Biodiversity, bioindicators and biogeography of freshwater algae.

Abstract

Abstract Biodiversity and the problems associated with it are outlined and then the focus turns to continental waters. Levels and factors affecting biodiversity are described and listed. Measures of diversity focus on species richness and the Shannon index using abundances and biovolumes. Spatial scales of measuring and monitoring of biodiversity are listed and explained. Diversity of algae is then discussed in detail, including phytoplankton and algae on substrates, and a discussion of the paradox of the plankton and the 'everything is everywhere' hypothesis. The biogeographic distributions of algal groups are mentioned, with a particular focus on endemism, followed by a brief consideration of trophic interactions. Biodiversity of algae is described and evaluated from five case studies using long-term data on phytoplankton from three lakes, a length profile of plankton from the River Danube and epilithic algae from an artificial system. The results and findings are critically discussed with respect to advantages and drawbacks in using single indices. The use of algae and their diversity as biological indicators (biomarkers) in environmental assessments is finally outlined, followed by concluding remarks.