Environmental Controls of Iron-Reducing Microorganisms in Antarctic Marine Sediments [ECIMAS]


Professor Dr. Michael Friedrich 
Universität Bremen
Fachbereich 02 - Biologie und Chemie
Arbeitsgruppe Mikrobielle Ökophysiologie

Project Description

Climate based warming has affected the western Antarctic Peninsula (WAP) strongly over the last 50 years resulting in massive losses of the west Antarctic ice shelf. As a consequence of melting glaciers, shelf sediment accumulation, including large amounts of reducible iron(III) oxides, has increased in the area. Microbial iron(III) reduction seems to be relevant in releasing dissolved iron from shelf sediment and thereby, contributing to export of iron compounds to the Southern Ocean, known for metal-limited primary productivity. However, the microorganisms involved in iron-reduction in Antarctic shelf sediments have not been studied so far.The aim of our project is to elucidate the ecology of iron-reducing microbial populations, and their environmental controls in Antarctic marine sediments. We will concentrate on (1) identifying microbial populations involved in iron reduction, as well as (2) determining their distribution, (3) abundance, and (4) activity in anoxic layers of coastal sediment relative to their anaerobically respiring competitors, sulfate-reducing microorganisms. In our project, we will focus on hots spots of environmental change, thus, sites that have been newly exposed because of receding glaciers, accumulating iron oxides and high dissolved iron concentrations compared to typical sulfidogenic sites as a reference, indicative of sulfate reduction. This will allow to link geochemical variations, and hot spots of iron reduction to microbial community differences; the latter will be analyzed by high-throughput amplicon sequencing of 16S rRNA genes and of 16S rRNA of physiologically active microorganisms (600 samples). These analyses will be augmented by quantifying microbial communities in sediment layers by qPCR, and most-probable number estimates of iron- and sulfate reducing microorganisms. The overall functional potentials of iron- and sulfate reducing microorganisms will be determined by incubation assays. Cutting-edge time-resolved 13C-stable isotope probing of RNA will be used to determine specific functions of individual iron-reducing microorganisms in microcosm incubations. Lastly, environmental controls of Antarctic iron-reducing microorganisms will be studied in microcosms by varying electron donor and acceptor availability, and quality, as well as temperature. This will allow to evaluate future scenarios of environmental change on iron release from Antarctic shelf sediments.

DFG Programme: Infrastructure Priority Programmes

International Connection: Argentinia

Term since 2018