Water Turbidity Research Articles

Evaluation of the impacts of turbidity on Gilgel-Gibe I reservoir storage, Omo-Gibe River Basin, Ethiopia

Quantity and quality of the water held in the reservoir fluctuates due to turbidity alterations. The influence of turbidity on the amount of the water held in a reservoir was described explicitly in this research. This study aimed to evaluate turbidity's impact on the Gilgel-Gibe I reservoir water. The samples were obtained by longitudinally stratifying the reservoir water throughout its course. Ten burrowed pools wrapped in transparent white plastic were used to retain water, for detection of the association between turbidity and surface water temperature, and to demonstrate the vertical variation in water temperature. The pan evaporation rate was measured using two Class A pans placed in the field to indicate the disparity in the amount of water evaporated from reservoir owing to reservoir turbidity variation. SPSS and MS Excel spreadsheet softwares were used to analyze the data. According to the results of this study, turbidity and water temperature have a significant direct relationship that is positive at 9:00 and 13:00 and negative at 17:00 observation hours. From the top layer of pool water to the bottom layer, the water temperature decreased vertically. Intensity of the light rays absorbed and scattered alters with turbidity variation and significant amounts of light rays was absorbed and scattered in the most turbid water. The reported water temperature differences between the top and bottom layers at 13:00 observation hour were 9.78 °C and 1.53 °C, for the most and least turbid pool water, respectively. Turbidity directly affects reservoir water by increasing both the water temperature and evaporation rates. Among all turbid-water samples, substantial quantity of water evaporated from the most turbid-water. For the most and least turbid water samples, the volume difference of the evaporated water from the reservoir was approximately 65.812 m3. According to these findings, if the reservoir water turbidity increases, the amount of water held in the reservoir significantly reduced due to substantial water loss.

Community Perception of Gold Mining Affecting the Water Quality of the Wariori River

This study examines community perceptions of gold mining and its impact on the water quality of the Wariori River in Aurmios Village. The population involved all residents of Aurmios Village with a sample size of 20 (twenty) people. Using a qualitative research approach based on postpositivism and interpretive philosophy, data were collected through triangulation, combining observation, questionnaires, and interviews. The results show significant negative impacts of illegal gold mining on water quality and community life. The majority of respondents (95%) reported an increase in river water turbidity after mining activities, in line with the findings of Yulianti et al. (2016) and Putri Ade Rahma Yulis (2018) on the increase in Total Suspended Solids (TSS) and heavy metal pollution. In addition, 100% of respondents reported reduced clean water sources, leading to economic and health challenges, such as increased healthcare costs and a shift in livelihoods from fisheries and agriculture to gold mining. Environmental impacts include ecosystem degradation and increased flood risk, and 100% of respondents recognized these issues. In order to address these adverse impacts, the study recommends strict government measures to regulate illegal mining, establish safe and legal mining operations, provide clean water infrastructure, as well as educate communities on the dangers of illegal gold mining. These measures are essential to restore the water quality of the Wariori River and ensure the sustainable well-being of Aurmios villagers. Further research is needed to monitor long-term impacts and develop effective mitigation strategies.

Evaluation of the physical parameters of water obtained from some groundwater sources of Tabuk city, Kingdom Saudi Arabia

After air, water is the second most important element for life, based on that, water quality parameters (physical, chemical and biological) should be concerned to detect contamination. The aim of this study was to evaluate the physical parameter of water brought from some groundwater sources of Tabuk City. A cross-sectional design was followed to collect groundwater from 12 sites (randomly selected) within Tabuk City to measure water temperature, color, odor, taste and turbidity, in addition to record the groundwater depth. In aseptic and clean plastic sample containers, 250 ml of the groundwater were collected. Water temperature was measured using a manual thermometer, immediately when it was collected. The data concerned the depth of the groundwater was obtained directly from the owners during groundwater sampling. The water color, odor, taste, in addition to turbidity were measured using the general human sense. The obtained physical parameters were compared with the local standards of the drinking water suggested by MEWA (2022). The results of this study show that, the groundwater temperature for the 12 samples obtained from Tabuk City ranged between 26oC and 33oC, with a mean of 29.33oC, while the groundwater depth (in meter) ranged between 120 m and 700 m with a mean depth of 479.2 m. The physical parameters of drinking water compared to the Saudi standards of quality showed that, all tested samples were agreed with the quality standards on color, odor, taste and turbidity. This work recommends for the prudent use of groundwater resources to keep its quality for long term usage as a drinking water.

