Distribution of Modern Benthic Foraminifera of McMurdo Sound, Antarctica

<p>This thesis presents the results of a study of benthic foraminifera from McMurdo Sound, Antarctica. The sound is 50 km across and more than 900 m deep, and is ice-covered for at least 9 months of the year. However, salinity and temperature of the bottom waters are constant (35 per mil and -1.8 degrees C). Sea floor sediment is mainly fine sand and mud with a little ice-rafted gravel. The aim of the study was to document the distribution of living and dead foraminifera and to determine the factor(s) controlling it. The twenty-six sites in water from 76 to 856m deep were sampled by gravity corer and grab, and nearly 40,000 specimens (2334 living and 36,875 dead) were identified. Three present day assemblages can be recognised: 1. Shallow open water assemblage (SWA): Trochammina glabra, Cribrostomoides jeffreysii, Trifarina earlandi, Ehrenbergina glabra, Fursenkoina earlandi and Globocassidulina crassa. 2. Deep open water assemblage (DWA): Reophax pilulifer, Reophax subdentaliniformis, Portotrochammina antarctica, Textularia antarctica and Miliammina arenacea. 3. Harbour/enclosed basin assemblage (HA): Reophax subdentaliniformis, Portotrochammina antarctica, Textularia antarctica, Fursenkoina earlandi and Globocassidulina crassa. The composition of the assemblages is controlled largely by calcium carbonate compensation depth (CCD). Calcareous species are abundant and varied (84 calcareous species) in the SWA above 620m, but are virtually absent from the DWA, which is found in deeper water. The dominance of agglutinated foraminifera in the HA indicates an even shallower CCD (about 270m) in restricted coastal settings. Death assemblages have a similar species diversity to corresponding life assemblages and are reasonably representative of them, except for the 200m zone above the offshore CCD, where death assemblages are depleted in calcareous taxa. The diversity of the agglutinated component of each assemblage remains nearly constant in all habitats and at all water depths, even though shallow water samples include a range of calcareous species. Thus competition from calcareous species appears not to be a stress factor for agglutinated species, which are considered to have reached the limit of their evolutionary potential in these waters.</p>

Distribution of Modern Benthic Foraminifera of McMurdo Sound, Antarctica

<p>This thesis presents the results of a study of benthic foraminifera from McMurdo Sound, Antarctica. The sound is 50 km across and more than 900 m deep, and is ice-covered for at least 9 months of the year. However, salinity and temperature of the bottom waters are constant (35 per mil and -1.8 degrees C). Sea floor sediment is mainly fine sand and mud with a little ice-rafted gravel. The aim of the study was to document the distribution of living and dead foraminifera and to determine the factor(s) controlling it. The twenty-six sites in water from 76 to 856m deep were sampled by gravity corer and grab, and nearly 40,000 specimens (2334 living and 36,875 dead) were identified. Three present day assemblages can be recognised: 1. Shallow open water assemblage (SWA): Trochammina glabra, Cribrostomoides jeffreysii, Trifarina earlandi, Ehrenbergina glabra, Fursenkoina earlandi and Globocassidulina crassa. 2. Deep open water assemblage (DWA): Reophax pilulifer, Reophax subdentaliniformis, Portotrochammina antarctica, Textularia antarctica and Miliammina arenacea. 3. Harbour/enclosed basin assemblage (HA): Reophax subdentaliniformis, Portotrochammina antarctica, Textularia antarctica, Fursenkoina earlandi and Globocassidulina crassa. The composition of the assemblages is controlled largely by calcium carbonate compensation depth (CCD). Calcareous species are abundant and varied (84 calcareous species) in the SWA above 620m, but are virtually absent from the DWA, which is found in deeper water. The dominance of agglutinated foraminifera in the HA indicates an even shallower CCD (about 270m) in restricted coastal settings. Death assemblages have a similar species diversity to corresponding life assemblages and are reasonably representative of them, except for the 200m zone above the offshore CCD, where death assemblages are depleted in calcareous taxa. The diversity of the agglutinated component of each assemblage remains nearly constant in all habitats and at all water depths, even though shallow water samples include a range of calcareous species. Thus competition from calcareous species appears not to be a stress factor for agglutinated species, which are considered to have reached the limit of their evolutionary potential in these waters.</p>

