Estuarine waters within the pycnocline, between the shore and the 4 meter depth contour.
Estuarine Coastal Lower Water Column Estuarine waters below the pycnocline (or mid-depth) and between the shore and the 4 meter depth contour.
Estuarine Open Water Surface Layer Estuarine waters at the surface, at or beyond the 4 meter depth contour.
Estuarine Open Water Upper Water Column Estuarine waters above the pycnocline (or mid-depth), at or beyond the 4 meter depth contour.
Estuarine Open Water Pycnocline Estuarine waters within the pycnocline, at or beyond the 4 meter depth contour.
Estuarine Open Water Lower Water Column Estuarine waters below the pycnocline (or mid-depth), at or beyond the 4 meter depth contour.
Estuarine Tidal Riverine Coastal Surface Layer Tidal fresh waters at the surface, from the land-water interface up to the 4 meter depth contour.
Estuarine Tidal Riverine Coastal Upper Water Column Tidal fresh waters above the pycnocline (or mid-depth), from the land-water interface up to the 4 meter depth contour.
Estuarine Tidal Riverine Coastal Pycnocline Tidal fresh waters within the pycnocline, from the land-water interface up to the 4 meter depth contour.
Estuarine Tidal Riverine Coastal Lower Water Column Tidal fresh waters below the pycnocline (or mid-depth), from the land-water interface up to the 4 meter depth contour.
Estuarine Tidal Riverine Open Water Surface Layer Tidal fresh waters at the surface, at or beyond the 4 meter depth contour.
Estuarine Tidal Riverine Open Water Upper Water Column Tidal fresh waters above the pycnocline (or mid-depth), at or beyond the 4 meter depth contour.
Estuarine Tidal Riverine Open Water Pycnocline Tidal fresh waters within the pycnocline, at or beyond the 4 meter depth contour.
Estuarine Tidal Riverine Open Water Lower Water Column Tidal fresh waters below the pycnocline (or mid-depth), at or beyond the 4 meter depth contour.
Marine Nearshore Surface Layer Marine waters at the surface, from the land-water interface up to the 30 meter depth contour.
Marine Nearshore Upper Water Column Marine waters above the pycnocline (or mid-depth), from the land-water interface up to the 30 meter depth contour.
Marine Nearshore Pycnocline Marine waters within the pycnocline, from the land-water interface up to the 30 meter depth contour.
Marine Nearshore Lower Water Column Marine waters below the pycnocline (or mid-depth), from the land-water interface up to the 30 meter depth contour.
Marine Offshore Surface Layer Marine waters at the surface, between the 30 meter depth contour and the shelf break.
Marine Offshore Upper Water Column Marine waters above the pycnocline (or mid-depth), between the 30 meter depth contour and the shelf break.
Marine Offshore Pycnocline Marine waters within the pycnocline, between the 30 meter depth contour and the shelf break.
Marine Offshore Lower Water Column Marine waters below the pycnocline (or mid-depth), between the 30 meter depth contour and the shelf break.
Marine Oceanic Surface Layer The interface between the atmosphere and the water column, extending to a depth of several centimeters. Surface films, floating vegetation, and aggregations of materials or biota accumulate at the surface, which also represents the surface of maximum exchange of atmospheric gases, heat, and light.
Marine Oceanic Epipelagic Upper Layer The Epipelagic Layer is the upper 200 meters of the oceanic water column. Within the Epipelagic, the Marine Oceanic Epipelagic Upper Layer is the region between the sea surface and the Epipelagic Pycnocline, if present, or mid-depth in the Epipelagic zone at 100 meters. This layer is generally well-mixed, well-lighted, and highly oxygenated, and supports photosynthesis largely throughout, although weakly in the lower depths. It has no contact with, and very minimal influence from land, and is very clear compared to coastal water masses. It is the zone of maximal productivity in the Oceanic Subsystem.
Marine Oceanic Epipelagic Pycnocline Within the Epipelagic Layer, the Marine Oceanic Epipelagic Pycnocline is the zone of maximum vertical change in density of the water normally due to a salinity or temperature gradient, which segregates the water column into two distinct layers that are of relatively homogeneous density. The presence of a pycnocline provides a barrier to mixing between the upper and lower water columns, and this layer enhances the stability of the water column preventing mixing to the bottom.
Marine Oceanic Epipelagic Lower Layer Within the Epipelagic Layer, the region below the Epipelagic pycnocline if present (or below mid-depth [100 meters]). Photosynthesis can generally occur through this layer although diminishing with depth to the critical depth for phytoplankton, which represents the point where production and respiration are in balance and no net productivity occurs. The lower bound of the Epipelagic Lower Layer is the bottom of the Epipelagic Layer at 200 meters.
Marine Oceanic Mesopelagic Layer The region where light is vertically attenuated to below the level required for photosynthesis, generally between 200 meters and 1,000 meters in depth. Oxygen declines rapidly to a minimum, corresponding with the lower limit of the Mesopelagic Zone—due to high bacterial respiration from settling organic material.
Marine Oceanic Bathypelagic Layer The region where light does not penetrate, rendering the water column totally dark except for bioluminescence, generally from 1,000 meters to 4,000 meters depth. Organisms at these depths are subjected to immense pressure; food webs depend on organic detritus rather than active photosynthetic production. Waters in this layer generally are composed of cold, bottom currents (from sinking water masses descending from polar latitudes).
Marine Oceanic Abyssopelagic Layer The region of the water column that is generally in contact with the abyssal seafloor, except in deep basins and trenches and represents the bottom layer of the ocean, generally from 4,000 meters to 6,000 meters depth. This layer is aphotic; it receives biogenic, detrital and mineral material descending from above and this layer acts as an accumulation zone. Oozes from tests of planktonic organisms form on the seafloor and fans of sedimentary material accumulate here. There are diverse and specialized faunal communities at these depths. Trophic webs are based on chemoautotrophic processes, hydrothermal vents, decomposition of organic matter and bacterial production.
Marine Oceanic Hadalpelagic Layer The deepest waters of the globe occur in trenches and deep basins generally at depths greater than 6,000 meters. There is a high degree of tectonic and thermal activity in these areas. Waters in this layer have unique characteristics of immense pressure, strong currents, accumulation of sediments and organic material; macrofauna that occur at these extreme depths have special feeding strategies and adaptations to intense pressure and total darkness.