Glossary of Terms

Abundance (species)

The number of individuals per species.


A procedure measuring the presence or amount or the functional activity of a target entity.

Atmospheric deposition

Chemicals or other substances that are deposited from the atmosphere onto the surface (e.g. land, water).


Bottom of a sea or lake.


The accumulation of substances, such as pesticides, or other organic chemicals in an organism.


Involves the use of live animal or plant or tissue or cell to determine the biological activity of a substance.


A biocide is a chemical substance or microorganism which can deter, render harmless, or exert a controlling effect on any harmful organism by chemical or biological means.


The variation of life forms within a given ecosystem, biome or for the entire Earth. Biodiversity is often used as a measure of the health of biological systems.

Biological sampling

Animals and plants are collected with specific devices and analysed regarding species composition and individual density. This data gives information about how natural the ecosystem is at a certain sampling site – i.e. how far away the ecosystem is from being in a completely undisturbed state. 

This kind of analysis is done for five specific groups that are also used within the EU-wide monitoring:

  • macrozoobenthos (small animals living on and in the sediments);
  • macrophytes (water plants);
  • phytobenthos (algae living attached to sediment surface);
  • phytoplankton (algae floating in water);
  • and fish.

During JDS4, zooplankton (small animals floating in water, only visible with a microscope) and microorganisms are also analysed.


A measurable indicator of a biological condition.


Biological material derived from living or recently living organisms.


Plants and animals.


Capable of causing cancer.

Chemical sampling

Water, sediment, or organism tissue is collected and analysed for chemical substances. Some of those substances are natural and good for the ecosystem, e.g. nutrients like nitrogen and phosphorus, or a variety of organic substances stemming from biodegradation. These only cause problems when their concentration is above or below certain limits. 

Other chemicals are pollutants, e.g. pesticides, pharmaceuticals or substances from industry. Limits set by the EU or by national laws exist for most of these, and their concentration should be as low as possible. However, nowadays the analytical methods are already extremely effective at detecting even minimal amounts of such substances, and thus a wide variety of them are often detected. During JDS4, water, sediment, and tissue in the Danube are all checked for thousands of chemical substances with modern methods, Searching for substances presenting a risk to both the environment and humans, and also for the information regarding which substances will have to be observed in more detail in the future. 


A green pigment found in plants and cyanobacteria.

Composition (species)

The identity of all the different organisms that make up an ecological community.


The meeting of two or more bodies of water.


This large group of species includes various familiar animals such as crabs, lobsters, crayfish, shrimp and barnacles. The majority of them are aquatic.


A type of bacteria that obtains its energy through photosynthesis (cyano means blue).

Danube River Basin Management Plan

The WFD requires all EU countries to have River Basin Management Plans, including a Programme of Measures, by 2009 and to update them in 2015 and 2021. The DRBM Plan Part A (Basin-wide overview) is coordinated by the ICPDR and based on the national RBM Plans.

Danube River Protection Convention

Signed in 1994 by Danube countries and the EU, it is the major legal instrument for cooperation and transboundary water management in the Danube River Basin.

Density (species)

The number of individuals of a species in an area.


A major algae group and one of the most common types of phytoplankton.

Diversity (species)

The number of species within a biological community (also known as “richness”).


Deoxyribonucleic acid is a molecule that encodes the genetic instructions used in the development and functioning of all known living organisms and many viruses.

Dominance (species)

The species that predominates in an ecological community, particularly when they are most numerous or form the bulk of the biomass.


(aka “Environmental DNA”). Animals and plants living in the Danube leave their traces in the water in the form of microscopic particles from their body. The DNA in those particles (eDNA found in the environment in contrast to the “organismic DNA” found directly in the body) can be analysed and compared to “barcodes” in a database. Such a “barcode” is the genetic information for a single species that is necessary for its identification. With this revolutionary method, the presence of animals and plants can be detected in a water sample without catching or collecting them – even without observing them directly! During JDS4, brand new eDNA methods are being tested in comparison to conventional methods of aquatic species identification. In the future, the use of eDNA could revolutionize biological research and biological monitoring for the assessment of ecological quality.

Electric fishing

The act of using an electric field in water to stun fish so they can be collected with a net, assessed and then released, usually unharmed.

Emerging substances

Chemicals discovered in water which have not been detected previously, or those detected at levels that may be significantly different than expected.

Endocrine disrupting compounds

Organic compounds which can significantly impact the hormones of animals such as humans, fish and snails.

Environmental quality standards (EQS)

Under the WFD, EQS refer to commonly agreed concentration levels that are acceptable for “good chemical status”, used by scientists as toxicity indicators.


Elevated production of biomass in waters mainly due to an overload of nutrients (typically nitrogen or phosphorus).

EU Watch List

A proposal designed to allow targeted EU-wide monitoring of substances of possible concern.


Excrement; or waste expelled from an animal's digestive tract.


A typical collection of animals found in a specific time or place.


Aquatic vertebrates (having a backbone) that are typically cold-blooded and covered with scales.

Flame retardant

Compounds added to manufactured materials to prevent the spread of fire.


Any land area susceptible to being inundated by floodwaters from any source.


A typical collection of plants found in a specific time or place.

Food chain (or web)

Shows how organisms are related with each other by the food they eat.

Good biological and ecological status

The quality required for a water body to meet WFD requirements.


The physical and biological environment on which a given species depends for its survival.


