What are Cyanophyta?
Cyanophyta or Cyanobacteria are a group of photosynthetic bacteria. They obtain their energy & manufacture their own food through photosynthesis. In the process, they release oxygen as a by-product. They are mostly aquatic. They thrive in moist soils & water. They are microscopic & are usually unicellular. They are one of the largest & oldest group of organisms to inhabit the earth.
Where do they exist?
Cyanobacteria are found in Fresh water, marine & terrestrial ecosystems. They mostly grow in colonies large enough to be visible to the naked eye. They can be free living or Symbiotic. Aquatic cyanobacteria are known for their large-scale & highly visible blooms. Typical cyanophytic blooms appear like scum, having blue-green color. They are toxic in nature. Cyanobacteria prefer calm waters, as in ponds and lakes. They cannot survive water currents especially those of fast flowing streams or fountains. That’s the reason blooms of cyanobacteria rarely occur in rivers or seas.
How do they help Us?
Cyanobacteria produce oxygen. Scientists believe that the oxygen atmosphere we depend on today, was created by numerous cyanobacteria. Earth’s early atmosphere had a very different chemistry, unsuitable for human life.
- Carbon Fixation
Cyanophytes indulge in oxygen photosynthesis. They take in inorganic carbondioxide & convert it into organic compounds.
- Nitrogen Fixation
Cyanobacteria also help in Nitrogen Fixation. But Oxygen photosynthesis & Nitrogen fixation cannot happen in a single system as Nitrogenase, the enzyme required for Nitrogen fixation is sensitive to Oxygen. Hence, Cyanobacteria fix atmospheric nitrogen in anaerobic conditions by means of specialized cells called Heterocysts. Heterocysts develop when fixed nitrogen is scarce. These cells have an additional cellular wall that keeps the oxygen concentration sufficiently low for nitrogen fixation to take place. Nitrogen fixation requires high energy. Since cyanobacteria are phototrophic i.e. obtain energy from sunlight to synthesize organic compounds, the energy demands are easily met.
How do they affect humans?
Cyanobacteria release harmful toxins that might cause serious illness.
The most common medium of exposure to cyanotoxins are:
- Drinking cyanotoxin-contaminated water sourced from lakes or rivers
- Consumption of fish,clams or mussels collected during cyanobacterial blooms
- Usage of Recreational water bodies (for example: public swimming pools)
Health Risks to Humans:
Short term exposure to cyanotoxins may cause mild skin rash to more severe health effects which include:
- Abdominal pain
- Vomiting & Nausea
Long term exposure causes damage to Liver & Kidney.
What effect do they have on aquatic flora & fauna?
Cyanophytic blooms facilitate the growth of algae & other flora. With the right conditions, a clear body of water can become very turbid with green, blue-green or reddish-brown colored algae within just days. There is a sudden surge in the BOD (Biological Oxygen Demand) of water body. Cyanobacteria cannot support the oxygen demands of the increased population. Insufficient oxygen causes hypoxia (deficiency in the amount of oxygen reaching the tissues) . As a result, fishes & other aquatic animal perish.