The blue-green algae, also known as Cyanobacteria, are some of the most common organisms on Earth. A research team that was led by the Leibniz-Institute of Freshwater Ecology and Inland Fisheries or IGB and Heidelberg University has now shown Cyanobacteria for the first time, and they stated that they produce relevant amounts of methane in the inland waters, oceans and even on land. Because of climate change, Cyanobacteria blooms and increases in extent and frequency, signaling the release of methane from oceans and inland waters to the atmosphere.
What is Cyanobacteria?
The only prokaryotes that are known to be capable of using sunlight as their energy source are Cyanobacteria. They can also use water as an electron donor and they can use air as a source of carbon and even nitrogen for some nitrogen-fixing strains.
Cyanobacteria are photosynthetic and aquatic, which means that they live in the water and that they can manufacture their food. Because they classify as bacteria, they are small and they are usually unicellular.
Though bacteria usually grow in colonies that are massive enough to see. They have the contrast of being the oldest known fossils on Earth because they are more than 3.5 billion years old. Cyanobacteria are recorded to still be around. Cyanobacteria are one of the most massive and most important groups of bacteria here on Earth.
The methane generation done by microorganisms is usually considered to take place only under strictly anoxic conditions by microbes of the domain named Archaea. This connection is refuted by the results of the current study led by Dr. Mina Bizic from IGB. The international research team from IGB investigated seventeen different cyanobacterial species. They were found resided in the freshwater, sea, and soil.
Dr. Mina Bizic stated that Cyanobacteria in the surface water are a previously unknown source of methane and that experts were able to show for the first time that these bacteria do produce the greenhouse gas methane during photosynthesis. To do so, a researcher from Heidelberg University, Thomas Klintzsch, used isotopically labeled carbon to evaluate and know how methane is formed in the cell during the conversion of light energy into chemical energy.
In a lot of laboratory experiments, the research team compared the amount of methane that was made by Cyanobacteria with the amounts that were made by methanogenic archaea and organisms with cell nuclei.
Co-author of the study, Frank Keppler, the professor at the Institute of Earth Sciences at Heidelberg University stated Cyanobacteria produce less methane than archaea, but more methane than eukaryotes. It is not easy to know the global amount of methane made by Cyanobacteria because there is a lack of detailed data and records on the biomass of these organisms found in the soil and water.
More Cyanobacteria blooms mean higher methane emissions
The researchers stated that it is possible that Cyanobacteria may have been producing the greenhouse gas methane already since the early days of Earth. Cyanobacteria are known because of the Great Oxygenation Event that happened 2.5 billion years ago. However, the oldest known fossils are deposits of Cyanobacteria like organism found in 3.5 billion-year-old rocks in Australia.
Cyanobacteria are known to be widespread all over the world happening in almost any illuminated environment. Some species make well in freshwater or seawater with high nutrient loads and warm temperatures. Because of climate change, mass developments of cyanobacteria already happened more frequently and will do so to a greater extent in the future. Professor Hans Peter Grossart, a researcher at IGB, said that according to their findings, this will also increase the emission of the greenhouse gas methane from various aquatic systems, which in turn increases climate change.
