Lake Samples Research Articles

Van Gölü’nde Sintine Suyu Kaynaklı Kirliliğin İncelenmesi

Van Gölü’nde faaliyet gösteren gemilerin sintine sularından kaynaklı su kirliliği araştırılmıştır. Gemilerin barındığı on ayrı istasyondaki göl suyunda multimetre ile yerinde ölçümler yapılırken, göl suyunda ve gemilerden alınan sintine sularında kimyasal oksijen ihtiyacı (KOİ) ve yağ-gres analizleri gerçekleştirilmiştir. Göl sularında en düşük ve en yüksek KOİ değerleri sırasıyla 32 ve 240 mg/L, en düşük ve en yüksek yağ-gres değerleri sırasıyla 23 ve 146.5 mg/L olmuştur. Sintine su örneklerinde ise en düşük ve en yüksek KOİ değerleri sırasıyla 22 ve 5890 mg/L, en düşük ve en yüksek yağ-gres değerleri sırasıyla 11.3 ve 10000.0 mg/L bulunmuştur. İstasyonlarda göl suyunda yapılan ölçümlerde Su Kirliliği Kontrolü Yönetmeliği’ne göre genel olarak su sıcaklığının I-II. sınıf, çözünmüş oksijenin I. sınıf, oksijen doygunluğunun I. sınıf ve göl suyunun sodalı özelliğinden dolayı pH’nın IV. sınıfta yer aldığı belirlenmiştir. İstasyon göl sularından alınan örneklerde ortalama KOİ ve yağ-gres değerleri ise IV. sınıfta bulunmuştur. Tüm teknelerdeki yağ-gres değerleri MARPOL 73/78’e göre sınır değerin (15 mg/L) üstünde çıkmıştır. Çalışma sonucunda barınak olarak kullanılan bölgelerin, gemilerin bıraktığı sintine sularından olumsuz etkilendiği belirlenmiştir.

Effects of water quality and bacterial community composition on dissolved organic matter structure in Daihai lake and the mechanisms

The migration of organic matter in salinized lakes was critical in maintaining ecological balance and material circulation process of inland shallow lakes. To clarify the ecological and microbial mechanism of material transport and transformation, the microbial community structure and the characteristics of dissolved organic matter (DOM) in the sediment of Daihai Lake, a typical saline lake at the Yellow River Basin, were explored with three-dimensional excitation and emission matrix fluorescence (3DEEM), parallel factor analysis (PARAFAC) and 16 S rRNA techniques. The correlation between environmental factors, DOM composition and the bacterial community structure were also studied for identifying the key factors of community formation. DOM in the lake demonstrated both terrigenous and endogenous characteristics. Protein-like materials accounted for 74% of the total fluorescence intensity in the sediment, where 1127 species, 671 genera, 468 families, 157 classes, 317 orders, 59 phyla of microorganisms were detected. Among the top 10 abundant taxa of each level, Firmicutes, Actinobacterota, Acidimicrobiia and Alphaproteobacteria had the greatest influence on the composition and structure of DOM (|R| > 0.7, p < 0.01). Microbial metabolism was a key process of transforming sediment organic matter from terrestrial humic-like to protein-like matter, accounting for 81% of total fluorescence signal in saline lake samples, while salinity, temperature, dissolved oxygen and electrical conductivity also had significant impacts during the process (|R|>0.7, p < 0.05). The research provides fundamental data and enlightenment for the improvement of the saline inland lake environment.

Propagule limitation affects the response of soil methane oxidizer community to increased salinity

