USE OF ALGAE AND OTHER PLANTS FOR MONITORING RIVERS

A brief account is given of the methods developed for use of algae, br yophytes and angiosperms to monitor rivers and streams. The methods fa ll broadly into those based on features of populations of representati ve species, those based on part or all of the whole photosynthetic com munity and those based on various types of bioassay and ecotoxicologic al test. The methodology for using bioaccumulation of heavy metals, in secticides and other organic molecules is well developed and has been applied widely in western Europe for practical purposes. Coarse filame ntous algae and bryophytes are especially useful, but some angiosperms are suitable, provided general information about bioaccumulation in t he particular species is available; it is difficult to use periphyton. Other methods based on species include measurement of genetic toleran ce, physiological approaches (chlorophyll: phaeophytin ratio, tissue N :P ratio and surface phosphatase assays) and observations on cyanobact erial and eukaryotic algal morphology. Among community-based methods f or monitoring, measurement of biomass is used widely for phytoplankton , but seems of little use for benthos. The use of indices based on ben thic communities, especially diatoms, has, however, been applied widel y. The earlier indices based on diversity have been replaced almost en tirely by ones integrating ecological information from component speci es. In addition, the authors have started to produce a diatom-based pa rallel to the macroinvertebrate-based RIVPACS by obtaining floristic d ata from 'clean' sites. Bioassays and ecological tests, mainly using a lgae or Lemna, are often carried out together with the other methods.