Sampling Stations Research Articles

Cytogenetic and photosynthetic responses of plants after exposure to water from a lake environment.

Plants are sensitive to environmental pollutants and are excellent organisms for genetic and physiological testing. Plant-based test systems are often used to study aquatic, aerial, and terrestrial pollution, especially Allium cepa, but studies with Tradescatia pallida specimens have gained prominence due to their sensitivity and applicability. Among the biomarkers, cytogenetic damage and chlorophyll levels are used in stress studies due to their responses to single or combined factors. The aim of this study was to evaluate cytogenetic and photosynthetic responses in T. pallida, and cytogenetic responses in A. cepa exposed to water from three sampling stations in the Juara lagoon (Municipality of Serra, ES, Brazil), collected in two sampling campaigns. The cytotoxic, genotoxic, and mutagenic potentials were analyzed using the T. pallida root tip mitosis assay and the Allium cepa test. Chloroplast pigment levels were measured in T. pallida leaves after chronic exposure to the lagoon water. The cytogenetic tests showed cytogenetic alterations at two sampling stations in at least one sampling campaign, suggesting the presence of potential pollutants, the effects of which were maximized during the rainy season. The study of photosynthetic metabolism in T. pallida showed a relationship between the levels of chloroplast pigments and the amount of nutrients present in the water.

Absolute Abundance of Dominant Freshwater Mollusks of an Irrigation Canal

Mollusks are a diverse group of invertebrates that perform fundamental ecological functions within freshwater ecosystems. This study evaluated the absolute abundance of dominant freshwater benthic mollusks in an irrigation canal, utilizing a partial count method across seven established sampling stations. Results revealed that the endemic freshwater snail (Jagora spp.) was the most abundant species, followed by golden apple snail (Pomacea spp.) and freshwater clam (Corbicula spp.), which are both invasive species. Effective monitoring and management strategies are essential to mitigate the adverse effects of the invasive species in their particular environment.

Augmenting Seafloor Characterization via Grain Size Analysis with Low-Cost Imagery: Minimizing Sediment Sampler Biases and Increasing Habitat Classification Accuracy

Bottom-grab samplers have long been the standard to describe nearshore marine habitats both qualitatively and quantitively. However, sediment samplers are designed to collect specific grain sizes and therefore have biases toward those sediments. Here, we discuss seafloor characterizations based on grain size analysis alone vs. grain size analysis augmented with quantitative benthic imagery. We also use both datasets to inform a prevalent benthic habitat classification system. The Coastal and Marine Ecological Classification Standard (CMECS) was used to test this hypothesis. CMECS was adopted by the federal government to standardize habitat classification in coastal U.S. waters. CMECS provides a hierarchal framework to define and interpret benthic habitats but does not prescribe specific sampling methods. Photography has been utilized for many decades in benthic ecology but has rarely been employed in habitat classification using CMECS. No study to date has quantitatively examined the benefit of incorporating benthic imagery into the classification of biotopes using CMECS. The objective of this study is to classify a roughly 1 km2 subtidal area within Herring Cove in Provincetown, MA with CMECS and quantify the benefit of augmenting classification with low-cost imagery. A benthic habitat survey of the study area included grab sampling for grain-size analysis and invertebrate taxonomy, benthic imagery, water quality sampling at 24 sampling stations, and acoustic mapping of the study area. Multivariate statistical analyses were employed to classify biotic communities and link environmental and biological data to classify biotopes. The results showed that benthic imagery improved the classification and mapping of CMECS components. Furthermore, the classification of habitats and biotopes was improved using benthic imagery data. These findings imply that the incorporation of low-cost benthic imagery is warranted in coastal benthic biotope classification and mapping studies and should be regularly adopted. This study has implications for coastal benthic ecologists classifying benthic habitats within the CMECS framework.

