Figure 7 - uploaded by Mats A. Granskog
Content may be subject to copyright.
(a) Relative positions of the dissolved organic matter (DOM) samples below 2000 m and the hydrothermal plume. (b) Heat-map representing the relation between hierarchical clustering of DOM compositions based on Bray-Curtis dissimilarity. (c) Principal coordinate analysis (PCoA) based on Bray-Curtis dissimilarity of DOM composition samples. Sample names are coded as station name and the approximate depth of the sample for background (BG), upper layer (UL), plume (PL) and non-plume (NP2) stations.
Source publication
Hydrothermal vents modify and displace subsurface dissolved organic matter (DOM) into the ocean. Once in the ocean, this DOM is transported together with elements, particles, dissolved gases and biomass along with the neutrally buoyant plume layer. Considering the number and extent of actively venting hydrothermal sites in the oceans, their contrib...
Contexts in source publication
Context 1
... influence of the plume dispersion on DOM composition was investigated in 11 samples from three stations below 2000 m: BG (background), PL (plume) and NP2 (nonplume). The approximate locations of these samples relative to hydrothermal vents and the possible route of the plume dispersion are depicted in Fig. 7a. PCoA and hierarchical clustering indicate a similar composition in the samples obtained from the same station (Fig. 7b and c). Exceptions are samples PL-3000 and BG-2000, which display higher molecular diversity and number of formulas and are therefore more similar to NP2 samples (Fig. 7b). Nevertheless, samples from different depths ...
Context 2
... 11 samples from three stations below 2000 m: BG (background), PL (plume) and NP2 (nonplume). The approximate locations of these samples relative to hydrothermal vents and the possible route of the plume dispersion are depicted in Fig. 7a. PCoA and hierarchical clustering indicate a similar composition in the samples obtained from the same station (Fig. 7b and c). Exceptions are samples PL-3000 and BG-2000, which display higher molecular diversity and number of formulas and are therefore more similar to NP2 samples (Fig. 7b). Nevertheless, samples from different depths but from the same station prominently group into three separate clusters (Fig. ...
Context 3
... the possible route of the plume dispersion are depicted in Fig. 7a. PCoA and hierarchical clustering indicate a similar composition in the samples obtained from the same station (Fig. 7b and c). Exceptions are samples PL-3000 and BG-2000, which display higher molecular diversity and number of formulas and are therefore more similar to NP2 samples (Fig. 7b). Nevertheless, samples from different depths but from the same station prominently group into three separate clusters (Fig. ...
Context 4
... in the samples obtained from the same station (Fig. 7b and c). Exceptions are samples PL-3000 and BG-2000, which display higher molecular diversity and number of formulas and are therefore more similar to NP2 samples (Fig. 7b). Nevertheless, samples from different depths but from the same station prominently group into three separate clusters (Fig. ...
Similar publications
Laohugou glacier No. 12 (LHG12), located in the northeast of the Qinghai–Tibet Plateau, is the largest valley glacier in the Qilian mountains. Since 1957, LHG12 has shrunk significantly. Due to the limitations of in situ observations, simulations and investigations of LHG12 have higher levels of uncertainty. In this study, consumer-level, low-altit...
Citations
... Nitrate, silicate, and phosphate concentrations were measured colourimetrically with a segmented flow nutrient analyser (ALPKEM Flow Solution IV, OI Analytical) with detection limits of 0.5 µM for nitrate, 0.06 µM for phosphate and 0.4 µM for silicate (Grasshoff et al., 1999). The precisions for the measurements were 0.1 µM for nitrate and silicate and 0.01 µM for phosphate (Sert et al., 2022). Dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) concentrations were measured by a high-temperature combustion method (MQ Scientific MQ-1001) against in-house calibration standards and reference deep ocean samples (Qian and Mopper, 1996). ...
