About
170
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Introduction
I am a marine geomicrobiologist. My research focusses on microbial processes in the ocean (sediments and water column). Current topics of research include marine methane cycling, oxygen minimum zone biogeochemistry, and deep biosphere processes. My group uses geochemical, microbial, molecular, and radiotracer methods to study microbial processes.
Additional affiliations
July 2018 - present
October 2014 - June 2018
December 2011 - September 2014
Education
July 2000 - January 2004
University of Bremen and Max Planck Insitute for Marine Microbiology
Field of study
- Marine Biogeochemistry (Biology)
October 1994 - July 1999
University of Kiel
Field of study
- Biological Oceanography (Biology)
October 1992 - September 1994
University of Hannover
Field of study
- Biology
Publications
Publications (170)
Methylotrophic methanogenesis in the sulfate reduction zone of wetland and marine sediment has recently been coupled to anaerobic oxidation of methane (AOM), now referred to as the cryptic methane cycle. In this study we present evidence of cryptic methane cycling activity within the sulfate-reducing zone, along a land-ocean transect within the Car...
Despite long-standing interest in the biogeochemistry of the Santa Barbara Basin (SBB), there are no direct rate measurements of different nitrogen transformation processes. We investigated benthic nitrogen cycling using in situ incubations with 15NO3- addition and quantified the rates of total nitrate (NO3-) uptake, denitrification, anaerobic ammo...
Rates of microbial processes are fundamental to understanding the significance of microbial impacts on environmental chemical cycling. However, it is often difficult to quantify rates or to link processes to specific taxa or individual cells, especially in environments where there are few cultured representatives with known physiology. Here, we des...
The trace metal iron (Fe) is an essential micronutrient that controls phytoplankton productivity, which subsequently affects organic matter cycling with feedback on the cycling of macronutrients. Along the continental margin of the US West Coast, high benthic Fe release has been documented, in particular from deep anoxic basins in the Southern Cali...
The Santa Barbara Basin naturally experiences transient deoxygenation due to its unique geological setting in the southern California Borderland and seasonal changes in ocean currents. Long-term measurements of the basin showed that anoxic events and subsequent nitrate exhaustion in the bottom waters have been occurring more frequently and lasting...
Methane in oil reservoirs originates mostly from thermogenic sources, yet secondary microbial methane production from petroleum biodegradation is known to be pervasive. The conventional approach for identifying this secondary microbial methane commonly relies on geochemical characteristics of other gas molecules such as the carbon isotopic composit...
The recently discovered cryptic methane cycle in the sulfate-reducing zone of marine and wetland sediment couples methylotrophic methanogenesis to anaerobic oxidation of methane (AOM). Here we present evidence of cryptic methane cycling activity within the upper regions of the sulfate-reducing zone, along a depth transect within the Santa Barbara B...
Despite long-standing interests in the biogeochemistry of the Santa Barbara Basin (SBB), there are no direct rate measurements of different nitrogen transformation processes. We investigated benthic nitrogen cycling using in-situ incubations with 15NO3- addition and quantified the rates of total nitrate (NO3-) uptake, denitrification, anaerobic amm...
The Santa Barbara Basin naturally experiences transient deoxygenation due to its unique geological setting in the Southern California Borderland and seasonal changes in ocean currents. Long-term measurements of the basin showed that anoxic events and subsequent nitrate exhaustion in the bottom waters have been occurring more frequently and lasting...
The recently discovered cryptic methane cycle in the sulfate-reducing zone of marine and wetland sediments couples methylotrophic methanogenesis to anaerobic oxidation of methane (AOM). Here we present evidence of cryptic methane cycling activity within the upper regions of the sulfate-reducing zone, along a depth transect within the Santa Barbara...
The trace metal iron (Fe) is an essential micronutrient that controls phytoplankton productivity, which subsequently affects the cycling of macronutrients. Along the continental margin of the U.S. West Coast, high benthic Fe release has been documented, in particular from deep anoxic basins in the Southern California Borderland. However, the influe...
