Cyanobacteria is the oldest known fossils on
earth, which can be dating back to more than 3.5 billion years ago.  Most cyanobacteria are photosynthetic, which
contains large number of chemical elements. Cyanobacteria are also very
important in the nitrogen cycle because it is able to transfer atmospheric
nitrogen into organic nitrogen, which are significant to most plants growth. However,
excessive cyanobacteria, which we called cyanobacteria blooms, is considered
harmful to the whole aquatic ecosystem. Specifically, as cyanobacteria become
increasingly dominant in a lake, the concentration of TP and TN also increase and
these all will lead to lake eutrophication. Besides all that, cyanobacteria
blooms will also cause bad odor in a lake and it will deplete the available
oxygen and lead to anoxic conditions. Because of these damages, some government
made policies to regulate the environment of some contaminated lake and brought
water to normal conditions after couple of decades by removing excessive