Biomagnification

Biomagnification is one aspect of bioaccumulation. It describes the enrichment of environmental pollutants in living organisms through the food. The accumulation of pollutants on the body surfaces of organisms (lungs, gills, skin ) is the second aspect of bioaccumulation and bioconcentration is called; this recording path, particularly for many aquatic organisms of importance include the substances via gills and skin.

Conditions of biomagnification

The biomagnification relates in particular to substances that have a long biological half-life, that is only slowly decomposed by living organisms due to their chemical properties (see octanol - water partition coefficient) in adipose tissue or, for example, accumulate in the bone. These substances accumulate and thus can use the continuous flow of material through the food chain in increasingly higher concentrations occur.

This process is mainly due to the fact that the substance is an end link of the food chain has been (eg Osprey ) from much more biomass of the next lower food chain member ( eg fish ) set up and the fat-soluble ( lipophilic ) substances mainly in eating organism remain and enriched ( accumulated ) are. For example, if an osprey has eaten twice as much contaminated fish mass, as his body weight, then with him can the additional concentration of the pollutant per kilogram of body weight to be twice as high as in fish. Some pollutants are partly excreted or biochemically degraded so that the load can be limited in time. However, interactions between different pollutants and their degradation products may occur. Biomagnification is significant especially for very lipophilic substances, as well as some heavy metals and radioactive substances as well as scarcely degraded or excreted from the body. With increasing length of the food chain bioaccumulation is increasingly greater under such conditions.

In addition, the accumulation in the assembly and support fabric plays an important role. These are the bones and cartilage in vertebrates.

Fat-soluble pollutants

A prime example of biomagnification was long the insecticide DDT, which is used for the control of malaria vectors. It is highly lipid soluble and is only very slowly metabolized in the body into water-soluble compounds. After a classic, with respect to data interpretation, however, partly speculative study, the concentration of DDT has on zooplankton in the ocean (0.04 ppm) to the final consumer of the suspected food chain, the osprey (25 ppm ) to increase the 625fache. According to this model is to be expected in fat-soluble persistent connections for the end links of the food chain the highest concentration and therefore, the most vulnerable. Another example is the Minamata disease, which is triggered in humans by consumption of fish when they are enriched through the food chain with organic mercury compounds.

Later investigations and experiments, however, have often shown that in purely aquatic food chains ( from water and plankton to fish ), the process of bioconcentration, ie the direct uptake of pollutants through the skin or gills of organisms quantitatively usually more important than the biomagnification has. However arises on these surfaces also some balance and a decrease in the concentration in the water (partially but only moderate ) leaching of the fat-soluble substance from the fish. If fish-eating birds have a significantly higher concentration than fish or invertebrates, therefore, this is also related to the fact that in them the connection is not in the same sense may be in an exchange equilibrium with the surrounding medium, but at most on excretion can be partially reduced. Biomagnification in the food chain plays it on the mainland a significant role in the accumulation of pollutants.

Consequences

As a result of biomagnification of the effects of toxins, pollutants and their degradation products can have devastating effects on the final links of the food chain (including the people ) have, which is why many of these compounds may no longer be applied today ( at least in Europe ).

Others

The term biomagnification is applied not only to consciously used poisons (eg chemical pesticides), but also eg for toxic substances such as mercury, which enter passively or by disposal in waters or contaminated sites ( munitions, waste disposal ) in soil are present. Thus accumulated mercury in the form of the lipophilic methyl mercury in fish tissue and subsequent fish consumption in humans.

The metabolism is observed that some substances are replaced by chemically similar, but actually undesirable substances. Radioactive cesium is highly concentrated in plants, because it is chemically behaves similarly to potassium. Cadmium is taken as a substitute for calcium deficiency.