It Turns Out You Can Photosynthesize In Dark Caves

Volcanic cavern, view from inside a large cave-shaped well in a humid forest.

Researchers found evidence of photosynthesizing microbes in the dark zones of caves. The microbes use far-red light and a special form of chlorophyll.

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Life finds a way. In this case, it's cyanobacteria that can photosynthesize in the dark. caves use far-red light and special versions of chlorophyll to generate energy. This type of light comes just before infrared light on the spectrum. Far-red light is reflected by the cave surfaces, reaching areas that visible light does not.

Researchers based in Australia, Denmark, Sweden, Switzerland and the U.S. studied the microbial communities in four caves in Carlsbad Caverns National Park, New Mexico. Light enters the first part of the cave easily—most of the cave entrances are 30 to 90 feet tall, with one cave entrance being about 12 feet tall. The cave openings have existed close to their current form for the last four to nine million years.

The scientists studied the microbes along the gradient of light formed as you move deeper in the cave, from areas with full sunlight to "twilight zones" to deep zones. To take detailed measurements on light levels, they used an irradiance meter to measure the level of photons present. The dark zone begins approximately 165 feet or more inside the caves.

The caves are composed of Capitan limestone, which they discovered reflects near-red light slightly better than visible light. This means near-red light can penetrate slightly further into the cave.

Generally, plants and cyanobacteria rely on chlorophyll a for photosynthesis, which gives plants and phytoplankton blooms their distinctive green color. Chlorophyll d and f are special types that are able to generate energy from the far-red light.

After scraping biofilm off the cave walls, the scientists found chlorophyll d and f were present in all parts of the cave, but were particularly common in the deepest light environments, followed by the twilight zone.

The microbiome of the deep zones was different than the microbiome of the twilight zone and cave entrances, which were similar to each other. The scientist say the limestone provides a great habitat for the cyanobacteria because of its reflective properties. Other minerals, like calcite, have similar spectral properties and also form other caves, making it likely that cyanobacteria are living in other cave systems.

Since the cave microbes are using different parts of the light spectrum, this is a unique example where light is allowing species to form their own niche, similar to how there are different species as you move up a mountain, tree canopy or water column.

The upcoming study, which will be published in Environmental Microbiology, highlights how caves are a promising natural model system, since conditions are stable and can offer unique insights on photopigments, like chlorophyll.

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Life finds a way. In this case, it's cyanobacteria that can photosynthesize in the dark. caves use far-red light and special versions of chlorophyll to generate energy. This type of light comes just before infrared light on the spectrum. Far-red light is reflected by the cave surfaces, reaching areas that visible light does not.

Researchers based in Australia, Denmark, Sweden, Switzerland and the U.S. studied the microbial communities in four caves in Carlsbad Caverns National Park, New Mexico. Light enters the first part of the cave easily—most of the cave entrances are 30 to 90 feet tall, with one cave entrance being about 12 feet tall. The cave openings have existed close to their current form for the last four to nine million years.

The scientists studied the microbes along the gradient of light formed as you move deeper in the cave, from areas with full sunlight to "twilight zones" to deep zones. To take detailed measurements on light levels, they used an irradiance meter to measure the level of photons present. The dark zone begins approximately 165 feet or more inside the caves.

The caves are composed of Capitan limestone, which they discovered reflects near-red light slightly better than visible light. This means near-red light can penetrate slightly further into the cave.

Generally, plants and cyanobacteria rely on chlorophyll a for photosynthesis, which gives plants and phytoplankton blooms their distinctive green color. Chlorophyll d and f are special types that are able to generate energy from the far-red light.

After scraping biofilm off the cave walls, the scientists found chlorophyll d and f were present in all parts of the cave, but were particularly common in the deepest light environments, followed by the twilight zone.

The microbiome of the deep zones was different than the microbiome of the twilight zone and cave entrances, which were similar to each other. The scientist say the limestone provides a great habitat for the cyanobacteria because of its reflective properties. Other minerals, like calcite, have similar spectral properties and also form other caves, making it likely that cyanobacteria are living in other cave systems.

Since the cave microbes are using different parts of the light spectrum, this is a unique example where light is allowing species to form their own niche, similar to how there are different species as you move up a mountain, tree canopy or water column.

The upcoming study, which will be published in Environmental Microbiology, highlights how caves are a promising natural model system, since conditions are stable and can offer unique insights on photopigments, like chlorophyll.

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I am a scientist studying how tiny microbes make big impacts in ecosystems. My research has brought me to scenic environments from deserts to boreal forests, and my fav

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