Blue-green algae (Dolichospermum)
Dolichospermum
Dolichospermum is a genus of filamentous cyanobacteria primarily found in freshwater plankton. The cells form chains and possess specialized heterocysts for atmospheric nitrogen fixation as well as akinetes for survival during adverse conditions. Many species within this genus can produce toxins such as microcystins or anatoxins and can severely impact water quality during mass developments known as algal blooms.
Details
Oxygen production
Oxygen release during photosynthesis during the day; high oxygen consumption through respiration and decomposition at night.
Habitat function
Serves as a microhabitat for bacterial films; in mass occurrences, displacement of submerged macrophytes due to light deprivation.
Nutrient uptake
Efficient uptake of dissolved phosphate and fixation of atmospheric nitrogen.
Food source for
Certain filter-feeding zooplankton and bivalves, provided there is no high toxicity.
Human use
No direct use; of high importance for water management and bathing water monitoring due to toxins.
Ecology
Ecological role
Primary producer and nitrogen fixer; can damage the ecosystem during mass blooms through oxygen depletion and toxin production.
Natural predators
Zooplankton (e.g., Daphnia), although palatability is often limited by toxins and filamentous structure.
Competitor species
Other phytoplankton such as green algae, diatoms, and other cyanobacteria (e.g., Microcystis).
Ecosystem service
Contribution to nitrogen fixation during nutrient-poor phases; base of the food chain (limited).
Threats
Control via herbicides or flocculants in affected waters; nutrient retention measures.
Scientific profile
Profile
Distinguishing features
Presence of heterocytes for nitrogen fixation and akinetes (resting spores); planktonic lifestyle enabled by gas vesicles; distinguished from Anabaena by being planktonic rather than benthic.
Reproduction
Asexual via fragmentation of trichomes (hormogonia formation) and germination of akinetes (resting cells).
Protection & threats
Status not on standard scale
Main threats
Not threatened; benefits from eutrophication and climate change (rising water temperatures).
Conservation measures
No conservation measures required; management focuses on nutrient reduction (phosphate elimination) to prevent mass developments.