Biomonitoring: appropriate technology for the 21 century

Biomonitoring is no more than a toolbox of techniques that we can use to keep a check on the integrity (or 'health') of aquatic ecosystems. Organisms that live their whole lives in water would not be present if conditions at any time during their lives had been too poor to sustain them. They can thus provide information on the environmental conditions that must have pertained in the river since they were born. In contrast, chemical analyses provide accurate measures of the amounts of individual substances in the water, but this will reflect the conditions in the river only at the instant of sampling. Thus biomonitoring methods provide us with an integrated view of the state of our ecosystems and the quality of their waters. Biomonitoring techniques vary from very simple to very complex. The South African Scoring System (SASS) is of intermediate complexity, requiring some knowledge of invertebrate taxonomy but usable by technicians in the field and able to pinpoint sources of pollution with remarkable accuracy. More complex systems, which require identification to species level, or chemical analyses of animal tissues, are sometimes used for more specific purposes. Biomonitoring truly is 'appropriate' technology because it makes use of existing, synthesised information already present, in the form of the animals and plants, in an aquatic ecosystem. Careful selection of tools can provide a quicker, cheaper and more integrated picture of water quality or ecosystem integrity than the expensive, routine monitoring of water chemistry.