Ribbon diatom
Fragilaria crotonensis
Fragilaria crotonensis is a planktonic diatom that forms characteristic ribbon-like colonies composed of multiple individual cells. The cells are rod-shaped, swollen in the middle, and tapered at the ends, being firmly connected to each other via mucilage pads. It occurs frequently in the pelagic zones of lakes and reservoirs and serves as an important primary producer in the aquatic ecosystem.
Details
Oxygen production
High during the main growth phases in spring and autumn.
Habitat function
Structuring the open water column for microorganisms.
Nutrient uptake
High demand for dissolved silicate for the construction of silica frustules.
Food source for
Herbivorous zooplankton and small filter-feeding fish larvae.
Human use
No direct economic use; important tool in paleolimnology for reconstructing past environmental conditions.
Ecology
Ecological role
Central primary producer; serves as a nutritional basis for zooplankton and contributes to oxygen saturation.
Natural predators
Filter-feeding zooplankton such as Daphnia (water fleas), rotifers, and various protozoa.
Competitor species
Other planktonic diatoms like Asterionella formosa as well as cyanobacteria at high phosphate levels.
Ecosystem service
Oxygen production, carbon dioxide fixation, and part of the biological carbon pump.
Threats
Strong climate warming of surface waters and extreme oligotrophication (nutrient depletion).
Scientific profile
Profile
Distinguishing features
Cells are connected only in the central region, creating distinct gaps between the cell ends. This distinguishes them from other Fragilaria species that often form continuous ribbons without gaps.
Reproduction
Asexual reproduction via cell division (longitudinal), with cells remaining within the colony. Sexual reproduction via auxospore formation to restore maximum cell size.
Protection & threats
Status not on standard scale
Main threats
Excessive eutrophication (hypertrophication) leading to dominance of cyanobacteria; climate change through alterations in lake stratification dynamics.
Conservation measures
Maintenance and restoration of moderate nutrient levels (re-oligotrophication); management of diffuse nutrient inputs from agriculture.