Numerical Modeling of Sampling Seafloor Sediments to Study Their Rheological Properties

&lt;p&gt;The work presents the results of applying SIMULIA Abaqus's capabilities to solve problems related to infrastructure development in the development of oil and gas fields on the continental shelf. The primary attention is paid to the stability of the load-bearing structures of infrastructure facilities. When developing oil and gas fields located in the continental shelf, several geomechanical problems not typical for onshore fields arise. First of all, there is a need to construct a detailed model of the mechanical properties of the upper layers of bottom sediments in conditions of limited data on these properties. This limitation of data is caused by the complexity and cost of engineering drilling, which in other conditions provides the necessary information regarding the properties of the upper layers of sediments. Current study describes the proposed set of methods for studying the mechanical properties of the upper layers of bottom sediments using sampling. It is shown that the process of bottom sampling itself makes it possible to estimate the mechanical properties of bottom sediments. Quantitatively, such estimations can be made based on a numerical solution of the contact problem of gravity corer indentation into visco-elastoplastic medium, the specific rheological properties of which are a priori unknown. The possibility of determining the possible values of these properties from the data obtained in the sampling process (the dependence of the acceleration of the contact point on time) is demonstrated in the study with solution of the inverse problem.&lt;/p&gt;

Dynamics and variability of POC burial in depocenters of the North Sea (Skagerrak), Cruise No. AL561, 2.08.2021 – 13.08.2021, Kiel – Kiel, APOC

The AL561 cruise was conducted in the framework of the project APOC (“Anthropogenic impacts on Particulate Organic Carbon cycling in the North Sea”). This collaborative project between GEOMAR, AWI, HEREON, UHH, and BUND is to understand how particulate organic carbon (POC) cycling contributes to carbon sequestration in the North Sea and how this ecosystem service is compromised and interlinked with global change and a range of human pressures include fisheries (pelagic fisheries, bottom trawling), resource extraction (sand mining), sediment management (dredging and disposal of dredged sediments) and eutrophication. The main aim of the sampling activity during AL561 cruise was to recover undisturbed sediment from high accumulation sites in the Skagerrak/Kattegat and to subsample sediment/porewater at high resolution in order to investigate sedimentation transport processes, origin of sediment/POC and mineralization processes over the last 100- 200 years. Moreover, the actual processes of sedimentation and POC degradation in the water column and benthic layer will be addressed by sampling with CTD and Lander devices. In total 9 hydroacoustic surveys (59 profiles), 4 Gravity Corer, 7 Multicorer, 3 Lander and 4 CTD stations were successfully conducted during the AL561 cruise. - (Alkor-Berichte ; AL561)

Spatio-temporal sublittoral macrobenthic distribution and dominant species in Guanabara Bay, Rio de Janeiro, Brazil

Soft-bottom macrobenthic invertebrates are sensitive to natural or anthropogenic changes in aquatic ecosystems. The distribution patterns of sublittoral macrobenthic species in Guanabara Bay were studied from 2005 to 2007. Samples were collected at ten stations during six surveys throughout the rainfall regime (dry, early and late rainy). Ten replicates were collected at each station by Gravity corer or skin diving. Van Dorn bottles (bottom water) and by Ekman sediment sampler (granulometry) provided material for abiotic data. Stations were grouped into sectors (Entrance, Intermediary and Inner) based on abiotic data and location. The Redundancy Analysis (RDA) and Parsimonious RDA for all years and each annual cycle showed indicator taxa with high dominance in each sector. PERMANOVA indicated a regular seasonality between the surveys for the first annual cycle (p <0.05), and an atypical pattern for the second (p> 0.05), possibly due the low rainfall observed during this period. The mosaic of soft-bottom substrates infers structural variables, and patterns of temporal distribution were basically influenced by parameters those indicating pollution and the SACW (South Atlantic Central Water) intrusion, as well as ecological attributes among species, such as: predation, competition. The Ervilia concentrica and Cypridinidae could be used as indicators for anthropic and natural impacts in the Guanabara Bay for the Entrance sector, while Cyprideis salebrosa and Cyprideis sp. for the Intermediary sector and Heleobia australis for the Inner sector.