The extent to which propagule limitation can govern the responses of microbially-mediated processes (such as methane oxidation) to sudden environmental changes, is poorly understood. Here, we compared the ability of the methanotroph community in lakeshore soils of two lakes to respond to an experimental increase in salinity. One set of samples was taken from lakeshore soils of a freshwater lake (Yang Lake), the other from a slightly brackish lake (Qinghai Lake), both on the Tibetan Plateau. Samples were incubated in microcosms by adding ∼ 5 % 13CH4 or 12CH4 and different concentrations of NaCl solution. DNA stable-isotope probing (DNA-SIP) followed by high-throughput sequencing was used to determine how the active methanotrophic populations differed in lakeshore soils with different salinity levels. Samples from saline and freshwater lake initially showed much-reduced methane oxidation ability and methanotrophic activity at increased salinity. For the freshwater samples with the salinity of 25 to 50 g/L after NaCl addition, there was no adaptation and increase in methanotrophy after 7 days. By contrast, samples from the brackish lake showed an initial depression of methane oxidation, followed by greatly increased rates after several days. Sequencing revealed that this recovery of methanotrophy in the brackish lake samples was associated with a major switchover in composition of active methanotroph community. In particular, the relative abundance of Type Ⅰa methanotrophs became more abundant at increased salinity. It appears that in this freshwater lake environment, isolation from any nearby high-salinity-tolerant bacterial sources has prevented the possibility of full adaptation to a high salinity change in the environment, and only a moderate salinity adaptation is possible by species-sorting from within the existing community. By contrast, in the higher-salinity environment, the highly salinity-tolerant Methylomicrobium was able to break the establishment limitation in the high salinity environment and become the dominant methanotroph. Our study provides an instance of propagule limitation preventing adaptation to changed conditions.

Development of ecological risk assessment for Diisobutyl phthalate and di-n-octyl phthalate in surface water of China based on species sensitivity distribution model

Phthalic acid esters (PAEs) are commonly used as plasticizer and are emerging concern worldwide for potent adverse effects of aquatic organisms. Certain PAEs were often detected in different environmental matrices but related toxicity data were still lacking to support their risk assessment. The study investigated the acute toxicity of Diisobutyl phthalate (DiBP) and Di-n-octyl phthalate (DnOP) using 6 Chinese resident aquatic organisms from 3 phyla and 6 species and constructed the species sensitivity distribution (SSD) models for ecological risk assessment. Lethal concentration 50% (LC50) ranges of DiBP and DnOP were 4.89–21.45 mg/L and 1.45–1200 mg/L, respectively. The derived acute and chronic predicted no-effect concentrations (PNECs) based on log-normal model of water were 0.54 and 0.04 mg/L for DiBP and 0.23 and 0.05 mg/L for DnOP, respectively. The ERA for DiBP and DnOP in the surface water and sediment of China was conducted. Water samples of Haihe Rive (RQ = 0.41) and Hun River (RQ = 0.16) of DiBP showed medium risk. And sediment samples of Yellow River (RQ = 0.71) and Chao Hu Lake (RQ = 0.42) of DiBP showed medium risk. Meanwhile, the above water and sediment samples (RQ＜0.1) of DnOP showed low risk.

Metagenomic views on taxonomic and functional profiles of the Himalayan Tsomgo cold lake and unveiling its deterzome potential.

Cold habitat is considered a potential source for detergent industry enzymes. This study aims at the metagenomic investigation of Tsomgo lake for taxonomic and functional annotation, unveiling the deterzome potential of the residing microbiota at this site. The present investigation revealed molecular profiling of microbial community structure and functional potential of the high-altitude Tsomgo lake samples of two different temperatures, harvested during March and August. Bacteria were found to be the most dominant phyla, with traces of genomic pieces of evidence belonging to archaea, viruses, and eukaryotes. Proteobacteria and Actinobacteria were noted to be the most abundant bacterial phyla in the cold lake. In-depth metagenomic investigation of the cold aquatic habitat revealed novel genes encoding detergent enzymes, amylase, protease, and lipase. Further, metagenome-assembled genomes (MAGs) belonging to the psychrophilic bacterium, Arthrobacter alpinus, were constructed from the metagenomic data. The annotation depicted the presence of detergent enzymes and genes for low-temperature adaptation in Arthrobacter alpinus. Psychrophilic microbial isolates were screened for lipase, protease, and amylase activities to further strengthen the metagenomic findings. A novel strain of Acinetobacter sp. was identified with the dual enzymatic activity of protease and amylase. The bacterial isolates exhibited hydrolyzing activity at low temperatures. This metagenomic study divulged novel genomic resources for detergent industry enzymes, and the bacterial isolates secreting cold-active amylase, lipase, and protease enzymes. The findings manifest that Tsomgo lake is a potential bioresource of cold-active enzymes, vital for various industrial applications.

