Lakes Tributaries Research Articles

Sequential migrations of diverse fish community provide seasonally prolonged and stable nutrient inputs to a river.

Animal migrations transport resources among spatially separate ecosystems, effectively linking them. In freshwater ecosystems, numerous fish species migrate between mainstream rivers or lakes and their tributaries, providing resources and nutrients during their spawning migrations. Multiple migratory species travel to the same destinations and contribute such nutrients, but knowledge remains limited about how the diversity of migratory animals influences the recipient ecosystem. We investigated how migrations of diverse fish community from Lake Biwa, Japan contribute to nutrient inputs in one of the lake's tributary rivers and how they influence the ecosystem. Sequential migration of six fish species continued for 8 months of a year, causing high-level nutrient concentration and primary production. The fish-derived resources were taken up by diverse members of the river community. Our results emphasize the extent to which migrations of diverse animals seasonally extend and stabilize the resource subsidy and how they extend pronounced effects on the recipient ecosystems.

Examining Bald Eagle Contaminant Exposure and Reproductive Risk Above and Below Dams on Great Lakes Tributaries.

Removing lowermost dams can reestablish fish passage on Great Lakes tributaries. This can increase the transfer of contaminants from anadromous fish to piscivorous wildlife upstream; however, concentrations of bioaccumulative contaminants in Great Lakes fish have decreased over the last several decades. We analyzed concentrations of PCBs and the toxic equivalence (TEQs) calculated from PCBs, DDTs, other organochlorine pesticides, and PBDEs in the plasma of bald eagle nestlings above and below lowermost dams on five river systems in Michigan from 1999 to 2013. We examined relationships between contaminants and metrics of reproductive success from 1997 to 2018, including the effects of year and location relative to the lowermost dam. Σ20PCB and p,p'-DDE were important in characterizing differences in contaminant mixtures above and below dams. Concentrations of contaminants were generally greater below dams than above. There were generally greater nest success and more nestlings per nest below dams, but nest location explained little variability (R2 values = 0.03-0.15). Neither Σ20PCB nor p,p'-DDE was a significant predictor of 5-year productivity means by river reach despite concentrations exceeding previously established effects thresholds for healthy bald eagle populations in the Great Lakes (≥ 1 nestling/nest). Our study indicates that dams may continue to reduce the upstream movement of contaminants to bald eagles, but at the measured concentrations, contaminants did not impair productivity and reproductive success as indicated by nestlings per nest. Additional information about population dynamics could clarify population-level effects of contaminants on bald eagles and to what degree these populations are self-sustaining throughout the Great Lakes.

A Tale of Two Tributaries: Source Delineation of Chloride in a Distressed Watershed (Grand Lake St. Marys, Ohio)

Various sources of pollution have been assigned as contributing to the Freshwater Salinization Syndrome (FSS), by which water bodies are undergoing concurrent salinization and alkalinization. In many urban areas that receive substantial snowfall, road salt application has been ascribed as the main source of chloride driving the FSS. In rural areas, however, inorganic (e.g. chemical) and organic (e.g. manure) fertilizer applications have been found to be the most important sources of chloride. Herein, we compared daily mean concentrations of chloride over the past decade of time between Coldwater Creek and Chickasaw Creek, two tributaries of Grand Lake St. Marys, the largest reservoir in Ohio. We also used Weighted Regressions on Time, Discharge, and Season (WRTDS) analyses to visualize trends in chloride data and compared chloride vs. nitrate levels to delineate likely sources of chloride for the two streams. We found that road salt application increased over time in both subwatersheds and that 37% and 25% of the chloride could be apportioned to road salt as a source in Coldwater Creek and Chickasaw Creek, respectively. Additionally, in Coldwater Creek, 37% of the chloride was apportioned to animal or septic sources, while 25% was apportioned to inorganic fertilizers, in comparison with 30% and 42% for Chickasaw Creek. Monitoring and assessing salinized streams for both chemical and biological water quality is important, particularly since the FSS has become increasingly linked to declines in water quality (e.g. harmful algal blooms, including recent upticks in Prymnesium parvum blooms) and is expected to be exacerbated with global climate change (e.g. increased precipitation causing increased runoff of chloride from the land).

Methylmercury in commercial fish species from the Erhai Lake Basin, Southwest China: concentrations, health risk assessment, and implications for future monitoring.

