This summer, people living near the coastline of northeastern China have been experiencing a biological phenomenon known as red tide. The sight of massive amounts of blood-red ocean water has left people wondering whether seafood from the nearby ocean is still safe to eat. So, what causes this unusual situation?

Members of the Pyrophyta — a type of algae — are dinoflagellates. Dinoflagelates are unicellular organisms that are usually surrounded by thick plates that give them an armored appearance. Many dinoflagellates are luminescent. When affected by sudden movements, they give off light. When optimal conditions exist in the oceans, the dinoflagellates reproduce at explosive rates. Their red pigments cause the water to turn the color of blood. This condition is the so-called red tide.

To find out more about the conditions that brought about the most recent red tides in China and how the situation may affect marine life in the area, check out this news report from Reuters.