Purple Sulfur Bacteria and Algae Return to Birch Bay

posted Jun 22, 2015, 10:42 AM by Ingrid Enschede   [ updated Jun 22, 2015, 10:43 AM ]
Purple sulfur bacteria on Cottonwood Beach.
With the unusually warm weather, algae and purple sulfur bacteria have returned to Birch Bay early this year.  Beach walkers will notice not only lots of green algae and eelgrass coating the tide flats, but also a zone of unusual "pink gooey stuff" along the upper reaches of Cottonwood Beach and Roger's Slough.  The pink stuff is purple sulfur bacteria.  This type of bacteria thrive in water with low levels of dissolved oxygen and high levels of sulfur.  A combination of warm water and decaying algae and eelgrass create low dissolved oxygen, or anoxic, conditions in the bay.  The rotten egg smell comes from hydrogen sulfide or similar gases, another by-product of decaying algae. Sulfur bacteria use hydrogen sulfide as a food source, so decaying algae creates the food source for the bacteria.  Some people may experience irritated eyes, nose, or throat; headaches; or nausea from exposure to the hydrogen sulfide gas.  If you have questions please contact Ingrid Enschede at (360) 715-7450 x50787.        

The Washington State Department of Ecology's publication Focus on Saltwater Beach Odors is a good reference for more information on the source of beach smells, possible health concerns, and connections to nutrient pollution in stormwater.  

Photo of Cottonwood Beach June 21, 2015 by C. Sandvig.

Different types of algae release biotoxins into the water that accumulate in the tissues of shellfish, making them unsafe to eat.  Be sure to check for updated information on biotoxin (red tide) harvest closure areas before harvesting any shellfish.  Read more about unusually large toxic algae blooms all along the west coast.