Smooth stonewort
Nitella flexilis
Nitella flexilis is a perennial macroalga that forms dense underwater meadows. It is characterized by its smooth, ecorticate stems and dichotomously branched branchlets. Unlike many Chara species, it is soft and flexible because it lacks significant calcium carbonate deposits and often prefers slightly acidic to neutral waters.
Details
Oxygen production
High, contributes significantly to oxygen enrichment in the hypolimnion.
Habitat function
Forms complex three-dimensional structures that serve as habitat for a diverse micro- and macrofauna.
Nutrient uptake
Efficient uptake of phosphates and nitrates directly from the water and via rhizoids from the sediment.
Food source for
Food source for various waterfowl (e.g., Red-crested Pochard) and invertebrates.
Human use
Occasional use as an indicator for water quality within the framework of the Water Framework Directive (WFD).
Ecology
Ecological role
Primary producer, stabilizes sediment, serves as a hiding place for juvenile fish and zooplankton, and contributes to oxygen saturation.
Natural predators
Waterfowl, herbivorous fish, and aquatic insect larvae.
Competitor species
Other macrophytes such as Elodea species or Myriophyllum in cases of increasing eutrophication.
Ecosystem service
Water clarification through nutrient sequestration, carbon storage, and erosion control on the water bed.
Threats
Eutrophication due to fertilizer runoff, mechanical disturbances (e.g., shipping, dredging), and herbicide use.
Scientific profile
Profile
Reproduction
Monoecious; sexual reproduction via oogonia and antheridia at branchlet nodes; formation of dark brown to black oospores; vegetative reproduction via budding from rhizoid bulbils.
Protection & threats
Main threats
Eutrophication (nutrient loading), turbidity from suspended solids, mechanical disturbances (dredging), and herbicide use.