The oceans are a very important reservoir for carbon in the system of the earth, but many aspects of the marine carbon cycle are still unknown. Scientists have now discovered that sugar plays an important role in this process.
In the sunlit surface layer of the ocean, photosynthetic microalgae such as diatoms convert more carbon dioxide into biomass than Earth’s tropical forests. Like land plants, diatoms sequester carbon dioxide into polymeric carbohydrates, or long-chained sugars. However, it has proven difficult to quantify how much carbon dioxide can be stored in the global oceans throughout this process.
Now, researchers at the Max Planck Institute of Marine Microbiology and the University of Bremen have dissected photosynthetic microalgae and measured concentrations of the long-chained sugar laminarin, an important energy source for microalgae including diatoms.
Based on microalgae obtained from the Arctic, Atlantic, and Pacific Oceans and the North Sea, the researchers estimated that this biomass is on average composed of 26 per cent laminarin, according to a statement.
Furthermore, the scientists found that laminarin comprises as much as 50 per cent of the organic carbon in sinking diatom-containing particles. “Thus laminarin plays a central role in carbon transfer from surface waters to the deeper ocean,” explained Jan-Hendrik Hehemann, leader of the research group Marine Glycobiology. “Whether laminarin is fixed in deep waters is an important further question that we will address in the future”.
As microalgae represent the all-important base of the marine food web, the findings show that laminarin occupies a prominent position in global ocean ecology. The researchers from Bremen found out that the amount of sugar in microalgae is high, but is not always the same.
Collectively, these findings highlight the prominent ecological role and biochemical function of the sugar laminarin in the ocean.
Photo credit: Reeve Jolliffe, flickr/Creative Commons