Plastisphere in lake waters: Microbial diversity, biofilm structure, and potential implications for freshwater ecosystems

Once dispersed in water, microplastic (MP) particles are rapidly colonised by aquatic microbes, which can adhere and grow onto solid surfaces in the form of biofilms. This study provides new insights on microbial diversity and biofilm structure of plastisphere in lake waters. By combining Fourier Confocal Laser Scanning Microscopy (CLSM), Transform Infrared Spectroscopy (FT-IR) and high-throughput DNA sequencing, we investigated the microbial colonization patterns on floating MPs and, for the first time, the occurrence of eukaryotic core members and their possible relations with biofilm-forming bacterial taxa within the plastisphere of four different lakes. Through PCR-based methods (qPCR, LAMP-PCR), we also evaluated the role of lake plastisphere as long-term dispersal vectors of potentially harmful organisms (including pathogens) and antibiotic resistance genes (ARGs) in freshwater ecosystems. Consistent variation patterns of the microbial community composition occurred between water and among the plastisphere samples of the different lakes. The eukaryotic core microbiome was mainly composed by typical freshwater biofilm colonizers, such as diatoms (Pennales, Bacillariophyceaea) and green algae (Chlorophyceae), which interact with eukaryotic and prokaryotic microbes of different trophic levels. Results also showed that MPs are suitable vectors of biofilm-forming opportunistic pathogens and a hotspot for horizontal gene transfer, likely facilitating antibiotic resistance spread in the environments.

Mapping Archaeal Diversity in Soda Lakes by Coupling 16S rRNA PCR-DGGE Analysis with Remote Sensing and GIS Technology

The haloarchaeal diversity of four hypersaline alkaline lakes from the Wadi El-Natrun depression (Northern Egypt) was investigated using culture-independent polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) of 16S rRNA gene phylotypes, which was combined with remote sensing and geographic information system (GIS) data to highlight the distribution pattern of the microbial diversity in water and sediment samples. The majority of archaeal sequences identified in all four lakes belonged to the phyla Euryarchaeota and Crenarchaeota. Sediment samples from Beida Lake and water samples from El-Hamra Lake showed the highest levels of archaeal diversity. Sequence similarities ≥ 95% were found between six of the acquired clones and uncultured Halorhabdus, Euryarchaeota, and archaeon clones. In addition, two clones shared a high level of sequence similarity (97%) with unclassified archaea, while other nine clones exhibited 96% to 99% sequence similarity with uncultured archaeon clones, and only one clone showed 97% identity with an uncultured Crenarchaeota. Likewise, 7 DGGE bands presented a sequence similarity of 90 to 98% to Halogranum sp., Halalkalicoccus tibetensis, Halalkalicoccus jeotgali, uncultured Halorubrum, Halobacteriaceae sp., or uncultured haloarchaeon. In conclusion, while the variety of alkaliphilic haloarchaea in the examined soda lakes was restricted, the possibility of uncovering novel species for biotechnological applications from these extreme habitats remains promising.

Ubiquity and Diversity of Cold Adapted Denitrifying Bacteria Isolated From Diverse Antarctic Ecosystems.

