Opaque Stonewort
Nitella opaca
The Opaque Stonewort is a perennial, dark green macroalga belonging to the Characeae family. It is characterized by being dioecious and having smooth, often branched main axes. This species prefers stagnant or slow-flowing waters that are low to moderately rich in lime. It often forms dense carpets on the water bed and is a significant component of benthic vegetation in cool water bodies.
Details
Oxygen production
Produces oxygen through photosynthesis directly within the water column.
Habitat function
Provides habitat and spawning substrate for fish as well as refuge for zooplankton.
Nutrient uptake
Efficient uptake of phosphates and nitrates directly from the water and sediment.
Food source for
Food source for various waterfowl species and aquatic snails.
Human use
Occasionally used as a bioindicator in water quality monitoring.
Ecology
Ecological role
Primary producer, stabilizes sediment, and acts as a pioneer species in newly formed water bodies.
Natural predators
Waterfowl (e.g., ducks), herbivorous fish, and aquatic invertebrates.
Competitor species
Other macrophytes such as Elodea species or Myriophyllum in case of increasing nutrient levels.
Ecosystem service
Water purification through nutrient sequestration and sediment stabilization.
Threats
Eutrophication from agriculture, mechanical disturbances from recreational use, and herbicide input.
Scientific profile
Profile
Reproduction
Sexual reproduction via oospores (dioecious); oospores are dark brown to black, approx. 350–550 µm long. Vegetative reproduction via shoot fragments or rhizoid bulbils.
Protection & threats
Main threats
Eutrophication (nutrient input), increasing water turbidity, mechanical destruction through bank stabilization or intensive boat traffic.