Small centric diatom
Cyclotella spp. / Stephanodiscus spp.
Small centric diatoms are unicellular algae characterized by their radially symmetrical, circular silica shells. They belong to the Bacillariophyceae class and constitute a significant portion of both freshwater and marine phytoplankton. Their cell wall consists of two overlapping valves, known as thecae, structured like a petri dish. These organisms are photoautotrophic and play a key role in the global carbon and silicon cycles.
Details
Oxygen production
Significant production of dissolved oxygen during photosynthesis within the euphotic zone.
Habitat function
Serves as the primary food source for pelagic zooplankton.
Nutrient uptake
Efficient uptake of dissolved silicate for cell wall construction, as well as nitrogen and phosphorus.
Food source for
Zooplankton, filter-feeding macrozoobenthos species, larval fish stages.
Human use
Use of fossil deposits (diatomaceous earth) in filters, abrasives, and as an absorbent for dynamite.
Ecology
Ecological role
Primary producer at the base of aquatic food webs; produces oxygen and fixes atmospheric CO2.
Natural predators
Zooplankton (e.g., Daphnia, rotifers), herbivorous fish larvae, filter-feeding bivalves.
Competitor species
Other phytoplankton groups such as green algae, cyanobacteria, and pennate diatoms.
Ecosystem service
Oxygen production, carbon sequestration, regulation of nutrient cycles in water bodies.
Threats
Eutrophication, herbicide input, climate change (alteration of water stratification and temperature).
Scientific profile
Profile
Distinguishing features
Silica frustules with radial symmetry. Cyclotella: Bipartite valve pattern with structured center and striated margin. Stephanodiscus: Marginal spines and radial rib structures.
Reproduction
Asexual binary fission with valve size reduction; sexual oogamy for auxospore formation to restore maximum cell size.