A Simple Neural Network for Estimating Fine Sediment Sources Using XRF and XRD

Suspended sediment (SS) has a wide range of negative effects such as increased water turbidity, altered habitat structures, sedimentation, and effects on hydraulic systems and environmental engineering projects. Nevertheless, the methods for accurately determining SS sources on a basin-scale are poorly understood. Herein, we used a simplified neural network analysis (NNA) model to identify the sources of SS in Japan’s Oromushi River Catchment Basin. Fine soil samples were collected from different locations of the catchment basin, processed, and separately analysed using X-ray fluorescence (XRF) and X-ray diffraction (XRD). The sampling stations were grouped according to the type of soil cover, vegetation type and land-use pattern. The geochemical components of each group were fed into the same neural network layer, and a series of equations were applied to estimate the sediment contribution from each group to the downstream side of the river. Samples from the same sampling locations were also analysed by XRD, and the obtained peak intensity values were used as the input in the NNA model. SS mainly originated from agricultural fields, with regions where the ground is covered with volcanic ash identified as the key sources through XRF and XRD analysis, respectively. Therefore, based on the nature of the surface soil cover and the land use pattern in the catchment basin, NNA was found to be a reliable data analytical technique. Moreover, XRD analysis does not incorporate carbon, and also provides detailed information on crystalline phases. The results obtained in this study, therefore, do not depend on seasonal uncertainty due to organic matter.

Linking Biodiversity and Functional Patterns of Estuarine Free-Living Nematodes with Sedimentary Organic Matter Lability in an Atlantic Coastal Lagoon (Uruguay, South America)

We examined the taxonomical and functional traits of free-living nematodes, focusing on their density by genus, maturity index (MI), and trophic diversity index (ITD) to determine whether these indices are sensitive to changes in the organic content of the sediment. Samples were collected in autumn and spring from 12 subtidal sampling stations in Rocha Lagoon, distributed between the outer (near the mouth) and the inner sector. We identified 26 genera, with higher abundance in the inner sector, likely due to increased organic matter and biopolymers. In spring, both sectors had sediments rich in fresh organic matter, dominated by deposit-feeding nematodes and showing low trophic diversity (high ITD values). In autumn, the inner sector maintained similar characteristics to spring sampling, while the outer one was dominated by older organic matter, predatory nematodes and higher trophic diversity. The MI showed low variation between sectors, suggesting a disturbed environment. Our findings support the use of ITD to assess other aspects of communities such as the response of trophic groups to the freshness of organic matter, while the MI seems less effective for assessing the ecological status of Rocha Lagoon. Understanding nematode biodiversity and functional traits is crucial for effective ecological quality assessments.

Unveiling Emerging Opportunistic Fish Pathogens in Aquaculture: A Comprehensive Seasonal Study of Microbial Composition in Mediterranean Fish Hatcheries

The importance of microbial communities in fish hatcheries for fish health and welfare has been recognized, with several studies mapping these communities during healthy rearing conditions and disease outbreaks. In this study, we analyzed the bacteriome of the live feeds, such as microalgae, rotifers, and Artemia, used in fish hatcheries that produce Mediterranean species. Our goal was to provide baseline information about their structure, emphasizing in environmental putative fish pathogenic bacteria. We conducted 16S rRNA amplicon Novaseq sequencing for our analysis, and we inferred 46,745 taxonomically annotated ASVs. Results showed that incoming environmental water plays a significant role in the presence of important taxa that constitute presumptive pathogens. Bio-statistical analyses revealed a relatively stable bacteriome among seasonal samplings for every hatchery but a diverse bacteriome between sampling stations and a distinct core bacteriome for each hatchery. Analysis of putative opportunistic fish pathogenic genera revealed some co-occurrence correlation events and a high average relative abundance of Vibrio, Tenacibaculum, and Photobacterium genera in live feeds, reaching a grand mean average of up to 7.3% for the hatchery of the Hellenic Center of Marine Research (HCMR), 12% for Hatchery A, and 11.5% for Hatchery B. Mapping the bacteriome in live feeds is pivotal for understanding the marine environment and distinct aquaculture practices and can guide improvements in hatchery management, enhancing fish health and sustainability in the Mediterranean region.

Ecological roles of nano-picoplankton in stratified waters of an embayment in the southern Benguela.

Nano-picoplankton are the dominant primary producers during the post-upwelling period in St Helena Bay, South Africa. Their dynamics on short time scales are not well understood and neither are the community composition, structure, and potential functionality of the surrounding microbiome. Samples were collected over five consecutive days in March 2018 from three depths (1 m, 25 m, 50 m) at a single sampling station in St Helena Bay. There was clear depth-differentiation between the surface and depth in both diversity and function throughout the sampling period for the archaea, bacteria and eukaryotes. Daily difference in eukaryote diversity, was more pronounced at 1 m and 25 m with increased abundances of Syndiniales and Bacillariophyta. Surface waters were dominated by photosynthetic and photoheterotrophic microorganisms, while samples at depth were linked to nitrogen cycling processes, with high abundances of nitrifiers and denitrifiers. Strong depth gradients found in the nutrient transporters for ammonia were good indicators of measured uptake rates. This study showed that nano-picoplankton dynamics were driven by light availability, nutrient concentrations, carbon biomass and oxygenation. The nano-picoplankton help sustain ecosystem functioning in St Helena Bay through their ecological roles, which emphasizes the need to monitor this size fraction of the plankton.

