Deep Water Bodies Research Articles

On the Existence and Instability of Solitary Water Waves with a Finite Dipole

This paper considers the existence and stability properties of two-dimensional solitary waves traversing an infinitely deep body of water. We assume that above the water is vacuum, and that the waves are acted upon by gravity with surface tension effects on the air--water interface. In particular, we study the case where there is a finite dipole in the bulk of the fluid, that is, the vorticity is a sum of two weighted $\delta$-functions. Using an implicit function theorem argument, we construct a family of solitary waves solutions for this system that is exhaustive in a neighborhood of $0$. Our main result is that this family is conditionally orbitally unstable. This is proved using a modification of the Grillakis--Shatah--Strauss method recently introduced by Varholm, Wahl\'en, and Walsh.

Biomarker paleo-reconstruction of the German Wealden (Berriasian, Early Cretaceous) in the Lower Saxony Basin (LSB)

During the Early Cretaceous (Berriasian; Wealden 3–4), Northwestern Germany was covered by an east–west elongated tentatively brackish lake in which locally more than 700 m-thick black shales were deposited. While the distribution of organofacies’ in the basin is relatively well documented, the paleoenvironmental conditions in the basin center (e.g., occurrence and spread of water column stratification) and the spatial record of biomarkers in Wealden 3–4 shales (and coals) are rarely known. We here present respective data from the entire basin. In large areas, total organic carbon (TOC) contents are above 5 wt% and HI values above 700 mg hydrocarbons (HC)/g TOC, supporting the high potential of shales in the central basin as petroleum source rocks. Furthermore, bulk geochemical data as well as biomarkers clearly mirror the Wealden 3–4 facies distribution with the differentiation of a predominantly terrestrial setting east of the Weser River and an aquatic and brackish lake setting in the west. Certain biomarkers such as isorenieratane, specific for green sulfur bacteria, indicate that the basin consisted of a permanently stratified water column with a brackish/marine deep water body and an oxic–anoxic transition zone in the photic zone. In the southwestern gate of the lake (including the Isterberg area) and towards the east, no water column stratification developed. Characteristic of Wealden 3–4 black shale organic matter are: high relative abundances of saturated versus aromatic hydrocarbons (most likely due to high Botryococcus algal input), highly negative δ13C values in the extract fractions, low isotopic “canonical variables” (sensu Sofer in AAPG Bull 68:31–49, 1984), and high gammacerane, dinosterane, and C35-homohopane relative abundances. Interpreting those data, the different sub-facies of the environmental setting can be excellently documented. Particularly, in the western part of the basin, Wealden 3–4 shales are important petroleum source rocks. However, an overlap of biomarker signatures with those from Jurassic Posidonienschiefer Formation (“Posidonia”) shales from the same area shows that oil–source rock correlations in this area remain challenging.

Comparison of two passive methods for sampling invasive round goby (Neogobius melanostomus) populations at different depths in artificial lakes

Sampling of benthic fish is complicated, especially in deep inland water bodies with a structured bottom. The catches were compared of rapidly spreading round goby (Neogobius melanostomus) using small fykes nets and benthic gillnets in three artificial lakes in The Netherlands over a two year period. Round gobies were captured at all depth layers in each sampled lake. Significantly larger individuals were captured in gillnets compared to fyke nets. Reference sampling in littoral areas captured a wide range in size of round gobies with beach seines. With fyke nets, the highest catches were usually achieved in the shallowest and deepest depth strata. Gillnets catch decreased at deeper layers. Both methods are passive sampling tools and did not provide the absolute catch per bottom area, however relative density estimates of round gobies at different depths or habitats are possible. Round gobies showed a significant size bias associated with capture method. Because it is important to understand the biology and ecology of invasive species like round goby, the combination of small fyke nets and gillnets appears to be a good solution to sample a variety of ranges in deep or/and structured benthic habitats.