Nitrogen cycle has been poorly investigated in Antarctic ecosystems. In particular, how extreme conditions of low temperature, dryness, and high radiation select the microorganisms involved in the cycle is not yet understood. Denitrification is an important step in the nitrogen cycle in which nitrate is reduced stepwise to the gases NO, N2O, and N2. Denitrification is carried out by a wide group of microorganisms spread in the phylogenetic tree. The aim of this work was to isolate and characterize denitrifying bacteria present in different cold environments from Antarctica. Bacterial isolates were obtained from lake, meltwater, sea, glacier ice, ornithogenic soil, and penguin feces samples from King George Island, Fildes peninsula in the Antarctic. Samples were taken during the deicing season in five sampling campaigns. From all the samples we were able to isolate denitrifying strains. A total of 199 bacterial isolates with the capacity to grow in anaerobic mineral media reducing nitrate at 4°C were obtained. The characterization of the isolates by 16S rRNA gene sequence analysis showed a high predominance of the genus Pseudomonas, followed by Janthinobacterium, Flavobacterium, Psychrobacter, and Yersinia. Other minor genera detected were Cryobacterium, Iodobacter, Kaistella, and Carnobacterium. The capacity to denitrify was not previously described for most of the bacteria related to our isolates and in many of them denitrifying genes were not present suggesting the presence of new genes in this extreme environment. Our work demonstrates the ubiquity of denitrification in the Maritime Antarctica and gives important information linking denitrification at cold temperature with taxa in an unequivocal way.

Ecology of Methanonatronarchaeia.

Methanonatronarchaeia represents a deep-branching phylogenetic lineage of extremely halo(alkali)philic and moderately thermophilic methyl-reducing methanogens belonging to the phylum Halobacteriota. It includes two genera, the alkaliphilic Methanonatronarchaeum and the neutrophilic Ca. Methanohalarchaeum. The former is represented by multiple closely related pure culture isolates from hypersaline soda lakes, while the knowledge about the latter is limited to a few mixed cultures with anaerobic haloarchaea. To get more insight into the distribution and ecophysiology of this enigmatic group of extremophilic methanogens, potential activity tests and enrichment cultivation with different substrates and at different conditions were performed with anaerobic sediment slurries from various hypersaline lakes in Russia. Methanonatronarchaeum proliferated exclusively in hypersaline soda lake samples mostly at elevated temperature, while at mesophilic conditions it coexisted with the extremely salt-tolerant methylotroph Methanosalsum natronophilum. Methanonatronarchaeum was also able to serve as a methylotrophic or hydrogenotrophic partner in several thermophilic enrichment cultures with fermentative bacteria. Ca. Methanohalarchaeum did not proliferate at mesophilic conditions and at thermophilic conditions it competed with extremely halophilic and moderately thermophilic methylotroph Methanohalobium, which it outcompeted at a combination of elevated temperature and methyl-reducing conditions. Overall, the results demonstrated that Methanonatronarchaeia are specialized extremophiles specifically proliferating in conditions of elevated temperature coupled with extreme salinity and simultaneous availability of a wide range of C1 -methylated compounds and H2 /formate.

Potentially toxic elements contamination, risk assessment via consumption, and spatial distribution of pollution and evaluation indices in the alpine lakes, Pakistan

ABSTRACT The current study investigated potentially toxic elements (PTE) contaminations in the water of alpine lakes of Gilgit-Baltistan, Northern Pakistan. Water samples (n = 46) of various alpine lakes were collected and analysed for PTE determination through atomic absorption spectroscopy (AAanalyst 700, PerkinElmer, USA). Arsenic (As) in water was measured using a mercury hydride generation system. PTE concentrations in water of alpine lakes were observed below the upper limit of the world health organisation (WHO) drinking water guidelines, except for iron (Fe, 14%), chromium (Cr, 10%), and As (2%) of samples. The highest mean concentrations of Fe (233 ± 22.4 µg/L) and Cr (36.3 ± 4.20 µg/L) were noted in the water of Rama Lake and the As (6.20 ± 0.65 µg/L) in the Lower Kachura Lake. PTE concentrations in the water of alpine lakes was evaluated for the elements pollution index (EPI), elements evaluation index (EEI), and risk indices. The values of EPI and EEI for PTE in the water of alpine lakes were found far below the threshold limits. Higher mean chronic daily intake (CDI) values were observed for Fe and zinc (6.67 ± 1.09 and 4.95 ± 2.65 µg/kg-day) in the Rama and Upper Kachura Lakes, respectively. Determined hazard quotient (HQ) values for PTE were noted as> 1. However, the HQ value for As was (1.4 ± 0.06) which may have a detrimental effect on the health of children. Cancer risk of As and HQ values for other elements were found within the allowable limits of consumption in drinking water. Statistical analysis revealed that geogenic sources are the main PTE contaminations contributors in the water of alpine lakes.

