Also known as phylum cyanophyta or Myxophyceae, blue-green algae is a highly adaptable aquatic plant that can be widely found in nature, especially in lakes, rivers and reservoirs.

It is a particularly mysterious creature: as not all species of blue-green algae pose a potential health threat.

While environmental conditions that encourage the growth of toxic algae are still uncertain, it is generally acknowledged that blue-green algae multiply very quickly in eutrophic water - that is, water with high nutrient levels.

Furthermore, as with all plants, they grow rapidly when the water is warm and sunshine is abundant.

Under the right climate conditions, nutrient-rich Taihu Lake has provided an ideal breeding ground for the toxic algal bloom.

High temperatures with no rain would naturally guarantee a lake with excessive nutrients and low water levels, which experts say is another key factor in algal outbreaks.

Taihu is China's third largest lake and contains large amounts of fertilizers from persistent pollution.

"Bloom" describes the condition when, as in Taihu's case, algae expands exponentially to a point where water is discolored, and its quality and oxygen level significantly reduces. Offensive odors are produced, and fish are also known to die.

Algal blooms also create adverse conditions to aquatic ecosystems.

Scientists today are still puzzled about how long blooms last, and when or where they will occur.

Although algal blooms frequently occur throughout the world, instances where human beings are poisoned from toxic blue-green algae have been rarely documented.

No known poisonings have occurred because of the Taihu Lake water crisis.