Friday, July 29, 2011
Brains? Creatures? Fish eggs?
None of the above: Those slimy blobs floating in the lake are bryozoa, invertebrates whose presence indicates a healthy lake.
Courtesy of Michiel van der Waaij
While underwater, bryozoa extend tentacles they use to feed on microplankton and nutrients.
Courtesy of TLAC
Courtesy of TLAC
A colony of bryozoa that clustered around a branch was brought to the Tri-County Lake Administrative Commission office by a concerned lake resident.
They were like something out of a horror film, maybe "The Blob," and they were everywhere.
When Paul and Denise Hegener arrived at their part-time home in The Waterfront a few weeks ago, Denise headed down to the dock to spruce things up and take a swim, but what she saw just beneath the surface stopped her dead in her tracks.
"I went to go in the water and there were like these huge 'footballs' attached to the ladder," she said. "They were like creatures from the lagoon."
About four or five football-sized jelly-looking masses were anchored to the swim ladder, along with another six or seven the length of a banana.
Hegener said she tried to use a broom to dislodge the creatures, which were hard despite their gelatinous appearance, but they held firm. A neighbor spotted Hegener and told her that the blobs had been at her dock in previous years. Then the woman headed over to help.
"She came over and started pulling them off with her hands," recalled Hegener. "I wouldn't go near them."
The rest her husband pried off with a shovel. Most sank in the lake, but the Hegeners dropped one into a plastic bag and brought it to the Smith Mountain Lake Association office.
Stan Smith, head of the nonprofit's water quality-monitoring program, said he'd never seen the likes of it, although it reminded him a bit of jellyfish. He checked in with professors at Ferrum College who quickly identified the mystery floater: bryozoa.
"Apparently, they have been in the lake forever," said Smith. "They were surprised I hadn't run into them before."
Bryozoa, commonly called moss animals, are itsy-bitsy invertebrates that, like coral, cluster together to form colonies. Those bloblike civilizations can be any size, depending on how many bryozoa are in the area and how much they reproduce, said Judith Winston, a bryozoologist who works at the Virginia Museum of Natural History in Martinsville.
"Probably the biggest one I've seen is about 4 feet high," she said. "It was surrounding a piling on someone's dock at Smith Mountain Lake."
Despite their monstrous, and, some say, disgusting appearance, bryozoa are harmless. They don't sting or bite and they have no natural predators in the lake. And believe it or don't, they're believed to be an indicator of good water quality, said Pam Dinkle, lake management and project coordinator for the Tri-County Lake Administrative Commission.
The lake's species, Pectinatella magnifica, feeds on microplankton and nutrients, said Winston, who added that the water quality must be good to allow either to live. Smith said he wasn't surprised to learn about bryozoa clustering just about anywhere on the lake; he said the water quality is good and doesn't vary much across the board.
"The water quality in Smith Mountain Lake is at its best down at the dam and it curates slightly as you go up either the Blackwater or Roanoke river," said Smith. "But even at the heads of the Blackwater and the Roanoke rivers, I think you'd find the bryozoas."
Smith said he hasn't found any near his own dock in Windmere Point, but he is glad to know bryozoa have been making their homes around Smith Mountain Lake. He's a water watchdog, keeping close tabs on the lake's trophic status, or overall health.
"Lakes can actually die," said Smith. "If they die, there can be no fish or anything living in the water."
SMLA and Ferrum College have been monitoring the lake's age for 25 years, testing for nutrients and contaminants. Over the past two years, the lake has actually gotten "younger," said Smith.
"That's very unusual," he said. "You fight to keep the number from increasing, but very seldom are you lucky enough to actually see the trophic status number improve."
Smith said it's unclear why the lake seems to be drinking from the fountain of youth. He said nonprofits and lake residents can't affect that kind of change; they only can try to keep the lake's trophic status from declining by, for example, using low-phosphorous fertilizer.
The lake's age reversal is as strange as the blobs that flourish in its depths. Correction: the strange-looking blobs. When Jean Nelson discovered a slew of fist-sized bryozoa colonies in Walton's Creek a few years ago, she said she thought they were fish eggs. A man once called the TLAC office to report hundreds of brains floating in the water, said Dinkle.
The jelly-like creatures won't be around for long, however. Winston said the colonies die off when the weather cools, usually around October. But, like creatures of horror film sequels, bryozoa don't disappear forever. A small portion of the bryozoa lays dormant until the water warms back up around May, said Winston.
Pulling them off the dock or killing them won't do the trick either. Winston said fossils indicate bryozoa have been around for about 500 million years.
"You can kill them all you want," she said, "but they'll be back."