WELLINGTON, April 18 (Xinhua) -- New Zealand scientific divers have made a successful search for the freshwater "freak of nature", deep-water bryophytes, in Otago's alpine lakes.

A team of the National Institute of Water and Atmospheric Research (NIWA) scientists have unearthed plants that comprise moss and liverwort species, collectively known as deep-water bryophytes when found deep within lakes, a NIWA statement said on Thursday.

Despite being simple organisms, deep-water bryophytes play a vital role in ecosystem functioning by providing habitats, improving water quality, and aiding biodiversity, said the Otago Regional Council (ORC) scientist Hugo Borges.

Deep-water bryophytes are highly sensitive gauges of water transparency, light transmission, sedimentation rates, temperature fluctuations, and changes in dissolved gases, all of which provide clues into the health of the freshwater environments, Borges said.

Deep-water bryophytes were first discovered by NIWA divers in Otago's lakes in the 1980s and 1990s and are a globally rare plant community, with New Zealand being one of the few places worldwide to support blankets of these species, the NIWA statement said.

The ORC commissioned NIWA to undertake a submerged plant survey in Lakes Whakatipu, Wanaka, and Hawea, hoping to build upon the knowledge gained over three decades ago and establish a regular monitoring protocol.

NIWA freshwater ecologist Mary de Winton, member of the dive team that first studied the bryophytes in the 1990s, was delighted to see the plants still thriving down there, after being apprehensive about whether they could be found again because climate and lake catchments have changed a lot in three decades.

Bryophytes are usually found in moist environments like damp forest floors and shady rock faces, but they were seen in Lakes Whakatipu and Wanaka up to 50 meters down, de Winton said.

"It's a really unusual place for them to grow, but we think they were washed into the lakes eons ago and have found a niche in the quiet twilight depths," said de Winton, adding this "freak of nature" would not have survived if it was not for the extreme transparency of the lake water.

Borges said they successfully revisited all sites and found deep-water bryophytes in some of them by using a remotely operated vehicle to explore the lakebed.

NIWA and ORC have scheduled a dive program every three years to monitor Otago's submerged plant communities, which will provide a baseline to monitor the health of this unusual community, crucial for tracking environmental change, while the depths they grow down to will provide an indicator of the long-term clarity of the lakes, Borges said.

Light levels where deep-water bryophytes are found have been estimated at less than 1 percent of the sunlight falling on the surface of the lakes. A record of 128 meters for deep-water bryophytes was described for an Oregon lake in the year 2000, according to NIWA. Enditem

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