Aphanizomenon flos-aquae

Aphanizomenon flos-aquae is a brackish and freshwater species of cyanobacteria of the genus Aphanizomenon found around the world, including the Baltic Sea and the Great Lakes.

Cyanobacteria were the first organisms to achieve photosynthesis. Chlorophyll and phycocyanine—two pigments contained in cyanobacteria—allow the vegetative cells to absorb light and transform it into nutrients.

The genus Aphanizomenon has defined as cluster of eight morphospecies, including Aphanizomenon flos-aquae.

Morphology
One of the main morphological characteristics of the genus Aphanizomenon is the tendency to form fascicles of trichomes containing mainly vegetative cells.

The individual vegetative cells that form Aphanizomenon flos-aquae are cylindrical and elongated. Each individual cell is composed of hyaline.

Aphanizomenon flos-aquae forms typically bent trichomes that are grouped into fascicles up to 2 centimeters long. These trichomes can also be found as single free floating units. Within these fascicles, heterocysts often appear at various intervals on the trichomes.

When attached to a trichome, heterocysts import carbohydrates which may act as a reducing agent and an energy source for nitrogen fixation. It has been shown that heterocysts contain a nitrogenase complex which allows them to take part in nitrogen-fixation. Other requirements for nitrogen fixation include ATP, low potential electrons, and an anaerobic environment.

Life cycle
The life cycle of Aphanizomenon flos-aquae depends on various environmental conditions such as water temperature, dissolved oxygen content, and pH.

During the winter, Aphanizomenon flos-aquae persists as akinetes deep in the layers of sediment. These dormant cyanobacterial cells will last all season until the water temperature rises again in the spring. During the springtime, the akinetes go through a recruitment phase as they germinate and disperse into the water column. Different species of phytoplankton can provide interspecific competition for Aphanizomenon flos-aquae if they are outnumbered. Due to higher temperatures, and higher levels of pH in the summer, Aphanizomenon flos-aquae begin to flourish and eventually form dense mats known as ‘blooms’ in late summer. The blooms begin to dissipate in autumn as the water temperature and ph drop again and the conditions are more favorable to akinete development.

Ecology
Aphanizomenon flos-aquae can form dense surface aggregations in freshwater (known as "cyanobacterial blooms"). These blooms occur in areas of high nutrient loading, historical or current.

During bloom formation, Aphanizomenon flos-aquae photosynthetically produces biomass. These accumulated mats of biomass are able to grow due to the concentration of nutrients available in eutrophic ecosystems accompanied with high reproductive rates and water temperatures.

At high concentrations, these blooms can be ecologically harmful to the aquatic species that cohabitate with the cyanobacteria. In addition to their odiferous presence, cyanobacterial blooms have been associated with lowered dissolved oxygen content, increased turbidity, and the accelerated release of nutrients from sediments.

Toxicity
Aphanizomenon flos-aquae has both toxic and nontoxic forms. Most sources worldwide are toxic, containing both hepatic and neuroendotoxins.

Most cyanobacteria (including Aphanizomenon) produce BMAA, a neurotoxin amino acid implicated in ALS/Parkinsonism.

Toxicity of A. flos-aquae has been reported in Canada, Germany and China.

Aphanizomenon flos-aquae is known to produce endotoxins, the toxic chemicals released when cells die. Once released (lysed), and ingested, these toxins can damage liver and nerve tissues in mammals. In areas where water quality is not closely monitored, the World Health Organization has assessed toxic algae as a health risk, citing the production of anatoxin-a, saxitoxins, and cylindrospermopsin. Dogs have been reported to have become ill or have fatal reactions after swimming in rivers and lakes containing toxic A. flos-aquae.

Microcystin toxin has been found in all 16 samples of A. flos-aquae products sold as food supplements in Germany and Switzerland, originating from Lake Klamath: 10 of 16 samples exceeded the safety value of 1 μg microcystin per gram. University professor Daniel Dietrich warned parents not to let children consume A. flos-aquae products, since children are even more vulnerable to toxic effects, due to lower body weight, and the continuous intake might lead to accumulation of toxins. Dietrich also warned against quackery schemes selling these cyanobacteria as medicine against illnesses such as attention deficit hyperactivity disorder, causing people to omit their regular drugs.

Medical research
The Klamath people have been ingesting A. flos-aquae for centuries. These bacteria contain significant amounts of various phenethylamines. This class of chemicals are often considered as general purpose neuromodulators, making them potentially effective at combating depression and anxiety.

Klamin is an extract of A. flos-aquae that concentrates the various phenylethylamine derivatives which can act as MAO-B inhibitors. This emerging nutritional supplement has been proved to aid neurodegenerative diseases.

Additionally, in a Canadian study studying the effect of A. flos-aquae on the immune and endocrine systems, as well as on general blood physiology, found that consuming A. flos-aquae had a profound effect on natural killer cells (NKCs). A. flos-aquae triggers the movement of 40% of the circulating NKCs from the blood to tissues. Once in the tissues, the NKCs main function is immune surveillance to eliminate cancerous or other infected cells.

As a food supplement
Some compressed tablets of powdered A. flos-aquae cyanobacteria (named as "blue green algae") have been sold as food supplements, notably those filtered from Upper Klamath Lake in Oregon.