are primitive single-celled organisms which are ubiquitously distributed throughout
the biosphere. They live in aqueous solution and
flourish in almost any kind of conditions from moist, fertile earth to barren
desert sands, from freshwater to extreme salinity. In experiments, microalgae
have even been known to survive for periods of up to twenty years at -20°C
in a vinyl bag placed in a dark room.
Microalgae were one of the first life forms to appear on earth almost 3.5
billion years ago, the first chlorophyll containing organisms with the ability
to photosynthesise ie. absorb sunlight and use water and carbon dioxide to produce
food and oxygen.
As oxygen in the atmosphere increased, partly produced and sustained
by rapidly multiplying microalgae, the ozone layer gradually formed and conditions
in the biosphere conducive to supporting other life forms evolved over millions
Right at the bottom of the food chain, microalgae are a primary source of
food and have a vital role in the complex interplay of processes that hold the
biosphere in balance. They are major producers of oxygen, producing 70%
of atmospheric oxygen, and are responsible for absorbing atmospheric
carbon dioxide and fixing carbon in organic forms.