A region at the bottom level of a body of water, including surface and sub-surface sediments and the organisms that reside within this region.
Benthos
The organisms and materials associated with or residing within the benthic region of a body of water.
Bioaccumulation
The accumulation of a substance from an environmental source within the tissue(s) of an exposed organism.
Biochemical Oxygen Demand (BOD)
A measurement of the oxygen required by aerobic microorganisms to decompose organic matter within a body of water.
Contaminant
A substance, present within sediment, porewater, or tissues at levels that have the potential to harm the marine environment. Substances are considered contaminants when they are present in concentrations greater than naturally expected or contained in areas where they would not be naturally present.
Dispersal
The spreading or movement of material from one area to another.
Disposal site
A site or area where aquatic disposal of a material is permitted in accordance with the terms and conditions of a valid disposal at sea permit. A disposal site is comprised of a release zone, and any associated footprint and area of influence.
Dissolved oxygen
A measure of the amount of oxygen dissolved in water that is available for use by organisms within a body of water, and an indicator of the ability of a body of water to support aquatic life.
Erodability
The tendency of a disposed material to be worn away by natural forces within the water body (versus its tendency to remain in place, despite the presence of natural forces that have the potential to disperse it).
Estuary
A coastal area, generally at the mouth of a river, where saltwater from the sea mixes with freshwater flowing from river and their catchment areas.
High Molecular Weight Hydrocarbons
Hydrocarbons are a class of organic compounds that consist of carbon and hydrogen bonds only. A hydrocarbon is considered to have a high molecular weight when it has five or more carbon rings. High molecular weight hydrocarbons are generally introduced into the environment as a result of industrial activities such as manufacturing, expending fossil fuels, or burning municipal and industrial waste.
In situ
In place or on site.
Littoral zone
Refers to the zone of water near or along the shoreline.
Macrofauna
For the purposes of disposal at sea, macrofauna are benthic organisms that are larger than 0.5 mmFootnote 19 in size.
Meiofauna
For the purposes of disposal at sea, meiofauna are benthic organisms between 0.5 mm and 0.062 mmFootnote 19 in size.
Microfauna
For the purposes of disposal at sea, microfauna are benthic organisms that are smaller than 0.062 mmFootnote 19 in size.
Nutrients
Substances considered to promote the growth of organisms (for example, nitrogen or phosphorus), but that can have adverse effects on the marine environment when present at elevated levels.
pH
For the purposes of disposal at sea, pH is a numeric value that measures the acidity or basicity of the sediment or water at the load or disposal site. pH values range on a scale of 0 to 14, with values less than 7 generally considered acidic and values greater than 7 generally considered basic. pH is one factor that affects the bioavailability of contaminants present in water or sediment.
Pycnocline
Refers to the layer of water in the ocean where the water density increases rapidly with depth due to changes in salinity and temperature. When the change in density is a result of temperature then it is referred to as the thermocline.
Quality assurance and quality control (QA/QC)
The management, procedures and techniques used to assess and ensure that reliable, accurate, and valid data are obtained.
Residual adverse effects
For the purpose of this document, a residual adverse effect is a harmful effect caused by the disposal of material after the act of disposal has occurred.
Salinity
A measure of the concentration of dissolved salts within a body of water.
Sediment
Sand, silt, clay, or other particulate materials that have accumulated at the bottom of a water body or are suspended within a water body.
Shoaling
A change in wave behaviour due to a change in the morphology of the seabed, such as the creation of a mound on the sea floor following the dumping of waste material, or the creation of a depression in the sea floor following the dredging of sediments.
Substrate
For the purpose of disposal at sea, the substrate refers to the sediment layer at the bottom of a water body.
Suspended sediment
Inorganic and organic particles that are suspended in water. Fine particles of sand, silt, and clay, as well as other biological or other solid materials may be suspended in the water column.
Thermocline
See Pycnocline.
Thin layer disposal
A method of disposing of dredged material in a controlled manner, typically involving high-pressure spraying over open water, resulting in a layer of sediment 30 cm thick or less, once settled, and often conducted to minimize the physical effects of disposal on biological resources.Footnote20
Tidal ellipse
A visual representation of the direction and magnitude (vectors) of tidal currents throughout one or more tidal cycles. The orientation of the tidal ellipse is measured in degrees, clockwise or counter-clockwise with respect to 1 of the 4 cardinal directions.
Total Organic Carbon (TOC)
A measurement of the total amount of organic material present within a body of sediment. TOC is often used as an indicator of potential sediment contamination, because many types of contaminants will bind preferentially to organic matter.
Toxicology
The study of toxicity, involving an analysis of the potential or ability of a contaminant to cause adverse effects in exposed organisms.
Turbidity
Turbidity is a measure of the transparency of a body of water. Variations in the amount of sediment that is suspended within the water column is one factor that can affect turbidity levels.
Turbidity plume
In the context of disposal at sea, a turbidity plume refers to a sudden visible increase in turbidity due to an increase in suspended sediments during disposal.