The early diagenetic interplay between reactive iron, sulfur, and organic matter in the bathymetrically isolated Santa Monica Basin (SMB) sediments are investigated in this study. We explore solid-phase and porewater profiles from the basin supplemented with a transect from 71 to 907 meters water depth that includes oxygenated (>60 μM O2) bottom wa...
This paper presents the results of a study on the response of living benthic foraminifera to progressing environmental successions in a cold-seep ecosystem. Sediment samples were collected from Vestnesa Ridge (79°N, Fram Strait) at ~1200 m water depth. The distribution of live (Rose Bengal-stained) foraminifera were analyzed in the upper sediment l...
Aerobic oxidation of methane (MOx) is an important biologically mediated process that consumes methane in a wide range of environments. Here we report results of culture experiments with the aerobic methane-oxidizing bacterium Methylosinus trichosporium (OB3b) that are used to characterize the mass-18 isotopologue (Δ13CH3D and Δ12CH2D2) signatures...
Most of the methane input to the world’s oceans is intercepted by microorganisms in sediment and the overlying water column and oxidized before it has an opportunity to reach the atmosphere, where it acts as a greenhouse gas. The factors controlling methane consumption in the ocean are not well established and its biogeochemistry in dynamic marine...
A fourth of the global seabed sediment volume is buried at depths where temperatures exceed 80 °C, a previously proposed thermal barrier for life in the subsurface. Here, we demonstrate, utilizing an extensive suite of radiotracer experiments, the prevalence of active methanogenic and sulfate-reducing populations in deeply buried marine sediment fr...
Fossil benthic foraminifera are used to trace past methane release linked to climate change. However, it is still debated whether isotopic signatures of living foraminifera from methane-charged sediments reflect incorporation of methane-derived carbon. A deeper understanding of isotopic signatures of living benthic foraminifera from methane-rich en...
Plain Language Summary
In the marine system, the greenhouse gas methane is primarily produced in sediments. Under specific geologic conditions, methane can accumulate in the sediment and be released as gas bubbles. Such gas seepage also occurs at abandoned oil or gas‐drilling sites. However, direct transport of methane from submarine seeps to the a...
Bacterial sulfate reduction (SR) is often determined by radiotracer techniques using 35S‐labeled sulfate. In environments featuring simultaneous sulfide oxidation, SR can be underestimated due to re‐oxidation of 35S‐sulfide. Recycling of 35S‐tracer is expected to be high in sediment with low concentrations of pore‐water sulfide and high abundance o...
Carbonates that exhibit obvious diagenetic alteration are usually excluded as archives in palaeoenvironmental studies. However, the potential impact of microbial alteration during early diagenesis is still poorly explored. To investigate the sensitivity of sulphur concentration, distribution, oxidation state and isotopic composition in marine arago...
Deep, hot, and more alive than we thought
Marine sediments represent a massive microbial ecosystem, but we still do not fully understand what factors shape and limit life underneath the seafloor. Analyzing samples from a subduction zone off the coast of Japan, Heuer et al. found that microbial life, in particular bacterial vegetative cells, decreas...
In the current era of rapid climate change, accurate characterization of climate-relevant gas dynamics – namely production, consumption, and net emissions – is required for all biomes, especially those ecosystems most susceptible to the impact of change. Marine environments include regions that act as net sources or sinks for numerous climate-activ...
The Southern California Bight is adjacent to one of the world's largest urban areas, Los Angeles. As a consequence, anthropogenic impacts could disrupt local marine ecosystems due to municipal and industrial waste discharge, pollution, flood control measures, and global warming. Santa Monica Basin (SMB), due to its unique setting in a low-oxygen an...