Bathyarchaeota Occurrence in Shallow Marine Methane-rich Sediments (Saco do Mamanguá, Rio de Janeiro, Brazil)

ABSTRACTMethane gas (CH4) reservoirs have previously been reported in tropical marine sediments of Saco do Mamanguá ria (Rio de Janeiro, Brazil). It is known that a methane microbiome can be established in methane seeps sites; however, they are still poorly characterised. In this study, we aimed to investigate the spatial and vertical distribution of the bacterial and archaeal composition and the community structure in the sediments of Saco do Mamanguá ria. For this purpose, we collected sediment samples through 100 cm long gravity corer at three different sites and performed community analysis based on 16S rRNA gene sequencing, quantification of the methyl coenzyme M reductase-encoding gene (mcrA) and geochemical analysis, including CH4 stable isotope. Our results revealed a biogenic trend for CH4 isotopic signature and a high proportion of archaeal sequences assigned as Bathyarchaeota, with a spatial distribution throughout the inner areas of the channel and the deepest strata. OTUs classified within Bathyarchaeota and Chloroflexi (Dehalococcoidia) showed positive correlation with methane concentrations, sediment depth and oxidation-reduction potential. Due to their prevalence in the microbial community, we also performed phylogenetic analysis to understand the closeness of our Bathyarchaeota OTUs with Bathyarchaeota subgroups, and the results demonstrated a close relationship particularly with Bathy-8 and Bathy-13, which possess genes for acetogenesis and methanogenesis. Although direct relations between microbial populations and the biogenic methane emissions in Saco do Mamanguá cannot be assured, our results emphasize the importance of further investigations about the potential role of Bathyarchaeota in the carbon cycling in methane-rich tropical shallow ecosystems.

The Hydrochemistry and Recent Sediment Geochemistry of Small Lakes of Murmansk, Arctic Zone of Russia

This paper presents the first study of five small lakes located in the city of Murmansk. Field work was carried out during 2018–2019. Water samples were collected using a bathometer, while the sediments were sampled using an Ekman grab and Limnos gravity corer. It was found that the water of the studied lakes in Murmansk belong to the sodium group of the chloride class and to the calcium group of the hydrocarbonate class. Compared to the background level, elevated pH, concentrations of the main cations of alkali and alkaline-earth metals, N compounds, total dissolved solids, and heavy metals were found in the lakes, which indicate exposure to anthropogenic impacts. The sediments of the lakes, composed of organomineral and mineral silts, also have an elevated content of heavy metals compared to the background. The most significant excessive concentrations were found for V, Ni, Sb, Pb, Co, Cr, and W. Based on the calculated pollution load index and geoaccumulation index of the sediments, the studied water bodies in Murmansk can be classified as lakes with heavy and extremely heavy pollution levels. The primary pollution sources are emissions from the Murmansk thermal power plant, coal port, road and, rail transport.

Testing lake-level reconstructions based on rock magnetic proxies for the sediment record of Laguna Cháltel (Patagonia, Argentina)

