Fluid composition of the sediment-influenced Loki’s Castle vent field at the ultra-slow spreading Arctic Mid-Ocean Ridge

Baumberger, Tamara; Früh-Green, Gretchen L.; Thorseth, Ingunn H.; Lilley, Marvin D.; Hamelin, C.; Bernasconi, Stefano M.; Økland, I.; Pedersen, Rolf B.

doi:10.1016/j.gca.2016.05.017

Cited by 43 publications

(70 citation statements)

References 107 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This would suggest that although a microbial community capable of denitrification is present in the surface sediments of the Schulz Bank, its activity was under detection limit. Low availability of reactive carbon in these Arctic sediments (Baumberger et al, 2016) may be the reason for this lack of detectable denitrification activity, in contrast to a high availability of reactive carbon within a living sponge. Our results indicate that in 15 the Arctic deep sea, sponge grounds play a much more important role for nitrogen cycling and benthic-pelagic coupling than the surrounding sediment.…”

Section: The Sponge Microbial Community Is Ready For Denitrificationmentioning

confidence: 97%

Deep-sea sponge grounds as nutrient sinks: High denitrification rates in boreo-arctic sponges

Rooks

Fang

Mørkved

et al. 2019

Preprint

View full text Add to dashboard Cite

Abstract. Sponges are commonly known as general nutrient providers for the marine ecosystem, recycling organic matter into various forms of bio-available nutrients such as ammonium and nitrate. In this study we challenge this view. We show that nutrient removal through microbial denitrification is a common feature in six cold-water sponge species from boreal and Arctic sponge grounds. Denitrification rates were quantified by incubating sponge tissue sections with 15NO3- &#8211; amended oxygen saturated seawater, mimicking conditions in pumping sponges, and de-oxygenated seawater, mimicking non-pumping sponges. Rates of anaerobic ammonium oxidation (anammox) using incubations with 15NH4+ could not be detected. Denitrification rates of the different sponge species ranged from 0 to 114&#8201;nmol&#8201;N&#8201;cm-3&#8201;sponge&#8201;day-1 under oxic conditions, and from 47 to 342&#8201;nmol&#8201;N&#8201;cm-3&#8201;sponge&#8201;day-1 under anoxic conditions. An exponential relationship between the highest potential rates of denitrification (in the absence of oxygen) and the species-specific abundances of nirS and nirK genes encoding nitrite reductase, a key enzyme for denitrification, suggests that the denitrifying community in these sponge species is both prepared and optimized for denitrification. The lack of a lag phase in the linear accumulation of the 15N labelled N2 gas in any of our tissue incubations is another indicator for an active community of denitrifiers in the investigated sponge species. High rates for coupled nitrification-denitrification (up to 89&#8201;% of nitrate reduction in the presence of oxygen) shows that under these conditions, the NO3- reduced in denitrification was primarily derived from nitrification within the sponge, directly coupling organic matter degradation and nitrification to denitrification in sponge tissues. Under anoxic condition when nitrification was not possible, nitrate to fuel the much higher denitrification rates had to be retrieved directly from the seawater. The lack of nifH genes encoding nitrogenase, the key enzyme for nitrogen fixation, shows that the nitrogen cycle is not closed in the sponge grounds. The denitrified nitrogen, no matter of its origin, is then no longer available as a nutrient for the marine ecosystem. Considering average sponge biomasses on typical boreal and Arctic sponge grounds, our sponge denitrification rates reveal areal denitrification rates of 0.8&#8201;mmol&#8201;N&#8201;m-2&#8201;day-1 assuming non-pumping sponges and still 0.3&#8201;mmol&#8201;N&#8201;m-2&#8201;day-1 assuming pumping sponges. This is well within the range of denitrification rates of continental shelf sediments. For the most densely populated boreal sponge grounds we calculated denitrification rates of up to 2&#8201;mmol&#8201;N&#8201;m-2&#8201;day-1, which is comparable to rates in coastal sediments. Increased future impact of sponge grounds by anthropogenic stressors reducing sponge pumping activity and further stimulating sponge anaerobic processes may thus lead to that deep-sea sponge grounds change their role in the marine ecosystem from nutrient sources to nutrient sinks.

show abstract

Section: The Sponge Microbial Community Is Ready For Denitrificationmentioning

confidence: 97%

Deep-sea sponge grounds as nutrient sinks: High denitrification rates in boreo-arctic sponges

Rooks

Fang

Mørkved

et al. 2019

Preprint

View full text Add to dashboard Cite

show abstract

“…Geochemical analysis of the hydrothermal fluid collected from the black smokers, that is, end‐member volatile concentrations, supports magmatic influence in the area (Pedersen, Thorseth , et al, ), confirming that Loki's Castle is a basalt‐hosted site. There are also indications of fluid interaction with ultramafic rocks and a significant footprint of sediment influence (Baumberger et al, ), which likely results from the deep fault and across‐axis circulation as shown in a recent deep electromagnetic imaging study across the ridge by Johansen et al ().…”

