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Algae as primary producers are highly important in aquatic ecosystems and provide a variety of environmental and anthropogenic services. In small lotic ecosystems in agriculturally influenced landscapes, algae are often the main constituent of the base of the food web and they contribute considerably to biodiversity. Within these small lotic ecosystems, algae are influenced by both natural stressors, such as flow regime and dry-out events, and anthropogenic factors. Agricultural practices especially influence algal communities by introducing plant protection products (PPP) and fertilizers into the water. The impacts of these exposures and how they affect planktonic algae in particular are not yet well studied in small lotic ecosystems. However, the protection of algae as primary producers is of high relevance and was thus included in official biomonitoring programs such as the European Water Framework Directive (WFD) or in risk assessment of e.g. PPPs. Hence, this thesis addresses this knowledge gap and links new information on algal communities in small lotic ecosystems with biomonitoring and risk assessment.
Data was gathered from small ditches and streams in central Germany as well as from laboratory algal assays. A technique to rapidly classify and quantify planktonic and benthic algae based on their photopigment concentration (measured via delayed fluorescence - DF) in ecological and ecotoxicological studies was assessed, both in the laboratory and in the field. This research provides insight into planktonic and benthic algal communities in small streams and ditches in order to improve management and protection strategies in the face of increased agricultural chemical input. ...