Rainbows in the Water

Posted on Oct 20, 2012

Aboard the Baykeeper vessel on an early fall water quality testing trip, Citizen Stewards Coordinator Peter Milholland suddenly spotted rainbows glimmering under the shallow waters of Quahog Bay. There, floating next to the boat were over a dozen translucent, eggplant-shaped sea creatures. He and the crew members recognized these gelatinous animals as ctenophores [pronounced teen-a-fours]. Ctenophores are commonly called comb jellies, although they are not jellyfish.

It was an unusual sight so late in the season. “Typically,” Peter explains, “we see ctenophores in the spring that range from the size of a dime to a quarter. These were the size of my outstretched hand!”

Their rainbow effect is created by sunlight pulsing down eight rows of comb-like cilia. Most ctenophores are bioluminescent, usually emitting an eerie glow at night in dark waters. To see this particular group of unusually large creatures emitting scintillating rainbows in the light of day was a rare treat.