Phytoplankton blooms as seen from above

Green phytoplankton blooms can be seen forming from above this Swedish island. Phytoplankton blooms are population explosions that occur when deep currents bring an abundance of nutrients up to sunlit waters. A lot of sea critters eat phytoplankton but these blooms can actually become toxic. 

Phytoplankton require nutrients such as nitrates, phosphates, and sulfur which they convert into proteins, fats, and carbohydrates. 

Credit: @USGS/NASA/Landsat 7