Erhai Lake, a highland lake situated in Southwest China, provides critical aquatic protein sources for the local community, and its preservation is vital due to the sensitivity of alpine freshwater ecosystems to disturbance. However, there is a lack of research on the contamination status of methylmercury (MeHg) in aquatic organisms of the Erhai Lake Basin. MeHg concentrations in important commercial fish species from the Erhai Lake were examined, and the potential health risks associated with human consumption were assessed. Our results showed significant inter-species differences in fish muscle MeHg: the carnivorous S. asotus exhibited the highest level (303ng/g; ww), while that of the detritivorous R. ocellatus was the lowest (3.86ng/g). Moreover, MeHg concentrations in P. fulvidraco and C. auratus collected from the Luoshi River (a major tributary of Erhai Lake) were significantly higher compared to those from the Erhai Lake, indicating possible river-based input of MeHg into the Erhai Lake. Additionally, our study revealed a significant positive correlation between the MeHg levels and the length as well as weight of the examined fish species. All the fish species analyzed in our study had MeHg concentrations within the limits of China's food safety standard. Nevertheless, a relatively low consumption quantity of 16g per day of certain species (i.e., S. asotus) may still pose potential health risks especially for children. The present study provides baseline data for MeHg monitoring and risk assessment in the Erhai Lake Basin, and warrants continued monitoring and source investigation.

Predictive Functional Profiling Reveals Putative Metabolic Capacities of Bacterial Communities in Drinking Water Resources and Distribution Supply in Mega Manila, Philippines

Assessing bacterial communities across water resources is crucial for understanding ecological dynamics and improving water quality management. This study examines the functional profiles of bacterial communities in drinking water resources in Mega Manila, Philippines, including Laguna Lake tributaries, pre-treatment plant sites, groundwater sources, and post-treatment plant sites. Using eDNA sequencing, flux balance analysis, and taxonomy-to-phenotype mapping, we identified metabolic pathways involved in nutrient metabolism, pollutant degradation, antibio- tic synthesis, and nutrient cycling. Despite site variations, there are shared metabolic pathways, suggesting the influence of common ecological factors. Site-specific differences in pathways like ascorbate, aldarate, and phenylalanine metabolism indicate localized environmental adaptations. Antibiotic synthesis pathways, such as streptomycin and polyketide sugar unit biosynthesis, were detected across sites. Bacterial communities in raw and pre-treatment water showed potential for pollutant degradation such as for endocrine-disrupting chemicals. High levels of ammonia-oxidizing and sulfate-reducing bacteria in pre- and post-treatment water suggest active nitrogen removal and pH neutralization, indicating a need to reassess existing water treatment approaches. This study underscores the adaptability of bacterial communities to environmental factors, as well as the importance of considering their functional profiles in assessing drinking water quality resources in urban areas.

Potential Hazards of Polycyclic Aromatic Hydrocarbons in Great Lakes Tributaries Using Water Column and Porewater Passive Samplers and Sediment Equilibrium Partitioning.

The potential for polycyclic aromatic hydrocarbon (PAH)-related effects in benthic organisms is commonly estimated from organic carbon-normalized sediment concentrations based on equilibrium partitioning (EqP). Although this approach is useful for screening purposes, it may overestimate PAH bioavailability by orders of magnitude in some sediments, leading to inflated exposure estimates and potentially unnecessary remediation costs. Recently, passive samplers have been shown to provide an accurate assessment of the freely dissolved concentrations of PAHs, and thus their bioavailability and possible biological effects, in sediment porewater and overlying surface water. We used polyethylene passive sampling devices (PEDs) to measure freely dissolved porewater and water column PAH concentrations at 55 Great Lakes (USA/Canada) tributary locations. The potential for PAH-related biological effects using PED concentrations were estimated with multiple approaches by applying EqP, water quality guidelines, and pathway-based biological activity based on in vitro bioassay results from ToxCast. Results based on the PED-based exposure estimates were compared with EqP-derived exposure estimates for concurrently collected sediment samples. The results indicate a potential overestimation of bioavailable PAH concentrations by up to 960-fold using the EqP-based method compared with measurements using PEDs. Even so, PED-based exposure estimates indicate a high potential for PAH-related biological effects at 14 locations. Our findings provide an updated, weight-of-evidence-based site prioritization to help guide possible future monitoring and mitigation efforts. Environ Toxicol Chem 2024;43:1509-1523. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Collective Córregos Da Tiririca- Restoration of Riparian Forest in a Stream Contributor of Itaipu Lagoon – Niterói- RJ- Brazil

