Nostocales

The Nostocales are an order of cyanobacteria containing most of its species. It includes filamentous forms, both simple or branched, and both those occurring as single strands or multiple strands within a sheath. Some members show a decrease in width from the base, and some have heterocysts.

Aphanizomenon is a genus of cyanobacteria that inhabits freshwater lakes and can cause dense blooms. These cyanobacteria are unicellular organisms that form linear (non-branching) chains known as trichomes. Parallel trichomes can further unite into aggregates called rafts. Cyanobacteria such as Aphanizomenon are known for using photosynthesis to create energy and thus rely on sunlight as their energy source. Aphanizomenon bacteria also play a significant role in the Nitrogen cycle due to their ability to perform nitrogen fixation. Studies on the species Aphanizomenon flos-aquae have shown that

Nodularia is a genus of filamentous nitrogen-fixing cyanobacteria, or blue-green algae. They occur mainly in brackish or salinic waters, such as the hypersaline Makgadikgadi Pans, the Peel-Harvey Estuary in Western Australia or the Baltic Sea. Nodularia cells occasionally form heavy algal blooms. Some strains produce a cyanotoxin called nodularin R, which is harmful to humans.

thumb|Heterocyst of [[Scytonema crispum]] Scytonema is a genus of photosynthetic cyanobacteria that contains over 100 species. It grows in filaments that form dark mats. Many species are aquatic and are either free-floating or grow attached to a submerged substrate, while others species grow on terrestrial rocks, wood, soil, or plants. Scytonema is a nitrogen fixer, and can provide fixed nitrogen to the leaves of plants on which it is growing. Some species of Scytonema form a symbiotic relationship with fungi to produce a lichen. thumb|Scyptolin A Scyptolins are a type of elastase inhibitors i

species of Cyanobacteria

Stigonema is a genus of cyanobacteria in the family Stigonemataceae. Established in 1824 and formally defined in 1886, this genus contains 68 species of filament-forming cyanobacteria that create visible mats or crusts. The organisms are distinguished by their true branching pattern, where side-branches arise from cells along the main filament, and by filaments that are typically several cells thick. Some species also serve as the photosynthetic partner () in certain lichens, embedded within fungal tissue.

Aulosira is a genus of cyanobacteria found in a variety of environmental niches that forms colonies composed of filaments of moniliform cells.

The Aphanizomenonaceae are a family of cyanobacteria containing mostly genera which produce aerotopes. Cyanobacteria from the family Aphanizomenonaceae may form blooms in lentic freshwater bodies which may be dangerous for humans.

The Hapalosiphonaceae are a family of cyanobacteria.

Gloeotrichia is a large (~2 mm) colonial genus of Cyanobacteria, belonging to the order Nostocales. The name Gloeotrichia is derived from the appearance of the filamentous body with prominent mucilage matrix. Found in lakes across the globe, gloeotrichia are notable for the important roles that they play in the nitrogen and phosphorus cycles.  Gloeotrichia are also a genus of concern for lake managers, as they have been shown to push lakes towards eutrophication and to produce potentially deadly Microcystin-LR.