Modern Pollen Assemblages From Lake Sediments and Soil in East Siberia and Relative Pollen Productivity Estimates for Major Taxa

Modern pollen–vegetation–climate relationships underpin palaeovegetation and palaeoclimate reconstructions from fossil pollen records. East Siberia is an ideal area for investigating the relationships between modern pollen assemblages and near natural vegetation under cold continental climate conditions. Reliable pollen-based quantitative vegetation and climate reconstructions are still scarce due to the limited number of modern pollen datasets. Furthermore, differences in pollen representation of samples from lake sediments and soils are not well understood. Here, we present a new pollen dataset of 48 moss/soil and 24 lake surface-sediment samples collected in Chukotka and central Yakutia in East Siberia. The pollen–vegetation–climate relationships were investigated by ordination analyses. Generally, tundra and taiga vegetation types can be well distinguished in the surface pollen assemblages. Moss/soil and lake samples contain generally similar pollen assemblages as revealed by a Procrustes comparison with some exceptions. Overall, modern pollen assemblages reflect the temperature and precipitation gradients in the study areas as revealed by constrained ordination analysis. We estimate the relative pollen productivity (RPP) of major taxa and the relevant source area of pollen (RSAP) for moss/soil samples from Chukotka and central Yakutia using Extended R-Value (ERV) analysis. The RSAP of the tundra-forest transition area in Chukotka and taiga area in central Yakutia are ca. 1300 and 360 m, respectively. For Chukotka, RPPs relative to both Poaceae and Ericaceae were estimated while RPPs for central Yakutia were relative only to Ericaceae. Relative to Ericaceae (reference taxon, RPP = 1), Larix, Betula, Picea, and Pinus are overrepresented while Alnus, Cyperaceae, Poaceae, and Salix are underrepresented in the pollen spectra. Our estimates are in general agreement with previously published values and provide the basis for reliable quantitative reconstructions of East Siberian vegetation.

The glacial–terrestrial–fluvial pathway: A multiparametrical analysis of spatiotemporal dissolved organic matter variation in three catchments of Lake Nam Co, Tibetan Plateau

The Tibetan Plateau (TP) is a sensitive alpine environment of global importance, being Asia's water tower, featuring vast ice masses and comprising the world's largest alpine grasslands. Intensified land-use and pronounced global climate change have put pressure on the environment of the TP. We studied the tempo-spatial variability of dissolved organic matter (DOM) to better understand the fluxes of nutrients and energy from terrestrial to aquatic ecosystems in the TP. We used a multiparametrical approach, based on inorganic water chemistry, dissolved organic carbon (DOC) concentration, dissolved organic matter (DOM) characteristics (chromophoric DOM, fluorescence DOM and δ13C of DOM) in stream samples of three catchments of the Nam Co watershed and the lake itself. Satellite based plant cover estimates were used to link biogeochemical data to the structure and degradation of vegetation zones in the catchments. Catchment streams showed site-specific DOM signatures inherited from glaciers, wetlands, groundwater, and Kobresia pygmaea pastures. By comparing stream and lake samples, we found DOM processing and unification by loss of chromophoric DOM signatures and a change towards an autochthonous source of lake DOM. DOM diversity was largest in the headwaters of the catchments and heavily modified in terminal aquatic systems. Seasonality was characterized by a minor influence of freshet and by a very strong impact of the Indian summer monsoon on DOM composition, with more microbial DOM sources. The DOM of Lake Nam Co differed chemically from stream water samples, indicating the lake to be a quasi-marine environment in regards to the degree of chemical modification and sources of DOM. DOM proved to be a powerful marker to elucidate consequences of land use and climatic change on biogeochemical processes in High Asian alpine ecosystems.