Effect of a tropical cyclone on the pelagic ecosystem of a continental shelf

AbstractThis study aimed to comprehend the effects of Typhoon Maria on the pelagic ecosystem in the southern East China Sea. Shipboard measurements were conducted at eight sampling stations before (2–4 d) and after (3–6 d) the typhoon, which enabled the evaluation of the potential impacts of the typhoon on this pelagic ecosystem, with particular focus on carbon dynamics. Following the typhoon's passage, there was a slight drop in sea surface temperature. The response of the variables to the typhoon, however, exhibited variations at different sampling stations. For further analysis, t‐tests compared variables, while type II regression assessed the linear correlation between two variables. Overall, during the post‐typhoon period, concentrations of nitrate, chlorophyll a, primary production, bacterial biomass and production, plankton community respiration, and abundance of large phytoplankton (> 2 μm) and the relative abundance of picophytoplankton among larger‐sized picoeukaryotes were higher compared to the pre‐typhoon period. The mean value of fugacity of CO2 was similar to or slightly lower than pre‐typhoon period. Although the typhoon‐induced vigorous primary production might have absorbed a significant amount of CO2, the decrease in fugacity of CO2 could have been offset by the plankton community respiration. The findings suggest that the typhoon enhanced physical disturbance and increased water column mixing, which, in turn, augmented nutrient availability and promoted plankton growth in the shallow water column. Overall, this study sheds light on the complex interactions between typhoons and marine ecosystems and highlights the importance of further investigating these phenomena to better understand their ecological implications.

Lead (Pb) Accumulation in Water, Sediment and Distribution of Macro-Invertebrates in Delimi River, Jos, Nigeria

Background: This study assessed the concentrations of lead (Pb) in the water column and sediment as well as macro-invertebrates in River Delimi with a view to determining its ability to support aquatic life. Methodology: Water and sediment samples were collected simultaneously between August and November 2019 at designated stations: A (Abattoir), B (British America bridge), and C (Farin Gada bridge). Composite method was employed to collect water samples from different points in each station in 250 ml capacity plastic bottles with screw caps. The plastic bottles had previously washed with detergent and finally rinsed using distilled water. The water samples were filtered using 0.4 mm Whatman filter paper. Samples were then digested with few drops of concentrated nitric acid (HNO3). Sediment samples were collected in decontaminated airtight polythene bags measuring 500_g each. Sub-samples of the material were sun-dried for three (3) days and homogenized by grinding in laboratory mortar and pestle and sieved (aperture 125 µm). Sediment samples were digested with 20 cm3 aqua regia (3HCl:1HNO3), filtrate were stored in glass bottles and transported to the laboratory for chemical analyses. Macroinvertebrates were collected using a D-frame kick-net (30) at each site over a three-minute period. The collected specimens were preserved in 70% formalin and transported to the laboratory for sorting, identification, and enumeration. Result: Showed that the concentration of lead (Pb) in all the water samples were found to be less than the permissible limit set by WHO/FAO except site WA3 (0.0874ppm) and WC3 (0.0678 ppm) which were higher than the permissible limit. The concentration of lead (Pb) in sediment was higher than the WHO/FAO permissible limit in all sampling stations which is most likely to pose serious health risks to macrobenthos. Also, 7 Micro-invertebrate taxa were identified in the sampling stations. Chironomidae, Eristalis Larva (Syrphidae), Tabanidae and Whirligig beetle (Gyrinidae) comprised more than 79% of the total abundance while stone fly Larva, hydrophilidae and beetle larva constituted the remaining. Conclusion: water samples suggest potential environmental contamination of lead in some locations while sediment samples indicate a significant contamination with lead, posing potential health risks to organisms living in the sediment, including macrobenthos.

The Core of the Matter-Importance of Identification Method and Biological Replication for Benthic Marine Monitoring.

