The climate system is based on microscopic particles


Scientists from EPFL and the Mediterranean Oceanographic Institute (MIO) have discovered a new source of organic phosphorus that fertilizes distant marine ecosystems via atmospheric particles. This discovery could help researchers better understand how marine ecosystems respond to climate change.

Earth’s climate is an extremely complex system that is driven by the subtle balance of many different processes – one of the main ones being the air-sea exchange of CO2. Monitor CO uptake by the ocean2 is the key to our understanding of climate change, and scientists from EPFL and the Mediterranean Institute of Oceanography (MIO, France) recently discovered a new part of the process. They identified a new source of organic phosphorus from the atmosphere that will potentially contribute to the growth of phytoplankton and microalgae, the latter playing a crucial role in making our planet habitable. Deposits of organic phosphorus in marine environments have not been studied so far, but this groundbreaking work has shown that it is an important – and completely overlooked – source of essential nutrients, with important implications. for the climate. The scientists’ findings were recently published in the journal Nature npj Climate and Atmospheric Science.

Phytoplankton, which lives on the surface of lakes, seas and oceans, need various chemical elements to thrive, the main ones being iron, nitrogen and phosphorus. An abundance of these nutrients allows phytoplankton to flourish and perform the critical function of photosynthesis, during which large amounts of CO2 is absorbed by the air and converted to biomass, while releasing oxygen. This makes them very important to living organisms and gives them a crucial role in regulating the Earth’s climate. Phytoplankton also form the basis of the aquatic food chain, which supports marine systems.

The supply and bioavailability of phosphorus affects the growth rate of phytoplankton, the rate at which they photosynthesize, hence the amount of CO2 they absorb. It is therefore important to identify all the ways in which marine ecosystems are fertilized; this can provide key information about the climate system and how human activities affect it.

Full picture

“Scientists already knew that large amounts of inorganic phosphorus are transported to marine ecosystems by airborne dust in the form of phosphate minerals and ions. But this picture is incomplete, ”explains Kalliopi Violaki, lead author of the study and scientist at the Laboratory of Atmospheric Processes and Their Impacts (LAPI), which is part of the School of Architectural, Civil and Environmental Engineering (ENAC). from EPFL.

Kalliopi Violaki organized and led a two-year research program at MIO. During this time, she discovered that bioaerosols – biological particles suspended in the air, such as viruses, bacteria, fungi, plant fibers and pollen – contain significant amounts of organic phosphorus. Although its exact amount is still uncertain, we know it is important because it is comparable to the amount of inorganic phosphorus that dust aerosols provide. Additionally, organic phosphorus is often found in the form of phospholipids, a key component of cell membranes.

“Being aware that terrestrial ecosystems can fertilize marine ecosystems via bioaerosols gives us a whole new perspective,” explains Athanasios Nenes, head of LAPI and co-author of the study. “This knowledge will help us better understand the processes that influence the carbon cycle and the climate.”

A major discovery

Organic phosphorus has not yet been incorporated into climate models, but it could prove to be a major improvement in understanding how marine ecosystems are responding to the ongoing climate crisis. Ocean layers differ from each other in terms of density, temperature, oxygen level and salinity, and climate change induces further changes. This makes mixing between the layers more difficult and disrupts the CO2 absorption. As the ocean becomes more stratified, it also becomes more difficult for the nutrients available in the deep waters to reach the different layers. This could negatively impact marine habitats and the food supply of many marine species, especially in remote areas where phosphorus supplies are limited. The new source of phosphorus could completely change the way Mediterranean (and other) seas are expected to respond to climate change.

This study shows how important atmospheric particles are to the environment. Despite their microscopic size, variations in their supply could lead to major changes throughout the climate system. Scientists will therefore conduct further research to better understand this new source of organic phosphorus and how it could influence the Earth’s climate.


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