By Russel Barsh, Kwiáht Director
Over the past week we have received many calls about large floating brown mats in East Sound, followed by a smelly white coating of beaches and rocks at Eastsound and Indian Island, and parts of West Sound. What was that stuff?
The brief answer is blue-green algae. Blue-green algae are not really algae at all, but cyanobacteria that can photosynthesize like algae and vascular plants. Some are red or brown in color, and many produce toxic substances to deter tiny planktonic herbivores from grazing on them.
Orcas Island has just experienced a massive, potentially harmful algal bloom that we believe was triggered by the rapid warming of local waters that began two weeks ago. Very rapid growth and proliferation of blue-green algae formed floating mats that washed up on rocks and beaches. Where they remained relatively dry, these mats of microscopic filaments bleached in the sun, forming sheets of a soft white paper-like material. Where they stayed wet on inter-tidal sandy beaches, the filaments decomposed, releasing a very conspicuous sulfurous odor and producing a silvery black organic mud.
Kwiáht researchers are still assessing the impact of last week’s bloom. At Indian Island, hundreds of dead crabs and live cockles laying exposed on the beach suggests that decaying cyanobacteria reduced oxygen levels in the sand and shallow water of the bay. Cyanobacteria coating seaweed or ingested by clams may poison fish, animals or humans that eat them; at least one person has reported burning and numbness after eating seaweed from a local beach this week. If you see any dead fish or seabirds around Indian Island or Crescent Beach, please contact Kwiáht’s resident biologist on Orcas, Anne Harmann, by cell phone at 763-360-1094 or annemharmann@yahoo.com.
It is important to remember that not all algal blooms are toxic, or affect the safety of local shellfish. But always check the Washington State Department of Health Biotoxin Program web page http://www.doh.wa.gov/ehp/sf/BiotoxinProgram.htm before collecting local clams, mussels or other shellfish as food.
We believe that last week’s bloom was Lyngbya majuscula, a filamentous brown cyanobacteria that ordinarily forms tufts on shallow sea bottoms. Lyngbya was involved in some recent toxic algal blooms in Puget Sound and appears to be causing blooms more frequently – possibly due to a combination of warming seas and nutrients such as nitrates from our region’s growing human population.
For further information, contact Russel Barsh at RLBarsh@gmail.com.
Kwiáht is a center for historical ecology of the Salish Sea based on Lopez Island. Researchers are currently operating a marine health observatory of Indian Island.
