Rates and signatures of methane turnover in sediments of continental margins

• Main Author: Niemann, Helge
• Other Authors: Boetius, Antje, Elvert, Marcus, Wolf-Gladrow, Dieter
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Universität Bremen 2005
• Subjects: continental margin; cold seep; methane; anaerobic oxidation of methane; AOM; sulphate reduction; biogeochemistry; green hous gas; biomarker; archaea; ANME; mud volcano; Haakon Mosby Mud Volcano; Tommeliten; Gulf of Cadiz; pockmark; 550; 550 Earth sciences and geology; ddc:550; Barents Sea
• Online Access: https://media.suub.uni-bremen.de/handle/elib/2163; https://nbn-resolving.org/urn:nbn:de:gbv:46-diss000100797

In this thesis, a variety of different cold seep systems (mud volcanoes and a gas seep) were investigated using a multidisciplinary approach to gain a more systematic understanding of these, methane-driven biogeosystems. The main goals were the detection and quantification of hot spots of methane oxidation as well as an assessment of environmental factors determining the activity and the distribution of methanotrophic communities. Furthermore, key microbial players were identified and the impact of Anaerobic Oxidation Of Methane (AOM) and Aerobic Oxidation Of Methane (MOx) on the surrounding, marine environment was studied. The investigations revealed the following:1. Submarine mud volcanoes are colonized by specialized microbial communities utilizing the fluxes of reduced substrates such as methane and sulphide as energy source. At the actively methane-seeping Haakon Mosby mud volcano (HMMV, Barents Sea), a distinct spatial zonation of several novel clades of free-living and symbiotic aerobic and anaerobic methanotrophs was found. The main selection mechanism determining vertical and horizontal distribution and dominance of the methanotrophic communities were fluid flow rates controlling access to electron acceptors for methane oxidation. 2. The analysis of archaeal and bacterial specific lipid concentrations and their associated delta 13C-values from three seepage areas at HMMV (thermal centre, grey mats and Beggiatoa site) showed a distinct distribution of methanotrophic biomass. At the centre, MOx mediated by a type I methanotroph was the primary biomass-generating process in surface sediments. In patches of reduced sediment, covered by greyish, thiotrophic, microbial mats at the boundary of the centre, a four-fold increase in 13C-depleted lipids specific for anaerobic methanotrophs, gave evidence of active microbial communities, which mediate AOM in the upper 20 cm of sediment. Further away from the centre, in the zone covered by Beggiatoa mats, sharp, vertical gradients of 13C-depleted archaeal and ...