First Observation of Unicellular Organisms Concentrating Arsenic in ACC Intracellular Inclusions in Lake Waters

In unicellular organisms, intracellular inclusions of amorphous calcium carbonate (ACC) were initially described in cyanobacteria and, later, in unicellular eukaryotes from Lake Geneva (Switzerland/France). Inclusions in unicellular eukaryotes, named micropearls, consist of hydrated ACCs, frequently enriched in Sr or Ba, and displaying internal oscillatory zonations, due to variations in the Ba:Ca or Sr:Ca ratios. An analysis of our database, consisting of 1597 micropearl analyses from Lake Geneva and 34 from Lake Titicaca (Bolivia/Peru), showed that a certain number of Sr- and Ba-enriched micropearls from these lakes contain As in amounts measurable by EDXS. A Q-mode statistical analysis confirmed the existence of five chemically distinct morpho-chemical groups of As-bearing micropearls, among which was a new category identified in Lake Geneva, where As is often associated with Mg. This new type of micropearl is possibly produced in a small (7–12 μm size) bi-flagellated organism. Micropearls from Lake Titicaca, which contain Sr, were found in an organism very similar to Tetraselmis cordiformis, which was observed earlier in Lake Geneva. Lake Titicaca micropearls contain larger As amounts, which can be explained by the high As concentration in the water of this lake. The ubiquity of this observed biomineralization process points to the need for a better understanding of the role of amorphous or crystalline calcium carbonates in As cycling in surface waters.

Hydroacoustic study of the basin of Biryuzovoe Karyernoe lake (Korsakovsky district, Sakhalin Island)

For the first time, the paper presents the results of a detailed hydroacoustic study of the basin of the Biryuzovoe Karyernoe Lake (Novikovo village, Korsakovsky District, Sakhalin Region), formed after the conservation of the germaniferous coal deposit of the same name. On the basis of 12 hydroacoustic profiles, a detailed bathymetric scheme of the lake was compiled, its main morphometric parameters were calculated, and the morphological appearance was described. Preliminary conclusions have been made about the rates of sedimentation within the basin of the lake, and perspective points for monitoring the dynamics of bottom and slope sedimentation have been established. Based on the results of the chemical analysis of the lake waters, a conclusion was made on the prospects of its use for tourist and recreational purposes.

Effects of Ice Freeze-Thaw Processes on U Isotope Compositions in Saline Lakes and Their Potential Environmental Implications

The dissolved uranium (U) content in the water column of saline lakes varies little between ice-free seasons throughout the whole water column. Such uniformity allows for the potential absolute dating and/or paleohydrologic interpretations of lake sediments and biogenic shell materials using U isotopes. Before using these methods in cold regions, however, it is necessary to evaluate the effects that ice freeze-thaw processes have on the distribution of U isotopes in saline lake waters, and to determine the amount of variation in U isotopic values when such processes occur. In this paper, we collected ice and dissolved water samples from six lakes with variable salinity in February 2021. Five groundwater and three water samples from rivers into Qinghai Lake were sampled in November 2020. The sampled water was analyzed for dissolved concentrations of 238U and the activity ratio of 234U/238U ([234U/238U]AR). The results show that the 238U concentration of ice samples was less than that of the underlying water. The [234U/238U]AR of ice in the five saline lakes was similar to that of the underlying water with less than a 10‰ variation, suggesting no observable fractionation between ice and dissolved water. Thus, the ice freeze-thaw processes have almost no effect on the uranium content and [234U/238U]AR of the sampled saline lakes, which were characterized by a limited recharge volume from surface runoff, groundwater, and ice volume, namely the close saline lake in arid alpine background. The results from the indoor freeze-thaw experiments also showed that the U isotopic composition of Qinghai Lake waters and ice were similar with the 238U concentration of the ice was about 40% of that of the dissolved lake water, supporting the data obtained from natural saline lakes. The above results provide important insights into whether it is feasible to use U isotopes for absolute dating and/or paleohydrologic analysis of lake sediments or biogenic shell materials. In addition, the results are important for evaluating the [234U/238U]AR and uranium concentrations in seawater when there exists a process of melting polar ice, and for determining the initial delta 234U variations needed for dating of coral and other fossil materials.

Forest defoliator outbreaks alter nutrient cycling in northern waters

Insect defoliators alter biogeochemical cycles from land into receiving waters by consuming terrestrial biomass and releasing biolabile frass. Here, we related insect outbreaks to water chemistry across 12 boreal lake catchments over 32-years. We report, on average, 27% lower dissolved organic carbon (DOC) and 112% higher dissolved inorganic nitrogen (DIN) concentrations in lake waters when defoliators covered entire catchments and reduced leaf area. DOC reductions reached 32% when deciduous stands dominated. Within-year changes in DOC from insect outbreaks exceeded 86% of between-year trends across a larger dataset of 266 boreal and north temperate lakes from 1990 to 2016. Similarly, within-year increases in DIN from insect outbreaks exceeded local, between-year changes in DIN by 12-times, on average. As insect defoliator outbreaks occur at least every 5 years across a wider 439,661 km2 boreal ecozone of Ontario, we suggest they are an underappreciated driver of biogeochemical cycles in forest catchments of this region.

Presencia de hormonas esteroides en el lago Titicaca y agua potable, Puno (Perú)

The presence of steroid hormones in lake waters causes contamination of aquatic ecosystems, which may cause endocrine alterations in the organisms that inhabit them. Moreover, many of these waters are purified and distributed to populations located around the lake. Therefore, these effects could be repeated in humans consuming the water. This study reports the presence of steroid hormone residues in the waters of the inner bay of Lake Titicaca and drinking water in the city of Puno (Peru). The solid phase extraction method was used for sample preparation, and the analyses were developed in an HPLC-DAD system. Results show maximum concentrations of steroid hormones estrone (E1) 1.56, 17 β- estradiol (E2) 2.27, 17 α- ethinylestradiol (EE2) 13. 88 ng L-1 respectively. These concentrations vary at the different monitoring points, and their presence could cause ecotoxicological effects to the endemic aquatic biota that inhabit this part of the lake. At the same time they also could affect the health of the human population that consumes this water

Monitoring the Influence of Anthropogenic Pollution on the Quality of Irrigation Water for Market Gardening in Yamoussoukro, Côte d’Ivoire

Background: The microbiological quality of three vegetable crops (cabbages, carrots, lettuces) and their irrigation water from the lake system of the city of Yamoussoukro were studied. The pollution indicator used is Escherichia coli (E. coli), of the thermotolerant coliform family. Methods: During the period 2017-2019, in four dry and four wet seasons, a total of 744 water samples and 13392 vegetable samples were collected in five (5) lakes belonging to the lake system. The lakes were selected because of their position in the system. The E. coli loads were evaluated after isolation on a specific COMPASS ECC Agar and confirmed with Polymerase chain reaction (PCR) and the physicochemical parameters of the lakes, evaluated according to their respective ISO standards. Result: In irrigation waters, bacterial loads and physico-chemical parameters generally have evolved from the upstream lakes to those downstream of the lake system (from lake A to lake E). Values were higher during the rainy seasons. E. coli loads on vegetables were strongly correlated with those of irrigation water, especially in dry seasons. Spearman’s correlations revealed significant correlations between turbidity, DOC and bacterial loads. The risk of bacterial transmission between lake waters and surrounding vegetables is proven.

Factors Governing Biodegradability of Dissolved Natural Organic Matter in Lake Water

Dissolved Natural Organic Matter (DNOM) is a heterogeneous mixture of partly degraded, oxidised and resynthesised organic compounds of terrestrial or aquatic origin. In the boreal biome, it plays a central role in element cycling and practically all biogeochemical processes governing the physico-chemistry of surface waters. Because it plays a central role in multiple aquatic processes, especially microbial respiration, an improved understanding of the biodegradability of the DNOM in surface water is needed. Here the current study, we used a relatively cheap and non-laborious analytical method to determine the biodegradability of DNOM, based on the rate and the time lapse at which it is decomposed. This was achieved by monitoring the rate of oxygen consumption during incubation with addition of nutrients. A synoptic method study, using a set of lake water samples from southeast Norway, showed that the maximum respiration rate (RR) and the normalised RR (respiration rate per unit of carbon) of the DNOM in the lakes varied significantly. This RR is conceived as a proxy for the biodegradability of the DNOM. The sUVa of the DNOM and the C:N ratio were the main predictors of the RR. This implies that the biodegradability of DNOM in these predominantly oligotrophic and dystrophic lake waters was mainly governed by their molecular size and aromaticity, in addition to its C:N ratio in the same manner as found for soil organic matter. The normalised RR (independently of the overall concentration of DOC) was predicted by the molecular weight and by the origin of the organic matter. The duration of the first phase of rapid biodegradation of the DNOM (BdgT) was found to be higher in lakes with a mixture of autochthonous and allochthonous DNOM, in addition to the amount of biodegradable DNOM.

Lead, zinc and arsenic contamination of pit lake waters in the Zeida abandoned mine (High Moulouya, Morocco)

In the Zeida abandoned mine, pit lake waters exhibit alkaline pH and high conductivity. The concentrations of the total dissolved lead and zinc are very low due to their adsorption on clay minerals and iron oxyhydroxides. Conversely, arsenic concentrations in two lakes (ZL1 and ZA) exceeded WHO water quality guidelines. The As content is relatively high in ZL1 lake and exists mainly as As(V). In ZA lake, As(III) occurs in low concentration compared to the total dissolved arsenic, while dimethylarsenic acid [H2AsO2(CH3)2, DMA) prevails. This means that arsenic was methylated by organic matter produced by microorganisms such as chlorella. The sequential extraction of floor sediments in two lakes shows that the bioavailable arsenic contents change between the two lakes. In ZA lake, the sediments show high concentrations of lead and arsenic compared to ZL1 sediment since it is surrounded by mining waste tailings, which are rich in such chemical elements. An arsenic leaching test of ZA sediment shows that bioavailable arsenic is distributed in equal proportion between clay/carbonates, sulfide-organic matter, and iron oxides (HFO) phases, while in ZL1, most of the arsenic is linked to hydrous iron oxides (HFO).Thematic collection: This article is part of the Hydrochemistry related to exploration and environmental issues collection available at: https://www.lyellcollection.org/cc/hydrochemistry-related-to-exploration-and-environmental-issuesSupplementary material:https://doi.org/10.6084/m9.figshare.c.5545316

Preliminary Investigation on Phytoplankton Dynamics and Primary Production Models in an Oligotrophic Lake from Remote Sensing Measurements

The aim of this study is to test a series of methods relying on hyperspectral measurements to characterize phytoplankton in clear lake waters. The phytoplankton temporal evolutions were analyzed exploiting remote sensed indices and metrics linked to the amount of light reaching the target (EPAR), the chlorophyll-a concentration ([Chl-a]OC4) and the fluorescence emission proxy. The latter one evaluated by an adapted version of the Fluorescence Line Height algorithm (FFLH). A peculiar trend was observed around the solar noon during the clear sky days. It is characterized by a drop of the FFLH metric and the [Chl-a]OC4 index. In addition to remote sensed parameters, water samples were also collected and analyzed to characterize the water body and to evaluate the in-situ fluorescence (FF) and absorbed light (FA). The relations between the remote sensed quantities and the in-situ values were employed to develop and test several phytoplankton primary production (PP) models. Promising results were achieved replacing the FA by the EPAR or FFLH in the equation evaluating a PP proxy (R2 > 0.65). This study represents a preliminary outcome supporting the PP monitoring in inland waters by means of remote sensing-based indices and fluorescence metrics.

Cyanobacterial Harmful Algal Blooms in Aquatic Ecosystems: A Comprehensive Outlook on Current and Emerging Mitigation and Control Approaches

An intensification of toxic cyanobacteria blooms has occurred over the last three decades, severely affecting coastal and lake water quality in many parts of the world. Extensive research is being conducted in an attempt to gain a better understanding of the driving forces that alter the ecological balance in water bodies and of the biological role of the secondary metabolites, toxins included, produced by the cyanobacteria. In the long-term, such knowledge may help to develop the needed procedures to restore the phytoplankton community to the pre-toxic blooms era. In the short-term, the mission of the scientific community is to develop novel approaches to mitigate the blooms and thereby restore the ability of affected communities to enjoy coastal and lake waters. Here, we critically review some of the recently proposed, currently leading, and potentially emerging mitigation approaches in-lake novel methodologies and applications relevant to drinking-water treatment.