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Glossary and acronyms

Advection – the transfer of heat or matter by horizontal movement of water masses.

Aerobic – with the presense of oxygen. Is used to describe chemical processes or organisms that require oxygen. See also anaerobic.

Algae – a large assemblage of lower plants, formerly regarded as a single group, but now usually classified in eight separate divisions or phyla, including the blue-green algae (Cyanophyta), green algae (Chlorophyta), brown algae (Phaeophyta), red algae (Rhodophyta), diatoms and (Chrysophyta). Marine macroalgae are commonly known as seaweeds.

Ammonia (NH3) – a colourless gas formed by decomposition of protein, nitrogenous bases and urea. It is easy soluble in water and its pungent smell is well known from ammonia water.

Ammonium (NH4+) – a nitrogen compound, an ion derived from ammonia.

Anaerobic – without the presense of oxygen. Is used to describe chemical processes or organisms that does not require oxygen. See also aerobic.

Anoxic – the state of oxygen depletion with absence of oxygen. Anoxic sediments and anoxic bottom waters are commonly produced where there is a depletion of oxygen, owing to very high organic productivity, and a lack of oxygen replenishment to the water or sediment, as in the case of stagnation or stratification of the body of water.

Aquatic – growing or living in or near water.

ASP – short for Amnesic Shellfish Poisoning. The poisoning is caused by intake of shellfish which has accumulated certain algal toxins.

Atmospheric deposition – deposition of nutrients, heavy metals and other pollutants from the atmosphere.

Autotroph – an organism which builds complex organic molecules from simple inorganic compounds. Also used to name organisms using photosynthesis in this process.

BAT – Best Available Techiques, means the most advanced activities, processes, and operating methods and the methods most effective in preventing or limiting pollution from a given sector.

Benthos – those organisms attached to, living on, in or near the sea bed, river bed or lake floor.

Bio-available – matter that is available for primary production or will become available within the residence time of the water in a given marine area.

Biomass – the weight of organisms in a certain area either described with reference to volume or area.

Bluegreen algae - marine and freshwater unicellular, colonial or filamentous bacteria. Resembles algae in the way that they have chlorophyll pigments and can perform photosynthesis.

Brackish water -water with a salt concentration between 5-18ppt.

C - carbon, see carbon biomass.

Carbon biomass – biomass as the amount of carbon (C) in a given area or volume.

Chlorophyll – Chlorophyll – any of several green pigments found in the chloroplasts of plants and in other photosynthetic organisms. They mainly absorb red and violet-blue light energy for the chemical processes of photosynthesis.

Chlorophyll a – a specific plant pigment essential for photosynthesis. It is quantitatively the most important pigment found in all photosynthetic phytoplankton cells.

Ciliate – a diverse group of one celled animal like organims. They possess cilia for locomotion and in many species for suspension feeding.

Cladoceran – water flea. A small crustacean with a carapace that forms a bivalved shield. The cladocerans are suspension feeders and collect food with fine bristles on the trunk appendages.

Contaminants – are substances that are toxic to living organisms. Most of them are hard to degrade in a natural environment.

Copepod – a small free-living or parasitic crustacean. One of the most abundant marine zooplankton organisms.

Cyanobacteria – see bluegreen algae.

Denitrification – reduction of nitrates to free nitrogen (N2) by certain bacteria.

Deposition – see atmospheric deposition

Detritus – small pieces of dead and decomposing plant and animal material, i.e. organic material.

Diatom – a unicellular algae with silicified walls. Diatoms often make up the majority of the spring bloom phytoplankton biomass.

Diffuse sources – larger geographical area, excluding city areas, from which nutrients or contaminants are washed out to the sea (see also point sources).

DIN – dissolved inorganic nitrogen. The sum of nitrate, nitrite and ammonium i.e. nitrogen that can be absorbed by plants.

Dinoflagellate – any of numerous minute, chiefly marine protozoans of the order Dinoflagellata, characteristically having two flagella and a cellulose covering and forming one of the chief constituents of plankton. They include bioluminescent forms and forms that produce red tides.

DIP – dissolved inorganic phosphorus. The chemical form in which phosphorus can be absorbed by plants.

DSP – short for Diarrhetic Shellfish Poisoning. The poisoning is caused by intake of shellfish that has accumulated certain algal toxins.