Ecological Drivers of Cladoceran Diversity in the Central European City (Łódź, Poland): Effects of Urbanisation and Size of the Waterbody

Łodź, one of the largest cities in Poland, is characterized by the presence of a large number of artificial and natural waterbodies. It, therefore, offers a great opportunity to study ways in which urbanisation affects cladoceran fauna associated with urban areas. We hypothesize that size of the waterbody is more important for the diversity and composition of cladocerans in urban ponds than direct effects of urbanisation. To test this assumption we analysed 21 ponds of different size and location along the urbanisation gradient. Redundancy analysis (RDA) based on 17 environmental factors and urbanisation parameters showed that distance from the city centre, number of plant species and pH were the most important factors shaping cladoceran fauna in urban ponds of Łodź. Non-metric multidimensional scaling (NMDS) based on the Bray-Curtis formula demonstrated that pond size (depth and surface area) was reversely related to the level of urbanisation, i.e., larger and deeper waterbodies were generally found in the outer city zone. The effect of urbanisation, resulting in a lower number of species and lower abundance in ponds located in the central part of the city, was indirect and resulted from the lower number of large ponds in this zone.

Land cover change detection using GIS and remote sensing techniques: A spatio-temporal study on Tanguar Haor, Sunamganj, Bangladesh

Tanguar Haor is one of the two listed Ramsar Site of this country which contains a rich amount of biodiversity as well as a highly productive ecosystem. But the valuable landscape undergoes a radical change in its form over the decades. This study uses past and recent satellite data to evaluate the typical landscape change over the decades. Both pre-classification and post classification change detection approach was used to assess the change result from 1980 to 2010. In pre-classification approach CVA, NDVI and NDWI analysis were implemented to assess the change scenario. Maximum likelihood supervised classification technique was performed to create the signature class of significant land cover category (deep water, shallow water, vegetation, and settlement). After ensuring satisfactory accuracy value for each classified image a detail post classification change detection analysis was executed. Image differencing, statistical change detection techniques (transition probability matrix), change dynamics analysis was also operated to evaluate the statistics of past change relative to present. This study illustrated that, about 40% land cover of the total study area has been converted over 30years period. Forested and high land vegetation’s are disappearing rapidly, deep water bodies consist of large lakes are becoming the rare feature of the study area. Widespread development of settlement and dominant shallow water feature are converting the natural wetland a permanent low lying agricultural land.

Typification of Lymans of the North-Western Black Sea According to the Recommendations of the Eu Water Framework Directive

Purpose. Typification of limans in the north-western Black Sea coast (NWBS) (so called “marine lagoons”) according to the EU Water Framework Directive methodological approaches on hydrological, morphometric, hydrochemical and genesis characteristics. Methods. Comparative & geographical, generalization, cluster analysis. Results. Five groups of limans have been determined by analysis of their crucial parameters: mean annual salinity, depth fluctuation, fresh water influx, water bodies’ and their catchments’ genesis, which were taken from the historical sources and from researches of the Odessa I.I. Mechnikov National University. The selected groups comprised water bodies having similar properties in their water balance regime, origin and hydrochemical regime. Brief description of properties for the each group of water bodies has been formulated. A comparison of the typification results with the work of another team on these objects has been conducted. Conclusions. Five types of limans have been identified in the NWBS: 1) floodplain lagoons, oligogaline, shallow, without free connection to the sea; 2) polygaline shallow sea lagoons; 3) very elongated deep mesohaline floodplain water bodies; 4) estuaries of large rivers with permanent connection to the sea; 5) floodplain shallow hyperhaline water bodies, without a natural connection to the sea. The typification performed makes it possible to use modern monitoring programs for large groups of water bodies in NWBS taking into account the European experience.

Can Protected Areas with Agricultural Edges Avoid Invasions? The Case of Bullfrogs in the Southern Atlantic Rainforest in Brazil.

Bruno Madalozzo, Camila Both, and Sonia Cechin (2016) The American bullfrog, Lithobates catesbeianus, is one of the 100 most harmful invasive species of the planet. Climatic and topographic models predict that the Atlantic Forest regions of southern Brazil are favorable for the establishment of invasive bullfrog populations. The predicted increase of temperature and concentration of gases associated with the greenhouse effect will augment the vulnerability of protected areas of the Atlantic forest to bullfrog invasions in the coming years. In this study we investigated to what extent protected areas of the Atlantic Forest surrounded by anthropogenic landscapes are vulnerable to bullfrog invasions. We conducted surveys in 36 waterbodies located either in a protected area or in anthropogenically modified adjacent locations on a forest-edge-agriculture gradient. We collected data on abundance and breeding to identify the main descriptors (local and landscape variables) that explain the distribution of bullfrogs along this gradient. The variance partitioning analysis showed a strongest association of bullfrog abundance with local waterbody descriptors (area-depth-hydroperiod) and secondarily with a forest-edge-agriculture gradient, i.e., the landscape. The observed distribution pattern suggests that protected areas are likely to be invaded by bullfrogs. Therefore, management strategies should focus on both scales: landscape and waterbody. Supervising the construction of large (permanent or deep) waterbodies in edge habitats of the park and adjacent areas can be effective and agriculture and forest management could importantly complement the prevention of invasions.

