Glossary related to the Black Sea

Some terminology explained

anoxic = anaerobic = conditions without oxygen or air present. Oxygen is needed to break down many compounds.

ballast water = not the same as bilge water. Large ships often carry ballast water in tanks and use it to maintain a ship's balance. It is usually taken in from local bays and estuaries and contains plants and animals. It is released again - with its organisms - at other ports when receiving or unloading cargo. This is how so-called exotic species can be introduced to for instance the Black Sea.

bioaccumulate = accumulate (a substance) in the bodies of animals and humans. The higher in the food web, the more of the substance tends to be accumulated. Fishes eat smaller fishes, birds eat fishes, humans eat birds and small fishes and large fishes.

bilge water = dirty water that collects in an area at the bottom of a ship. It is often polluted with - for instance - oil. Not the same as ballast water.

erosion = denudation, degradation of the earth's surface. Mainly used to indicate the results of a range of terrestrial breakdown processes, such as weathering, transportation (rivers), chemical and mechanical actions of wind, water and ice. Example of results of mechanical action of a river: the Grand Canyon. A landslide is also a form of erosion.

eutrophication = the process that renders water eutrophic, which means that it contains abundant or too many plant nutrients (mainly nitrate and phosphate). Eutrophication = overfertilisation. It often leads to a severe disturbance in the ecological balance, causing a shift in species composition: some plants and animals dissappear and different plants and animals take over. Use of agricultural fertilizers and detergents and lack of wastewater cleanup are factors that can contribute to eutrophication.

euxinic = refers to a water environment in which there is very little water circulation and no oxygen. The word was actually derived from the Black Sea (=Pontus Euxinus). The word is also used for the black sediments that are typically found on the bottom of such a sea. Because there is no oxygen, organic materials (from plants and animals) does not break down and this results in the black colour (think of coal of black shales).

exotic species = animal or plant species that do not belong in a certain geographic area, but were usually accidentally introduced. Examples are certain parakeets in Europe and the United States as well as certain jellyfish in the Black Sea.

heavy metals: a term often used to indicate polluting metal ions that are persistent in the environment and potentially toxic, such as arsenic, cadmium, lead, mercury, vanadium and zinc. It is not a chemically correct term. See this article in IUPAC's magazine Chemistry International, Vol. 23, No. 6 (November 2001) and this other article in IUPAC's magazine Chemistry International, Vol. 24, No. 5 (September 2002).

limiting nutrient = the nutrient that runs out first and is therefore limiting to biological growth. This is not necessarily the nutrient with the lowest dissolved concentration in the water.

• First of all, the issue of bioavailability may play a role: what is around may not be in a form that is suitable as nutrient for the organism (may not be bioavailable). (In other words, chemical speciation plays a role.)
• Second, of one nutrient much more may be needed than of another.
• Third, there is constant turnover and many nutrients are actually in the organism. If there is sufficient oxygen (in the upper water layers), dying organisms degrade into nutrients. Picture a situation in which these nutrients are immediately taken up by the living organisms. The nutrient concentrations in the water may be very low, yet there may be plenty of nutrients.

nutrients = essential components of food = nourishing substances. Phosphate, silicate and nitrate are the main nutrients for marine organisms. Metals such as cobalt and iron are important too (for enzyme function, for instance). Use of agricultural fertilizers and detergents and lack of wastewater cleanup are factors that can contribute to 'overfeeding' of the aqueous environment. This is called eutrophication.

organic matter = basically, nature's waste. To a large degree, also our own household waste and sewage.

PCBs = polychlorinated biphenyls = commercially manufactured compounds. The US Department of Labor defines them as 'nonflammable liquids that are highly resistent to electrical current. These related chlorinated hydrocarbon chemicals are used to fill electrical devices such as transformers to aid in the storage of electrical charge. PCBs are extremely toxic to humans and wildlife, posing carcinogenic and other health risks to humans.'.

POPs = Persistent Organic Pollutants = pollutants with a certain chemical composition that do not break down easily (are persistent). The United Nations define POPs as 'organic substances that:

1. possess toxic characteristics;
2. are persistent;
3. bioaccumulate;
4. are prone to long-range transboundary atmospheric transport and deposition; and
5. are likely to cause significant adverse human health or environmental effects near to and distant from their sources'.

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Most recent update: January 16, 2008