On the morning of New Year’s Day, Whidbey Islanders gathered at Double Bluff Beach for the annual Polar Bear Plunge before stampeding into the winter water.

For those wondering how cold the water was exactly, surveyors with the Island County Marine Resource Committee have it down to a science.

Regularly monitoring temperature can tell a lot about the marine environment, said Ken Collins, a committee member. Extreme fluctuations, like when Holmes Harbor reached a balmy 20 degrees Celsius in August, can kill species like bull kelp that have sweeping effects across the ecosystem.

“The whole thing with climate change is that it’s not so much as the average temperatures going up, but the extremes are getting higher,” he said, “and I think the change that we get you, all you need is a couple days of that really warm water, and the shellfish start to die and eelgrass, in essence the bull kelp dies.”

Several organizations monitor water temperature around Whidbey Island, Collins said, though there isn’t a collective system for it. A few months ago, the committee launched a pilot program to gather temperature where there may be gaps across the island.

The team set up two sensors in Holmes Harbor and two at different depths at Langley.

On the morning of New Year’s Day, the surveyor’s data showed that the Langley Seawall was 47.8 degrees Fahrenheit, Freeland Dock was 46.3 degrees and Double Bluff was 45.4 degrees.

There was one location colder than the Polar Bear Plunge, though — Goss Lake displayed a temperature of 44.6 degrees.

“Goss Lake’s usually colder in the winter and warmer in the summer,” said Greg Easton, a Marine Resource Committee member. “It doesn’t take much to warm that small body of water. On a calm day like (New Year’s), it’s very sensitive there in terms of temperature.”

The team uses submersible waterproof thermometers that take readings every ten seconds or so at various depths.

While New Year’s showed normal temperatures for this time of year, the interesting days are after a good rainstorm, Collins said, where different waters mix.

In Langley, Easton sees large day-to-day swings in temperature, he said. Whether the largest variable is daylight, tides or something else, he tends to see bigger day-to-day variance than month-to-month, even.

The tide can cause an 8 degrees C change in a matter of hours, he said, especially the closer the sensor is to the surface.

The committee will soon monitor other aspects along with temperature, such as salinity and dissolved oxygen, which are also indicators of marine health, Collins said. Eventually there will be opportunities for community involvement to expand the data.

In Langley, the committee will post temperatures at the South Whidbey Harbor and eventually provide more comprehensive data online.

“Short term, we just want to make sure people are aware and have some fun with it,” Collins said.

Despite the brisk reading on the sensor the morning of Jan. 1 at Double Bluff, he added, “camaraderie in the warmth and the fire and the cookies make up for it.”

Photo by David Welton Jesse Yates sports a red, white and blue outfit during the Polar Bear Plunge. Photo by David Welton Jesse Yates sports a red, white and blue outfit during the Polar Bear Plunge.

(Photo provided) The Island County Marine Resource Committee’s sensor records temperature at depth.