Characteristics of forest sites used by a Danish forest preschool

Outdoor stays in green settings are regarded as beneficial for preschoolers, but not much is known about the characteristics of the sites that are chosen and used by outdoor preschools, the so-called ‘forest sites’. Therefore, this paper investigates the characteristics and use of forest sites in a Danish forest preschool and the activities and features in use during time for child-initiated activities.Staff and children (approx. 3–6.5 years) walked to a forest site and stayed for 2–5h on a daily basis. Fifteen forest sites were observed in school hours at 24 stays during one year. This was supplemented by short interviews and informal talks with children and staff to learn more about the forest sites. The findings were organised according to the following ten classes of outdoor features: Open Ground, Sloping Terrain, Shielded Places, Rigid Fixtures, Moving Fixtures, Loose Objects, Loose Material, Water, Creatures and Fire.Most forest sites were glades or pillar halls, often situated at the intersection between different plantings. Staff avoided locations near deep water bodies with steep sides, but at most sites open water was either available at the site or nearby. The daily choice of forest site was connected to the location and features of the site, as well as the weather and season, the actual group of children, and the level of staffing. Children and staff opinion on sites often coincided. Children used features from all classes, but ‘loose objects’ were most often referred to in the interviews. Children as well as staff valued ‘shielded places’, but for staff this was only to a certain degree, since surveillance was important.It is suggested that the results, although derived from a single case, may inspire design and management of green spaces and forest in relation to preschools.

Reservoir characterization of Chang 7 member shale: A case study of lacustrine shale in the Yanchang Formation, Ordos Basin, China

The shale portion of Chang 7 member (C7M) can be divided into two sub-members (SM): the Chang 7-2 sub-member (C7-2SM) and Chang 7-3 sub-member (C7-3SM). An analysis of trace elements shows that C7M shale developed under a freshwater sedimentary environment. C7-3SM shale was formed under conditions of comparatively higher salinity and a much deeper waterbody than C7-2SM shale.C7-3SM shale exhibits a larger content of an illite/smectite mixed layer (70.35%) and reducing minerals (12.94%), but less quartz content (22.31%). Although C7-3SM shale has lower Ro values, it displays much higher S1 values and productivity of hydrocarbon per gram of total organic carbon (TOC) due to Type II1 kerogen, which are mainly Type II2 and possibly Type III in C7-2SM shale.Samples with a drilling orientation perpendicular to sedimentary stratification (“vertical” samples) display relatively lower porosity and permeability. Although no apparent difference of permeability occurs between the two shale sections, C7-2SM shale exhibits higher porosity for both “vertical” and “parallel” samples. Moreover, C7-3SM shale displays lower values of specific surface area and adsorption quantity.The composition of minerals, together with residual hydrocarbon, leads to the lower porosity and adsorption quantity for C7-3SM shale. Compared with C7-2SM shale, C7-3SM shale is not good at generating and storing natural gas. Overpressure may be the reason for the increase in acoustic travel time (AC) values with progressive burial depth for C7-3SM shale.