The lake system Itaipu-Piratininga in Niterói at north from the Guanabara Bay is drained by a set of streams. As a result of urban expansion at oceanic region of the city those streams became dirty and polluted. In a time-scale of twenty-five years after studies on water biodiversity, the lake system became eutrophized, with shallow waters. One way to recover the health of the ecossystem is to restore the freshwater rivers draining the system. The present study proposes to inform the experience of agroforestry restoration of the riparian forest in a tributary of Itaipu lake as well as bring an evaluation of local biodiversity – arboreal plants, terrestrial and aquatic vertebrates. After the inventory made, there followed the agroforestry planting of riparian forest by the organized civil society through the collective Córregos da Tiririca [streams at Tiririca mountains]. The technique employed for restoration is related, as corresponds to an adaptation of the principles of syntropic agriculture to the reality of an urban stream.

Adfluvial migration and passage of Steelhead before and after dam removal at a major Great Lakes tributary

Despite the importance of Great Lakes fisheries and the increasing popularity of dam removal as a method to restore river connectivity and increase fish passage, the adfluvial migration of Steelhead (Oncorhynchus mykiss) has been drastically understudied and only relatively few published studies have examined the impacts of dam removal on fish movement and timing. To help fill these knowledge gaps, spawning migrations of Great Lakes adfluvial Steelhead tagged in spring and fall were monitored for two years before and three years after removal of a dam that partially blocked upstream movement for 100 years. Removal of the dam not only reduced downstream delay and increased passage at the site of the dam removal itself, but increased travel speeds and increased passage at remaining upstream dams for both spring and fall run fish, underscoring the cumulative impact of successive dam passage on fish migration. Fall fish were most impacted by the dam removal and were able to pass not only the dam footprint, but, for the first time, were also able to pass both remaining upstream dams, allowing them to overwinter at locations closer to known spawning areas. For these fish, delay at the footprint was reduced from the order of 100+ days to < 1 hour and the number of days passage occurred compared to the number of days fish were present and blocked increased from 2% to 82%. The benefits of dam removal should ultimately equate to increases in fish production, as more critical habitat becomes reconnected and more fish are able to pass dams and arrive at spawning beds. The observation that fish are likely able to remain in better condition and retain more energy for continued migration and reproduction warrants further study.

Collective Córregos Da Tiririca- Restoration of Riparian Forest in a Stream Contributor of Itaipu Lagoon – Niterói- RJ

The lake system Itaipu-Piratininga in Niterói at north from the Guanabara Bay is drained by a set of streams. As a result of urban expansion at oceanic region of the city those streams became dirty and polluted. In a time-scale of twenty-five years after studies on water biodiversity, the lake system became eutrophized, with shallow waters. One way to recover the health of the ecossystem is to restore the freshwater rivers draining the system. The present study proposes to inform the experience of agroforestry restoration of the riparian forest in a tributary of Itaipu lake as well as bring an evaluation of local biodiversity – arboreal plants, terrestrial and aquatic vertebrates. After the inventory made, there followed the agroforestry planting of riparian forest by the organized civil society through the collective Córregos da Tiririca [streams at Tiririca mountains]. The technique employed for restoration is related, as corresponds to an adaptation of the principles of syntropic agriculture to the reality of an urban stream.

Transcriptomics-Based Points of Departure for Daphnia magna Exposed to 18 Per- and Polyfluoroalkyl Substances.

Per- and polyfluoroalkyl substances (PFAS) represent a large group of contaminants of concern based on their widespread use, environmental persistence, and potential toxicity. Many traditional models for estimating toxicity, bioaccumulation, and other toxicological properties are not well suited for PFAS. Consequently, there is a need to generate hazard information for PFAS in an efficient and cost-effective manner. In the present study, Daphnia magna were exposed to multiple concentrations of 22 different PFAS for 24 h in a 96-well plate format. Following exposure, whole-body RNA was extracted and extracts, each representing five exposed individuals, were subjected to RNA sequencing. Following analytical measurements to verify PFAS exposure concentrations and quality control on processed cDNA libraries for sequencing, concentration-response modeling was applied to the data sets for 18 of the tested compounds, and the concentration at which a concerted molecular response occurred (transcriptomic point of departure; tPOD) was calculated. The tPODs, based on measured concentrations of PFAS, generally ranged from 0.03 to 0.58 µM (9.9-350 µg/L; interquartile range). In most cases, these concentrations were two orders of magnitude lower than similarly calculated tPODs for human cell lines exposed to PFAS. They were also lower than apical effect concentrations reported for seven PFAS for which some crustacean or invertebrate toxicity data were available, although there were a few exceptions. Despite being lower than most other available hazard benchmarks, D. magna tPODs were, on average, four orders of magnitude greater than the maximum aqueous concentrations of PFAS measured in Great Lakes tributaries. Overall, this high-throughput transcriptomics assay with D. magna holds promise as a component of a tiered hazard evaluation strategy employing new approach methodologies. Environ Toxicol Chem 2024;00:1-16. © 2024 SETAC. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