Algal Diversity of a Freshwater Lake of Tumkur City, Karnataka, India

Water is a universal solvent, where almost all the living being’s carry out their biochemical reactions. Fresh water usually contains nutrients for all types of microorganisms, one of which, algae found commonly inlakes. Phosphorous and nitrates are the principal nutrient for algae. The study of algal diversity in freshwater is very useful to determine quality of water and nature of aquatic ecosystem. Amanikere lake inTumakuru city is one of the major lakes to receive residential sewage. Water samples were collected for thestudy of diversity of algae from June, 2017 to May, 2018. The algal samples were isolated and identifiedusing standard laboratory method of Clesceri et al., (1998). About 38 species of algae were found in randomly selected areas (1 to 6) of water samples of Amanikere lake. Some of the algae found to be in high in Amanikere lake like Cyanophyceae – Oscillatoria, Nostoc, Anabaena., Chlorophyceae – Spirogyra, CosmeriumandBacillariophyceae – Navicula, Diatoma, Fragellaria. The study carried out reveals a diversity of algae in the lake.

A detailed study of diatoms a Bacillariophyta community from Rewalsar and Prashar lakes of Himachal Pradesh, their bio-monitoring characteristics and forensic significance

Diatoms are ubiquitous, unicellular, siliceous walled, aquatic, autotrophic in nature and a part ofBacillariophyceae class of algae. Diatoms are ecologically very much helpful. They act as a very good Biomonitoring agents. Their sensitive character towards the environmental factors makes them a monitor.Diatoms shows their affect towards temperature, chloride content, Ammonia and Biochemical oxygendemand quantity. The species are studied from water samples of Rewalsar and Prashar lakes of HimachalPradesh. Diatoms are utilized by forensic investigators in solving the drowning cases occurred due toaccidental or by suicidal modes. So these diatoms are very significant even with forensic angle.

Influence of DNA extraction kits on freshwater fungal DNA metabarcoding.

BackgroundEnvironmental DNA (eDNA) metabarcoding is a common technique for efficient biodiversity monitoring, especially of microbes. Recently, the usefulness of aquatic eDNA in monitoring the diversity of both terrestrial and aquatic fungi has been suggested. In eDNA studies, different experimental factors, such as DNA extraction kits or methods, can affect the subsequent analyses and the results of DNA metabarcoding. However, few methodological studies have been carried out on eDNA of fungi, and little is known about how experimental procedures can affect the results of biodiversity analysis. In this study, we focused on the effect of DNA extraction method on fungal DNA metabarcoding using freshwater samples obtained from rivers and lakes.MethodsDNA was extracted from freshwater samples using the DNeasy PowerSoil kit, which is mainly used to extractmicrobial DNA from soil, and the DNeasy Blood & Tissue kit, which is commonly used for eDNA studies on animals. We then compared PCR inhibition and fungal DNA metabarcoding results; i.e., operational taxonomic unit (OTU) number and composition of the extracted samples.ResultsNo PCR inhibition was detected in any of the samples, and no significant differences in the number of OTUs and OTU compositions were detected between the samples processed using different kits. These results indicate that both DNA extraction kits may provide similar diversity results for the river and lake samples evaluated in this study. Therefore, it may be possible to evaluate the diversity of fungi using a unified experimental method, even with samples obtained for diversity studies on other taxa such as those of animals.