Benthic macrofauna are important and widely used biological indicators of marine ecosystems as they have limited mobility and therefore integrate the effects of local environmental stressors over time. Recently, environmental DNA (eDNA) analysis has provided a potentially more resource-efficient approach for benthic biomonitoring than traditional morphology-based methods. Several studies have compared eDNA with morphology-based monitoring, but few have compared the two approaches using the exact same sediment cores. In addition, the meiofauna and pelagic organisms obtained as 'bycatch' using eDNA have largely been disregarded from comparisons. Here, we address these shortcomings through comparative invertebrate analyses of six sediment sample replicates from each of four stations in Denmark, using eDNA metabarcoding and morphological identification. Our results revealed large variation between the six replicates for both methods and little overlap in taxon compositions between methods. While the morphological dataset was dominated by molluscs and annelids, the eDNA dataset was dominated by arthropods and annelids. Using community composition data, we found that sampling stations could be distinguished both with eDNA and morphology. Finally, we inferred expected total richness from extrapolated accumulation curves of detected taxa from each method. This indicated that eDNA metabarcoding requires less replication than morphology for maximum coverage of diversity to be reached. However, both methods required high levels of replication, and our results on taxonomic composition add to the evidence that morphological and eDNA-based methods should preferably be used as complimentary tools for marine bioassessment.

The Potential Role of Phytoplankton Functional Groups Under Anthropogenic Stressed Wetlands: Characterizing The Environmental Sensitivity.

Anthropogenic and climatic changes are continuously altering the freshwater plankton, necessitating an evaluation of the complex structure of plankton communities to understand and mitigate these impacts. In this context, the present study focuses on evaluating the structure of plankton communities, specifically Phytoplankton Functional Groups (FGs) for assessing the environmental sensitivity of wetlands under changing scenario. These FGs are defined by shared adaptive features rather than taxonomic traits. Over the period from 2016 to 2018, two ecologically distinct wetlands were examined, analysing their phytoplankton FGs and their relationship with water quality parameters. Ecohydrological data revealed significant seasonal variations (p ≤ 0.05) in key parameters such as water depth, temperature, pH, electrical conductivity, dissolved oxygen, total alkalinity, total hardness, NO3-N, and PO4-P. Notably, there were no significant differences observed among the sampling stations within each wetland. A total of 125 phytoplankton genera/species were classified into 23 FGs in the open wetland and 22 FGs in the closed wetland. Spatial and seasonal analyses of dominant FGs suggested both wetlands were experiencing pollution pressures. This study highlights the powerful role of phytoplankton functional groups (FGs) as bioindicators of wetland health, uncovering pollution pressures. In open wetlands, 15 phytoplankton FGs with 36 key taxa (Indicator Value ≥ 40%) emerged as critical indicators, while in closed wetlands, only 10 FGs with 17 taxa were identified. To assess eutrophication, the occurrence of these indicator species was evaluated using BVSTEP function analysis. The study recommends pollution reduction in catchment areas and restoration of riverine connectivity to enhance FG diversity. Phytoplankton FG methodologies are deemed effective for assessing the environmental sensitivity of wetlands significantly impacted by human activities. This research offers a scientific foundation for the evaluation and restoration of wetland ecosystems.

