Peer Review #3 of "Fauna associated with shallow-water methane seeps in the Laptev Sea (v0.1)"

We present the initial data on the distribution of benthic foraminifera (BF) on East Siberian Sea shelf. Previous researchers analyzed BF in the sediment cores from the continental slope and basin areas of the East Siberian Sea (Wollenburg et al., 2000; Mackensen et al, 2014; Barrientos et al, 2018) but not from central shelf. Last year we received boxcorer samples of bottom sediments from the shelf of the East Siberian Sea and the Laptev Sea during the 78th cruise of research vessel Akademik Mstislav Keldysh (September-October 2019). We examined the species composition of BF assemblages of Rose Bengal-stained surface samples from 2 stations in the East Siberian Sea and 7 stations in the Laptev Sea, and compared this data set with an existing data set along the East Siberian Sea and the Laptev Sea.Recent studies (Shakhova et al, 2007, 2009, 2015; Nicolsky et al, 2009) state that the East Siberian Sea is one of the largest sources of methane emission into the atmosphere due to degradation of permafrost, ice complex retreat and decaying gas hydrates deposits. Perhaps this has an impact on the species composition of the BF assemblages and the morphological changes and defects of their shells, which we have identified. Samples from active methane seeps of the Laptev Sea have been studied to identify the relationship between methane emission and the reaction of benthic foraminifera. This data have been compared with &#8220;background&#8221; (i.e. non-venting, without any methane seeps activity) stations of the Laptev Sea and the East Siberian Sea.The identified features require further detailed study.

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Fauna associated with shallow-water methane seeps in the Laptev Sea

PeerJ ◽

10.7717/peerj.9018 ◽

2020 ◽

Vol 8 ◽

pp. e9018 ◽

Cited By ~ 1

Author(s):

Andrey A. Vedenin ◽

Valentin N. Kokarev ◽

Margarita V. Chikina ◽

Alexander B. Basin ◽

Sergey V. Galkin ◽

...

Keyword(s):

Cluster Analysis ◽

Shallow Water ◽

Control Area ◽

Laptev Sea ◽

Methane Seep ◽

Methane Seeps ◽

Methane Seepage ◽

Macrobenthic Community Structure ◽

Benthic Ecosystems ◽

Siberian Shelf

Background Methane seeps support unique benthic ecosystems in the deep sea existing due to chemosynthetic organic matter. In contrast, in shallow waters there is little or no effect of methane seeps on macrofauna. In the present study we focused on the recently described methane discharge area at the northern Laptev Sea shelf. The aim of this work was to describe the shallow-water methane seep macrofauna and to understand whether there are differences in macrobenthic community structure between the methane seep and background areas. Methods Samples of macrofauna were taken during three expeditions of RV Akademik Mstislav Keldysh in 2015, 2017 and 2018 using 0.1 m2 grabs and the Sigsbee trawl. 21 grabs and two trawls in total were taken at two methane seep sites named Oden and C15, located at depths of 60–70 m. For control, three 0.1 m2 grabs were taken in area without methane seepage. Results The abundance of macrofauna was higher at methane seep stations compared to non-seep sites. Cluster analysis revealed five station groups corresponding to control area, Oden site and C15 site (the latter represented by three groups). Taxa responsible for differences among the station groups were mostly widespread Arctic species that were more abundant in samples from methane seep sites. However, high densities of symbiotrophic siboglinids Oligobrachia sp. were found exclusively at methane seep stations. In addition, several species possibly new to science were found at several methane seep stations, including the gastropod Frigidalvania sp. and the polychaete Ophryotrocha sp. The fauna at control stations was represented only by well-known and widespread Arctic taxa. Higher habitat heterogeneity of the C15 site compared to Oden was indicated by the higher number of station groups revealed by cluster analysis and higher species richness in C15 trawl sample. The development of the described communities at the shallow-water methane seeps can be related to pronounced oligotrophic environment on the northern Siberian shelf.

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Intraplate magmatism of the De Long Islands: A response to the propagation of the ultraslow-spreading Gakkel Ridge into the passive continental margin in the Laptev Sea

Russian Journal of Earth Sciences ◽

10.2205/2004es000150 ◽

2004 ◽

Vol 6 (3) ◽

pp. 153-183 ◽

Cited By ~ 13

Author(s):

S. A. Silantyev ◽

S. F. Karpenko ◽

Yu. A. Kostitsyn ◽

O. G. Bogdanovskii ◽

P. I. Fedorov

Keyword(s):

Continental Margin ◽

Passive Continental Margin ◽

Laptev Sea ◽

Gakkel Ridge ◽

Intraplate Magmatism ◽

The Laptev Sea

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Composition of Sedimentary Organic Matter across the Laptev Sea Shelf: Evidences from Rock-Eval Parameters and Molecular Indicators

Water ◽

10.3390/w12123511 ◽

2020 ◽

Vol 12 (12) ◽

pp. 3511

Author(s):

Elena Gershelis ◽

Andrey Grinko ◽

Irina Oberemok ◽

Elizaveta Klevantseva ◽

Natalina Poltavskaya ◽

...

Keyword(s):

Organic Matter ◽

Surface Sediments ◽

Continental Margins ◽

Laptev Sea ◽

Lena River ◽

Nearshore Sediments ◽

Rock Eval ◽

Molecular Indicators ◽

Sedimentation Regime ◽

The Laptev Sea

Global warming in high latitudes causes destabilization of vulnerable permafrost deposits followed by massive thaw-release of organic carbon. Permafrost-derived carbon may be buried in the nearshore sediments, transported towards the deeper basins or degraded into the greenhouse gases, potentially initiating a positive feedback to climate change. In the present study, we aim to identify the sources, distribution and degradation state of organic matter (OM) stored in the surface sediments of the Laptev Sea (LS), which receives a large input of terrestrial carbon from both Lena River discharge and intense coastal erosion. We applied a suite of geochemical indicators including the Rock Eval parameters, traditionally used for the matured OM characterization, and terrestrial lipid biomarkers. In addition, we analyzed a comprehensive grain size data in order to assess hydrodynamic sedimentation regime across the LS shelf. Rock-Eval (RE) data characterize LS sedimentary OM with generally low hydrogen index (100–200 mg HC/g TOC) and oxygen index (200 and 300 CO2/g TOC) both increasing off to the continental slope. According to Tpeak values, there is a clear regional distinction between two groups (369–401 °C for the inner and mid shelf; 451–464 °C for the outer shelf). We suggest that permafrost-derived OM is traced across the shallow and mid depths with high Tpeak and slightly elevated HI values if compared to other Arctic continental margins. Molecular-based degradation indicators show a trend to more degraded terrestrial OC with increasing distance from the coast corroborating with RE results. However, we observed much less variation of the degradation markers down to the deeper sampling horizons, which supports the notion that the most active OM degradation in LS land-shelf system takes part during the cross-shelf transport, not while getting buried deeper.

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