The analysis of volcanic brines by freezing stage tandem LIBS-ICP-MS

Volcanic crater lakes pose unique hazards to the local population both during eruption and quiescence. The composition of crater lake fluids is therefore commonly monitored to aid hazard prediction and mitigation. Some of these fluids, such as at Kawah Ijen in Indonesia and Poas in Costa Rica, are hyper-acidic, concentrated brines (SO4–5 wt%, Cl - 2.5 wt%, Al - 5000 ppm). Analysis of such fluids requires extreme dilution due to the high total dissolved element load, which risks contamination and precipitate formation. To circumvent this undesired sample preparation and speed up the turn-around time on the analysis, we tested approaches which involved freezing the fluids to −30 °C and analysing them by simultaneous Laser Ablation-Inductively Coupled Plasma Quadrupole Mass Spectrometry (LA-ICP-QMS) and Laser-Induced Breakdown Spectroscopy (LIBS). LIBS is highly matrix sensitive, requiring matrix-matched reference materials. At the same time, LA-ICP-MS owes its success to being relatively insensitive to the matrix after accounting for differences in ablation yield. Analysing the fluids as a solid and sampling them by laser circumvents the usual dilution step. Fluid reference materials were prepared by adding the elements of interest to one of the crater lake fluid samples at known, but varying concentrations and by stepwise dilution of one of these fluids. Differences in ablation yield, resulting mainly from variations in the coupling of the laser with the sample, were accounted for by adding a known quantity of lithium as an internal standard. Working curves for both ICP-MS and LIBS were obtained for Al, Mg, Fe, Ca, K, Na, S and Cl, yielding relative trueness values for 4 crater lake samples of known composition of Al-7%, Ca-5%, Fe-1%, K < 1%, Mg-4%, Na-5%, S-3%, and Cl-6% for ICP-MS and Al-2%, Ca-9%, Fe-17%, K-10%, Mg-4%, Na < 1%, S-8%, and Cl-9% for LIBS. For these elements, ranging in concentration from around 400 mg/kg to 25 g/kg, LIBS yielded similar trueness results to ICP-MS. LIBS calibration without an internal standard produces acceptable results for Li only, allowing the cryo-LIBS to analyse the major elements while optimising the ICP-MS for trace-element analysis and obtaining a full suite of elements simultaneously without the need for sample dilution.

Estimating phytoplankton stoichiometry from routinely collected monitoring data.

Accurately estimating the elemental stoichiometry of phytoplankton is critical for understanding biogeochemical cycles. In laboratory experiments, stoichiometric ratios vary among species and with changes in environmental conditions. Field observations of total phosphorus (P) and total nitrogen (N) collected at regional and national scales can supplement and expand insights into factors influencing phytoplankton stoichiometry, but analyses applied to these data can introduce biases that affect interpretations of the observed patterns. We introduce an analytical approach for estimating the ratio between phytoplankton N and P from the particulate fraction of nutrient pools in lake samples. We use Bayesian models to represent observations of particulate P and N as the sum of contributions from nutrients bound within phytoplankton and nutrients associated with non-phytoplankton suspended sediment. Application of this approach to particulate nutrient data collected in Missouri impoundments yields estimates of the mass ratio of N:P in phytoplankton ranging from 8-10 across a variety of lakes and seasons. N:P in particulate matter ranged from 6 to 70, a variability driven by differences in nutrients bound to non-phytoplankton suspended sediment. We adapted the Bayesian models to estimate N:P using more commonly available measurements of total P and total N and applied this model to a continental-scale monitoring data set. We compared phytoplankton nutrient content estimated from the two analyses and found that when datasets lack direct measurements of particulate nutrient concentrations, the model estimate of phytoplankton nutrient content includes contributions from nutrients within phytoplankton and dissolved nutrients that are associated with changes in phytoplankton biomass.

Ecological Study of an Artificial Saline Lake Ecosystem in Wadi Al-Shatti, Libya

This study provided the first data related to the ecosystem of Ain Al-Mashashiya Lake. It is likely the new apperance of a saline artificial lake formed from agricultural drainage water from surounded local farms, small lakes provide an opportunity to understand intra-ecosystem connectivity and its dynamics. Water samples were collected representing two stations along edges and at the middle of the lake and other samples surrounded soil and vegetation. Lake depth was &gt; 5 meters, the pH was found to be relatively high at edge of the lake (7.46 &amp; 7.44) compared to at middle of the lake (7.38 &amp; 7.32). Highly saline water, i.e., 129.79 &amp; 125.48 dS/m &amp; 126.82 &amp; 133.74 dS/m at edge and middle of the lake respectively. The average level of PO4 and NO3 during winter is slightly lower than summer. The water cations abundances were typically Na &gt; K &gt; Ca &gt; Mg, where were for anions, Cl &gt; SO4 &gt; HCO3 &gt; PO4 &gt; NO3. The lake is valuable for biodiversity and provide habitat for many species. Five phytoplankton types have been registered, i.e., Cocconeis, Notholca Pandorina, Oscillatoria, Chlamydomonas. The most common species were Pandorina &amp; Oscillatoria. Soils of the study zone were classified as sandy loam, with a porosity of 44.53%. and saturated hydraulic conductivity (Ks) values was 4×10-3 cm/h and 6.4% of OM content. The soil reaction (pH) was 7.24 and its EC value was 19.42 dS/m that indicated high saline affected soil. The concentrations of Na, Ca &amp; Mg, were as high as 193, 48 &amp; 14.4 mg/kg, respectively, with low NO3 content 0.293 mg/kg. Tamarix (Tamarix aphylla) commonly found along the lake edges. The dry desert climate of the area played a main role in imposing the lake ecosystems.