Eelgrass (Zostera marina) – a submerged flowering plant that grows along the major part of the Danish coasts.

Emission – release of chemicals to the atmosphere.

EQO – Ecological Quality Objective.

Estuary – the transition area between a river and the sea, i.e. an estuary is a body of water that is formed when fresh water from rivers flow into and mixes with salt water from the ocean. In estuaries, the fresh river water is blocked from directly entering the open ocean either by the surrounding mainland, peninsulas, barrier islands, or fringing salt marshes.

EU –EU – European Union.

Euphotic zone – Euphotic zone – the upper, illuminated zone of aquatic ecosystems. The zone of effective photosynthesis. In marine ecosystems it is much thinner than the deeper aphotic zone which is below the level of effective light penetration. It typically reaches 20–30 meters in coastal waters but extending to 100–200m in open ocean waters.

Eutrophication – is enhanced inputs of nutrients and organic matter. Eutrophication can be a natural process, but is most often caused by humans. See also box 1.

Fauna – animal organisms.

Flagellates – microscopic unicellular organisms in aquatic systems. They move by the use of one or more flagella, a string-like extension from the cell. Amongst the flagellates are both heterotophs, autotrophs and mixotrophs.

Flora – plant organisms.

Food chain – refers to direct links between organisms that describes how food energy is transfered through the ecosystem from the smallest primary producers to top predators. An example from the marine ecosystem is planktonic algae - › copepods - › fish - › seal.

Food web – a description of who eats who in an ecosystem. In its most simple form a food chain, but more commonly a net of organisms where several organisms are capable of eating the same food item.

Grazing – literally to feed on growing grasses and herbage the term refers to feeding habits of animals in the terrestrial environment. In the aquatic environment the analogue is organisms feeding on plant or plant like organisms. An example is copepods that graze on phytoplankton.

H2S – hydrogensulfide.

Halocline – a zone in which there are rapid, vertical changes in salinity. The halocline is usually well-developed in coastal regions where there is much freshwater input from rivers producing surface waters of low salinity, a zone where salinity increases rapidly with depth (the halocline) and a deeper zone of more saline, denser waters.

HELCOM – the Helsinki Commission.

Heterotroph – an organism that cannot synthesise its own food and is dependent on complex organic substances for nutrition. That is, it eats other organisms.

Hypoxia – S – see oxygen depletion.

ICES – International Council for the Exploration of the Sea.

Inorganic – a chemichal substance that does not involve neither organic life nor the products of organic life, i.e. hydrocarbon groups.

Ks – half-saturation constant. Nutrient concentration at which the phytoplankton nutrient uptake rate is reduced to half the maximum uptake rate.

Macroalgae – are plants that lack true roots, stems, leaves, and flowers. They mostly live attached to a hard substrate.

Macrozoobenthos – are animals larger than 1 mm living attached to, on, in or near the sea bed, river bed or lake floor.

Marine – of, or pertaining to, the sea, the continuous body of water covering most of the earth’s surface and surrounding its land masses. Marine waters may be fully saline, brackish or almost fresh.

Mesozooplankton – animal plankton of the size 0.2 – 2.0 mm.

Metabolism – the chemical change, constructive and destructive, occuring in living organisms.

Metazooan – multicellular, motile animal organisms with cells organized into tissues and controlled by a nervous system.

µ(prefix) – micro, 10-6.

Microbial loop – a part of the pelagic planktonic food web consisting of bacteria, flagellates and ciliates. Organisms in the microbial loop transfers energy from dissolved organic carbon back to the copepods.

Microzooplankton – animal plankton of the size 0.02 – 0.2 mm.

Mixotroph – an organism which is capable of performing photosynthesis as well a living partly as a heterotroph. Mixotrophy is commonly found among dinoflagellates. The mixotrophy appears to have different functions in different dinoflagellates; in some primarily phototrophic dinoflagellates feeding appears to be a mechanism for obtaining limiting inorganic nutrients, in some primarily heterotrophic dinoflagellates photosynthesis appears to be a mechanism for supplementing carbon metabolism..

Molar – designating a solution that contents one mole of solution per litre.

N – see nitrogen.

NAO – North Atlantic Oscillation is an index that is based on the difference in atmospheric pressure between the Azores and Iceland.

Nitrate (NO3) – an important nitrogen containing nutrient. The chemical form in which plants uptake most of their nitrogen. It is the salt of nitric acid.

