Freshwater Ostracodes in Quaternary Permafrost Deposits in the Siberian Arctic

Ostracode analysis was carried out on samples from ice-rich permafrost deposits obtained on the Bykovsky Peninsula (Laptev Sea). A composite profile was investigated that covers most of a 38-m thick permafrost sequence and corresponds to the last ca. 60 kyr of the Late Quaternary. The ostracode assemblages are similar to those known from European Quaternary lake deposits during cold stages. The ostracode habitats were small, shallow, cold, oligotrophic pools located in low centred ice wedge polygons or in small thermokarst depressions. In total, 15 taxa, representing 7 genera, were identified from 65 samples. The studied section is subdivided into six ostracode zones that correspond to Late Quaternary climatic and environmental stadial-interstadial variations established by other paleoenvironmental proxies: (1) cold and dry Zyrianian stadial (58–53 kyr BP); (2) warm and dry Karginian interstadial (48–34 kyr BP); (3) transition from the Karginian interstadial to the cold and dry Sartanian stadial (34–21 kyr BP); (4) transition from the Sartanian stadial to the warm and dry Late Pleistocene period, the Allerød (21–14 kyr BP); (5) transition from the Allerød to the warm and wet Middle Holocene (14–7 kyr BP); and (6) cool and wet Late Holocene (ca. 3 kyr BP). The abundance and diversity of the ostracodes will be used as an additional bioindicator for paleoenvironmental reconstructions of the Siberian Arctic.     

Geochemistry of carbonate precipitation from the groundwater in a coastal region

Groundwater samples were collected from a coastal region of Andhra Pradesh to assess the possible conditions of the formation of carbonates. The area experiences a semi-arid climate and is underlain by khondalites, over which the Quaternary sediments occur. The study of the geochemistry of groundwater indicates that groundwater is mostly of fresh, with alkaline nature. The study further suggest that the breakdown of feldspars as kaolinite during rock-water interaction, releases Ca²⁺. Soils/weathered products contribute high CO₂ under the open system. The Ca²⁺ and CO₂ are added to the groundwater through the infiltrating recharge water. They subsequently precipitate as fine-grained carbonates in the weathering profile due to evapotranspiration under a freshwater environment.     

Seasonal insect emergence from three different temperate lakes

Knowing the aquatic resources, such as emerging insects, that are entering terrestrial systems is important for food web and conservation studies, especially when water availability or quality is limited. Even though studies concerning benthic macroinvertebrates are numerous, insect emergence from lakes is less studied.To understand if water parameters (e.g., water temperature, oxygen concentration etc) determine insect emergence and the possible seasonal differences, we collected emergent insects from three different lakes in South Germany, during three seasons. We searched for common patterns of insect emergence at the three lakes. Moreover, the relative contribution of insects of aquatic origin to aerial flying arthropods was assessed, with collecting aerial flying arthropods at the shore.Chironomidae constituted the highest number of emerged insects in all lakes, however different patterns of emergence occurred in each lake (unimodal vs. bimodal) with different season-dependent times for the emergence peaks (spring, summer, beginning of autumn). Aquatic insects constituted a considerable proportion (at least 17%) of the aerial flying arthropods at the shore. The variation in insect emergence was explained by water temperature, however not by other water parameters or the nutrient values. Seasonal and spatial differences in insect emergence, should be considered when investigating aquatic-terrestrial interactions and designing conservation plans. A total biomass of up to 1.8 g m⁻² of emerging insects from the littoral zone of Lake Constance can enter the terrestrial system in a year. We also provide length-dry weight relationships for emerged (adult) Chironomidae. These equations are useful to estimate the dry insect biomass from length data and currently such data lack for adult aquatic insects.     

