Tahoe's hidden landscape

A research biologist who participated in a complex underwater experiment involving scuba diving techniques recalled how he first became involved in research scuba diving.

"In 1985, I missed out on a research trip to the Galapagos Islands because I wasn't certified for research scuba diving," said Brant Allen, a research biologist for the Tahoe Environmental Research Center, who has spent the past 23 years diving under Lake Tahoe's cobalt surface. "The next day, I went out and began the certification process."

Since then, Allen has conducted underwater research projects in an array of the Sierra Nevada's alpine lakes as well as taking trips to far away exotic locales such as Papa New Guinea.

However, since 1988, when Allen first arrived in the Lake Tahoe Basin to conduct fish surveys, he has spent most of his underwater time in the lake, studying fish behavior, implementing experiments, identifying aquatic invasive species and helping to facilitate projects conducted by visiting professors and scientists.

"I've been down in other pristine mountain lakes in the area," said Allen. "But, nothing surpasses the clarity of Tahoe."

Allen said obtaining a view of Tahoe from beneath the lake's surface is essential for scientists attempting to understand the complex ecosystem.

"It is really important for those who study the lake to get their face in the water and find ways to actually view it," he said. "Whether it's by diving our just putting a mask on and snorkeling, you have to see what's happening."

Allen said one of the most interesting things he encountered on his initial dives was the visible difference in layers of the lake.

"Tahoe has a strongly visible thermocline and the temperature of the lake changes rapidly with very little change in depth," he said.

As he went down farther, he could visibly discern the difference between the warmer, less dense layer of water on the surface and the colder, more dense water toward the lake bottom.

"It looked like pouring fresh water into a bucket of salt water and watching it mix," he said.

The unique view of Tahoe afforded by diving expeditions have changed greatly in the past 23 years, said Allen.

"One thing that stands out is the decrease in clarity," he said. "When I'm working with a diving buddy, we have to stay closer, you can't see fish from as far away and there is a general decline in sharpness of objects down there."

Another pronounced difference is the presence of aquatic invasive species, which have effected local shifts in ecology, according to Allen.

Allen also said the increased presence of invasive aquatic botany has altered the underwater landscape, as the lake bottom used to be relatively desolate.

"There was some non-native aquatic vegetation here when I arrived, but it is surprising to see the large areas," said Allen.

Allen said those with more than a passing interest in the underwater environment of Tahoe should strap on a mask and begin snorkeling before investing heavy money and training into scuba diving equipment.

Allen said observing fish behavior is easy in a place like Taylor Creek - where Kokanee salmon spawn in late September or late October.

"You have to remember fish always face upstream, so if you swim or crawl upstream they won't see you coming," said Allen.

Despite his fondness for snorkeling, Allen said there is no feeling quite like diving.

"When you put on all the equipment and gear, you think you're going to drown, it's all so heavy," Allen said. "But once you get in the water you are essentially weightless.

"It's very relaxing," he said.