PHYSICO-CHEMICAL ANALYSIS OF OGUTA LAKE WATER AND ITS EFFECT ON PHYTOPLANKTON POPULATION

Samples were collected from the three sampling stations namely; Up, Mid and Downstream respectively to investigate the effect of nutrients concentration on the phytoplankton in Oguta Lake. The methods used were electrometric, argentometric titration, phenate spectrophotometric, colorimetric, cadmium reduction and acetone extraction spectrophotometric methods were used to determine the pH of water sample, chlorides, sulphate, ammonia, phosphorus, nitrate, nitrite, chlorophyll-A, conductivity, turbidity, chemical oxygen demand, copper, colour, total dissolved solid, respectively. However, serial dilution was carried out using the spread plate or pour plate method was used to determine the microbial analysis of the sample. At the end of these researches, the Physico-chemical parameters analysed showed that Oguta Lake had total dissolved solids values of 6.50 ± 0.06mg/l, 6.50 ± 0.14 and 6.50 for upstream, mid stream and downstream respectively. The result showed there was no significance total dissolved solids difference between the various stream points (P0.05). the colour of the Lake showed significant difference ranging from 17.00 ± 1.41 and76.00 V 1.41 in upstream and downstream and the lowest value at upstream. The pH range in this study indicates that the water may be acidic (5.54-7.31). Phytoplankton assemblages obtain across the three stream points showed only three divisions and 78 species. The identified divisions and species are comprised of Eurcharyta (44), Cyanophyta (25) and Chlorophyta (9). Eurkaryta recorded 100%, 5% and 15% abundance in upstream, midstream and downstream respectively, while Cyanophyta recorded the highest abundance at downstream with 75%, Chlorophyta only was identified at the midstream and was least abundance with 23%. The phytoplankton diversity indices done showed that downstream was most diverse having the highest Shannon Weiner Index and Evenness Index of 3.631 and 1.212 respectively. In relation to physicochemical and phytoplankton abundance, the findings in this study is contradictory to some researches. They reported positive correlation of phytoplankton with phosphate and nitrate. There was negative correlation of phosphate with Eurkaryta and Chlorophyta, except for Cyanophyta that showed positive correlation with phytoplankton but not very significant. These low levels of phosphate and nitrate may be the cause of low phytoplankton levels.

Spatial and seasonal variations in trace metals in marine sediments from the Dubai coastal environment.

This study was conducted to assess sediment trace metals (Cd, Cr, Cu, Pb, Ni and Zn) contamination using a systematic approach by collecting sediment samples from 8 transects along the Dubai coastline, each 10 km long, and each transect included its nearshore sediment sampling station. Additionally, 10 sediment samples were collected from the Dubai creek and other potential sources of metal pollution. The sediment samples were collected in December and again in August. However, no significant difference in sediment metal concentration was found between the two sampling campaigns. The sediment trace metal concentrations (0.92-1.31mg Cd/kg, 2.82-176.6mg Cr/kg, 2.27-621.67mg Cu/kg, 0.88-23.6mg Pb/kg, 1.92-192.2mg Ni/kg and 9.1-391.05mg Zn/kg) showed considerable variability, except for Cd (1.08 ± 0.06mg/kg, 5.55% variability). Despite this, no significant differences in sediment metal concentrations were found between the sampled transects. However, significant variations in Cr, Cu, Pb and Zn were evident between distances from the shoreline to offshore stations along the Dubai coast, and the nearshore locations presented clear evidence of elevated/maximum sediment metal concentrations. Most of the sediment trace metal concentrations, however, were found well within the sediment quality guidelines (SQGs) for nearshore sediments. Trace metal contamination hotspots, nonetheless, were identified at some nearshore stations as determined by metal level exceedance over the SQGs, background levels and the pollution load index, with limited potential ecological risk. Overall, the findings suggest that sediments in the Dubai coastal environment are mainly influenced by anthropogenic activities in stations located in the proximity of ship maintenance, ports, and industrial areas such as Dry Dock, Jaddaf, Jebel Ali Port, Wharfage, Hamriya and DUBAL.

A methodology to assess the phenology patterns of a eutrophic water body, using remote sensing data and principal component analysis

Chlorophyll-a concentrations in coastal and inland waters is acknowledged as an important factor to estimate Water Bodies Quality Status. Remote sensing analysis is a fast, cost-effective, and reliable methodology that can be used to assess the phenological patterns of aquatic ecosystems. The purpose of this study is to assess the phenology patterns of a eutrophic water body and present a novel methodology to fill in the missing values of the daily Surface Reflectance MODIS Aqua dataset. The proposed methodology is to apply Principal Component Analysis to generate the missing values from the chlorophyll-a concentrations and better assess Water Body's Trophic Status. The pilot study is Aitoliko Lagoon, a semi-closed Greek water body with eutrophication. The analysis reveals that sampling stations of swallow waters have higher variance in chlorophyll-a concentrations, favoring the deep waters sampling pixels for evaluating the water body's trophic status. The proposed PCA methodology showed a clear phenological pattern of chlorophyll-a with algae bloom from April and high chlorophyll-a concentrations until August, which is what is expected from a eutrophic lagoon and specifically for Aitoliko lagoon.