Demonstration of an 8-Gbit/s quadrature-phase-shift-keying coherent underwater wireless optical communication link using coherent heterodyne detection under scattering conditions.

In this paper, we experimentally demonstrate an 8-Gbit/s quadrature-phase-shift-keying (QPSK) coherent underwater wireless optical communication (UWOC) link under scattering conditions at 532 nm. At the transmitter, we generate the 532-nm QPSK signal using second-harmonic generation (SHG), where the 1064-nm signal modulated with four phase levels of an 8-phase-shift-keying (8-PSK) format is phase doubled to produce the 532-nm QPSK signal. To enhance the receiver sensitivity, we utilize a local oscillator (LO) at the receiver from an independent laser source. The received QPSK data beam is mixed with the independent LO for coherent heterodyne detection. Results show that the bit error rates (BERs) of the received QPSK signal can reach below the 7% forward error correction (FEC) limit under turbid water with attenuation lengths (γL) up to 7.4 and 6.1 for 2- and 8-Gbit/s QPSK, respectively. The corresponding receiver sensitivities are -34.0 and -28.4 dBm for 2- and 8-Gbit/s QPSK, respectively.

Classification of water quality based on dissolved solids and turbidity parameters with the utilization of total dissolved solids sensor and turbidity sensor

Clean water quality is essential for public health, but its scarcity is increasing amid population growth and industrialization. Monitoring turbidity and total dissolved solids (TDS) is essential to determine the quality of clean water. This study addresses the urgent need for accurate and reliable water quality monitoring to test the applicability of TDS and turbidity sensors in taking measurements, aiming to develop efficient monitoring solutions for public health and sustainable water management. The TDS sensor operates according to the principle of electrical conductivity, with a range of 0 to 1000 ppm and an accuracy of ±10%. The turbidity sensor detects water turbidity by determining the level of turbidity particles. The ESP32 microcontroller integrates Wi-Fi and USB capabilities. The hardware and software design ensures accurate sensor readings, which are critical to successful water quality measurement and monitoring. The test results show satisfactory accuracy of the TDS sensor with an average error of 0.09% and good accuracy of the turbidity sensor with an average error of about 1.536%. Concerning the above two parameters, in this study, among 15 water samples, seven were clean, meeting the standard, while eight water samples were dirty, exceeding the limit, making them unsafe for human consumption.

Temporal temperature shifts govern the population succession of picoeukaryotes and picocyanobacteria in a coastal ecosystem

Picophytoplankton are vital components of the marine microbial food web. Being the smallest in the phytoplankton group, their short life cycles make them excellent bioindicators of environmental conditions. Given this, an investigation was conducted at the Kandla Port ecosystem (Latitude 23º 01' N; Longitude 70º 13' E) in the state of Gujarat, India to assess the response of picophytoplankton community structure to temporal and spatial environmental conditions. The sampling was conducted in July 2015, October-November 2015, and February 2016 at twenty-six stations. The results revealed a wide annual temperature range due to the study site's proximity to the Tropic of Cancer. The salinity ranged up to 40 while the turbulence caused by the macrotides resulted in highly turbid waters, especially during July due to precipitation. The picophytoplankton community was represented by picocyanobacteria (three sub-groups of Synechococcus) and picoeukaryotes (three sub-groups including Cryptophytes). The picocyanobacteria were abundant during the less turbid, warmer October-November period and lower during the cooler February period. The dominant Synechoccocus groups are associated positively with NH4+ and negatively with PO43-. The Cryptophytes were present during the warm and cool periods indicating tolerance to a wide range of temperature, salinity, and light. Their positive correlation with PO43- and NH4+ concentrations during February and October-November, respectively suggests a causal relationship. The picoeukaryotic group dominated the picophytoplankton community during the cooler period (February). The relative importance of the two picophytoplankton groups changed throughout the year exhibiting temporal niche segregation and hence establishing their role as bioindicators of temperature.

