Hotspot volcanoes

Biological hot spots are windows in the basement

Hydrothermal ventilation of magmatic gas at the Cone site in the Brothers volcano. Credit: Image courtesy of Anna-Louise Reysenbach, NSF, ROV Jason and 2018 © Woods Hole Oceanographic Institution.

Hydrothermally active submarine volcanoes make up a large portion of Earth’s volcanism and are mineral-rich biological hotspots, but very little is known about the dynamics of microbial diversity in these systems. Recently in Proceedings of the National Academy of Sciences (PNAS), Reysenbach and his colleagues, show that on one of these volcanoes, the Brothers underwater arc volcano, in northeastern New Zealand, the geological history and the paths of subterranean hydrothermal fluids bear witness to the complexity of the microbial makeup of the seabed, and also provide insight into how past and present subterranean processes might be imprinted in microbial diversity.

“Hot spring microbes around the world get their energy in part from the geochemistry of hot water / fluids. The same goes for the hot springs on the seabed of the Brothers volcano. Since hydrothermal systems influenced by seawater and magmatic gas coexist at Brothers, we predicted that the microbes in the active magmatic cone sites (image at the top of the page) would be very different from those in the wall. caldera (image below) which are affected in large part by altered seawater, ”said Reysenbach, professor of microbiology at Portland State University. But what they didn’t expect is that there would also be two very different microbial communities close to each other on the caldera wall.

Magmatic gas thydothermal ventilation

Image 1. Deep sea hydrothermal vent chimneys on the northwest caldera wall of Brothers Volcano. Credit: Image courtesy of Anna-Louise Reysenbach, NSF, ROV Jason and 2018 © Woods Hole Oceanographic Institution.

From recent drilling and geophysical measurements by the International Ocean Discovery Program (IODP), it is proven that after the volcanic caldera of the original stratovolcano collapsed to form the current caldera, the first magmatic-hydrothermal system was overprinted by a system more dominated by seawater. The authors show that one of the communities in the caldera aligns with microbes in hydrothermal vents influenced by magmatic from the most recent cone that developed from the floor of the caldera. It is likely that a combination of different subterranean mineral assemblages intersected by circulating hydrothermal fluids help form distinct microbial communities on the caldera wall.

“Having studied the Brothers volcano for 20 years, this work really amazed me because for the first time I was able to link the points of magmatic gases and hydrothermal fluids to microbial communities,” said co-author Cornel de Ronde. , Senior Scientist at GNS Science, New Zealand.

This study also describes more than 90 new bacterial and Archean families, and nearly 300 heretofore unknown genera, highlighting how little we know about biodiversity in these systems and how the complexity of underground geology may contribute to a high microbial biodiversity. Additionally, these sites include many potentially deep branching and symbiotic microbes whose prospective study will contribute to our understanding of the evolution of life on Earth and the interactions that shape underground communities.

“I hope this work will encourage others to see that geology, geochemistry and even geophysics can in fact go hand in hand with microbial studies. You just have to translate the different information into a language understood by all, then you will discover new paradigms, ”said de Ronde.

Reference: “Complex subterranean hydrothermal fluid mixture on submarine arc volcano supports distinct and highly diverse microbial communities” by Anna-Louise Reysenbach, Emily St. John, Jennifer Meneghin, Gilberto E. Flores, Mircea Podar, Nina Dombrowski, Anja Spang, Stéphane L’Haridon, Susan E. Humphris, Cornel EJ de Ronde, Fabio Caratori Tontini, Maurice Tivey, Valerie K. Stucker, Lucy C. Stewart, Alexander Diehl and Wolfgang Bach, December 4, 2020, Proceedings of the National Academy of Sciences.
DOI: 10.1073 / pnas.2019021117