Plants that grows in a marsh, partly submerged in water.


As defined by the WFD, the physical characteristics of the shape, boundaries and content of a water body.


Free-floating or submerged plants.


Toxicity to the immune system.


A reservoir formed by a dam.

International Commission for the Protection of the Danube River (ICPDR)

The international organisation which has been established to implement the Danube River Protection Convention.

Invasive species

Non-indigenous species (e.g. plants or animals) that adversely affect the habitats they invade economically, environmentally or ecologically.


The first Joint Danube Survey coordinated by the ICPDR in 2001.


The second Joint Danube Survey coordinated by the ICPDR in 2007.


The third Joint Danube Survey coordinated by the ICPDR in 2013.

JDS x,y…

JDS sampling site numbers

Joint Program of Measures

Part of the DRBM Plan Part, this is a summary of the national Programmes of Measures and some of the common activities of the Danube Basin countries in the ICPDR.


Aquatic insects, worms, clams, snails and other animals without backbones that can be determined without the aid of a microscope and that live in or on sediments.


Aquatic plants, either free-floating or attached to the bottom, which can be determined by the naked eye without the need for a microscope.


(Also Macroinvertebrates): Small animals without backbones that live on or in the sediments underwater and can be seen without the help of a microscope (i.e. larger than 0.5 mm). A huge variety of aquatic insects, worms, snails, clams, crabs and other animals belong to this group.


Includes all the things your body does to turn food into energy and keep you going.


The study of microscopic organisms that are unicellular or exist in cell clusters.


Can damage genes and possibly cause cancer.


Substances such as nitrogen and phosphorus, used by organisms to grow.

Nutrient pollution

Contamination of water resources by excessive inputs of nutrients. In surface waters, excess algal production is a major concern.

Nutrient retention

Plants are able to absorb and retain nutrients, and therefore reduce nutrient pollution.

Order of magnitude

An amount equal to ten times a given value.

Organic compounds

Natural or synthetic substances based on carbon.

Organic pollution

Occurs when an excess of organic matter, such as manure or sewage, enters the water.

Passive Sampling

“Passive sampling” is a technique used to monitor an environment, whereby a medium is collected over time in something, such as a man-made device or biological organism. This is in contrast to “grab sampling”, which involves taking a sample directly from the media of interest at a single point in time. In passive sampling, average chemical concentrations are calculated over a device's deployment time, which avoids the need to visit a sampling site multiple times to collect multiple representative samples.

Currently, passive samplers have been developed and deployed to detect toxic metals, pesticides, pharmaceuticals, radionuclides, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and other organic compounds in water. Notably, some passive samplers can be used to detect hazardous substances in the air.


A characteristic, feature, or measurable factor that can help in defining a particular system.


Bacteria, viruses, parasites or fungi that can cause disease.


Any water in a sea or lake that is neither close to the bottom nor near the shore.

Perfluorinated acids

Chemicals that repel water and oil and are resistant to heat and chemical stress.

Persistent organic pollutants (POPs)

Chemicals that remain intact in the environment for long periods, become widely distributed geographically, accumulate in the fatty tissue of living organisms and are toxic to humans and wildlife.


A substance, usually chemical, used to kill unwanted plants and animals.


Microscopic plants such as algae that live in the bottom layers of the river and seabed.


Plants, mainly microscopic, existing in water bodies.

Point source

A well defined source of pollution from a single point, such as a pipe. Non-point sources of pollution enter water from a dispersed (or “diffuse”) and uncontrolled source, such as runoff from land or from the atmosphere, rather than through a pipe.


Substances that increase the plasticity or fluidity of a material, especially for plastics such as polyvinyl chloride (PVC).

Ponto-Caspian origin

From the Black, Caspian or Azov Sea.

Primary producers

Use sunlight, water, chlorophyll and carbon dioxide to synthesize organic compounds.

Priority substances

The EU’s ‘Priority Substances’ or groups of substances which have been shown to be of major concern for European waters. Priority Substances include organic compounds and heavy metals.


The spontaneous discharge of radiation from atomic nuclei.


The Danube is split into three “reaches” (see page 9 box for more).


Large boulders that have been artificially placed to fix riverbanks, especially at channelized and impounded river sections.


Distance in the river upstream from the river’s mouth (for the Danube River, distance from the Danube Delta).


Material that was suspended in water and that settles at the bottom of a body of water.

Species abundance

The number of individuals per species. Relative abundance species is the species abundance relative to the abundances of other species represented in the community.

Species diversity

The number of species within a biological community (also known as “species richness”).


The surface on which a plant lives. Suspended sediment refers to the solid particles, suspended within the water column, which the water is carrying. Also known as suspended particulate matter (SPM).

Taxon (sg), Taxa (pl)

A group or category of living organisms.


Capable of causing birth defects.


The degree to which a substance can damage an organism.


Study of the effects of chemicals on living organisms.

Trans-National Monitoring Network (TNMN)

Coordinated by the ICPDR, it comprises over 75 monitoring stations and provides a regular overview of the main chemical and physical parameters important for assessing water quality.


A river that flows into a larger river or other body of water.


The cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye. 

Vascular plants

Having tissues for conducting water and minerals throughout the plant.

Water Framework Directive (WFD)

Directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000 establishing a framework for Community action in the field of water policy.


Tiny invertebrates (animals without backbones) that float freely in water bodies.