Developing an innovative corrosion and scaling index for industrial cooling water using artificial intelligence

The present study developed an intelligent model to predict the corrosion and scaling potential (CSP) of industrial cooling water circuits using artificial intelligence (AI) techniques. AI techniques have attracted a lot of attention due to the high accuracy and speed of calculations, as well as possible analysis of large datasets. The study analyzed nine years of data on cooling water quality parameters, including pH, alkalinity, hardness, dissolved solids, chloride, turbidity, suspended solids, and iron, from electric arc furnaces at the Khuzestan Steel Company. Multiple linear regression (MLR), multiple nonlinear regression (MNLR), and multi-layer perceptron neural network (ANN-MLP) models were applied to predict CSP. The ANN-MLP model achieved the best performance with an R2 of 0.75, Mean Absolute Error of 0.34, and Mean Squared Error of 0.35, demonstrating that neural networks can effectively predict CSP in industrial cooling water. The results also showed that total hardness and chloride have the greatest impact on CSP in the circulating water circuits.

On-line measurement of COD and nitrate in water against stochastic background interference based on ultraviolet–visible spectroscopy and physics-informed multi-task learning

Traditional ultraviolet–visible spectroscopic quantitative analytical methods face challenges in simultaneous and long-term accurate measurement of chemical oxygen demand (COD) and nitrate due to spectral overlap and the interference from stochastic background caused by turbidity and chromaticity in water. Addressing these limitations, a compact dual optical path spectrum detection sensor is introduced, and a novel ultraviolet–visible spectroscopic quantitative analysis model based on physics-informed multi-task learning (PI-MTL) is designed. Incorporating a physics-informed block, the PI-MTL model integrates pre-existing physical knowledge for enhanced feature extraction specific to each task. A multi-task loss wrapper strategy is also employed, facilitating comprehensive loss evaluation and adaptation to stochastic backgrounds. This novel approach significantly outperforms conventional models in COD and nitrate measurement under stochastic background interference, achieving impressive prediction R2 values of 0.941 for COD and 0.9575 for nitrate, while reducing root mean squared error (RMSE) by 60.89 % for COD and 77.3 % for nitrate in comparison to the conventional chemometric model partial least squares regression (PLSR), and by 30.59 % and 65.96 %, respectively, in comparison to a benchmark convolutional neural network (CNN) model. The promising results emphasize its potential as a spectroscopic instrument designed for online multi-parameter water quality monitoring against stochastic background interference, enabling long-term accurate measurement of COD and nitrate levels.

Assessment of Atmospheric Correction Algorithms for Sentinel-3 OLCI in the Amazon River Continuum

Water colour remote sensing is a valuable tool for assessing bio-optical and biogeochemical parameters across the vast extent of the Amazon River Continuum (ARC). However, accurate retrieval depends on selecting the best atmospheric correction (AC). Four AC processors (Acolite, Polymer, C2RCC, OC-SMART) were evaluated against in situ remote sensing reflectance (Rrs) measurements. K-means classification identified four optical water types (OWTs) that are affected by the ARC. Two OWTs showed seasonal differences in the Lower Amazon River, influenced by the increase in suspended sediment concentration with river discharge. The other OWTs in the Amazon River Plume are dominated by phytoplankton or by a mixture of optically significant constituents. The Quality Water Index Polynomial method used to assess the quality of in situ and orbital Rrs had a high failure rate when the Apparent Visible Wavelength was >580 nm for in situ Rrs. OC-SMART Rrs products showed better spectral quality compared to Rrs derived from other AC processors evaluated in this study. These results improve our understanding of remotely sensing very turbid waters, such as those in the Amazon River Continuum.

