Calcifying blue-green alga
Rivularia haematites
The calcifying blue-green alga is a cyanobacterium that forms characteristic, often zoned limestone crusts on stones in lime-rich, clean waters. These colonies are usually hemispherical, hard, and dark green to brownish in color. By absorbing carbon dioxide during photosynthesis, lime is precipitated, which significantly contributes to the formation of biogenic tufa.
Details
Oxygen production
Produces oxygen as a byproduct of photosynthesis directly on the water bed.
Habitat function
Serves as a stable habitat and grazing ground for specialized microorganisms and macrozoobenthos.
Nutrient uptake
Efficient uptake of phosphates and nitrates at very low concentrations.
Food source for
Snails (e.g., Theodoxus species) and certain caddisfly larvae.
Human use
No direct economic use; scientific importance for geology and limnology.
Ecology
Ecological role
Important primary producer and main actor in the formation of tufa structures in streams.
Natural predators
Grazing aquatic insect larvae and snails.
Competitor species
Filamentous algae and diatoms with increasing nutrient supply.
Ecosystem service
Water purification through nutrient binding and CO2 fixation; formation of solid substrate for other organisms.
Threats
Eutrophication (nutrient input), river engineering, acidification, and drying up of springs.
Scientific profile
Protection & threats
Main threats
Eutrophication (especially phosphorus enrichment leads to disappearance), river engineering, extraction of calcareous tufa, and alteration of the natural flow regime.