March 28, 2015
Take a look back at some of the EPODs our viewers found particularly eye-catching. Today, and every Saturday, EPOD invites you to rediscover favorites from the past. Saturday posts feature an EPOD that was chosen by viewers like you in our monthly Viewers’ Choice polls. Join us as we look back at these intriguing and captivating images.
On the warm summer evening of July 27, 2009 I saw the bioluminescence pictured above as faint blue sparkles at the edges of shallow waves lapping on the shore of Putuo Island southeast of Shanghai. The sparkles disappeared after a few seconds. In addition to the examples in the photo, bioluminescence could be seen that night as a blue glow in the foam and on the crests of clashing waves offshore. Foot impressions in the sand also lit up with blue sparkles.
Some marine organisms such as dinoflagellates and algae are capable of emitting visible light with a chemical reaction known as bioluminescence. Bioluminescent marine organisms produce cold light mostly in the green and blue spectrum which includes wavelengths that transmit easily through seawater. Mechanical stress of the cells seems to be a trigger for the reaction. Marine bioluminescence is not limited to tropical oceans and can be observed in Europe and America as well. As the phenomenon is rather faint, long exposure times and high ISO settings were necessary to capture it. The long exposure makes the water surface look much smoother than it really was.
Photo details: Nikon D 90, 67 seconds at 2500 ISO, f/5.6.