This is from an article I read. They say bluegreen algae can release toxins to kill when it is "stressed."
I am curious about this because bluegreen algae is a popular supplement right now. I am not sure if there is a safety concern but it's something to take into consideration. Also I heard there was going to be a way for people to grow their own- I think David Wolfe is working on this..
http://www.msnbc.msn.com/id/33541539/ns/technology_and_science-scie...
Toxic algae
Algae are simple organisms that get their energy from the sun and lack many features found in plants, such as roots and leaves. Some algae species produce toxins that are harmful to other aquatic organisms and even us. For instance, one group of algae called dinoflagellates can release neurotoxins that act on nerve cells.
When nutrients abound, the algae and other primitive microbes can grow rapidly and can aggregate to form dense populations, known as algae blooms. Such outbreaks of toxic algae can have devastating effects on ecosystems, killing fish, birds, marine mammals and even people.
The most problematic group of toxin-producers are cyanobacteria, commonly known as blue-green algae. While cyanobacteria are not technically algae — they were reclassified from algae to bacteria — they can produce their own energy from the sun, and some researchers still place them in the algae group. Also, their "blooms," which cover the water with a blue-green film, are referred to as algal blooms.
Instead, they view the algae as what they call a "kill mechanism," a way for environmental change to contribute to increased death.
"The toxins tend to become stronger and released when there's something that stresses the algae, [such as] a change in salinity of the water, a change in temperature," said Castle. "There could have been an impact or volcanic eruption, and that may have stressed the algae, [and] by changing the conditions, they released toxins that kill the organisms."