The Variation in the Water Level of Lake Baikal and Its Relationship with the Inflow and Outflow

Lake Baikal is the largest freshwater lake in the world, accounting for about 20% of the world’s fresh surface water. The lake’s outflow to the ocean occurs only via the Angara River, which has several hydroelectric power plants (HPPs) along its watercourse. The first such HPP, Irkutsk HPP, was built in 1956 and is located 60 km from the Angara River’s source. After two years, the backwater from this HPP expanded to the lake shores and began raising the Baikal Lake level. Currently, there is a dynamic balance between the new lake level, the lake inflow from its tributaries, and the Angara River discharge through the Irkutsk HPP. However, both the Angara River discharge and the Baikal Lake level were distorted by the HPP construction. Thus, to understand the changes to the lake basin over the past century, we first needed to estimate naturalized lake levels that would be if no HPP was ever built. This was an important task that allowed (a) the actual impact of global changes on the regional hydrological processes to be estimated and (b) better management of the HPP itself to be provided through future changes. With these objectives in mind, we accumulated multi-year data on the observed levels of Lake Baikal, and components of its water budget (discharge of main tributaries and the Angara River, precipitation, and evaporation). Thereafter, we assessed the temporal patterns and degree of coupling of multi-year and intra-annual changes in the lake’s monthly, seasonal, and annual characteristics. The reconstruction of the average monthly levels of Lake Baikal and the Angara River water discharge after the construction of the Irkutsk HPP was based on the relationship of the fluctuations with the components of the Lake water budget before regulation. As a result, 123-year time series of “conditionally natural” levels of Lake Baikal and the Angara River discharge were reconstructed and statistically analyzed. Our results indicated high inertia in the fluctuations in the lake level. Additionally, we found a century-long tendency of increases in the lake level of about 15 cm per 100 years, and we quantified the low-frequency changes in Lake Baikal’s water levels, the discharge of the Angara River, and the main lake tributaries. An assessment of the impact of the Irkutsk HPP on the multi-year and intra-annual changes in the Lake Baikal water level and the Angara River discharge showed that the restrictions on the discharge through the HPP and the legislative limitations of the Lake Baikal level regime have considerably limited the fluctuations in the lake level. These fluctuations can lead to regulation violations and adverse regimes during low-water or high-water periods.

Hydrochemical Characteristics and Its Origin of Surface Water and Groundwater in Dianbu River Basin