Tracing of Peroxidase Activity in Humic Lake Water

An enzyme assay was developed for studies on peroxidase activities in humic lake water. 3,4-Dimethoxybenzyl alcohol (veratryl alcohol, VeraOH) was used as tracer substrate, and peroxidase (EC 1.11.1.7) activity was measured by high-performance liquid chromatography. The chemical stability of VeraOH and its application as peroxidase substrate was tested under light and dark conditions, different hydrogen peroxide (H₂O₂) concentrations and humic matter contents. VeraOH was stable under low UV radiation at in situ conditions in lake water (<0.010...0.25 kJ m^–2 d^–1), laboratory conditions (<0.05...0.30 kJ m^–2 d^–1), and low (1...100 μM) H₂O₂ concentrations. However, peroxides oxidized VeraOH above 1...10 mM H₂O₂ concentration in sterile Millipore-Q and humic lake water. Dark incubations showed little VeraOH oxidation products. The developed peroxidase assay was tested in the growth medium of Phanerochaete chrysosporium and a bacteria isolate (P.M.D. 20.4.3.1) from mesohumic lake Pääjärvi. Peroxidase activities were also measured in natural microbial communities under standard laboratory and under in situ conditions in humic lake water. Incubation times of about 5 to 12 days were usually needed to record significant (P < 0.05) peroxidase activities, in lake waters. In situ peroxidase activities varied in pelagial surface water (0...0.5 m) on a seasonal scale between 74 nmol L^–1 h^–1 and 273 nmol L^–1 (mean: 176 nmol L^–1 h^–1) and within the water column between 110 nmol L^–1 h^–1 and 800 nmol L^–1 h^–1 (mean: 500 nmol L^–1 h^–1) in polyhumic lake Mekkojärvi.     

Evaluation of aquatic ecological systems through dynamics of ichthyofaunal diversity in a Himalayan torrential river,Murti

The biodiversity hotspot region of the Eastern Himalayas consists of a vast freshwater network enriched with species diversity. Many small-scale torrential rivers and water reaches contribute to the species pool of all the major rivers by converging downstream. These reaches are most likely to be degraded at a faster rate as compared to the large-scale rivers following an increased rate of urbanization, habitat alterations, and changing climatic conditions. Therefore, this study aims to explore River Murti, which is a representative small scale river system characterized by a large altitudinal gradient and a diverse watershed area. Ichthyofaunal diversity (i.e., diversity, evenness & richness) and 21 environmental variables are measured through a tri-seasonal sampling effort conducted along 14 selected locations. A total of 41 fish species (including species belonging to 4 Near Threatened, 8 Vulnerable, and 1 Endangered) are found inhabiting this river. Ichthyofaunal assemblage is found to be primarily modulated by habitat diversity and landscape variables. Three Aquatic Ecological Systems (AES) have been identified along this river in a top-down approach based on recorded environmental variables. We have calculated an observed/expected ratio for each diversity indices along 14 locations based on predicted temporal variability using boosted regression (BRT) models. The evaluation of diversity status has been kept at 0.5 to account for a 50% loss or deviation from observed (O/E50). This evaluation has been successfully used to delineate AES1 with majorly “Impaired” status and thus ensures its importance in terms of species conservation. Our study indicates the contribution of 11 major environmental drivers modulating the species assemblage patterns in these AES. Amongst them, altitude, substrate coarseness, river morphology, and shelter availability are strongly associated with species diversity as per the BRT models. These underlying factors are also correlated with “basin pressure,” suggesting that anthropogenic disturbances, as well as the changing climate, might play an important role in the gradual change in environmental conditions, which in turn could cause a shift in species assemblage structure.     

洱海湖滨带冬季水鸟的水质指示作用

水鸟在物种或群落水平上可以对湿地营养状态有所响应,预警生态系统有害的改变.以大型淡水湖泊洱海为例,基于2015年2月沿岸17个观察点的冬季水鸟调查与水质同步监测,研究小(Podiceps ruficollis)、白骨顶(Fulica atra)和黑水鸡(Gallinula chloropus)密度对沿岸水体中总磷和总氮浓度的响应关系.结果发现白骨顶和小密度均与总氮浓度呈显著正相关,也均与总磷浓度呈显著正相关;黑水鸡密度与总氮和总磷浓度无显著相关性.结果表明,水鸟可以在物种水平上对洱海湖滨带水中营养物质变化有所响应,也强调了根据具体指示物种的生态学习性选择水鸟指示物种尤为重要.白骨顶和小在更大空间和时间尺度上的水质指示作用有待于更多湖泊或水库水体的长期相关研究.     

