… In the past 540 million years, five massive extinctions are thought to have killed off, in each case, some 50 percent to 90 percent of animal species. A new study suggests that toxins from algae played a major role in all five extinctions, including the most recent and most well-known — the death of the dinosaurs 65 million years ago. The idea was presented at the annual Geological Society of America meeting Oct. 19. …
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.