Lyngbya majuscula is a species of cyanobacteria in the genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 Lyngbya

Lyngbya

Lyngbya is a genus of cyanobacteria, unicellular autotrophs that form the basis of the oceanic food chain.Lyngbya form long unbranching filaments inside a rigid mucilage sheath. Sheaths may form tangles or mats, intermixed with other phytoplankton species...

. Lyngbya majuscula grows on seagrass and is one of the causes of the human skin irritation seaweed dermatitis

Seaweed dermatitis

Seaweed dermatitis is a cutaneous condition characterized by inflammation of the skin caused by marine alga, specifically Lyngbya majuscula....

. It is known as fireweed in Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

 and stinging limu

Limu (algae)

Limu is the Hawaiian word for algae. There are approximately one hundred Hawaiian names for kinds of limu, sixty of which can be matched with scientific names. Limu played an important part in the ancient Hawaiian diet. It was used to add flavor to an otherwise particularly bland diet of kalo ,...

in Hawai'i.

The prevalence of this organism appears to be on the increase due to pollution

Pollution

Pollution is the introduction of contaminants into a natural environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms. Pollution can take the form of chemical substances or energy, such as noise, heat or light...

 and overfishing

Overfishing

Overfishing occurs when fishing activities reduce fish stocks below an acceptable level. This can occur in any body of water from a pond to the oceans....

. Nutrients such as nitrogen and human waste flow to the ocean due to rain and sewage runoff; these added nutrients increase the population of microbes, which in turn remove oxygen

Oxygen

Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

 from the water. Reduced numbers of fish to eat the microbes further enhances the microbe populations. Cyanobacteria are evolutionarily optimized for environmental conditions of low oxygen. Lyngbya majuscula can also fix

Nitrogen fixation

Nitrogen fixation is the natural process, either biological or abiotic, by which nitrogen in the atmosphere is converted into ammonia . This process is essential for life because fixed nitrogen is required to biosynthesize the basic building blocks of life, e.g., nucleotides for DNA and RNA and...

 its own nitrogen from atmospheric nitrogen dissolved in the seawater. This implies that pollution with phosphorus

Phosphorus

Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...

 and iron

Iron

Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

 may be more important than nitrogen pollution.

L. majuscula is known for its toxicity, producing Lyngbyatoxin-a

Lyngbyatoxin-a

Lyngbyatoxin-a is a cyanotoxin produced by certain cyanobacteria species, notably Lyngbya majuscula. It is used as a defensive secretion to protect this cyanobacteria from predation by fish, being a potent irritant and vesicant, as well as a carcinogen. Low concentrations more commonly encountered...

 and other "antifungal and cytotoxic agents, including laxaphycin A and B and curacin A."

A major outbreak occurred in Darwin Harbour in May- June 2010.