Applications

For the most part, ABC curves have been used to indicate pollution or disturbance effects on marine and estuarine macrobenthic assemblages, which are the main target for detection and monitoring programs in these habitats. For example, ABC curves for the macrobenthos in Loch Linnhe, Scotland in response to organic pollution between 1963 and 1973 are given in Figure 2. The time course of pollution from a pulp mill, and changes in species diversity (H), are shown top left. Moderate pollution started in 1966, and by 1968 species diversity was reduced. Prior to 1968 the ABC curves had the unpolluted configuration. From 1968 to 1970 the ABC plots indicated moderate pollution. In 1970 there was an increase in pollutant loadings and a further reduction in species diversity, reaching a minimum in 1972, and the ABC plots for 1971 and 1972 show the grossly polluted configuration. In 1972 pollution decreased and by 1973 diversity had increased, and the ABC plots again indicated the unpolluted condition. Thus, the ABC plots provide a good snapshot of the pollution status of the benthic community in any one year, without reference to the historical comparative data which would be necessary if a single species diversity measure based on the abundance distribution was used as the only criterion.

Most studies suggest that the ABC curves respond to anthropogenic perturbations but are not affected by long-term natural stresses, since the organisms living in such environments have evolved adaptations to the prevailing ecological conditions. Unperturbed ABC plots may be found, for example, in estuaries where the organisms are subjected to low and fluctuating salinities, provided there are no anthropogenic disturbances. ABC plots indicated that macrobenthic communities near an oil refinery in Trinidad were grossly to moderately stressed, while those close to the Trinidad Pitch Lake (one of the largest natural oil seeps in the world) were not. There is little evidence, however, that the method can distinguish between different types of anthropogenic disturbances. Responses to organic pollution and to physical disturbance caused by demersal trawl fisheries, for example, appear to be similar.

The method has been less well explored with respect to other components of the biota. However, it has been used successfully to indicate environmental impacts on marine phytoplankton, the cryptofauna and mollusks of rocky shores, invertebrates of freshwater streams, and fish assemblages in both marine and freshwater.

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