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Research trip to the Azores region: What happens in the underwater plume?
July 27, 2021
They form when hot solutions heated by igneous magma escape from the earth's crust in the deep sea and encounter cold seawater: Hydrothermal plumes are enriched in many compounds, supplying the oceans with nutrients and metals. In an area not far from the Azores in Portugal, Researchers at Jacobs University Bremen want to investigate exactly which geochemical processes take place within these clouds in a detailed study. The three-member team is led by Andrea Koschinsky, Professor of Geosciences at Jacobs University. Also on board the research vessel FS Meteor is bachelor student Vignesh Menon, who will be taking samples and blogging about the cruise together with PhD student Lukas Klose and postdoctoral researcher Sandra Pöhle.
The target of the expedition is a hydrothermal field named "Rainbow", which is located south of the Azores region in Portugal at a water depth of 2,300 meters in the middle of the Mid-Atlantic Ridge. The submarine mountain range divides the Atlantic Ocean into an eastern and a western half. The heat source for the underwater plume is located in a valley; it rises upwards in the water, drifting with the ocean currents while it mixes with the surrounding seawater. Complex bio-geochemical processes occur as it does so. "We will follow this plume along the valley for 60 kilometers, all the way to the border of the Azores Exclusive Economic Zone," said Koschinsky.
Hydrothermal vents and the plumes they produce are of major importance for biological cycles in oceans. They provide supplies of iron, manganese, copper, zinc and other essential elements that are often found thousands of kilometers away from the original source. "The plumes are highly productive regions where quite a lot happens," Koschinsky explained.
The scientists are not only investigating the concentration of individual substances within the plume: "We are particularly interested in the chemical and physical forms in which they occur," Koschinsky emphasized. For example, dissolved iron can be quickly taken up by organisms, but it can also oxidize quickly in the oxygen-rich ocean water, bind to the small particles, and sink to the ocean floor. It is then no longer bioavailable. The Jacobs University team will filter and preserve water samples in a multi-stage process in order to find out in which form the iron and other trace metals are transported within the water. In the end, even ions and molecules smaller than three nanometers can be separated and examined using ultrafiltration. Chemical analysis of the samples will then take place in the home laboratory.
Andrea Koschinsky’s research group has long been conducting research on material cycles in marine mixing zones, such as hydrothermal plumes or estuaries within the ocean. Research expeditions have taken them to the Kermadec Arc in the southwest Pacific, one of the most active eruption zones in the world, and to the Amazon River estuary. The current expedition aboard the Meteor, which is led by the GEOMAR Helmholtz Centre for Ocean Research Kiel, is taking place under pandemic conditions. The journey starts and finishes in the north German city of Emden from the end of August until the beginning of October. Only international waters may be visited; stopovers in ports of other countries are not possible.