Chaohu lake is a key water body for water pollution prevention and treatment in our country. However， it has been at a higher eutrophication level recently. Here， the surface water and groundwater in the Dianbu River Basin， a secondary tributary of Chaohu Lake， were taken as the research object. In order to test the hydrochemical composition and hydrogen and oxygen isotope values of different water bodies， 30 groups of surface water samples， 36 groups of groundwater samples， 16 groups of hydrogen and oxygen stable isotope samples， and 18 groups of groundwater hydrogen and oxygen stable isotope samples were collected in August 2021 （wet season）， November 2021 （normal season）， and February 2022 （dry season）. The seasonal and spatial variation characteristics were analyzed to explore the hydrochemical characteristics and formation mechanism of water bodies by means of mathematical statistics， Piper triangular diagram， Gibbs figures， and ion ratios. The following results were obtained： ① precipitation was the main source of surface water and groundwater in Dianbu River Basin， and the evaporation fractionation effect of surface water was more significant than that of groundwater. At different periods， the surface water was more enriched with stable isotopes of hydrogen and oxygen than groundwater. The stable isotopes of hydrogen and oxygen in water showed seasonal variation， relative enrichment in the wet season， and depletion in the dry season. ② Both surface water and groundwater in the Dianbu River Basin were weakly alkaline， and the concentration of ions in surface water was significantly lower than that in groundwater. Ca2+ and Na+ were the main cations in surface water， Ca2+ was the main cation in groundwater， and the dominant anion in all water was HCO3-. The hydrochemical typology of surface water was mainly HCO3·Cl-Na·Ca， and that of groundwater was mainly HCO3-Na·Ca. ③ The concentrations of the main hydrochemical indexes of surface water and groundwater showed certain seasonal and spatial differences. From the wet season to the dry season， the concentrations of TDS， K+， Na+， Ca2+， Mg2+， Cl-， and SO42- in surface water showed an increasing trend on the whole. The concentrations of Na+， Ca2+， and Mg2+ in groundwater showed little change but increased slightly， whereas the concentrations of Cl-， SO42-， and NO3- showed an increasing trend on the whole. The concentrations of Cl-， SO42-， and NO3- in the water showed relatively large seasonal fluctuations. From upstream to downstream， the concentrations of the main hydrochemical indexes in surface water first decreased and then increased， among which the concentration of NO3- increased the most. The concentrations of the main hydrochemical indexes of groundwater in the direction of runoff changed little overall， but the concentration in the discharge area was higher than that in the recharge area. ④ The formation of hydrochemical characteristics of the water was mainly controlled by water-rock interaction but was also influenced by human factors. The water-rock action was mainly the weathering dissolution of silicate rock， salt rock， and carbonate rock. Man-made pollutants such as sewage from a sewage treatment plant， domestic sewage， and feces had obviously changed the hydrochemical characteristics of the local water. ⑤ Compared with that in 2016， the concentration of NO3- in surface water showed a certain degree of reduction. The nitrogen pollution control work carried out by the local government had achieved certain results， but it was still necessary to strengthen the pollution prevention and control of sewage and feces in the downstream of the Dianbu River， some tributaries （such as the Dingguang River and Maqiao River）， and some residential areas.

Combining Hydrological Modeling and Regional Climate Projections to Assess the Climate Change Impact on the Water Resources of Dam Reservoirs

Climate change may significantly impact the availability and quality of water resources in dam reservoirs by potentially altering the hydrological regime of lake tributaries and the corresponding flow–duration curves. Hydrological models driven by climate projections (downscaled to the watershed scale and bias corrected to eliminate systematic errors) are effective tools for assessing this potential impact. To assess the uncertainty in future water resource availability, resulting from the inherent uncertainty in climate model projections, an ensemble of climate models and different climate scenarios can be considered. The reliability and effectiveness of this approach were illustrated by analyzing the potential impact of climate change on the water availability at Brugneto Lake in northern Italy. This analysis was based on climate projections derived from an ensemble of 13 combinations of General Circulation Models and Regional Climate Models under two distinct scenarios (RCP4.5 and RCP8.5). The semi-distributed HEC-HMS model was adopted to simulate the hydrological response of the basin upstream of the lake. The hydrological model parameters were calibrated automatically via the PEST software package using the inflows to the lake, estimated through a reverse level pool routing method, as observed values. Future water availability was predicted for short- (2010–2039), medium- (2040–2069), and long-term (2070–2099) periods. The results indicate that the uncertainty in reservoir inflow is primarily due to the uncertainty in future rainfall. A moderate reduction in water availability is expected for Brugneto Lake by the end of the current century, accompanied by modifications in the flow regime. These changes should be considered when planning future adaptation measures and adjusting reservoir management rules.

Riverscape genetics of the orangethroat darter complex.

Freshwater darters belonging to the orangethroat darter species complex, or Ceasia, are widely distributed in the Central and Southern United States, with ranges that span both glaciated and unglaciated regions. Up to 15 species have been recognized in the complex, with one, Etheostoma spectabile, having a widespread northern distribution and another, Etheostoma pulchellum, having a sizeable southern distribution. The other species in the complex have much more restricted distributions in unglaciated regions of the Central Highlands. We sampled 384 darters from 52 sites covering much of the range of Ceasia and evaluated patterns of genetic diversity, genetic structure, and pre- and post-glacial patterns of range contraction and expansion. We anticipated finding much stronger signals of genetic differentiation and diversification in unglaciated regions, given the higher species diversity and levels of endemism reported there. Surprisingly, microsatellite genotyping revealed two well-differentiated genetic clusters of E. spectabile in samples from glaciated regions, one confined to the Illinois River basin and another found in the Wabash drainage and Great Lakes tributaries. This suggests that there was expansion from two isolated glacial refugia, with little subsequent post-glacial gene flow. Fish collected from throughout the unglaciated region were less genetically differentiated. Fish assigned to Etheostoma burri and Etheostoma uniporum based on collection sites and morphological characters were not genetically differentiated from E. spectabile samples from the region. Hybridization and introgression occurring in the Central Highlands may confound genetic delineation of species in this region of high endemism and diversity.

