2021-06-16 17:31:47
Since the appearance of life on Earth, the organisms that have inhabited the planet have been leaving a trace of their presence in the sediments and, with it, information that can be used by scientists to find out what the environmental conditions were like on the planets. that developed. However, the task of knowing the climate of the past is not easy, the biological remains are very dispersed and difficult to interpret. Now, the research carried out by our guest, María Raja, a postdoctoral researcher at the Autonomous University of Barcelona, comes to provide new clues about the richness of phytoplankton in times past and a way to quantify it from the study of organic molecules stored in the sediments.
María Raja has focused her research on molecules called alkenones, which are produced by organisms capable of photosynthesis, that is, those that obtain their food from the Sun’s energy. Marine phytoplankton, made up of a multitude of photosynthetic microorganisms and algae, capture carbon dioxide from the atmosphere and, with the help of solar energy, generate their organic matter. This is what is known as primary production.
Phytoplankton inhabits surface waters and when they die, they begin to slowly fall to the depths. Although a good part is lost along the way, either because organic matter deteriorates or is eaten by other creatures as food, a small part reaches the seabed and accumulates as sediment. Thus, a portion of the carbon dioxide that these creatures extracted from the atmosphere during their lives is stored on the seabed, which produces a decrease in global carbon dioxide if there are no sources to replace it.
The job of scientists who study climate and environmental conditions in the past consists of going back in the described process, that is, locating the sediments, dating them in time to find out when they correspond, and analyzing the organic molecules trapped in them. he. A correct assessment of the abundance of certain substances indicates, in turn, how abundant the microorganisms that generated them were on the surface, as well as the amount of CO2, temperature and other environmental parameters that existed on Earth at that time.
Although there are many ways to deal with the problem of establishing what the environment and climate were like at times in the past, the value of alkenones as a bioindicator had been questioned on the grounds that certain little-known processes could affect conclusions about the cycle of the carbon.
María Raja and Antoni Rosell-Melé have carried out a study of the concentration of alkenones accumulated in the most superficial layer of oceanic sediments extracted in many parts of the planet during the last 20 years and have used current climatic and environmental data to establish a relationship that allows obtaining a quantitative assessment of primary production on the planet.
The results suggest that there is a global carbon export rate to sediments that occurs everywhere and is not regionally constrained. Thus, the organisms that produce alkenones play a very important role in moving carbon from the atmosphere and surface waters to the seabed, where it is stored in sediments.
The study has been published in the scientific journal PNAS and provides scholars of the terrestrial paleoclimate with a tool that allows the use of sedimentary alkenones as a bioindicator that makes it possible to estimate the phytoplankton biomass in the past, a value that, in turn, can be used to calculate primary production in the set of Earth’s oceans.
I invite you to listen to María Raja, Postdoctoral Researcher at the Institute of Environmental Science and Technology (stroke–UAB)
References:
Assessment of sedimentary alkenones for the quantitative reconstruction of phytoplankton biomass
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