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New study highlights the impact of two new marine gases on climate models’ accuracy

January 31, 2023

A new study published in Science Advances led by the Institut de Ciències del Mar (ICM) has revealed that plankton in polar oceans emits benzene and toluene, two gases of biological origin that contribute to cloud formation and affect climate. In addition to oxygen, nitrogen or carbon dioxide, the air we breathe contains small amounts of organic gases, such as benzene and toluene. These oxidize into small particles or aerosols that contribute to the condensation of water in the droplets that form clouds. The new study describes the first measurements of benzene and toluene in polar oceans and indicates that these compounds have a biological origin. Until now, their presence in polar marine air was thought to be a proof of the extent of human pollution from coal and oil combustion or solvent use, among others. To carry out the study, the team measured the concentrations of benzene and toluene in surface water and air during the course of two oceanographic campaigns: one in the Arctic and the other in the Southern Ocean. The distribution of these gases, their relationship to the amount of phytoplankton, and the fact that the ocean was constantly emitting them into the atmosphere rather than capturing them from it, led the researchers to conclude that they were of biological origin. Then, by incorporating the data into a global atmospheric chemistry and climate model, the scientific team realized that benzene and toluene emitted by the ocean contributed significantly to aerosol production. This was especially true in the extremely clean and unpolluted atmosphere of the Southern Ocean, where these two gases increased the amount of organic aerosols by 8% and up to 80% in transient situations. According to the authors of the paper, the natural effect of marine benzene and toluene on atmospheric chemistry was most likely a widespread and global phenomenon before the Industrial Revolution. However, it would now be masked by the widespread impact of pollution.

Wohl, C., Li, Q., Cuevas, C. A., Fernandez, R. P., Yang, M., Saiz-Lopez, A., and Simó, R. (2023). Marine biogenic emissions of benzene and toluene and their contribution to secondary organic aerosols over the polar oceans. Science Advances, 9, eadd9031.

 

Earth's environmental stability allowed marine biodiversity to flourish

July 13, 2022

A diversification model has been developed that allows reconstructing the history of marine animal diversity from the Cambrian explosion, some 540 million years ago, to the present day. The work, published in Nature, indicates that today's biodiversity is the result of long periods of environmental stability on Earth that allowed the development of biodiversity hotspots, regions with a high number of species. The fossil record shows that life on our planet has been hit by at least five great mass extinctions over the past 500 million years. The mass extinction that occurred at the end of the Permian period, the largest of all time, wiped out more than 90% of marine species and brought ecosystems on the verge of collapse. Today, 250 million years later, life in the sea is more diverse than ever. To understand this, and overcome the problem that the fossil record is incomplete, a new computational approach has been developed that allows reconstructing the history of biodiversity. The model is able to recreate the geographical distribution of diversity in today's oceans, especially the hotspots, and reveals the mechanisms that have created them. This model illustrates that the time between one mass extinction event and the next is key to allowing biodiversity hotspots to develop. The new model also sheds light on one of the most controversial questions in evolutionary ecology: whether or not there is a limit to the global diversity that the Earth can support. Ecological theory states that as diversity increases and biological interactions, such as competition, intensify, the process of diversification slows to a halt. At this point, the emergence and establishment of a new species will inevitably lead to the extinction of an old one. However, some scientists have argued that Earth's ecosystems are so heterogeneous that there will always be room for more species. The results from the new model reconcile both views. While most of the oceans have levels of diversity well below their maximum, regions harboring biodiversity hotspots may be close to their limit. This modelling tool is very powerful because it allows to explore many things, including what would have happened if some of the great mass extinctions had never happened, or if they had happened at another time in Earth's history. Human interference in the natural functioning of Earth systems has prompted what experts call the sixth great mass extinction. According to the United Nations, as many species have disappeared in the last century as would have become extinct in 10,000 years assuming a normal scenario. In addition, 25% of the species evaluated by the International Union for Conservation of Nature are today in danger of extinction. This study shows that, if current trends continue, projected loss of biodiversity could take millions of years to recover, arguably beyond our own existence as a species.

Cermeño, P., García-Comas, C., Pohl, A., Williams, S., Benton, M. J., Chaudhary, C., et al. (2022). Post-extinction recovery of the Phanerozoic oceans and biodiversity hotspots. Nature, 607, 507–511.