Mikrobiologie an Hydrothermalquellen des Tyrrhenischen Meeres
Final Report Abstract
The primary goal during POS412 was to obtain a better understanding of the variability of the shallow water hydrothermal ecosystems in the Aeolian Arc being located in the Tyrrhenian Sea, Western Mediterranean. Therefore, samples were taken from various hydrothermally influenced habitats for subsequent geological, chemical (sulfur species, fluid chemistry, and heavy metal chemistry) and microbiological (molecular and culture‐based studies) analysis. This included two tubeworm colonies at the Palinuro western summit (PAL‐1), fluid emissions in PAL‐1 and the Panarea hydrothermal vent field (PAN) and the sampling of bacterial mats on sediments and around fluid or gas emissions. Sediments from PAL‐1 and PAN were sampled with the aim to assess the microbial community in massive sulfide containing sediments. Onboard analysis of fluid samples from PAN during POS412 resulted in 1.8 mM hydrogen sulfide (H. Strauss), indicating a specific sulfur‐metabolism related bacterial community composition featuring also possibly phototrophic bacteria. At Palinuro, a fluid outlet with emanating warm fluid was discovered and sampled. Maximal measured in situ temperature within the fluid was 58.3 °C. Samples were taken and preserved from these stations in order to assess microbial community composition and metabolic potential. Videos from previous cruises (M73/2, POS340) showed sediments to be covered by microbial mats, several of which could be successfully sampled during POS412 in PAL‐1 and PAN. Boiling of hydrothermal fluids due to the shallow situation of the hydrothermal systems in the Aeolian Arc leads to ore‐forming processes beneath the seafloor and thus, to massive sulfide formation. Gravity corers operated at PAL‐1 during cruise POS412 revealed a special sediment core exhibiting a temperature of 48°C at 3 m core depth as well as further cores with sulfur crusts within the sediments and elemental sulfur deposits at the surface, which are of particular interest and were preserved for geological, chemical and microbiological analysis. Two tubeworm colonies were sampled by the ROV and molecular analysis performed in the home lab to identify the tubeworms based on sequences of the 18S rRNA and COI genes. A single Gammaproteobacterium was detected as endosymbiont from the trophosome of 11 different tubeworms from colonies at PAL‐1 with a sulfur‐oxidizing chemoautotrophic metabolic potential.
