Algindikatorer

Algindikatorer (algal indicators) are measurements derived from algal communities used to assess the environmental status of lakes, rivers, estuaries and coastal waters. They serve as biological indicators of nutrient enrichment, pollution and ecosystem health because algae respond directly to changes in nutrients, light, temperature and hydrology. Indicators can be based on species composition, biomass, or physiological status, and are often integrated into water quality classification schemes.

Common indicator types include: species assemblages (phytoplankton or periphyton) whose presence or absence signals eutrophication or acidification; biomass proxies such as chlorophyll-a concentration; pigment and biochemical indicators (for example pigment ratios, photosynthetic efficiency measured by fluorometry); and functional indicators like the prevalence of fast-growing cyanobacteria or toxin-producing species. Diatoms and cyanobacteria are frequently used as taxon-specific indicators in freshwater and marine systems.

Applications are widespread in environmental monitoring and regulatory programs. In freshwater systems, algal indicators help detect nutrient loading from agricultural runoff or wastewater; in estuaries and coastal zones they assist in assessing salinity stress, nutrient pulses and HAB risk. Data are gathered from water sampling, microscopic identification of species, pigment analyses (e.g., HPLC), chlorophyll-a measurements, and increasingly, remote sensing for large-scale bloom detection.

Limitations include natural seasonal variability, multispecies responses, and the need for taxonomic expertise. Indicators should be interpreted alongside physical and chemical data to provide robust assessments of ecological status.