A site at the gas hydrate stability limit was investigated offshore northwestern Svalbard to study methane transport in sediment. The site was characterized by chemosynthetic communities (sulfur bacteria mats, tubeworms) and gas venting. Sediments were sampled with in situ porewater collectors and by gravity coring followed by analyses of porewater...
Benthic microorganisms transported into the water column potentially influence biogeochemical cycles and the pelagic food web structure. In the present study six gas-releasing vent sites in the Coal Oil Point seep field (California) were investigated, and the dislocation of microorganisms from the sediment into the water column via gas bubbles rele...
Abstract. The Southern California Bight is adjacent to one of the world's largest urban areas, Los Angeles. As a consequence, anthropogenic impacts could disrupt local marine ecosystems due to municipal and industrial waste, pollution, and flood control measures. Superimposed on the growth of an urban metropolis, the impact of climate change has be...
Abstract The study investigates the in-situ strength of sediments across a plate boundary décollement using drilling parameters recorded when a 1180-m-deep borehole was established during International Ocean Discovery Program (IODP) Expedition 370, Temperature-Limit of the Deep Biosphere off Muroto (T-Limit). Information of the in-situ strength of...
During Earth's history, precipitation of calcium carbonate by heterotrophic microbes has substantially contributed to the genesis of copious amounts of carbonate sediment and its subsequent lithification. Previous work identified the microbial sulfur and nitrogen cycle as principal pathways involved in the formation of marine calcium carbonate depo...
The anaerobic oxidation of methane (AOM) is a crucial component of the methane cycle, but its enzymatic versatility under environmental conditions is still poorly understood. We use sediment samples collected during IODP Expedition 347 to the Baltic Sea to show that relative abundances of ¹² CH 2 D 2 and ¹³ CH 3 D molecules in methane gas trace the...
The Kryos Basin is a deep-sea hypersaline anoxic basin (DHAB) located in the Eastern Mediterranean Sea (34.98°N 22.04°E). It is filled with brine of re-dissolved Messinian evaporites and is nearly saturated with MgCl2-equivalents, which makes this habitat extremely challenging for life. The strong density difference between the anoxic brine and the...
Benthic microbial methanogenesis is a known source of methane in marine systems. In most sediments, the majority of methanogenesis is located below the sulfate-reducing zone, as sulfate reducers outcompete methanogens for the major substrates hydrogen and acetate. The coexistence of methanogenesis and sulfate reduction has been shown before and is...
Despite its potential to provide new nitrogen (N) to the environment, knowledge on benthic dinitrogen (N2) fixation remains relatively sparse, and its contribution to the marine N budget is regarded as minor. Benthic N2 fixation is often observed in organic-rich sediments coupled to heterotrophic metabolisms, such as sulfate reduction. In the prese...
Full volume available at http://publications.iodp.org/proceedings/370/370title.html
The earliest diagenetic post mortem exposure of biogenic carbonates at the sea floor and in the uppermost sediment column results in the colonization of hard-part surfaces by bacterial communities. Some of the metabolic redox processes related to these communities have the potential to alter carbonate shell properties, and hence affect earliest dia...
Anaerobic microbial hydrocarbon degradation is a major biogeochemical process at marine seeps. Here we studied the response of the microbial community to petroleum seepage simulated for 190 days in a sediment core from the Caspian Sea using a sediment-oil-flow-through (SOFT) system. Untreated (without simulated petroleum seepage) and SOFT sediment...
The microbial community response to petroleum seepage was investigated in a whole round sediment core (16 cm length) collected nearby natural hydrocarbon seepage structures in the Caspian Sea, using a newly developed Sediment-Oil-Flow-Through (SOFT) system. Distinct redox zones established and migrated vertically in the core during the 190 days-lon...
Coastal seas may account for more than 75 % of global oceanic methane emissions. There, methane is mainly produced microbially in anoxic sediments from which it can escape to the overlying water column. Aerobic methane oxidation (MOx) in the water column acts as a biological filter, reducing the amount of methane that eventually evades to the atmos...