The evolution of a mining lake - From acidity to natural neutralization

Along the border of Poland and Germany (central Europe), many of the post-mining lakes have formed “an anthropogenic lake district”. This study presents the evolution of a mining lake ecosystem (TR-33) based on subfossil phyto- and zooplankton, isotopic data (δ13C, δ15N), elemental analyses of organic carbon and nitrogen (C/N ratio and TOC) and sedimentological analyses. Recently, lake TR-33 became completely neutralized from acidification and an increase in eutrophication began a few years ago. However, the lake has never been neutralized by humans; only natural processes have influenced the present water quality. From the beginning of the existence of the lake (1920s) to the present, we can distinguish four stages of lake development: 1) very shallow reservoir without typical lake sediments but with a sand layer containing fine lignite particles and very poor diatom and cladoceran communities; 2) very acidic, deeper water body with increasing frequencies of phyto- and zooplankton; 3) transitional period (rebuilding communities of diatoms and Cladocera), meaning a deep lake with benthic and planktonic fauna and flora with wide ecological tolerances; and 4) a shift to circumneutral conditions with an essential increase in planktonic taxa that prefer more fertile waters (eutrophication). In the case of lake TR-33, this process of natural neutralization lasted approximately 23years.

Impact of revised thermal stability on pollutant transport time in a deep reservoir

Thermal stability (Schmidt stability) and water age, which are significantly related to water quality and algae bloom in deep reservoirs, are two crucial indicators of stratification strength and pollutant transport time, respectively. Here, the original Schmidt stability, which was derived from a one-dimensional assumption, was theoretically extended to a three-dimensional water body. In addition, a three-dimensional model was verified for the case study of Hongfeng Reservoir in China based on data from 2009 and 2010. Although the revised stability was similar to the original stability of Hongfeng Reservoir, which occurred at a relatively low level, the greater stratification in other deep water bodies would enhance their difference. Air temperature and water depth were the most important factors of the temporal variation in stability and the spatial variation in stability, respectively. The pollutant transport processes in the Hongfeng Reservoir was very complex with alternate appearances of overflow, interflow and underflow, depending on the season. The spatial water age was primarily determined by the morphometry and the inflow/outflow (with the highest water age in North Lake), whereas the vertical difference in the water age among the layers was primarily controlled by thermal stratification. Negative linear relationships between the average stability and the water ages of the bottom layers in three representative sites during summer were observed. Positive linear relationships between the average stability and the water ages of the surface layers were also observed. These findings enable a better understanding of the hydrodynamic and pollutant transport processes in a deep reservoir.

The palaeo-environmental history of Big Willum Swamp, Weipa: An environmental context for the archaeological record

The environmental history of Big Willum (Waandriipayn) Swamp and the surrounding landscape is reconstructed for the last 8000 years through the analysis of pollen, charcoal and mineral magnetics. The data provide a Holocene record of vegetation and fire in an area where few records exist. Swamp initiation at Big Willum began prior to 8000 cal. BP, with swamp–like conditions maintained until 2200 cal. BP, after which it became a permanent deep water body, reaching its present day extent between 600–400 cal. BP. From 7000–1200 cal. BP the surrounding woodland was essentially stable. Fire is present throughout the record, with only one period of pronounced burning outside of the historic period, at around 1000 cal. BP, leading to a slightly more open understorey/woodland. The hydrological change at 2200 cal. BP that led to Big Willum becoming a more permanent water body overlaps with the end of the most intensive period of shell mound formation and the commencement of earth mound building at nearby Wathayn. This is suggestive that change in, or diversification of, mound types may in part be linked to environmental transformations in the late Holocene. One possibility is that greater water security allowed for increasing and more permanent exploitation of inland locations.

The origin and formation model of Permian dolostones on the northwestern margin of Junggar Basin, China

This study investigates the mechanism of dolostone formation and establishes a dolomitization model in the Permian strata on the northwestern margin of Junggar Basin, China. Dolomitic rock samples are collected from the Permian Fengcheng Formation in Urho area and then characterized by petrological, mineralogical, carbon and oxygen isotope, and trace element geochemical analyses. Results show that the major types of dolomitic rocks include dolomitic mudstone, dolomitic siltstone, dolomitized tuffaceous siltstone, and dolomitized tuffaceous mudstone. The dolomitized rocks are dominated by euhedral or subhedral powder- and fine-crystal dolomites formed by replacement lacustrine argilla-calcareous and siliceous (tuffaceous) components and commonly filled with residual and late calcite cements. The parameters of dolomitic rocks show great variations, including the V/Ni ratio (1.02–4.88), Sr content (95.9–783.6μg/g), Mg/Ca ratio (0.68–5.13), degree of ordering (0.39–1.00), δ18OPDB (−14.8‰ to 3.2‰), and δ13CPDB (−1‰ to 5.2‰). The dolomitic rocks have multi-stage origins and were formed in a semi-closed continental brackish-saltwater bay with weak hydrodynamic processes, deep water bodies, and relatively quiet conditions. In the Permian depositional stage, a combination of complex tectonic activities, fault development, hot subtropical climate, and frequent volcanic activities provided not only Mg2+ source for dolomitization but also channels for rapid flow and seepage of Mg-rich fluids. The origins of dolostones in the study area include penecontemporaneous dolomitization, burial dolomitization, and hydrothermal dolomitization. This study lays a foundation for further studies on dolomite formation and dolomite reservoir, and provides effective methods for researching complex dolostone (tuffaceous, shale and silty dolomite) formation.

