Gerdhard L Jessen

Universidad Austral de Chile · Instituto de Ciencias Marinas y Limnológicas UACh

At convergent margins, plates collide producing a subduction process. When an oceanic plate collides with a continental plate, the denser (i.e., oceanic) plate subducts beneath the less dense (continental) plate. This process results in the transportation of carbon and other volatiles into Earth’s deep interior and is counterbalanced by volcanic ou...

Microbial communities, in particular bacterial assemblies, play pivotal roles in sustaining biogeochemical processes within ecosystems. They are also responsible for the degradation of toxic chemicals, while the development of resistance against antimicrobial drugs jeopardises human health. Bacterial communities respond to environmental conditions...

Subduction of the Cocos and Nazca oceanic plates beneath the Caribbean plate drives the upward movement of deep fluids enriched in carbon, nitrogen, sulfur, and iron along the Central American Volcanic Arc (CAVA). These compounds fuel diverse subsurface microbial communities that in turn alter the distribution, redox state, and isotopic composition...

Achieving sustainability in natural resource mining is a persisting challenge. On global and local scales, a wide-scale shift across the mining industry and interconnected governing bodies towards sustainability is required. For emerging nations, such as the Democratic Republic of the Congo (DRC) and the Central African regions in general that hist...

Microbial communities in terrestrial geothermal systems often contain chemolithoautotrophs with well-characterized distributions and metabolic capabilities. However, the extent to which organic matter produced by these chemolithoautotrophs supports heterotrophs remains largely unknown. Here we compared the abundance and activity of peptidases and c...

Microbial communities in terrestrial geothermal systems often contain chemolithoautotrophs with well-characterized distributions and metabolic capabilities. However, the extent to which organic matter produced by these chemolithoautotrophs supports heterotrophs remains largely unknown. Here we compared the abundance and activity of peptidases and c...

Subducting oceanic crusts release fluids rich in biologically relevant compounds into the overriding plate, fueling subsurface chemolithoautotrophic ecosystems. To understand the impact of subsurface geochemistry on microbial communities, we collected fluid and sediments from 14 natural springs across a ~200 km transect across the Costa Rican conve...

Despite being one of the largest microbial ecosystems on Earth, many basic open questions remain about how life exists and thrives in the deep subsurface biosphere. Much of this ambiguity is due to the fact that it is exceedingly difficult and often prohibitively expensive to directly sample the deep subsurface, requiring elaborate drilling program...

Despite being one of the largest microbial ecosystems on Earth, with >1029 microbial cells, many basic open questions remain about how life exists and thrives in the deep subsurface biosphere, inside Earth’s crust. Much of this ambiguity is due to the fact that it is exceedingly difficult and (often prohibitively expensive) to directly sample the d...

Subduction zones represent the interface between Earth’s interior (crust and mantle) and exterior (atmosphere and oceans), where carbon and other volatile elements are actively cycled between Earth reservoirs by plate tectonics. Helium is a sensitive tracer of volatile sources and can be used to deconvolute mantle and crustal sources in arcs; howev...

Here, we examine the geobiological response to a whole-lake alum (aluminum sulfate) treatment (2016) of Base Mine Lake (BML), the first pilot-scale pit lake established in the Alberta oil sands region. The rationale for trialing this management amendment was based on its successful use to reduce internal phosphorus loading to eutrophying lakes. Mod...

Water-capped tailings technology (WCTT) is a key component of the reclamation strategies in the Athabasca oil sands region (AOSR) of northeastern Alberta, Canada. The release of microbial methane from tailings emplaced within oil sands pit lakes, and its subsequent microbial oxidation, could inhibit the development of persistent oxygen concentratio...

The subsurface is among Earth’s largest biomes, but the extent to which microbial communities vary across tectonic plate boundaries or interact with subduction-scale geological processes remains unknown. Here we compare bacterial community composition with deep-subsurface geochemistry from 21 hot springs across the Costa Rican convergent margin. We...

We characterized the sulfur geochemistry and microbial community structure of seven circumneutral wastewaters from two Canadian nickel mines collected in summer, winter, and spring, in 2014 and 2015. We also established and characterized sulfur oxidizing enrichments for these wastewater samples in two pH corrals of 7–5 and 5–3. Mine 1 exhibited low...

Extraction of minerals through mining is essential for industrial and societal development. However, mining activities and catastrophic mining accidents across the globe have caused severe environmental impacts. Here we call for an urgent paradigm shift and outline a new vision, published in the Science Policy Report “A new vision of sustainable ma...

Anthropogenically-impacted environments offer the opportunity to discover novel microbial species and metabolisms, which may be undetectable in natural systems. Here, a combined metagenomic and geochemical study in Base Mine Lake, Alberta, Canada, which is the only oil sands end pit lake to date, revealed that nitrification was performed by members...

Fonsibacter represents a significant microbial group of freshwater ecosystems. Although the genomic and metabolic features of these bacteria have been well studied, no phage infecting them has been reported. In this study, we reconstructed complete genomes of Fonsibacter and infecting phage and revealed their close relatedness to the phage infectin...

