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close this bookBiological Monitoring: Signals from the Environment (GTZ, 1991)
close this folderBioindicators and biomonitors in aquatic ecosystems with special attention to potential applications in developing countries
View the document(introduction...)
View the document0. Abstract
View the document1. The context
Open this folder and view contents2. Means of detecting water pollution
Open this folder and view contents3. Biological assessment
View the document4. Water evaluation by remote sensing
View the document5. Summary: Use of bioindicators and biomonitors in developing countries
View the documentReferences

1. The context

As the population of the world grows, human beings are placing ever-increasing demands on their environment. This also applies to the earth's bodies of water: oceans, seas, lakes, rivers. Water is not just used for drinking. In the "developed" countries enormous environmental problems have already been caused by contamination of bodies of water with excrete and substances used in agriculture (such as mineral fertilizers and pesticides), as well by the adverse effects of industrial activities, namely chemical pollutants such as heavy metals and organic compounds, and thermal pollution caused by the discharge of heated cooling water. Under the climatic and other conditions of the subtropics and tropics, increasing industrialization and population growth are leading to particularly serious problems of this kind, although they are often not recognized as such for lack of appropriate investigational means. The situation is further aggravated by the fact that numerous industrial production facilities are being shifted, for cost-related reasons, from the "developed countries" to parts of the world in which wages are lower and less stringent environmental legislation exists. Moreover, many of these countries do not have sufficient financial resources for implementation of measures to combat water pollution.

71% of the earth's surface is covered by water, but fresh water- vital for human beings, animals and plants - accounts for only 0.6% of the planet's total water volume. The industrialized nations of Central Europe are situated in a climatically favorable zone, as a result of which they generally have a generous supply of water at their disposal. They also possess the technological know-how and economic resources required to supply drier areas with water from regions that enjoy a surplus. By contrast, many of the developing countries are located in parts of the world with low precipitation levels and/or long dry seasons, where water is inherently a scarce commodity. Rivers or lakes that carry water all the year round are thus rare in these countries. And "rivers and lakes that carry low water volumes", especially if subject to seasonal variations, "are characterized by a greater susceptibility to pollution" (1).

Both fresh and salt water also form the habitats for innumerable organisms that play a role in human nutrition, such as seaweed, shellfish, crabs and fish, just to name a few. In Europe and North America, years ago impaired health and reproductive disorders were observed in aquatic animals and animal species that derive their sustenance from the water (2). The causes were discovered to be contaminants in the water, such as organochlorines, e.g. DDT and other insecticides, and organic heavy metal compounds, e.g. methyl mercury, which had been assimilated by the animals via their skin and respiratory systems or through food chains with associated concentration (biomagnification). In Japan heavy metal accumulation in marine animals has caused health problems in human beings who have eaten them, in some cases quite severe, and even led to fatalities (as in the so-called Minamata and Itai-ltai diseases) (3). Nonetheless, these discoveries represented only the beginning: a large number of other contaminants were subsequently diagnosed and their dispersal paths identified.

In addition to restrictions in the utilization of water bodies as sources of drinking water or otherwise, contamination of fresh water and marine water can also have a multitude of indirect deleterious effects on human beings. It is therefore of overriding importance to find and improve means of monitoring the quality of water and bodies of water as well as, if called for, changes in their pollution levels and of evaluating these factors, possibly combined with predictions for the future, in order to remedy and/or prevent harm to human beings and their environment.