天津潮间带春季贝类资源调查

为研究天津潮间带贝类资源的分布特征,2017年5月,作者对天津滩涂开展贝类资源调查。共采集贝类30种,分属2纲、4亚纲、10目、19科,在汉沽鲤鱼门、大港减河口、大港滨海湿地分别采集贝类20种、19种、19种;高潮区、中潮区、低潮区分别采集贝类11种、22种、10种;H'值大小顺序为鲤鱼门滨海湿地减河口,中潮区高潮区低潮区;经济贝类主要分布于中潮区,鲤鱼门与减河口滩涂的优势经济种均为菲律宾蛤仔(Ruditapes philippinarum),生物量分别为562.8、828.5 g/m~2,滨海湿地的优势经济种为四角蛤蜊(Mactra veneriformis),生物量为1 403.8 g/m~2。对比2013年,大港减河口滩涂的贝类种数及生物量均升高,鲤鱼门滩涂的贝类种数增加,滨海湿地滩涂的贝类资源为首次报道。     

Diagenesis and reservoir quality of sandstones with ancient “deep” incursion of meteoric freshwater——An example in the Nanpu Sag,Bohai Bay Basin,East China

An example of diagenesis and reservoir quality of buried sandstones with ancient incursion of meteoric freshwater is presented in this study. The interpretation is based on information including porosity and permeability, petrography, stable isotopic composition of authigenic minerals, homogenization temperatures (T_h) of aqueous fluid inclusions (AFIs), and pore water chemistry. These sandstones, closely beneath or far from the regional unconformity formed during the late Paleogene period, are located in the thick Shahejie Formation in the Gaoliu area of Nanpu Sag, Bohai Bay Basin, East China. Early-diagenetic calcite cements were leached to form intergranular secondary pores without precipitation of late-diagenetic calcite cements in most sandstones. Feldspars were leached to form abundant intragranular secondary pores, but with small amounts of concomitant secondary minerals including authigenic quartz and kaolinite. The mass imbalance between the amount of leached minerals and associated secondary minerals suggests that mineral leaching reactions occurred most likely in an open geochemical system, and diagenetic petrography textures suggest that advective flow dominated the transfer of solutes from leached feldspars and calcites. Low salinity and ion concentrations of present pore waters, and extensive water rock interactions suggest significant incursion of meteoric freshwater flux in the sandstones. Distances of the sandstones to the regional unconformity can reach up to 1800 m, while with significant uplift in the Gaoliu area, the burial depth of such sandstones (below sea level) can be less than 800–1000 m during the uplift and initial reburial stage. Significant uplift during the Oligocene period provided substantial hydraulic drive and widely developed faults served as favorable conduits for downward penetration of meteoric freshwater from the earth's surface (unconformity) to these sandstone beds. Extensive feldspar leaching has been occurring since the uplift period. Coupled high T_h (95∼115 °C) of AFI and low δ¹⁸O_(SMOW) values (+17∼+20‰) within the quartz overgrowths show that quartz cementation occurred in the presence of diagenetic modified meteoric freshwater with δ¹⁸O_(SMOW) values of −7∼−2‰, indicating that authigenic quartz only have been formed during the late reburial stage when meteoric fresh water penetration slowed down. Secondary pores in thin sections and tested porosity suggest that meteoric freshwater leaching of feldspars and calcite minerals generated approximately 7–10% enhanced secondary porosity in these sandstones. Meteoric freshwater leaching reactions cannot be ignored in similar sandstones that located deep beneath the unconformity, with great uplift moving these sandstones above or close to sea level and with faults connecting the earth's surface with the sandstone beds.     

Ecology of water mite assemblages in Panama – First data on water mites (Acari,Hydrachnidia) as bioindicators in the assessment of biological integrity of neotropical streams

The ecological integrity of freshwater ecosystems is regularly examined through assessment of their macroinvertebrate assemblages. The various methods used in such biomonitoring all have one characteristic in common – the neglect of water mites. Even though this group perfectly fulfills all necessary requisites for successful bioindicators, these invertebrates are either completely ignored or lumped together as “Acari”.This study, for the first time, uses water mites (Hydrachnidia) as bioindicators in the Neotropics to compare the anthropogenic stress in 15 streams at three different levels of contamination (pristine, rural, urban). In total, 4371 water mite specimens, belonging to 31 genera and 14 families, were collected.Diversity, abundance, and richness of water mite assemblages were significantly reduced with increasing levels of contamination. These differences were clearest in the dry season. Atractidella turned out to be, by far, the most tolerant water mite genus, having the greatest abundance at the most contaminated sites. In contrast, Pseudotorrenticola was found only in pristine waters, while Hydrodroma, Limnesia, Koenikea, Torrenticola, Monatractides and the family Aturidae showed clear preferences for pristine waters.Our data show, that water mites, identified to genus level, are well suited for water quality assessment in neotropical lowland streams, clearly distinguishing different levels of contamination/anthropogenic stress.