Extraction and use of minerals through mining is essential for industrial and societal development. However, the mining industry carries significant risks of long-lasting negative impacts on the environment, particularly on water resources and landscapes, as well as on local communities. Catastrophies such as the Brumadinho dam collapse in Brazil i...

The biogeochemistry of acid mine drainage (AMD) derived from waste rock associated sulphide mineral oxidation is relatively well characterized and linked to Acidithiobacillus spp.. However, little is understood about the microbial communities and sulphur cycling that occurs in circum-neutral mining impacted water (MIW) in tailing reservoirs associa...

Fonsibacter (LD12 subclade) are among the most abundant bacterioplankton in freshwater ecosystems. These bacteria belong to the order Pelagibacterales (SAR11) and are related to Pelagibacter (marine SAR11) that dominate many marine habitats. Although a handful of Pelagibacter phage (Pelagiphage) have been described, no phage that infect Fonsibacter...

The biogeochemistry of acid mine drainage (AMD) derived from waste rock associated sulfide mineral oxidation is relatively well-characterized and linked to Acidithiobacillus spp.. However, little is understood about the microbial communities and sulfur cycling before AMD develops, a key component of its prevention. This study aimed to examine circu...

Bottom-water oxygen supply is a key factor governing the biogeochemistry and community composition of marine sediments. Whether it also determines carbon burial rates remains controversial. We investigated the effect of varying oxygen concentrations (170 to 0 μM O2) on microbial remineralization of organic matter in seafloor sediments and on commun...

At the Black Sea chemocline, oxygen- and sulfide-rich waters meet and form a niche for thiotrophic pelagic bacteria. Here we investigated an area of the Northwestern Black Sea off Crimea close to the shelf break, where the chemocline reaches the seafloor at around 150–170 m water depth, to assess whether thiotrophic bacteria are favored in this zon...

The outer western Crimean shelf of the Black Sea is a natural laboratory to investigate effects of stable oxic versus varying hypoxic conditions on seafloor biogeochemical processes and benthic community structure. Bottom-water oxygen concentrations ranged from normoxic (175 μmol O2 L−1) and hypoxic (< 63 μmol O2 L−1) or even anoxic/sulfidic condit...

The outer Western Crimean Shelf of the Black Sea is a natural laboratory to investigate effects of stable oxic vs. varying hypoxic conditions on seafloor biogeochemical processes and benthic community structure. Bottom water oxygen concentrations varied between normoxic (175 μmol O2 L−1) and hypoxic (< 63 μmol O2 L−1) or even anoxic/sulfidic condit...

The outer western Crimean shelf of the Black Sea is a natural laboratory to investigate effects of stable oxic versus varying hypoxic conditions on seafloor biogeochemical processes and benthic community structure. Bottom-water oxygen concentrations ranged from normoxic (175 µmol O2/L) and hypoxic (

Today's rapid global warming together with the eutrophication of oceans appears to promote a deoxygenation of some of the world's water bodies, which eventually leads to hypoxia and even anoxia in regions of low ventilation. Under hypoxic conditions (less than 60 µM oxygen) most animals are negatively impacted and microorganisms dominate benthic pr...

Hypoxia occurs where oxygen concentrations fall below a physiological threshold of many animals, usually defined as <63 µmol L-1. Oxygen depletion can be caused by anthropogenic influences, such as global warming and eutrophication, but as well occurs naturally due to restricted water exchange in combination with high nutrient loads (e.g. upwelling...

We analyzed C and N stable isotope ratios of benthic fauna and their potential food sources at an intertidal methane seep site and a control site without emanation at Mocha Island (central Chile). The objective was to trace the origin of the main food sources used by the local heterotrophic fauna, based on the hypothesis that chemosynthetic product...

The colorless, large sulfur bacteria are well known because of their intriguing appearance, size and abundance in sulfidic settings. Since their discovery in 1803 these bacteria have been classified according to their conspicuous morphology. However, in microbiology the use of morphological criteria alone to predict phylogenetic relatedness has fre...

We studied for the first time the intertidal and subtidal gas seepage system in Mocha Island off Central Chile. Four main seepage sites were investigated (of which one site included about 150 bubbling points) that release from 150 to 240 tonnes CH4 into the atmosphere per year. The total amount of methane emitted into the atmosphere is estimated in...

The enzymatic activity of aerobic and anaerobic metabolic pathways in Hyalinoecia artifex, a polychaete inhabiting the deep ocean, is reported. In addition, the allometry of its anaerobic and aerobic enzymatic activity is analysed. The aerobic metabolism was measured using the electron transport system activity technique (ETS), whereas the anaerobi...

The aerobic and anaerobic metabolism of Paraprionospiopinnata were estimated under laboratory conditions. Paraprionospiopinnata is a widely distributed, often dominant polychaete inhabiting sublittoral sediments on the continental shelf off central Chile, where there is a pronounced oxygen minimum zone (OMZ). The aerobic respiration rates ranged fr...

Respiration is a key variable to understand the flux of energy and matter in any ecosystem. In fact, ecosystem respiration is a critical component of the carbon cycle and might be important in regulating biosphere response to global climate change. Respiration is the basic process used by the biota to yield energy from the degradation of organic ma...