Blue‑green bacteria, Lyngbya majuscula, Oscillatoria, Phormidium, Anabaena
Cyanobacteria during a lyngbya bloom
Lyngbya species form long, unbranching filaments inside a rigid mucilagenous sheath. Sheaths may form tangles or mats, intermixed with other phytoplankton species. They reproduce asexually. Their filaments break apart and each cell forms a new filament.
Some Lyngbya species cause the human skin irritation called seaweed dermatitis.
Some Lyngbya species can also temporarily monopolize aquatic ecosystems when they form dense, floating mats in the water.