Spatial patterns of resource subsidies in Great Lakes tributaries from migratory fishes

Migratory fish can influence the stream ecosystems where they spawn by depositing large amounts of energy rich eggs, carcasses, and excrement which can increase primary and secondary productivity. Past research in the Great Lakes has focused on individual tributaries; accordingly, there is a poor understanding of how wide-spread resource subsidies are amongst tributaries. To determine which Great Lake tributaries received subsidies, we compared carbon stable isotope values (δ13C) of resident stream fishes above and below 54 barriers (e.g., low-head lamprey weirs, natural waterfalls) in 31 tributaries. Subsidies, as indicated by the difference in δ13C values above and below barriers, were common. The magnitude of the subsidy varied among Great Lakes with Lake Superior having significantly larger subsidies than the other three lakes. Barrier type (complete, partial) was not related to subsidy magnitude; however, the classification of barrier type was imperfect. Correspondence analysis of regional and local environmental factors showed that large subsidies were associated with oligotrophic streams with steep channels on the Canadian Shield with little agricultural land. The association between subsidies and canopy cover and substrate size were poor. Migratory fish supply resource subsidies to rivers across the Great Lakes basin, though their magnitude is contextually dependent. The presence of barriers are likely limiting the production of migratory fishes that depend on streams for juvenile production. The importance of resource subsidies should be considered when decisions are made about the fate of existing, and the construction of new, barriers that may reduce stream productive capacity.

Geochemical behavior of heavy metals and radionuclides in a pit lake affected by acid mine drainage (AMD) in the Muskau Arch (Poland)

Pit lakes in the ‘anthropogenic lake district’ in the Muskau Arch (western Poland; central Europe) are strongly affected by acid mine drainage (AMD). The studied acidic pit lake, ŁK-61 (pH <3), is also exposed to floods due to its location in the flood hazard area, which may significantly influence the geochemical behavior of elements. The elemental compositions of water and lake sediment samples were measured with ICP–OES and ICP–MS. The sediment profile was also examined for 137Cs and 210Po activity concentrations using gamma and alpha spectrometry, respectively. Grain size distribution, mineralogical composition, diatoms, and organic matter content in the collected core were also determined. The key factors responsible for the distribution of selected heavy metals (e.g., Cu, Ni, Pb, Zn) and radioisotopes (137Cs and 210Po) in the bottom sediments of Lake ŁK-61 are their coprecipitation/precipitation with Fe and Al secondary minerals and their sorption onto authigenic and allogenic phases. These processes are likely driven by the lake tributary, which is an important source of dissolved elements. The data also showed that the physiochemical parameters of Lake ŁK-61 water changed during an episodic depositional event, i.e., the flood of the Nysa Łużycka River in the summer of 2010. The flood caused an increase in the water pH, as interpreted from the subfossil diatom studies. The down-core profiles of the studied heavy metal and radionuclide (HMRs) contents were probably affected by this depositional event, which prevented a detailed age determination of the collected lake sediments with 137Cs and 210Pb dating methods. Geochemical modeling indicates that the flood-related shift in the physicochemical parameters of the lake water could have caused the scavenging of dissolved elements by the precipitation of fresh secondary minerals. Moreover, particles contaminated with HMRs have also possibly been delivered by the river, along with the nutrients (e.g., phosphorus and nitrogen).

