Hantzsch's diatom
Stephanodiscus hantzschii
Stephanodiscus hantzschii is a single-celled, centric diatom belonging to the family Stephanodiscaceae. It is well-known for forming massive algal blooms during spring, particularly in nutrient-rich (eutrophic to hypertrophic) freshwater bodies. The cells are disc-shaped and feature a heavily silicified cell wall with characteristic spines along the margin. Due to its high reproduction rate, it plays a central role in the carbon cycle of river and lake ecosystems.
Details
Oxygen production
Produces significant amounts of oxygen as a byproduct of photosynthesis, especially during the spring bloom.
Habitat function
Provides food for primary consumers and influences the chemical composition of the water through silicate binding.
Nutrient uptake
Extremely high uptake rates of phosphate and nitrate; requires dissolved silicate for the construction of the exoskeleton.
Food source for
Zooplankton, benthic filter feeders, and juvenile fish.
Human use
Used in paleolimnology to reconstruct historical nutrient levels in water bodies.
Ecology
Ecological role
Primary producer; forms the base of the aquatic food web; important consumer of dissolved silicate.
Natural predators
Zooplankton (e.g., Daphnia, copepods), filter-feeding bivalves, and ciliates.
Competitor species
Other diatoms (e.g., Asterionella formosa) as well as green algae and cyanobacteria during nutrient shifts.
Ecosystem service
Oxygen production through photosynthesis; sequestration of atmospheric CO2.
Threats
Reduction in nutrient concentrations (oligotrophication), silicate deficiency, and significant temperature changes due to climate change.
Scientific profile
Profile
Distinguishing features
Characteristic ring of fine spines (setae) at the valve margin; radial striae on the valve with 2-3 rows of pores between ribs; absence of a central area pattern compared to Cyclotella.
Reproduction
Asexual reproduction by binary fission (with associated cell size reduction); sexual reproduction via oogamy to form auxospores for restoring maximum cell size.
Protection & threats
Status not on standard scale
Main threats
No threats; the species benefits from anthropogenic eutrophication and water pollution.
Conservation measures
No conservation measures required; management measures usually aim at reducing nutrient inputs (P-elimination) to avoid mass developments.