The Influence of Habitat Configuration on Anuran Species Composition in Subtemperate Wetlands of Southernmost Brazil

Wetlands of southern Brazil exhibit unique habitat attributes, such as climate pattern and vegetation cover, that can function as an environmental filter for the establishment of species of Neotropical anurans and influence the composition of anuran assemblages. We examined the role of habitat heterogeneity in the composition and relative abundance of anuran species in subtemperate wetlands of southernmost Brazil. We carried out standardized sampling between May 2009 and April 2011 to examine anuran assemblages in marshes associated with grasslands and coastal dunes, as well as habitat heterogeneity. Habitat heterogeneity and anuran species richness were higher in grasslands. Abundance and species dominance, on the other hand, were higher in dunes. This might be due to more restrictive abiotic filters in dunes, such as the low heterogeneity of vegetation cover and lower availability of water bodies. The most common species in grasslands, Leptodactylus cf. latrans, Elachistocleis bicolor, and Pseudis minuta, exhibited a stronger association with habitats with larger and deeper water bodies and with the presence of floating vegetation. The most abundant species found in dunes, Rhinellla arenarum, Odontophrynus maisuma, and Physalaemus biligonigerus, had a stronger association with low vegetation. In addition to habitat associations, the ability to bury themselves might be a behavioral adaptation to dunes that favor species such as O. maisuma and P. biligonigerus, even under extreme microclimatic conditions. Our findings support the importance of the configuration of vegetation cover as well the heterogeneity of water bodies for the establishment of anuran species in subtemperate marshes of southern Brazil.

Freshwater Crustacea (Cladocera, Copepoda) of Iceland: taxonomy, ecology, and biogeography

Of the many types of freshwater bodies across Iceland (e.g., lakes, springs, rivers, and ponds), greater effort has been invested in researching the freshwater Crustacea (Cladocera, Copepoda) of more permanent, larger, and deeper water bodies than on smaller or more ephemeral sites. To address this, we described the fauna of 12 shallow freshwater bodies distributed from the coast to the central highlands of Iceland. We identified 16 species in 11 genera belonging to six families of Cladocera, and 12 species in eight genera belonging to four families of Copepoda. Five of the species we identified (Alona werestschagini, Cyclops vicinus, Daphnia cristata, Diacyclops abyssicola, and Heterocope borealis) represent new distribution records for Iceland, increasing the number of species now known from this region to 34 Cladocera and 38 Copepoda taxa. Additionally, we discuss the taxonomy of some species with doubtful taxonomical status. Six crustacean taxocenes are described, each characterized by the dominance of different taxa, with bottom sediment characteristics best explaining species assemblage structure. We evaluated the relationships between Icelandic Cladocera and Copepoda faunas and those of the adjacent Svalbard, Faroe, and Shetland Islands, Greenland, and the mainland Norway. The taxonomic composition of the Icelandic fauna is dominated by widely distributed Holarctic, and secondarily Palaearctic and Nearctic species, and is more similar to the faunas of the major North Atlantic islands (64.2–71.8 % similarity) than it is to that of continental Norway.