Metagenomic analysis of deep-sea bacterial communities in the Makassar and Lombok Straits

The extreme conditions of the deep-sea environment, including limited light, low oxygen levels, high pressure, and nutrient scarcity, create a natural habitat for deep-sea bacteria. These remarkable microorganisms have developed unique strategies to survive and adapt to their surroundings. However, research on the diversity of deep-sea bacteria, both culture-dependent and culture-independent, in Indonesian waters remains insufficient. This study focused on exploring the biodiversity of deep-sea bacteria, specifically in the Makassar and Lombok Strait, the main Indonesian throughflow pathway characterized by relatively fertile water, which serves as an important deep-sea region. High-throughput DNA sequencing of full-length 16S rRNA was employed to construct a genomic database. The results of the bioinformatic analysis revealed that two stations, 48 and 50 (Makassar Strait), exhibited a more similar community structure of deep-sea bacteria than did station 33 (Lombok Strait). Among the predominant phyla found at a depth of 1000 m, the top ten were Proteobacteria, Firmicutes, Bacteroidetes, Actinobacteria, Planctomycetes, Acidobacteria, Nitrospinae, Verrucomicrobia, Candidatus Melainabacteria, and Cyanobacteria. Furthermore, the genera Colwellia, Moritella, Candidatus Pelagibacter, Alteromonas, and Psychrobacter consistently appeared at all three stations, albeit with varying relative abundance values. These bacterial genera share common characteristics, such as psychrophilic, halophilic, and piezophilic tendencies, and are commonly found in deep-sea ecosystem. The environmental conditions at a depth of 1000 m were relatively stable, with an average pressure 10 MPa, temperature 4.68 °C, salinity 34.58 PSU, pH 8.06, chlorophyll-a 0.29 µg/L, nitrate 3.19 µmol/L, phosphate 6.32 µmol/L and dissolved oxygen (DO) 2.90 mg/L. The bacterial community structures at the three sampling stations located at the same depth (1000 m) exhibited similarities, as indicated by the closely aligned similarity index values.

Metal contamination in mangrove tissues, seeds, and associated sediments from the Vattanam mangrove forest of Palk Bay, southeastern India: An ecological risk assessment

In the present work, the concentrations of toxic heavy metals in mangrove sediments, mangrove leaves, and seeds collected from five stations in the Vattanam mangrove of Palk Bay, southeastern India, as well as the effects of the monsoon season on toxic heavy metals concentrations were determined. The concentrations were 17.5 μg/g for zinc (Zn), 9.11 μg/g for copper (Cu), and 6.03 μg/g for lead (Pb) in sediments; 10.71 μg/g (Zn) and 8.94 μg/g (Cu) in mangrove leaves; and 26.24 μg/g (Zn) and 17.01 μg/g (Cu) in mangrove seeds. At all sampling stations, the Cd concentration was below the limit of detection. These mangroves seem to have adapted successfully to their environment given their selective intake of only essential metals (Cu and Zn) and the restricted movement of non-essential metals (Cd and Pb). The concentrations of metals were below the maximum residual limits regulated by national and international standard limits.

Environmental DNA Metabarcoding of Cephalopod Diversity in the Tyrrhenian Deep Sea

The deep sea, the largest biome on Earth, is the least explored and understood. This lack of knowledge hampers our ability to understand and protect this important environment. In this study, water and sediment samples were collected at different depths in the central Mediterranean (224–780 m), specifically, within the Dohrn Canyon and the Palinuro Seamount, to investigate the diversity of cephalopods and establish a baseline knowledge of their distribution in these sites to preserve their habitats and estimate the impacts of human-driven environmental changes. Key taxa identified included Heteroteuthis sp., Loligo sp., and Histioteuthis sp., which were the most abundant across all sampling stations. A low overlap in species detection was observed between water and sediment samples, confirming previous findings that the typology of environmental matrices used in eDNA metabarcoding has a significant impact on the organisms detected and, therefore, the integrated use of different matrices to better represent local biodiversity is recommended. Furthermore, this study highlights the limitations posed by gaps in reference databases, particularly for deep-sea organisms, and addresses these by emphasising the need for improved multi-marker approaches and expanded reference databases to enhance the accuracy of eDNA-based biodiversity assessment.

