Variable cyanobacterium
Trichormus variabilis
Trichormus variabilis (formerly Anabaena variabilis) is a filamentous cyanobacterium capable of nitrogen fixation. The species occurs worldwide in freshwater ecosystems as well as in moist terrestrial habitats. It is characterized by the formation of specialized cells such as heterocysts for nitrogen fixation and akinetes for survival during unfavorable conditions.
Details
Oxygen production
High, produces oxygen as a byproduct of oxygenic photosynthesis.
Habitat function
Component of the phytoplankton; provides microhabitats for associated bacteria.
Nutrient uptake
Fixation of N2; highly efficient uptake of phosphates and ammonium from the water.
Food source for
Various aquatic microorganisms, filter feeders, and zooplankton.
Human use
Model organism in molecular biological research; potential as biofertilizer in agriculture (e.g., rice cultivation).
Ecology
Ecological role
Important primary producer and source of biologically available nitrogen in aquatic systems.
Natural predators
Zooplankton such as Daphnia and rotifers, as well as specialized viruses (cyanophages).
Competitor species
Other cyanobacteria (e.g., Microcystis) and eukaryotic algae of the phytoplankton.
Ecosystem service
Nitrogen enrichment in nutrient-poor soils and waters; oxygen production.
Threats
Use of herbicides/algicides and drastic changes in water chemistry.
Scientific profile
Profile
Distinguishing features
Possesses specialized cells: intercalary heterocysts for nitrogen fixation and akinetes (resting cells) that usually form in chains and are often remote from heterocysts (distinguishing feature from Anabaena sensu stricto).
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
No known threats; the species benefits from anthropogenic eutrophication and rising water temperatures due to climate change.
Conservation measures
No conservation measures required; management efforts focus on reducing nutrient inputs to prevent harmful algal blooms.