Machine learning-based understanding of aquatic animal behaviour in high-turbidity waters

Inspired by the ambitions envisioned in the Fourth Industrial Revolution for aquaculture, also known as Aquaculture 4.0, the aquaculture (marine animal farming) industry is seeking to adopt data-driven Artificial Intelligence (AI) to help significantly improve business operations. One of the major barriers is the manual annotation of animal behaviour data, which is a time-consuming task that demands high levels of concentration from biologists. To address this challenge, this paper proposes novel automatic animal behaviour monitoring tailored for industrial scenarios. Our approach introduces a real-time machine-learning-based instance segmentation system that is specialised for underwater environments, where large groups of shrimp are farmed. The implemented system achieves an accuracy rate of 89% at 30 frames per second (fps) and can accurately detect shrimp in high-density areas under poor lighting conditions and high turbidity waters, despite the challenges of occlusion and overlapping. A key innovation of our method is the implementation of a new density cluster algorithm for time series and video analysis. This approach provides a more efficient and accurate way of monitoring animal behaviour, significantly saving time and effort for biologists and advancing the capabilities of automated aquaculture systems.

Submerged macrophyte self-recovery potential behind restoration treatments: sources of failure.

When exploring the challenges of restoring degraded lakes, we often do not observe the expected results despite executing all planned activities. Our study elucidates the reasons that impede the recovery of submerged macrophytes despite ameliorated light conditions. When prolonged lake degradation occurs, subsequent efforts to increase light availability often prove insufficient, resulting in a persistent turbid water state. In this study, we attempted to determine the reasons for these failures through a germination test and propagule bank analysis conducted in bottom sediments from a severely degraded lake, which underwent restoration. Although the bottom sediments indicate relative potential in the number of oospores and seeds, their germination efficacy remained dismally low. Based on the germination test results and factors affecting the development of submerged macrophytes (physical and chemical parameters, lake morphology), we stated that improvement of light conditions in the lake could be insufficient to recover the vegetation, especially when the potential to renew diverse plant communities from sediments naturally is low. Our findings advocate for a paradigmatic shift in lake restoration strategies. A holistic approach that includes propagule bank assessments before embarking on restoration initiatives and enabling the identification of macrophyte resurgence potentials is recommended. We also advocate for a multifaceted restoration framework, emphasizing the indispensability of augmenting natural recovery mechanisms with targeted interventions. Consequently, in some cases, macrophyte reintroduction could be the only solution. By reintroducing autochthonic species to site-specific ecological dynamics, we anticipate an increased success rate in restituting submerged vegetation, thus catalyzing ecological regeneration within degraded lake ecosystems.

Development of polysaccharide bioplastic: Analysis of thermo-mechanical properties and different environmental implications

Despite the distinct benefits of plastics, the environmental impacts stemming from their production and accumulation in the environment have become a global concern. Therefore, the development of new technologies that mitigate these impacts is of notable importance. The present study aimed to evaluate the physicochemical properties of starch-xylan-based bioplastic, and to discuss the viability of this material in terms of applications and ecological impacts. Holocellulose, xylan, and α-cellulose were extracted from waste biomass and combined with starch for bioplastic production. Solubility in food simulants (3% acetic acid, and 90% ethanol) was performed for xylan and starch-based bioplastics. Bioplastic was evaluated to grow Aspergillus versicollor for xylanase production. The bioplastic was evaluated as a photoprotector with yeast exposed to UVC light-covered by the bioplastic for 2 h. Bioplastic disintegration was evaluated in different soil moistures and the disintegration on the surface of the compost. Liquid washes from soils exposed to bioplastic biodegradation were tested for Lactuca sativa seed germination/inhibition. Water from a local lake was exposed to bioplastic and microbial cell density modification was verified. Images of the surface of the bioplastics were obtained by scanning electron microscopy, and characterized by thermogravimetric and dynamic-mechanical analysis. The xylan addition in bioplastic led to a material with a 40–50% decreased ultraviolet light transmittance. An increase in xylan concentration reduced solubility in lipid food simulant solutions, with no fatty solubilization with 25% of xylan. It suggests potential applications in photoprotective and packaging contexts. The thermal degradation temperature of the pure starch bioplastic was 324 °C, and the addition of 10% (287 °C), 15% (286 °C), and 25% (296 °C) xylan (w/w) indicated a reduction in thermal resistance, possibly due to suboptimal interaction between polymer chains. The decrease in crystallinity in the compositions 10/90% (Xc = 20%), 15/85% xylan/starch (Xc = 21%) compared to 25/75% xylan/starch (Xc = 11%) also underscored the complexity of polymer interactions within the bioplastic matrix. Tensile strength of pure starch was 1.21 MPa, while the composition of 15/85% xylan/starch exhibited improved strength 2.99 MPa. Further investigation into the interaction between starch and xylan is warranted. Concerning the disintegration of the 25/75% xylan/starch formulation in the soil, the humidity of the soil matrix played a significant role. The disintegration occurred over 5 days and 16 days in compost (55% humidity) and soil (32.6% humidity), respectively. The results of phytotoxicity (Lactuca sativa seeds) and changes in the physicochemical and biological profile of water (smell, turbidity, phosphorus and nitrogen levels, pH, and bacterial and phytoplankton density/richness), in response to exposure to bioplastics, highlight the necessity of developing this biologically-based and biodegradable technology in concerns about potential environmental impacts. Furthermore, the present study introduces the approach of bioplastic waste recycling using enzyme production biotechnology. In line with the legitimacy of bioplastics as important materials for addressing the challenges posed by their non-biodegradable synthetic counterparts, the presented results broaden the discourse on the feasibility of this biologically based material, contributing to the development of a sustainable society.