The presence of surface methanogenesis, located within the sulfate-reducing zone (0–30 centimeters below seafloor, cmbsf), was investigated in sediments of the seasonally hypoxic Eckernförde Bay, southwestern Baltic Sea. Water column parameters like oxygen, temperature and salinity together with porewater geochemistry and benthic methanogenesis rat...
International Ocean Discovery Program (IODP) Expedition 370 aimed to explore the limits of life in the deep subseafloor biosphere at a location where temperature increases with depth at an intermediate rate and exceeds the known temperature maximum of microbial life (~120°C) at the sediment/basement interface ~1.2 km below the seafloor. Drilling Si...
Coastal seas may account for more than 75% of global oceanic methane emissions. There, methane is mainly produced microbially in anoxic sediments from where it can escape to the overlying water column. Aerobic methane oxidation (MOx) in the water column acts as a biological filter reducing the amount of methane that eventually evades to the 15 atmo...
Large quantities of the greenhouse gas methane (CH4) are stored in the seafloor. The flux of CH4 from the sediments into the water column and finally to the atmosphere is mitigated by a series of microbial methanotrophic filter systems of unknown efficiency at highly active CH4-release sites in shallow marine settings. Here, we studied CH4-oxidatio...
Benthic nitrogen (N2) fixation and sulfate reduction (SR) were investigated in the Peruvian oxygen minimum zone (OMZ). Sediment samples, retrieved by a multiple corer were taken at six stations (70–1025 m) along a depth transect at 12°S, covering anoxic and hypoxic bottom water conditions. Benthic N2 fixation was detected at all sites, with high ra...
Large quantities of methane are stored in hydrates and permafrost within shallow marine sediments in the Arctic Ocean. These reservoirs are highly sensitive to climate warming, but the fate of methane released from sediments is uncertain. Here, we review the principal physical and biogeochemical processes that regulate methane fluxes across the sea...
Microbial transformation of hydrocarbons to methane is an environmentally relevant process taking place in a wide variety of electron acceptor-depleted habitats, from oil reservoirs and coal deposits to contaminated groundwater and deep sediments. Methanogenic hydrocarbon degradation is considered to be a major process in reservoir degradation and...
Hydrocarbons are abundant in anoxic environments and pose biochemical challenges to their anaerobic degradation by microorganisms. Within the framework of the Priority Program 1319, investigations funded by the Deutsche Forschungsgemeinschaft on the anaerobic microbial degradation of hydrocarbons ranged from isolation and enrichment of hitherto unk...
We
studied the concurrence of methanogenesis and sulfate reduction in surface
sediments (0–25 cm below sea floor) at six stations (70, 145, 253,
407, 990 and 1024 m) along the Peruvian margin (12° S). This
oceanographic region is characterized by high carbon export to the seafloor
creating an extensive oxygen minimum zone (OMZ) on the shelf, both f...
To date, the longevity of plastic litter at the sea floor is poorly constrained. The present study compares colonization and biodegradation of plastic bags by aerobic and anaerobic benthic microbes in temperate fine-grained organic-rich marine sediments. Samples of polyethylene and biodegradable plastic carrier bags were incubated in natural oxic a...
We studied the concurrence of methanogenesis and sulfate reduction in surface sediments (0-25 cm below sea floor, cmbsf) at six stations (70, 145, 253, 407, 770 and 1024 m) along the Peruvian margin (12° S). This oceanographic region is characterized by high carbon export to the seafloor, creating an extensive oxygen minimum zone (OMZ) on the shelf...
Large amounts of methane are delivered by fluids through the erosive forearc
of the convergent margin offshore of Costa Rica and lead to the formation of
cold seeps at the sediment surface. Besides mud extrusion, numerous cold
seeps are created by landslides induced by seamount subduction or fluid
migration along major faults. Most of the dissolved...