Blue–Red–NIR Model for Chlorophyll- a Retrieval in Hypersaline–Alkaline Water Using Landsat ETM+ Sensor

A conceptual three-band model has been proposed previously and efficiently used to retrieve the chlorophyll-a (C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">chla</sub> ) concentration (C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">chla</sub> ) in deeper water bodies. In this study, we have proposed an empirical C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">chla</sub> estimation model using Landsat ETM+ image reflectance and laboratory-based C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">chla</sub> measurements from hypersaline-alkaline shallow lake (HSASlake) water. This study aims to use remote sensing technique to determine the quantity and distribution of chlorophyll (as an indicator of cyanobacterial biomass) rendering an indirect estimate of food availability for flamingos and other aquatic animals, thus providing valuable information for their future conservation. Using proposed empirical method named blue-red- NIR model, it has been found that the C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">chla</sub> ranges from 3.43 to 43.75 μg L <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> with the mean Chl-a value of 5.45 μg L <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> , in the lake investigated. A variety of regression functions have been implemented for the single and multiband ratios. The best-fitted regression model was developed for the band combination of [R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rs</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> (660) - R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rs</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> (482)] × R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rs</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> (825) having an R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> of 0.88 and model errors of 0.93, 0.8, and 4.74 for standard error of estimate (SEE), Nash-Sutcliffe coefficient (E), and mean absolute percentage error (MAPE), respectively. Our finding evinces that the proposed blue-red-NIR model may be appraised as a robust solution for the estimation of C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">chla</sub> in optically shallow waters, provided that the local inherent optical properties (IOPs) should be scrutinized and reinitialized.

Multiple sulfur isotopes fractionations associated with abiotic sulfur transformations in Yellowstone National Park geothermal springs.

BackgroundThe paper presents a quantification of main (hydrogen sulfide and sulfate), as well as of intermediate sulfur species (zero-valent sulfur (ZVS), thiosulfate, sulfite, thiocyanate) in the Yellowstone National Park (YNP) hydrothermal springs and pools. We combined these measurements with the measurements of quadruple sulfur isotope composition of sulfate, hydrogen sulfide and zero-valent sulfur. The main goal of this research is to understand multiple sulfur isotope fractionation in the system, which is dominated by complex, mostly abiotic, sulfur cycling.ResultsWater samples from six springs and pools in the Yellowstone National Park were characterized by pH, chloride to sulfate ratios, sulfide and intermediate sulfur species concentrations. Concentrations of sulfate in pools indicate either oxidation of sulfide by mixing of deep parent water with shallow oxic water, or surface oxidation of sulfide with atmospheric oxygen. Thiosulfate concentrations are low (<6 μmol L-1) in the pools with low pH due to fast disproportionation of thiosulfate. In the pools with higher pH, the concentration of thiosulfate varies, depending on different geochemical pathways of thiosulfate formation. The δ34S values of sulfate in four systems were close to those calculated using a mixing line of the model based on dilution and boiling of a deep hot parent water body. In two pools δ34S values of sulfate varied significantly from the values calculated from this model. Sulfur isotope fractionation between ZVS and hydrogen sulfide was close to zero at pH < 4. At higher pH zero-valent sulfur is slightly heavier than hydrogen sulfide due to equilibration in the rhombic sulfur–polysulfide – hydrogen sulfide system. Triple sulfur isotope (32S, 33S, 34S) fractionation patterns in waters of hydrothermal pools are more consistent with redox processes involving intermediate sulfur species than with bacterial sulfate reduction. Small but resolved differences in ∆33S among species and between pools are observed.ConclusionsThe variation of sulfate isotopic composition, the origin of differences in isotopic composition of sulfide and zero–valent sulfur, as well as differences in ∆33S of sulfide and sulfate are likely due to a complex network of abiotic redox reactions, including disproportionation pathways.

Comparative studies of pelagic microbial methane oxidation within the redox zones of the Gotland Deep and Landsort Deep (central Baltic Sea)

Abstract. Pelagic methane oxidation was investigated in dependence on differing hydrographic conditions within the redox zone of the Gotland Deep (GD) and Landsort Deep (LD), central Baltic Sea. The redox zone of both deeps, which indicates the transition between oxic and anoxic conditions, was characterized by a pronounced methane concentration gradient between the deep water (GD: 1233 nM, 223 m; LD: 2935 nM, 422 m) and the surface water (GD and LD &lt; 10 nM). This gradient together with a 13C CH4 enrichment (δ13C CH4 deep water: GD −84‰, LD −71‰; redox zone: GD −60‰, LD −20‰; surface water: GD −47‰, LD −50‰; δ13C CH4 vs. Vienna Pee Dee Belemnite standard), clearly indicating microbial methane consumption within the redox zone. Expression analysis of the methane monooxygenase identified one active type I methanotrophic bacterium in both redox zones. In contrast, the turnover of methane within the redox zones showed strong differences between the two basins (GD: max. 0.12 nM d−1, LD: max. 0.61 nM d−1), with a nearly four-times-lower turnover time of methane in the LD (GD: 455 d, LD: 127 d). Vertical mixing rates for both deeps were calculated on the base of the methane concentration profile and the consumption of methane in the redox zone (GD: 2.5 × 10–6 m2 s−1, LD: 1.6 × 10–5 m2 s−1). Our study identified vertical transport of methane from the deep-water body towards the redox zone as well as differing hydrographic conditions (lateral intrusions and vertical mixing) within the redox zone of these deeps as major factors that determine the pelagic methane oxidation.

