Harmful Algae Rapidly Adapting to Earth’s Rising Carbon dioxide Levels


NOAA MERIS image of large cyanobacterial bloom confirmed as Microcystis aeruginosa Credit: Wikimedia commons

Evolution is causing animals and plants to adapt to environment stress in ways previously unheard of. Take for example, the recent finding by scientists at University of Amsterdam, who found that Microcystis, a common type of blue-green algae is adapting to Earth’s rising Co2 levels, suggesting that many of these related species are getting more adept at adapting to changing climatic conditions than previously supposed.

This blue-green algae (cyanobacteria) is commonly seen proliferating in lakes and reservoirs in summer and are capable of forming harmful algal blooms and toxins. This finding by a team of microbiologists suggest implications for clean drinking water, swimming safety and freshwater ecosystems.

The team led by Jef Huisman, Professor of Aquatic Microbiology analysed the genetic composition of this cyanobacteria, Microcystis in a laboratory setup and also at the Kennemer lake, under CO2-rich and poor conditions.

“Before this, the adaptive potential of these harmful cyanobacteria in response to increasing CO2 concentrations had never been studied systematically, even though this can help us predict how algal blooms will develop in future”, explains Xing Ji, a PhD researcher on the team.

They observed that the cyanobacteria’s genetic makeup changed in response to increasing CO2 concentrations in both the lab and the lake.

“It’s a textbook example of natural selection”, says lead author Giovanni Sandrini.

“Cyanobacteria absorb CO2 during photosynthesis to produce their biomass, and we observed that the strain best equipped to absorb dissolved CO2 eventually gains the upper hand.”

Some strains of the algae, Microcystis have an efficient carbon capture system that allows them to uptake even the last bit of CO2 available in water, at very low concentrations. So naturally, these strains become dominant in low CO2 conditions. However, some strains have the capability of taking up dissolved CO2 at very high rates, even at high concentrations.

“We discovered that these high-speed strains enjoy a major selective advantage in CO2-rich water”, Sandrini continues. “Given the rising atmospheric CO2 values, these strains are poised to thrive.”

Why should you be worried?

The ability of these cyanobacteria to adapt to the rising CO2 levels is definitely a cause of concern, because they produce algal blooms, that are of economic and ecological importance. Moreover, Microcystis can produced a toxin called microcystin, that can cause liver damage in birds and mamals.

In high concentrations, cyanobacteria also disrupt , killing fish and aquatic plants. In the Netherlands, blue-green algal blooms regularly put swimming areas off limits.

The lead author Ji shared his personal experience about how these algal blooms affected his life in 2007, when he was living in Eastern China where Lake Taihu, a 2000 square km lake was entirely covered with cyanobacteria leading to a drinking water crisis affecting five million people.

“I watched my mother arguing with other supermarket shoppers who all had their sights set on the last bottles of drinking water. It’s precisely because I’m aware of how poor water quality can impact society that I am happy to be doing research that can yield relevant insights.”

Source: University of Amsterdam

Original paper can be accessed here: PNAS

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