Making Lehman Caves Less Green: Fighting Lampenflora

By Gretchen Baker, ecologist. From The Midden (Great Basin National Park), Vol. 20, No. 1, Summer 2020.

Growth near cave lights can include moss and bacteria as well as algae. NPS / Gretchen Baker.

While Great Basin National Park works to be greener — more energy-efficient and conservation-minded — it's trying to make Lehman Caves literally less green. The green next to the cave's artificial lights is algae, moss and bacteria, called lampenflora. It:

• gives cave wildlife an unnatural food source;
• can grow into speleothems (cave formations), harming their growth and beauty;
• discolors formations and may speed the loss of historic cave signatures.

A wet year

The park has experimented with different light wavelengths and switched most bulbs to LEDs. But a very wet winter and spring meant months of dripping water — refilling pools and growing formations, and encouraging algae. BYU researcher Steve Leavitt and his students sampled the algae in May and November 2019 and found very different communities each time.

Spraying algae with a 10% bleach solution kills it, but adds a chemical to the delicate cave environment. NPS / Gretchen Baker.

Spraying

After the sampling, selected algae was sprayed with a 10% bleach solution in November and December 2019; during two lint camps in January nearly all accessible algae was sprayed; and in March once more. Each round needed less:

From over 1,000 square feet on January 17 to 445 on March 20, the average per light fell from 5.9 to 2.6 square feet — still a lot.

Algae discolors speleothems and may hasten the loss of historic signatures. NPS / Gretchen Baker.

Darkness helps

With the cave's lights off for weeks or months, much of the algae may finally die. Caves closed in winter, such as Timpanogos Cave and Crystal Cave in Sequoia National Park, have far less algae than those open year-round, such as Mammoth Cave, Carlsbad Caverns and Lehman Caves.

One future option: lantern or flashlight Explorer Tours in winter — less light in the cave, no bleach (which harms native cave life), and a chance for visitors to feel like explorers while helping conserve the cave.

Sources

Based on "Making the Cave Less Green," by Gretchen Baker, The Midden, Great Basin National Park, National Park Service; a work of the United States government in the public domain. Its table, published as an image, is transcribed.