Section: Geological Settingmentioning

confidence: 98%

“…The Mohns ultra‐slow‐spreading ridge hosts five vent sites (Figure a), two of these sites are discussed in this paper. Loki's Castle is an active basalt‐hosted vent field investigated by several research cruises (Baumberger et al, ; Johansen et al, ; Ludvigsen et al, ; Pedersen, Thorseth , et al, ). High‐resolution magnetic data, however, are presented in this paper for the first time.…”

Section: Introductionmentioning

confidence: 99%

Hydrothermal Activity at the Ultraslow‐Spreading Mohns Ridge: New Insights From Near‐Seafloor Magnetics

Lim

Brönner

Johansen

et al. 2019

Geochem Geophys Geosyst

View full text Add to dashboard Cite

Hydrothermal circulation is a process fundamental to all types of mid-ocean ridges that largely impacts the chemical and physical balance of the World Ocean. However, diversity of geological settings hosting hydrothermal fields complicates the exploration and requires thorough investigation of each individual case study before effective criteria can be established. Analysis of high-resolution bathymetric and magnetic data, coupled with video and rock samples material, furthers our knowledge about mid-ocean-ridge-hosted venting sites and aid in the interpretation of the interplay between magmatic and tectonic processes along the axial volcanic ridges. The rock-magnetic data provide constraints on the interpretation of the observed contrasts in crustal magnetization. We map the areal extent of the previously discovered active basalt-hosted Loki's Castle and inactive sediment-hosted Mohn's Treasure massive sulfide deposits and infer their subsurface extent. Remarkably, extinct hydrothermal sites have enhanced magnetizations and display clear magnetic signatures allowing their confident identification and delineation. Identified magnetic signatures exert two new fossil hydrothermal deposits, MT-2 and MT-3. The Loki's Castle site coincides with negative magnetic anomaly observed in the 2-D magnetic profile data crossing the deposit. First geophysical investigations in this area reveal the complexity of the geological setting and the variation of the physical properties in the subsurface.

show abstract

“…Smoker fluids are rich in non-aqueous volatiles, particularly in NH4 + , H2, CH4, CO2, and C2+, with low Fe + Mn and δ 13 C in CO2 and CH4 [8,31], which could imply ultramafic or sedimentary and ridge rift, adjacent dome structure, and inset of (b) mound topography. Bathymetric after data from [29].…”

Section: Introductionmentioning

confidence: 99%

“…These sediments display a rare earth element (REE) signature similar to the North American Shale Composite [21]. [8,31], which could imply ultramafic or sedimentary interactions [32,33]. Based on fluid chemistry, water-rock interactions probably occurred at a depth of approximately 2 km beneath the seafloor [8].…”

Section: Introductionmentioning

confidence: 99%

Characterisation of Mineralised Material from the Loki’s Castle Hydrothermal Vent on the Mohn’s Ridge

et al. 2018

View full text Add to dashboard Cite

Loki's Castle on the Arctic Mid-Ocean Ridge (AMOR) is an area of possible seafloor massive sulphide (SMS)-style mineralisation under Norwegian jurisdiction, which, due to mounting social pressure, may be a strategic future source of base and precious metals. The purpose of this study is to characterise mineralised material from a hydrothermal vent system on the AMOR in detail for the first time, and to discuss the suitability of methods used; reflected light microscopy, X-ray diffraction (XRD), whole rock geochemistry, electron probe micro-analysis (EPMA), and QEMSCAN. The primary sulphide phases, identifiable by microscopy, are pyrite and marcasite with minor pyrrhotite and galena, but multiple samples from the Loki's Castle contain economically interesting quantities of copper (hosted in isocubanite and chalcopyrite) and zinc (hosted in sphalerite), as well as silver and gold. This reinforces the notion that slow spreading ridges may host significant base metal deposits. Micro-textures (chalcopyrite inclusions and exsolutions in sphalerite and isocubanite respectively) are typically undefinable by QEMSCAN, and require quantitative measurement by EPMA. QEMSCAN can be used to efficiently generate average grain size and mineral association data, as well as composition data, and is likely to be a powerful tool in assessing the effectiveness of SMS mineral processing.

show abstract

Fluid composition of the sediment-influenced Loki’s Castle vent field at the ultra-slow spreading Arctic Mid-Ocean Ridge

Cited by 43 publications

References 107 publications

Deep-sea sponge grounds as nutrient sinks: High denitrification rates in boreo-arctic sponges

Deep-sea sponge grounds as nutrient sinks: High denitrification rates in boreo-arctic sponges

Hydrothermal Activity at the Ultraslow‐Spreading Mohns Ridge: New Insights From Near‐Seafloor Magnetics

Characterisation of Mineralised Material from the Loki’s Castle Hydrothermal Vent on the Mohn’s Ridge

Contact Info

Product

Resources

About