Cold seeps release methane (CH4) from the seafloor to the water column, which fuels microbially mediated aerobic methane oxidation (MOx). Methane-oxidising bacteria (MOB) utilise excess methane, and the MOB biomass serves as a carbon source in the food web. Yet, it remains unclear if and how MOx modifies the composition of dissolved organic matter (DOM) in cold seeps. We investigated MOx rates, DOM compositions and the microbial community during ex-situ incubations of seawater collected from a cold seep site at Norskebanken (north of the Svalbard archipelago) in the Arctic Ocean. Samples were incubated with and without methane amendments. Samples amended with methane (∼1 µM final concentration) showed elevated rates of MOx in both seep and non-seep incubations. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analyses showed that the number of DOM formulas (i.e., molecular diversity) increased by up to 39% in these incubations. In contrast, the number of formulas decreased by 20% in samples not amended with methane, both from non-seep and seep locations. DOM composition was thus altered towards a more diverse and heterogeneous composition along with elevated methanotrophic activity in methane-amended conditions. In addition to microbial DOM production, abating microbial diversity indicates that elevated DOM diversity was potentially related to grazing pressure on bacteria. The diversity of DOM constituents, therefore, likely increased with the variety of decaying cells contributing to DOM production. Furthermore, based on a principal coordinate analysis, we show that the final DOM composition of non-seep samples amended with methane became more resemblant to that of seep samples. This suggests that methane intrusions will affect water column DOM dynamics similarly, irrespective of the water column’s methane history.
... Advanced sampling, spectroscopic and chromatographic techniques have also started to unravel the compositions, sources and decomposition of DOC and complex organic compounds in hydrothermal systems [227][228][229][230] . The continued development of compound specific radiocarbon analyses and new sampling and analytical techniques are needed to further understand the composition, age and fate of seawater and hydrothermally-derived DOC and its potential contribution to deep-ocean DOC. ...
Hydrothermal circulation and alteration at mid-ocean ridges and ridge flanks have a key role in regulating seawater chemistry and global chemical fluxes, and support diverse ecosystems in the absence of light. In this Review, we outline tectonic, magmatic and hydrothermal processes that govern crustal architecture, alteration and biogeochemical cycles along mid-ocean ridges with different spreading rates. In general, hydrothermal systems vary from those that are magmatic-dominated with low-pH fluids >300 °C to serpentinizing systems with alkaline fluids <120 °C. Typically, slow-spreading ridges (rates <40 mm yr−1) have greater variability in magmatism, lithology and vent chemistry, which are influenced by detachment faults that expose lower-crustal and serpentinized mantle rocks. Hydrothermal alteration is an important sink for magnesium, sodium, sulfate and bicarbonate, and a net source of volatiles, iron and other nutrients to the deep ocean and vent ecosystems. Magmatic hydrothermal systems sustain a vast, hot and diverse microbial biosphere that represents a deep organic carbon source to ocean carbon budgets. In contrast, high-pH serpentinizing hydrothermal systems harbour a more limited microbial community consisting primarily of methane-metabolizing archaea. Continued advances in monitoring and analytical capabilities coupled with developments in metagenomic technologies will guide future investigations and discoveries in hydrothermal systems. Oceanic spreading centres are sites of extensive tectonic, magmatic and hydrothermal activity that provide nutrients to the ocean and multifaceted habitats for life. This Review explores processes governing variations in hydrothermal vents, microbial ecosystems and global fluxes from ocean ridges. Spreading rates control variations in heat sources, magma input and tectonic processes along mid-ocean ridges and influence crustal architecture and hydrothermal processes, providing multifaceted habitats for life.Approximately one-third (7 × 1012 to 11 × 1012 W) of the global oceanic heat flux (32 × 1012 W) occurs through hydrothermal convection at ridges and ridge flanks. Seawater circulation, hydrothermal alteration and microbial interactions regulate seawater chemistry and change the composition and physical properties of the lithosphere.Roughly 50% of the global mid-ocean ridges are spreading at rates <40 mm yr−1, where major detachment faults expose lower-crustal and upper-mantle rocks, creating asymmetric ridge segments with large variability in structure, hydrothermal processes and vent fluid chemistry.Serpentinization decreases bulk density (<2.9 g cm−3) and seismic velocities (Vp < 6 km s−1) of mantle rocks and weakens the oceanic lithosphere along detachment faults. Serpentinization reactions produce highly reduced fluids with high H2, CH4 and other organic molecules that provide energy for microbial life.Hydrothermal processes govern global chemical fluxes (such as Mg, Fe, Mn and volatiles) and provide nutrients (for example, Fe flux ~4–6 × 109 mol yr−1) to the deep ocean. Approximately 0.05 GtC yr−1 of organic carbon is estimated to be produced through microbial interactions and oxidation of organic compounds within hydrothermal plumes.Basalt-hosted systems support a vast, hot and diverse microbial biosphere, in contrast to serpentinizing systems, which sustain more limited microbial communities primarily dominated by methane-metabolizing archaea. Advanced technologies allow better characterization of the genetic makeup and metabolism of microbes and the role of viruses in shaping diversity. Spreading rates control variations in heat sources, magma input and tectonic processes along mid-ocean ridges and influence crustal architecture and hydrothermal processes, providing multifaceted habitats for life. Approximately one-third (7 × 1012 to 11 × 1012 W) of the global oceanic heat flux (32 × 1012 W) occurs through hydrothermal convection at ridges and ridge flanks. Seawater circulation, hydrothermal alteration and microbial interactions regulate seawater chemistry and change the composition and physical properties of the lithosphere. Roughly 50% of the global mid-ocean ridges are spreading at rates <40 mm yr−1, where major detachment faults expose lower-crustal and upper-mantle rocks, creating asymmetric ridge segments with large variability in structure, hydrothermal processes and vent fluid chemistry. Serpentinization decreases bulk density (<2.9 g cm−3) and seismic velocities (Vp < 6 km s−1) of mantle rocks and weakens the oceanic lithosphere along detachment faults. Serpentinization reactions produce highly reduced fluids with high H2, CH4 and other organic molecules that provide energy for microbial life. Hydrothermal processes govern global chemical fluxes (such as Mg, Fe, Mn and volatiles) and provide nutrients (for example, Fe flux ~4–6 × 109 mol yr−1) to the deep ocean. Approximately 0.05 GtC yr−1 of organic carbon is estimated to be produced through microbial interactions and oxidation of organic compounds within hydrothermal plumes. Basalt-hosted systems support a vast, hot and diverse microbial biosphere, in contrast to serpentinizing systems, which sustain more limited microbial communities primarily dominated by methane-metabolizing archaea. Advanced technologies allow better characterization of the genetic makeup and metabolism of microbes and the role of viruses in shaping diversity.
... During each of these casts, the CTD-rosette was raised and lowered through the deep-water column as the ship drifted with ice-movement. Further CTD casts were conducted in 2019 16 but those were targeted at the periphery of the Aurora non-buoyant plume 17 and are not included in the results discussed here. In 2014, our initial search strategy was focused on the shallowest summit of the Aurora mound, but buoyant plume signals were subsequently detected~500 m downslope to the southwest, presaging first imaging of active venting on the final deployment of that cruise 6 . ...
The Aurora hydrothermal system, Arctic Ocean, hosts active submarine venting within an extensive field of relict mineral deposits. Here we show the site is associated with a neovolcanic mound located within the Gakkel Ridge rift-valley floor, but deep-tow camera and sidescan surveys reveal the site to be ≥100 m across—unusually large for a volcanically hosted vent on a slow-spreading ridge and more comparable to tectonically hosted systems that require large time-integrated heat-fluxes to form. The hydrothermal plume emanating from Aurora exhibits much higher dissolved CH4/Mn values than typical basalt-hosted hydrothermal systems and, instead, closely resembles those of high-temperature ultramafic-influenced vents at slow-spreading ridges. We hypothesize that deep-penetrating fluid circulation may have sustained the prolonged venting evident at the Aurora hydrothermal field with a hydrothermal convection cell that can access ultramafic lithologies underlying anomalously thin ocean crust at this ultraslow spreading ridge setting. Our findings have implications for ultra-slow ridge cooling, global marine mineral distributions, and the diversity of geologic settings that can host abiotic organic synthesis - pertinent to the search for life beyond Earth.
Evidence of hydrothermal venting on the ultra-slow spreading Gakkel Ridge in the Central Arctic Ocean has been available since 2001, with first visual evidence of black smokers on the Aurora Vent Field obtained in 2014. But it was not until 2021 that the first ever remotely operated vehicle (ROV) dives to hydrothermal vents under permanent ice cover in the Arctic were conducted, enabling the collection of vent fluids, rocks, microbes, and fauna. In this paper, we present the methods employed for deep-sea ROV operations under drifting ice. We also provide the first description of the Aurora Vent Field, which includes three actively venting black smokers and diffuse flow on the Aurora mound at ~3,888 m depth on the southern part of the Gakkel Ridge (82.5°N). The biological communities are dominated by a new species of cocculinid limpet, two small gastropods, and a melitid amphipod. The ongoing analyses of Aurora Vent Field samples will contribute to positioning the Gakkel Ridge hydrothermal vents in the global biogeographic puzzle of hydrothermal vents.