Strong Magnetic p-n Heterojunction Fe3O4-FeWO4 for Photo-Fenton Degradation of Tetracycline Hydrochloride

With the abuse of antibiotics, its pollution poses an increasing threat to the environment and human health. Effective degradation of organic pollutants in water bodies is urgent. Compared to traditional treatment methods, advanced oxidation processes that have developed rapidly in recent years are more environmentally friendly, efficient and applicable to a wider range of organic compounds. FeWO4 was used in this study as the iron-based semiconductor material to modify and optimize the material design. Fe3O4/FeWO4 composites were prepared by a two-step hydrothermal method. The crystal structure, surface morphology, electrochemical properties and separability of the composite semiconductor were analyzed by XRD, XPS, UV-vis, SEM, EDS and Mott-Schottky. The results showed that, when the initial contaminant concentration was 30 mg/L, the initial solution pH was 4, the dosage of the catalyst was 25 mg and the dosage of hydrogen peroxide was 30 μL, the degradation efficiency of tetracycline hydrochloride (TCH) could reach 91% within 60 min, which was significantly improved compared to the performance of the single semiconductors Fe3O4 and FeWO4. In addition, the catalyst prepared in this experiment can be easily recovered by magnetic separation technology in practical application, which will not affect the turbidity of water while reducing the cost of catalyst separation and recovery.

Biological Control Options for the Management of Tadpole Shrimp (Triops longicaudatus (LeConte)) in California Rice

Tadpole shrimp (Triops longicaudatus) has become a major pest for California rice farmers. Currently, management relies solely on the insecticide lambda-cyhalothrin. However, resistance to this pyrethroid was confirmed in 2016; thus, identifying an effective and practical biological control method for TPS is a priority. Field trials were conducted from 2017 to 2018 to (1) evaluate the efficacy of the predatory fish Gambusia affinis and the predatory beetles, Laccophilus maculosus (Say) and Tropisternus lateralis (Fabricius), in controlling TPS, (2) test the efficacy of several inoculation rates of Gambusia affinis at controlling TPS and (3) to explore early indicators of TPS activity and damage as monitoring tools. Both Gambusia affinis and the predatory beetle treatments were not significantly different from the commercial standard (lambda-cyhalothrin). Both four and five Gambusia per 1 m2 controlled TPS as well as lambda-cyhalothrin, and we observed that Gambusia affinis was able to reproduce in the field. Water turbidity was significantly correlated with TPS counts (R = 0.85, N = 20, p < 0.0001 (2017); R = 0.58, N = 30, p = 0.0007 (2018)). The number of dislodged seedlings was less reliably correlated with TPS count; in 2017, correlations were significant (R = 0.84, N = 20, p < 0.0001); however, in 2018, correlations were not significant (R = 0.18, N = 30, p = 0.35). With further refinement, water turbidity could play a valuable role in monitoring TPS populations.