This study was carried out on sediment cores collected with a gravity corer from Laguna Cháltel, an almost circular crater lake located in Patagonia, Argentina (49.9°S, 71°W). The main magnetic carrier was Ti-magnetite in the pseudo–single domain range. A model using magnetic grain size and concentration, previously applied to Laguna Potrok Aike to infer lake-level changes, was used for Laguna Cháltel. The main requirement to apply the model is uniform magnetic mineralogy, which is the case for Laguna Cháltel. After magnetic data were compared with previously studied lake levels, it was found that the magnetic proxies that best follow hydrologic changes are ARM/SIRM (anhysteretic remanent magnetisation/saturation of isothermal remanent magnetisation) and ARM. The concentration proxy (ARM measured with a 100 mT alternating field and 0.05 mT direct field) was also used as wind indicator. High wind strength was found at around 3650 cal yr BP, and low wind strength for the last century. ARM/SIRM and ARM were used to infer the strength of fluvial runoff into the lake for a core collected close to the shore and near a tributary. The results show that the magnetic model is promising for inferring lake-level variations, particularly in Patagonian lakes.

Impact of mining on geochemical signatures of riverine sediments in adjacent ecosystems

&lt;p&gt;As a result of the open-cast lignite mining in Lusatia (Eastern Germany), large quantities of iron (Fe) and sulphate (SO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;2-&lt;/sup&gt;) are fed into small streams discharging into the Spree river system. The study examined whether the inputs of Fe and SO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;2-&lt;/sup&gt; lead to longitu&amp;#173;dinal and depth-dependent gradients in the riverine sediments downstream the mining region in terms of element composition and mineral formations.&lt;/p&gt;&lt;p&gt;We sampled the surface (upper 0-3, 3-6 cm) sediment using a gravity corer at 18 sites from the heavily mining impacted Spreewald region downstream 200 km to the B&amp;#228;nke at Lake M&amp;#252;ggelsee. We also included sampling sites at a pit water purification system in Vetschau, one neutral mining lake and a reference site without mining impact. Sedi&amp;#173;ments were analysed for total C, N using an element analyser, for various elements (incl. Fe, S, Mn, Al, P, heavy metals) by ICP-OES after digestion with hot aqua regia. A sequential Fe-extraction from fresh sediments and XRD was performed to differenti&amp;#173;ate solid iron forms and other minerals, respectively. &amp;#160;Characteristic sediment signatures are investigated with the help of a Principal Component Analysis (18 sites, 19 parameters).&lt;/p&gt;&lt;p&gt;We discovered a decreasing sedimentary Fe-content in flow direction from 300 mg g-1 in Vetschau, 130 mg g-1 close to the mining region in L&amp;#252;bbenau down to 30 mg g-1 at B&amp;#228;nke near Lake M&amp;#252;ggelsee. In contrast, the S-content increased with decreasing mining impact from 3 mg g-1 in Vetschau up to 35 mg g-1. Minimum Fe- and S-contents are similar to Bautzen reservoir as a non-mining impacted reference location with Fe 28 mg g-1 and S 4 mg g-1. The statistical analysis with the PCA revealed the longitudinal influence of mining products within Spree river. Two major groups emerge from the score plot. First, there are those samples, which are clearly influenced by mining activities. Second, there are samples, which include the reference point and samples more distant from mining, where we expect no or only minor mining impact. This separation becomes even more apparent after taking heavy metals into account. Furthermore, the Fe binding shifts from more easily reducible Fe/amorphous minerals to less easily reducible Fe/more crystalline minerals in flow direction, which probably has consequences for the microbial degradability of organic matter and the strength of the ability of Fe to bind phosphorus. &amp;#160;&lt;/p&gt;&lt;p&gt;We were able to prove that the sedimentary ele&amp;#173;ment composition and especially the Fe mineral characteristics are influenced by mining activities at least 100 km downstream the Spree river system, probably affecting the phosphorus availability and carbon turnover.&lt;/p&gt;

Research on cruise 38 of the R/V Akademik Nikolaj Strakhov in the Barents sea

The first results of the multidisciplinary expedition onboard research vessel Akademik Nikolaj Strakhov in the Barents Sea in August-September 2018 are given. On 41 stations the hydrophysical sounding was carried out, sampling of the bottom sediments was done using both grab and gravity corer. As a result of geophysical investigations the areas with the signs of modern dangerous natural processes were identified. Four seismic bottom stations were installed in the Pechora Sea.