Ancient algae discovered in Peruvian peaks

Striking algae found in Peruvian ice. Photo credit: Bruce Brinson/Rice University

Striking algae found in Peruvian ice. Photo credit: Bruce Brinson/Rice University

Algae are a problem for fish tank and pond owners alike. Finding algae in bodies of water is no surprise, but it can also be found in some very unexpected places. Take, for example, algae found all the way up in the ice caps of tropical mountains.

There are more kinds of algae than the slimy, green stuff you may have seen in a goldfish bowl. They range in size from microscopic single cells to multi-celled giant sea kelp. Whatever their size, algae live in bodies of water all over the world.

The mountain ice cap algae are not just interesting because of their location, they can also tell us about ancient climates.

One type of ice-cap algae comes from a single-celled group called diatoms. They are microscopic and gorgeous. Diatoms have geometric, glass-like outer shells. Like plants, diatoms create their own energy through photosynthesis in sunny waters.

Drilling deep cores in massive glaciers can unearth diatoms trapped in the ice. Because snow is laid down in sheets, similar to sediment in a river, an “ice core” provides a snapshot of many different time periods, all layered up. The age of different sections can then be dated using knowledge of snow accumulation rate and ice flow.

Algae have been found in the ice caps of the Arctic and Antarctic, but the recent discovery of diatoms in tropical peaks was a surprise to the scientists. This remarkable cache was discovered at Quelccaya Summit Dome Glacier in the Peru’s Andes mountain range. Multiple species of diatom were discovered dating from the 6th to the 12th century. “I’m convinced there’s no end to what you can find in these glaciers, commented researcher Ed Billups.

Peruvian Quelccaya Glacier. Photo Credit: Edu Bucher

Peruvian Quelccaya Glacier. Photo Credit: Edu Bucher

Diatoms can be blown like dust from freshwater sources and deposited in far away polar locations. However, lead researcher of the Peruvian diatoms Sherilyn Fritz suspects this algae came from a closer source. “These are beautifully preserved, and most of the ecology we know about indicates they’re not from global diatom dust sources,” she explained. The researchers agree that these samples likely came from ancient Peruvian lakes and wetlands.

Because they are such a diverse group, diatoms give a unique glimpse into ancient environmental conditions. The many different species are adapted to different living conditions including temperature and water depths. By looking at what species are common in ice from different time periods scientists can reconstruct what the environment was like at different periods in the past.

Investigating past climate with diatoms has successfully been used across the world. The presence of cold-water loving diatoms in the dirt at the bottom of Great Britain’s seas tells us the waters used to be icy cold. Alternating layers of shallow and deep-water diatoms in the cliffs of desert Africa indicate there were lakes of rapidly changing depths in this now dry land.

While the research team that found the Peruvian diatoms has not yet investigated climatic conditions represented in their ice cores, the option remains. Fritz is already considering next moves, including collecting modern diatoms in local lakes. “I’ve contemplated doing some more sampling, just because it’s an interesting question,” she said. Having examples of diatoms currently living in the lakes will give the team an idea of how Peruvian climate has changed over time.

The researchers recognize that these cores may not be around forever. Current climate conditions have not been friendly to glaciers. “Unfortunately, these valuable ice archives of our past are rapidly disappearing under the present climate conditions,” commented researcher Lonnie Thompson.

Rice chemists Ed Billups and Bruce Brinson, Ohio State climatologist Lonnie Thompson and Nebraska geoscientist Sherilyn Fritz’s paper is titled “Diatoms at >5000 Meters in the Quelccaya Summit Dome Glacier, Peru”. Their work appears in the May 2015 issue of Arctic, Antarctic, and Alpine Research, a journal published by the University of Colorado-Boulder.


Read the abstract at http://www.bioone.org/doi/abs/10.1657/AAAR0014-075

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