ABSTRACT
Algae are an autotrophic group of plants with about 33,000 species. The algae occupy an unique position among primary producers: they are an important link in the food chain and are essential to the economy of freshwater and marine environments as food organisms.1 Algae exhibit extreme diversity of forms and shapes, some occur as single cells, others are colonial and the remaining form thallus. Most of them live in aquatic habitats, few occur on land, usually on tree trunks, soil surface, rocks and snow surface. Some algae are symbiotic to fungi forming lichens or they occur in cytoplasm of lower animals, eg in Ciliates.2 They are characterized by a high adaptive ability to the environmental conditions both physical and chemical occurring in waterways. Thus, these organisms can serve as biological monitors of water quality and as indicator species in the assessment of environmental impact of pollutants. They are used as ecological indicators of the algal bioassays.3-6
Since 1900, the concept of algal assays has provided a methodology for determining of limits toxic factors for growth and productivity of algae. The use of algal assays methods is indispensable in obtaining necessary information concerning different factors that act together in various environments and cause distortive effects in the ecosystem. Algal assays are the source of relevant, quantitative information regarding the availability of chemical substances to algae and their different stimulative and inhibitory effects.7 Moreover, algal assays contribute to efficient analysis of biological water quality and are necessary to obtain appropriate quantitative data expressing the relationship between the pollution load and the biological response of the receiving water.8-11 Algal bioassays (in the laboratory and experiments in situ) introduce the possibility of a fruitful combination of different measurements in ecotoxicological tests.