Sub-Bottom Profiler and Side Scan Sonar investigations, with the assistance of hydrochemical and isotopic analysis of Sawa Lake, Al-Muthana Governorate, Southern Iraq

A marine geophysical survey are including Sub Bottom Profilers and Side Scan Sonar integrating with under-water imagery, as well as hydrochemical and isotopic investigations have been carried out for Sawa Lake, one of the unique, shallow and closed water body in Iraq. The results showed that the depth of the Lake is shallow, ranged between 1 m in areas near the edges of the Lake and 2 m in the Lake center. The Recharge site has been detected exactly (this is a first recording (Nov. 2012)), as a hole. It has a longitudinal an axis of 50 m with NW-SE tren, which resembles the trending of the longitudinal axis of the Lake and Abu-Jir fault trending. The maximum width of this hole ranging from 23.0-29.5 m. The hole depth about 20 m, but may be greater then, because the emergence of a high proportion of noise in the geophysical sections. The Lake bottom is homogeneity and does not has any diacritical features. Also, the results showed discontinuous layers on either side of the hole due to the existance a number of caves under the bottom of the Lake extends into several meters with different dimensions and forms. Hydrochemical analysis of the water samples collected from different depths inside the hole by scientific diving with specefic equibments and the result showed that the water is NaCl type, with domination of Mg and Cl over Ca and SO4. The Stiff diagram, detected that very high TDS arising mainly from sodium and chloride, it is mostly typical marine water. Values of δ18O and δ2H in water samples of Sawa Lake, when plotted along the global meteoric water line shows that the three collected water samples from the lake, which have a similar isotopic composition, indicating that all of them are receiving water from the same flow zones, with diffuse recharge type. Also, the isotopic parameter showed that the Sawa lake water suffering from strong evaporation.

Anthropogenic rare earth elements in urban lakes: Their spatial distributions and tracing application

Anthropogenic activities associated with various new technologies are increasingly disrupting the geochemical cycles of rare earth elements (REEs). For example, samarium (Sm) and gadolinium (Gd) have emerged as microcontaminants in the natural waters of developed areas. Surface water samples of 13 urban lakes were collected in Wuhan, the largest city in central China, with a population of over 11 million. The aim of this study was to examine to what extent REE anomalies occur and the relationship between the concentration of anthropogenic REEs in lakes and the surrounding environment. In this study, based on land-use type and point of interest (POIs) data, buffer extraction, density estimation and Spearman correlation analysis were first proposed to identify different sources of anthropogenic REEs, which mainly included hospitals, factories, population, urban land and cropland. The PAAS-normalized REE patterns indicate that all lake samples display pronounced positive Sm and Gd anomalies, ranging from 5.92 to 19.88 and 1.73 to 14.97, respectively. Spearman correlation analysis showed that hospital density was positively correlated with anthropogenic Gd concentration, and a positive relationship between proportion of cropland and the concentration of anthropogenic Sm. By utilizing Gdanth, Smanth, and the conventional ion ratio (NO3−/Cl−), a three-dimensional tracer system was established, and the system accurately obtained a characterization of the impact of WWTPs, hospitals, factories and agriculture on the lakes. Moreover, the results from this hydrochemical method were consistent with the analysis of geographic information systems, which indicated that this anthropogenic contaminant as a tracer was reliable for analysing the source of urban water pollution.