Anabaena
Anabaena
Anabaena is a genus of filamentous cyanobacteria found as plankton in freshwater environments worldwide. They are notable for their ability to fix atmospheric nitrogen using specialized cells called heterocysts, allowing them to thrive in nitrogen-poor waters. Some species are known to produce potent neurotoxins and can form harmful algal blooms that negatively impact aquatic ecosystems and water safety.
Details
Oxygen production
Produces oxygen during the day; can lead to massive oxygen depletion at night or during bloom collapse.
Habitat function
Base of the food web in oligotrophic waters (via nitrogen fixation), often harmful in eutrophic waters.
Nutrient uptake
High uptake of phosphate; fixation of atmospheric nitrogen during N-deficiency.
Food source for
Zooplankton and filter-feeding microorganisms.
Human use
Used in agriculture (rice paddies) as a biofertilizer in symbiosis with the water fern Azolla; subject of biological research.
Ecology
Ecological role
Primary producer and important nitrogen fixer; however, it can disrupt ecological balance through toxin production and oxygen depletion.
Natural predators
Zooplankton (e.g., Daphnia), silver carp, and various filter-feeding organisms (limited by toxicity).
Competitor species
Green algae, diatoms, and other cyanobacteria such as Microcystis.
Ecosystem service
Nitrogen enrichment in aquatic systems; symbiotic partner for plants (e.g., Azolla).
Threats
Not threatened; benefits from global warming and nutrient runoff.
Scientific profile
Profile
Distinguishing features
Presence of heterocytes for nitrogen fixation and akinetes (resting spores). Many species possess gas vacuoles for buoyancy regulation in the water column. Distinguished from Dolichospermum by morphological details of akinete arrangement.
Reproduction
Asexual reproduction via fragmentation of trichomes (hormogonia formation) and through the germination of akinetes after resting periods.
Protection & threats
Status not on standard scale
Main threats
Not threatened; the genus benefits globally from water eutrophication and global warming.
Conservation measures
No conservation measures required; management measures aim at reducing nutrient inputs (P-elimination) to prevent blooms.