Validation of physicochemical water quality results through cross-checking with biological indices

ABSTRACT Biological assessment of rivers is critical for evaluating ecosystem health, detecting ecological changes, validating physicochemical monitoring data, assessing the effectiveness of water treatment systems, conserving biodiversity, and guiding water resource management. In this study, the surface water quality of the Karkheh River basin was evaluated using the National Sanitation Foundation Water Quality Index (NSFWQI) and the Iranian Surface Water Quality Index (IRWQIsc) for qualitative analysis. For biological monitoring, the Biological Monitoring Working Party (BMWP) index, along with the Average Score per Taxon (ASPT) and the Hilsenhoff Biotic Index (HFBI), was employed to provide a comprehensive assessment. Water quality was analyzed across 18 sampling stations, revealing significant spatial variation. Upstream areas exhibited relatively good conditions, with NSFWQI and IRWQIsc values of 59 and 68, respectively. In contrast, downstream locations near urban and agricultural areas demonstrated poor water quality, with values of 27 and 33, respectively. Overall, approximately 70% of the river's length has been severely impacted, highlighting the need for targeted planning and management to mitigate pollution. The biological indices corroborated the physicochemical results, revealing severe ecological stress in polluted regions. The close alignment between the NSFWQI and biological indicators emphasizes the importance of a multifaceted approach in assessing aquatic health. Key factors contributing to the river's degradation include excessive water extraction, untreated wastewater discharge, and diminished self-purification capacity, particularly in downstream areas.

A spatial matrix factorization method to characterize ecological assemblages as a mixture of unobserved sources: An application to fish eDNA surveys

Abstract Understanding how ecological assemblages vary in space and time is essential for advancing our knowledge of biodiversity dynamics and ecosystem functioning. Metabarcoding of environmental DNA (eDNA) is an efficient method for documenting biodiversity changes in both marine and terrestrial ecosystems. However, current methods fail to detect and display the biodiversity structure within and between eDNA samples limiting ecological and biogeographical interpretations. We present a spatial matrix factorization method that identifies optimal eDNA sample assemblages—called pools—assuming that taxonomic unit composition is based on a fixed number of unknown sources. These sources, in turn, represent taxonomic units sharing similar habitat properties or characteristics. The method aims to reduce the multi‐taxa composition structure into a low number of dimensions defined by these sources. This method is inspired by admixture analysis in population genetics. Using a marine fish eDNA survey on 263 sampling stations detecting 2888 molecular operational taxonomic units (MOTUs), we apply this method to analyse the biogeography and mixing patterns of fish assemblages at regional and large scales. At large scale, our analysis reveals six primary pools of fish samples characterized by distinct biogeographic patterns, with some mixtures between these pools. We identify pools composed of unique sources, corresponding to distinct and more isolated regions such as the Mediterranean and Scotia Seas. We also identify pools composed of a greater mix of sources, corresponding to geographically connected areas, such as tropical regions. Additionally, we identify the taxa underpinning the formation of each pool. In the regional analysis of Mediterranean eDNA samples, our method successfully identifies different pools, allowing the detection of not only geographic gradients but also human‐induced gradients corresponding to protection levels. Spatial matrix factorization adds a new method in community ecology, where each sample is considered as a mixture of K unobserved sources, to assess the dissimilarity of ecological assemblages revealing environmental and human‐induced gradients. Beyond the study of fish eDNA samples, this method has the potential to shed new light on any biodiversity survey and provide new bioindicators of global change.

Risk assessment for the surface water quality evaluation of a hydrological basin

This paper proposes a risk assessment methodology for evaluating the surface water quality of hydrological basins based on physico-chemical parameter concentrations. Considering the Douro River basin in Portugal and monthly recorded dissolved oxygen and conductivity parameter measurements in 18 water sampling stations from January 2002 to December 2013, the work intends to answer the research question of identifying the riskiest periods for water pollution in the year and classifying the water sampling stations in terms of risk for water pollution. The methodology consists first in determining the pollution risk implied by the physico-chemical parameters, based on the monthly water station measurements, using six different risk measures, namely mean, variance, loss probability, entropy, mean excess loss and value at risk. The risk values are ordered according to each risk measure and a final ranking is established through a ranking aggregation method. The final ranking permitted identifying the high risk period as ranging from May to October and the low risk period from November to April. Furthermore, July was classified as riskiest month concerning the dissolved oxygen concentration, and August as riskiest month regarding the conductivity levels. On the other hand, the ranking allowed classifying the water sampling stations, previously grouped in clusters, in terms of similar risk for water pollution: six sampling stations in the west of the basin formed the riskiest cluster in the dry period considering the dissolved oxygen concentrations, and four of those stations formed also the riskiest cluster concerning the conductivity levels.