Radiative transfer simulations of water-leaving radiance from the Skylight-Blocked Approach.

Radiative transfer simulations of measurements performed with the Skylight-Blocked Approach (SBA) for water exhibiting diverse optical properties confirmed the non-negligible impact of the depth z0 of the radiometer shield in the determination of the water-leaving radiance Lw. In particular, results showed that the shield-shaded water volume lowers the measured Lw value by a few up to tens of percent as a function of the depth z0, water attenuation, and wavelength. The study also confirmed the potential applicability of an analytical correction scheme based on the sole water absorption and backscattering coefficients to support operational SBA measurements, still at the expense of decreased accuracy with increasing depth z0 and water turbidity.

Underwater light source changes nitrogen and phosphorus removal pathways by Vallisneria spinulosa Yan growth system

Vallisneria spinulosa Yan (V.spinulosa Yan) with good ability of water purification is often used for ecological restoration of polluted water bodies. However, it is difficult to survive in turbid water bodies due to the low lighting condition. This study explored the feasibility of introducing artificial underwater light source into water bodies with high turbidity to strengthen the water restoration by V.spinulosa Yan. Addition of underwater light source promoted the clonal reproduction ability of V.spinulosa Yan, thus enhancing the removal loads of total nitrogen (TN), total phosphorus (TP), and nitrate nitrogen (NO3−-N\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\mathrm{NO}}^{-}_{3}{\\mbox{-}}{\\mathrm{N}}$$\\end{document}) by 1.60–3.43 × 10−2, 1.49–3.49 × 10−3, and 0.80–2.06 × 10−2 g m−2 d−1, respectively. Underwater light source significantly reduced the abundance of microbial community on V.spinulosa Yan leaves, as well as most nitrifying bacteria (Nitrosomonadaceae) and denitrifying bacteria (Nitrospira, Comamonadaceae, and Rhodocyclaceae) in the system. But the attachment of some Cyanophyta (Chloroplast and Cyanobacteria) and Photosynthetic bacteria (Rhodobacter) onto the leaves and the growth of Methyloligellaceae in water and sediments were promoted. Nitrogen and phosphorus removal by the growth system of V.spinulosa Yan without underwater light source mainly depended on the biological processes by functional bacteria, while the absorption and co-assimilation effect of V.spinulosa Yan with underwater light source.

Biogeography of freshwater plants in four major lakes in Kenya

Freshwater plants play a pivotal role in the health and functioning of freshwater ecosystems, and they also offer a variety of benefits to humans. Despite their importance, there is a significant gap in our understanding of the macroecology of freshwater plants in tropical regions, where biodiversity is typically high, and ecosystems face substantial pressures from human activities. To bridge this knowledge gap, we conducted extensive field surveys and applied statistical methods to understand the patterns of distribution, density, and diversity of freshwater plants and their relationship with abiotic components in four freshwater lakes in Kenya. We aimed to answer four key questions: (1) How many freshwater plant species occur in these lakes? (2) What proportion of these freshwater plant species are native and alien to Kenya? (3) What proportion of these species have a history of being invasive somewhere in the world, including in Kenya? (4) Which water and sediment characteristics are significantly associated with the presence, density, and diversity of freshwater plants in the lakes? We inventoried a total of 163 freshwater plant species, of which 114 were native to Kenya and 49 were alien. Online database searches revealed that 114 species had a history of invasion globally, with 22 species already invasive in Kenya. Our statistical analysis showed that the presence and density of plant species were positively correlated with pH and turbidity, but negatively correlated with soluble reactive phosphorus in both water and sediments, ammonia-nitrogen in sediments, and nitrate-nitrogen in water. Shannon-Wiener diversity of the plant species was positively correlated with ammonia-nitrogen in water and nitrate-nitrogen in sediments but negatively correlated with longitude and electrical conductivity of the water. Pielou’s evenness within the communities showed positive correlations with soluble reactive phosphorus in both water and sediments, ammonia-nitrogen in sediments, and nitrate-nitrogen in water but was negatively correlated with water turbidity and pH. The number of species with a history of invasion was positively correlated with longitude and electrical conductivity but negatively correlated with ammonia-nitrogen and nitrate-nitrogen in water. This extensive inventory not only enriches our understanding of the biodiversity within these freshwater plant communities but also highlights the potential risks posed by species with a history of being invasive. The findings regarding environmental variables linked to the presence, density, diversity, and invasive potential of these species underscore the complexity of freshwater ecosystems and the array of factors influencing the composition of freshwater plant communities.