Geochemical evidence of human impacts on deep Lake Fuxian, southwest China

Human activities in Lake Fuxian and its catchment have caused environmental changes that are preserved in the geochemical records of lake sediments. Human activities responsible for the environmental changes include agriculture, mining, industrial development, and fishery management. To elucidate human impacts on this deep water body during the past several decades, two short sediment cores were collected from the lake, dated by 137 Cs, and analyzed for several geochemical variables (total organic carbon (TOC), total nitrogen (TN), δ 13 C and heavy metals). The multi-proxy geochemical and isotopic evidence can be used to divide the limnological record into a 3-part history. Although increasing inputs of chromium (Cr) had begun as early as the 1950s, human activities, including heavy metal contamination, apparently had little effect on lacustrine production, as δ 13 C, TOC, TN and TOC/TN were relatively constant until the 1980s. Mining and industry have generated large amounts of heavy metal elements such as Zn, Pb and Cd that have been deposited into the lake since the 1980s, increasing to their highest concentrations over the last decades. Zn, Pb and Cd probably were released by industrial processes such as the manufacture of cement. Cr concentrations increased at site FB, but declined at site FZ, most likely due to the closer proximity of site FB to the source of metal production. From the middle of the 1980s, the decreased δ 13 C, and increased TOC, TN and TOC/TN suggest a broad change in lake ecology. In the 1980s, a new fish species was introduced into Lake Fuxian and fish yields increased quickly, which may mark the beginning of a change in ecosystem structure.

Re-assessment of the paleoclimate implications of the Shell Bar in the Qaidam Basin, China

The Shell Bar in the Qaidam Basin, China, is a prominent geological feature composed of millions of densely packed Corbicula shells. Since the mid 1980s, it has been regarded as evidence for existence of a large lake during Marine Isotope Stage (MIS) 3 in the presently hyper-arid Qaidam Basin. Early studies suggested the bivalve shells accumulated at the shore of a large lake, whereas more recent work led to the conclusion that the Shell Bar was formed within a deeper water body. Based on our re-assessment of sediments and fossils from the Shell Bar, investigation of exposed fluvio-lacustrine sections upstream of the Shell Bar and study of nearby modern streams, we infer that the Shell Bar represents a stream deposit. Corbicula is a typical stream-dweller around the world. Preservation of Corbicula shells of different sizes, as well as occurrence of many articulated shells, provide evidence against post-mortem transport and accumulation along a lake shore. Additionally, the SE-NW alignment of the Shell Bar is similar to modern intermittent stream beds in its vicinity and corresponds to the present-day slope towards the basin centre further NW, and furthermore, the predominantly sandy sediments also indicate that the Shell Bar was formed in a stream. Abundant ostracod shells in the Shell Bar sediments originated from stream-dwelling species that are abundant in modern streams in the vicinity of the Shell Bar, or in part from fluvio-lacustrine sediments exposed upstream of the Shell Bar, as a result of erosion and re-deposition. Deflation of alluvial fine-grained sediments in the Shell Bar region and protection of the stream deposits by the large and thick-walled Corbicula shells reversed the former channel relief and yielded the modern exposure, which is a prominent morphological feature. Occurrence of Corbicula shells in the Qaidam Basin indicates climate was apparently warmer than present during the formation of the Shell Bar because Corbicula does not live at similar or higher altitudes in the region today. Because the Shell Bar is no longer considered a deposit formed within a lake, its presence does not indicate paleoclimate conditions wetter than today.