Needle diatom
Fragilaria acus
The needle diatom is a widespread diatom characterized by its extremely long, narrow, and needle-like cells. It occurs in both the plankton and benthos of freshwater bodies. Its cell walls are composed of silica and exhibit fine striation patterns under a microscope. This algal species plays a crucial role as a primary producer in aquatic ecosystems.
Details
Oxygen production
High; produces oxygen as a byproduct of photosynthesis.
Habitat function
Provides a food base in the open water zone (pelagic).
Nutrient uptake
Absorbs dissolved silicates, nitrates, and phosphates from the water.
Food source for
Zooplankton, rotifers, and filter-feeding organisms.
Human use
Scientific use in paleolimnology to reconstruct past environmental conditions.
Ecology
Ecological role
Important primary producer; base of the aquatic food web; contributes to oxygen enrichment.
Natural predators
Zooplankton (e.g., Daphnia), herbivorous protozoa, and small fish larvae.
Competitor species
Other phytoplankton species such as green algae or other diatoms (e.g., Asterionella).
Ecosystem service
Oxygen production and carbon dioxide fixation in water bodies.
Threats
Water pollution, excessive herbicide input, and extreme climate changes.
Scientific profile
Profile
Distinguishing features
Possesses a silica shell (frustule) consisting of epitheca and hypotheca. Characterized by fine striae (transapical striae, approx. 12-18 in 10 µm) and a distinct, often rectangular central area. Taxonomically often referred to as Ulnaria acus.
Reproduction
Asexual reproduction by cell division, leading to a successive decrease in valve size. Sexual reproduction via auxospore formation to restore the original cell size.
Protection & threats
Status not on standard scale
Main threats
Severe eutrophication (shift towards cyanobacteria), chemical herbicide inputs, and extreme acidification of water bodies.
Conservation measures
Maintenance and restoration of natural water quality; reduction of diffuse nutrient inputs from agriculture.