Suspended sediment exchange between the Changjiang Estuary and Hangzhou Bay and their key driving mechanisms

Nowadays estuarine deltas are threatened by factors such as insufficient terrigenous sediment supply and rising sea levels. The Changjiang Estuary is adjacent to Hangzhou Bay, characterized by high turbidity waters, and the suspended sediment exchange between the two will inevitably affect the erosion and deposition of subaqueous delta in the future. Based on in situ observation data and numerical model, we found that suspended sediment is transported from the Changjiang Estuary into Hangzhou Bay during spring tides, while from Hangzhou Bay into the Changjiang Estuary during neap tides. The key driving mechanisms for the difference during spring-neap tides were expounded by momentum analysis and numerical sensitivity experiments. The barotropic pressure gradient force during spring tides is the key force that drives the suspended sediment from the Changjiang Estuary into Hangzhou Bay. Conversely, the baroclinic pressure gradient force during neap tides is the key force that drives the suspended sediment from Hangzhou Bay into the Changjiang Estuary. This study can provide valuable scientific evidence for erosion and deposition in estuaries and adjacent seas, as well as the sustainable utilization of regional coastal sediment resources.

Spawning migration and habitat characteristics of Labeobarbus species in the Gumara River and its tributaries, Lake Tana subbasin, Ethiopia

Information on the spawning migration and habitat use of migratory fish is critical to protect and restore threatened or endangered populations. Twenty-two individuals of three species, namely Labeobarbus platydorsus, L. megastoma, and L. truttiformis, were implanted with radio tags to study their spawning migration in the Gumara River and its tributaries between July and October of 2018 to 2021. Fourteen individuals were found at least twice throughout their migration, eleven moved upstream up to 41.0 and 44.4 river kilometers (rkm), and three were tracked when moving downstream. The upstream spawning movement of the tagged fish lasted 9 to 27 days, and their ground speeds ranged from 0.07 to 1.50 km h-1. The habitat use of untagged Labeobarbus specimens in the spawning sites was also assessed using fyke nets, cast net fishing, and data from fishermen’s catches. Labeobarbus truttiformis mainly exploited the Kizen tributary stream with gravel substrates and less turbid water for spawning. Several small-sized individuals of L. megastoma spawned in the Wonzuma and Dukalit tributaries. By contrast, larger-sized specimens of L. platydorsus and L. megastoma spawned in the main river channel at the riffles and the gravel/pebble size substrate. Destructive fishing using gillnet dragging, filtering, and damming/fencing has recently intensified at the spawning areas (~ 41.0 rkm to 45.0 rkm), which likely affects spawning populations. Therefore, we recommend that fishing in the main river channel and tributaries must be banned during the months of August, September, and October to safeguard and conserve the threatened Labeobarbus species.

Distribution of an Isopod Parasite Mothocya renardi in the Host Strongylura leiura from Arabian Sea Gujarat Coast, India

Crustacean isopod parasites, particularly in the marine environment, are prevalent around warmer seas and can significantly impact local fish populations. Mothocya renardi, a notable species of isopod parasites, commonly infests fishes in shallow, turbid coastal waters. This study aimed to investigate the occurrence, taxonomy, and morphology of M. renardi infesting Strongylura leiura in the Arabian Sea around the northwest coast of India. Samples were collected from Dholai fishing harbor (Navsari District of Gujarat), during the post-monsoon months. Three specimens of S. leiura were found infected with pairs of male and female M. renardi in the brachial chambers, with all female parasites being brooded ovigerous. Detailed morphological analysis confirmed the presence of M. renardi, extending its known geographical range to the Arabian Sea.