Nitrogen (N) - is a chemical element that constitutes about 80% of the atmosphere by volume. Nitrogen is an important part of proteins and is essential to living organisms.

Nutrient – chemical elements which are involved in the construction of living tissue that are needed by both plants and animals. The most important in terms of bulk are carbon, hydrogen and oxygen, with other essential ones including nitrogen, potassium, calcium, sulphur and phosphorus.

Oligotrophic – applied to waters or soils that are poor in nutrients and have low primary productivity. (See also eutrophic).

Organic – organic compounds contain the element carbon. Of, relating to, or derived from living organisms.

Organism – an individual form of life. An animal, plant or bacteria.

OSPAR – the Oslo and Paris Commission.

Oxides of Nitrogen (NOx) – chemical compounds, gases, formed by nitrogen and oxygen. NOx are formed by the combustion of oil, gasoline, coal and gas. NOx is soluble in water and reacts with water or substances in water to form nitrate.

Oxygen depletion – a situation where the demand for oxygen has exceeded the supply of oxygen leading to low concentrations of oxygen. Low oxygen concentrations are normally found in the water close to the sea bottom. In Denmark, concentrations below 4 mg O2 per liter are defined as oxygen depletion and concentrations below 2 mg O2 per liter are defined as severe acute oxygen depletion.

Oxygen – a non-metallic element constituting 21 percent of the atmosphere by volume. Oxygen is produced by autotrophic organisms and is vital to oxygen breathing organisms.

P – see phosphorus.

Parthenogenesis – litterally it means virgin descent and refers to production og offspring where the female has not been fertilized by a male.

Pelagic – the open-water environment, or water column, as distinct from the bed or shore, inhabited by swimming marine organisms.

Phosphate (PO4) – is an important phosphorus containing nutrient. It is the chemical form in which plants uptake phosphorus.

Phosphorus (P) – a non-metallic chemical element.

Photosynthesis – the process in green plants and certain other organisms by which carbohydrates are synthesised from carbon dioxide and water using light as an energy source. Most forms of photosynthesis release oxygen as a by-product..

Phytoplankton – the plant plankton and primary producers (i.e. drifting, more or less microscopic, photosynthetic organisms) of aquatic ecosystems.

Plankton – free passively floating organisms (animals, plants, or microbes) in aquatic systems.

Point source – discharge from one point. The sources are sewage treatment plants, industrial plants, storm water runoff, fresh water aquaculture and mariculture.

Population –all the organisms that constitute a specific group or occur in a specified habitat.

Predator – an organism that lives by preying on other organisms.

Primary production – the production by autotrophs.

Protozooplankton – zooplankton consisting of only one cell.

Rotifer – or rotatoria commonly called wheel animals. A microscopic aquatic animal with at ciliated organ called a corona, which looks like a rotating wheel. Mostly a freshwater animal although some marine species exist.

Runoff – that part of rainfall that is not absorbed in soil but falls on or flows directly into streams and rivers.

Salinity – a measure of the total quantity of dissolved substances in water, in parts per thousand (ppt, per mille) by weight, when all organic matter has been completely oxidised, all carbonate has been converted to oxide, and bromide and iodide to chloride. The salinity of ocean water is in the range 33-38 ppt, with an average of 35 ppt.

Secchi depth – a measure of the clarity of the water.

Sediment – any material transported by water that will ultimately settle to the bottom after the water loses its transporting power. Fine waterborne matter deposited or accumulated in beds. Includes mobile or soft substrates such as cobbles, pebbles, sand and mud.

Stratification – Stratification – in the sea it is a boundary between two water masses of different specific gravity. The stratification is typically formed by differences in temperature or salinity or both.

TN – total nitrogen, which includes dissolved inorganic nitrogen and organically bound nitrogen.

Tot-N – see TN.

Tot-P – see TP.

TP – total phosphorus, which includes disssoleved inorganic phosphorus and organically bound phosphorus.

Water column – the open-water environment, as distinct from the bed or shore, which may be inhabited by swimming marine or freshwater organisms. (See pelagic).

WFD – EU Water Framework Directive.

Wet deposition – deposition of matter by rain.

Zooplankton – small planktonic animals in fresh- or sea water with almost none or no swimming capacity. They are, therefore, transported randomly by water movements.


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Danish Environmental Protection Agency & National Environmental Research Institute • updated: