Application of the Isolation Forest Algorithm to Substantiate the Uniqueness of Water Bodies in the Group of Karst Lakes

Improving the scientific foundations for the development and expansion of the network of specially protected natural areas requires the search for algorithms that could be used to identify unique ecosystems. Algorithmization of the anomaly identification process provides an opportunity not only to process large amounts of data but also leads to obtaining objective and comparable estimates. The purpose of this research is to identify the most optimal mechanisms for identifying anomalous values for the morphometric characteristics of karst lakes, which may indicate the uniqueness of the entire lake ecosystem. Within the framework of this article, the study was carried out based on a mathematical analysis of samples built for various characteristics based on the WORLDLAKE database. Statistical methods and the Isolation Forest (iForest) machine learning algorithm were used as methods of analysis. As a result of applying the iForest algorithm to a sample of morphometric parameters of karst lakes, consisting of 738 objects, 43 anomalous water bodies were identified. An expert assessment of the final set of lakes for the uniqueness of their ecosystems showed that the chosen method for identifying anomalous values is well suited for the task at hand. Many lakes with an anomaly index above 60% can be recognized as unique due to the unusualness of their abiotic characteristics; a number of them also have a peculiar biota. The anomalous objects included such well-known lakes as Tserik-Kol’, Crveno, Salda Lake, Trihonida, Vegoritida, Petron, etc. Moreover, for most of them, anomalies were detected for several parameters at once. Thus, the applied algorithm for identifying anomalous morphometric characteristics of lakes made it possible to obtain interesting samples for further expert analysis of the entire lake ecosystem for its uniqueness.

TRACES OF HIGH SEISMIC ACTIVITY IN THE UPPERMOST SEDIMENTS OF LAKE BAIKAL, SIBERIA

Sedimentation in Lake Baikal is significantly affected by continuous seismic activity in the Baikal Rift Zone. Our study shows that historical earthquakes, as well as recent seismic events, considerably influenced sedimentation in this deep tectonic basin. Here we present some of the results of extensive international research activities during the period of 1996–2019. To identify traces of seismic events in the uppermost sediments (<1.5 m), short cores were recovered from many coring stations throughout the entire lake. Based on lithological descriptions, measurements of magnetic susceptibility, and concentration of inorganic and organic components, we identified earthquake indicators in the sediment cores. Impacts of historical earthquakes were traced within South Baikal (near the Sharyzhalgai Station and the Station 106-km of the Circum-Baikal railway, hereafter CBR) and Proval Bay (near the Selenga River delta).

Ciprofloxacin Effects On Nitrogren Cycling Processes In Freshwater Aquatic Sediments

Four experiments were designed to assess the effect of ciprofloxacin (cipro) on the function of microbial populations in freshwater environments, specifically on nitrogen cycling. Cipro is a broad-spectrum fluoroquinolone antibiotic used in the treatment of both human and veterinary pathogenic diseases. Previous studies reported the presence of cipro in aquatic environments. This study investigates whether cipro has adverse effects on environmental bacteria which perform critical ecosystem processes associated with the nitrogen cycle. Microcosms containing sediment and synthetic lake water were amended with a series of environmentally relevant concentrations of cipro ranging from 0.5 to 2.5 mg cipro per kg of sediment. Nitrogen cycling processes including nitrification, denitrification and ammonification were measured using a combination of flux measurements (NH4+, NO3-, NO2-), stable isotope techniques ( 15[superscript]N NO₃- dilution) and changes in N₂:Ar and O₂:Ar using Membrane Isotope Mass Spectroscopy (MIMS). Results indicate that cipro has a dose-dependent effect on nitrification, while denitrification is dependent on nitrate availability and may be stimulated by cipro. Ammonification and respiration were not affected at these concentrations. Impacts on nitrification and denitrification are likely to be realized only at the highest concentrations measured in the environment. At the lower end of the environmentally relevant concentration range, observed impacts are not likely to be ecologically important, especially when averaged over an entire lake ecosystem.

Ciprofloxacin Effects On Nitrogren Cycling Processes In Freshwater Aquatic Sediments

Four experiments were designed to assess the effect of ciprofloxacin (cipro) on the function of microbial populations in freshwater environments, specifically on nitrogen cycling. Cipro is a broad-spectrum fluoroquinolone antibiotic used in the treatment of both human and veterinary pathogenic diseases. Previous studies reported the presence of cipro in aquatic environments. This study investigates whether cipro has adverse effects on environmental bacteria which perform critical ecosystem processes associated with the nitrogen cycle. Microcosms containing sediment and synthetic lake water were amended with a series of environmentally relevant concentrations of cipro ranging from 0.5 to 2.5 mg cipro per kg of sediment. Nitrogen cycling processes including nitrification, denitrification and ammonification were measured using a combination of flux measurements (NH4+, NO3-, NO2-), stable isotope techniques ( 15[superscript]N NO₃- dilution) and changes in N₂:Ar and O₂:Ar using Membrane Isotope Mass Spectroscopy (MIMS). Results indicate that cipro has a dose-dependent effect on nitrification, while denitrification is dependent on nitrate availability and may be stimulated by cipro. Ammonification and respiration were not affected at these concentrations. Impacts on nitrification and denitrification are likely to be realized only at the highest concentrations measured in the environment. At the lower end of the environmentally relevant concentration range, observed impacts are not likely to be ecologically important, especially when averaged over an entire lake ecosystem.

Assessing Water Withdrawals in Scarce-Data Transboundary Areas by Use of Dynamic Precipitation–Flow Relationships: The Case of the Hasbani River Basin

The present study proposes a nonstandard solution to the problem of assessing water withdrawals (AWW) in the scarce-data transboundary basin. The applied AWW method operates with the open-source available data on precipitation and river flow and thereby overcomes the usual restriction due to lack of data on shared water use in the Middle East. Analysis of dynamic precipitation-flow relationships enable to separate the effect of water withdrawals from the total decline of river flow under the decreasing precipitation. This study is the first which provides complete information (1972–2020) on water withdrawals from total, surface, and base flow of the Hasbani River (Lebanon). The resulting values that exceed by far earlier published estimates were confirmed by (i) indirect indices (area of irrigated land and population), and (ii) validation of the AWW method based on independent data on water use (Israel Water Authority). The study results are useful for water balance estimations, as well as for management of water resources in the Jordan River headwaters basin and in the entire Lake Kinneret Basin. The AWW method can be applied to other transboundary basins and enables historical and real-time monitoring of water withdrawals as a necessary database for settlement of riparian water relations.

The ice cover shapes the spatial and temporal characteristics of water quality in Hulun Lake during winter

Being the largest boreal steppe lake in Northeast China, Hulun Lake has been characterized by eutrophication induced by abnormally high organic matter. This work investigated therefore the physicochemical and water quality parameters of Hulun Lake, and that of the inflowing Crulen River and Orshen River through winter, to reveal the spatial and temporal characteristics of water quality without impact of algal bloom, atmospheric deposition, wind or allochthonous nutrient input. Results showed that the prevention of wind-induced sedimentary resuspension accompanied with the minimized volume of tributary inflows is supposed to predominate the eutrophication alleviation. The formation of ice cover had a slight concentrative effect on water ion content. However, ice cover resulted in an increasingly homogenous distribution of phosphorus and oxygen-depleting organic matter over the entire lake. The two headwater streams demonstrated limited impact on water quality in estuaries in winter without showing evident coordination in upstream water nutrient level. It is suggested that the prevention of wind disturbance by ice cover and the subsequently modified hydrodynamic and water ecological processes are the determinant factors on water quality in Hulun Lake during winter.

First insights into the diversity of gill monogeneans of‘Gnathochromis’andLimnochromis(Teleostei, Cichlidae) in Burundi: do the parasites mirror host ecology and phylogenetic history?

Monogenea is one of the most species-rich groups of parasitic flatworms worldwide, with many species described only recently, which is particularly true for African monogeneans. For example,Cichlidogyrus, a genus mostly occurring on African cichlids, comprises more than 100 nominal species. Twenty-two of these have been described from Lake Tanganyika, a famous biodiversity hotspot in which many vertebrate and invertebrate taxa, including monogeneans, underwent unique and spectacular radiations. Given their often high degrees of host specificity, parasitic monogeneans were also used as a potential tool to uncover host species relationships. This study presents the first investigation of the monogenean fauna occurring on the gills of endemic ‘Gnathochromis’ species along the Burundese coastline of Lake Tanganyika. We test whether their monogenean fauna reflects the different phylogenetic position and ecological niche of‘Gnathochromis’ pfefferiandGnathochromis permaxillaris. Worms collected from specimens ofLimnochromis auritus, a cichlid belonging to the same cichlid tribe asG. permaxillaris, were used for comparison. Morphological as well as genetic characterisation was used for parasite identification. In total, all 73Cichlidogyrusindividuals collected from ‘G.’ pfefferiwere identified asC. irenae. This is the only representative ofCichlidogyruspreviously described from‘G.’ pfefferi, its type host.Gnathochromis permaxillarisis infected by a species ofCichlidogyrusmorphologically very similar toC. gillardinae. The monogenean species collected fromL. auritusis considered as new for science, but sample size was insufficient for a formal description. Our results confirm previous suggestions that‘G.’ pfefferias a good disperser is infected by a single monogenean species across the entire Lake Tanganyika. AlthoughG. permaxillarisandL. auritusare placed in the same tribe,Cichlidogyrussp. occurring onG. permaxillarisis morphologically more similar toC. irenaefrom‘G.’ pfefferi, than to theCichlidogyrusspecies found onL. auritus. Various evolutionary processes, such as host-switching or duplication events, might underlie the pattern observed in this particular parasite-host system. Additional samples for theCichlidogyrusspecies occuring onG. permaxillarisandL. auritusare needed to unravel their evolutionary history by means of (co-)phylogenetic analyses.

Biogeochemical processes controlling density stratification in an iron-meromictic lake

Biogeochemical processes and mixing regime of a lake can control each other mutually. The prominent case of iron meromixis is investigated in Waldsee near Doebern, a small lake that originated from surface mining of lignite. From a four years data set of monthly measured electrical conductivity profiles, we calculated summed conductivity as a quantitative variable reflecting the amount of electro-active substances in the entire lake. Seasonal variations followed changing chemocline height. Coinciding changes of electrical conductivities in the monimolimnion indicated that a considerable share of substances, precipitated by the advancing oxygenated epilimnion, re-dissolved in the remaining anoxic deep waters and contributed considerably to the density stratification. In addition, we constructed a lab experiment, in which aeration of monimolimnetic waters removed iron compounds and organic material. Precipitates could be identified by visual inspection. Introduced air bubbles ascended through the water column and formed a water mass similar to the mixolimnetic Waldsee water. The remaining less dense water remained floating on the nearly unchanged monimolimnetic water. In conclusion, iron meromixis as seen in Waldsee did not require two different sources of incoming waters, but the inflow of iron rich deep groundwater and the aeration through the lake surface were fully sufficient.

Are beetles good indicators of insect diversity in freshwater lakes?

The study verifies the usefulness of aquatic beetles as an indicator of biodiversity of a simple ecological system. Detailed analyses were carried out at the elementary level for the purpose of determining the significance of correlations between the biodiversity of Coleoptera and other groups of aquatic insects in single samples. The relation of selected taxa to selected habitats of the lake Wukśniki (north-eastern Poland) was also investigated. Moreover, the possibility of application of biodiversity surrogates, i.e. higher taxonomic units (genera and orders), in the determination of biodiversity was examined. A significant high correlation was determined between Coleoptera and the total remaining taxa (RR - Remaining Richness) in samples collected in the entire lake. The correlation has the highest value at the species level. The complementarity analysis reveals that the percentage contribution of Coleoptera in the overall biodiversity of the lake is similarly high at the species and genus level, and substantially lower at the family level. In accordance with the hypothesis, aquatic beetles can be used as indicators of the overall biodiversity of insects in the ecosystem of a mesotrophic lake. Biodiversity surrogates, i.e. higher taxonomic units (genera and families), can be applied instead of the species level.