Behaviour of synthetic musk fragrances in freshwaters: occurrence, relations with environmental parameters, and preliminary risk assessment

The aims of this study were to investigate the presence, possible sources, and potential ecological risks of synthetic musk fragrances in freshwaters and sediments of the main tributaries of a deep subalpine lake in Northern Italy. The total musk concentrations ranged from few ng L−1 up to values > 500 ng L−1, depending on river characteristics: water flow and the presence of wastewater effluents proved to be the main factors affecting fragrance concentrations. The water flow may indeed dilute fragrance input mainly deriving from treated wastewaters. Good correlations (determination coefficients > 0.60) between synthetic fragrances concentrations and parameters related to anthropogenic impacts confirmed this hypothesis: synthetic fragrances were mainly detected in most polluted rivers crossing urbanized areas. Sediment analysis highlighted accumulation of fragrances in this matrix. Concentrations of synthetic fragrances up to 329 ng g−1 organic carbon were measured in sediments of the most contaminated rivers Boesio and Bardello, which also show the highest nutrient content. The preliminary environmental risk assessment revealed that present levels of synthetic musk fragrances do not pose any risk to the studied environmental compartments. However, a probable medium risk level was evidenced during the dry season in the most contaminated rivers Boesio and Bardello. For these reasons, small rivers draining urbanized watersheds and affected by wastewater effluents should be considered synthetic musk contamination hotspots that warrant further research.

Microalgal diversity assessment of Laguna Lake (Philippines) tributaries using Next-Generation Sequencing for water quality

Abstract. Santos JA, Mejia JA, Galarion MAJ, Vital P. 2023. Microalgal diversity assessment of Laguna Lake (Philippines) tributaries using Next-Generation Sequencing for water quality. Biodiversitas 24: 4636-4644. The species composition and density of microalgae have been successfully used as bioindicators of water quality as they respond quickly to any change in the water chemistry brought about by pollution. Laguna Lake in the Philippines, one of the country's most important hotspots for aquaculture, continues to be threatened by eutrophication, yet its microalgal profile has been understudied. The presence of microalgae, especially those identified to become causative agents of harmful algal blooms in lakes, can cause corresponding health effects in humans and the environment. This study determined microalgal diversity in samples from tributaries of Laguna Lake, Philippines, through 18S rRNA metagenomic sequencing or Next-Generation Sequencing (NGS). Out of the five sampling sites, only two sites passed the NGS quality control pipeline. Chlorella M.Beijerinck, dominated the eukaryotic microbial population in the Alabang-Cupang River sample, which is 95% of the total population. While in the Biñan River sample, relevant species found were Cyclotella scaldensis Muylaert &amp; Sabbe, Teleaulax acuta (Butcher) Hill, Cryptomonas curvata Ehrenb., and Peridiniopsis penardii (Lemmerm.) Bourr. This is the first study to use NGS to detect microalgae in Laguna Lake and warrants further elucidation of the microalgal population through increased sampling efforts in other recreational and livelihood hotspots. Furthermore, the study results open the importance of implementing new schemes for water quality assessments focused on molecular-based approaches.

Using a retention pond to capture agricultural contaminants from surface waters

To meet the demand of a constantly growing population, agriculture is intensifying, causing an increased use of fertilizers and pesticides. Excessive nutrients transfer to aquatic ecosystems can disrupt the water quality and impact the aquatic life. Pesticides can also have toxic effects on non-target organisms from aquatic systems. The purpose of this study was to evaluate the efficiency of an agricultural retention pond in reducing the supply of nutrients, pesticides and suspended solids to the Nicolet River, a tributary of Lake St. Pierre in the St. Lawrence River. Research combining the study of the fate of a wide range of contaminants in both pond water and sediments, their toxicity to microcrustaceans, microalgae and amphipods, and the effectiveness of contaminant removal, has rarely been carried out in the past. Peak contaminant concentrations occurred one to two months after pesticide and fertilizer applications, and during the months with the highest rainfall. Toxic effects were only observed on microalgae, with suspended solids apparently responsible for this effect through light inhibition on growth rates. However, the pond was not effective in removing this toxicity even if suspended solids were largely removed. Pesticides removal varied widely among sampling dates and pesticide types, with an efficiency reaching 95 % for thiamethoxam, but generally remaining low and often negative (higher concentrations in outflowing water) for other pesticides. On the other hand, the mean fractional removal of suspended solids, phosphorus, and nitrogen based on concentrations was 71 %, 44 % and 22 %, respectively. These are conservative estimations since the removal rates based on loads were above 94 %. The use of retention ponds thus seems an efficient approach to reduce the quantity of fertilizers in rivers draining agriculture areas, but the studied pond was not systematically effective in removing pesticides.

The Comet Assay, a Sensitive Biomarker of Water Quality Improvement Following Adoption of Beneficial Agricultural Practices?

Numerous actions have been undertaken by farmers to attenuate the impact of agricultural activities on aquatic ecosystems. The identification of biomarkers that respond quickly to water quality improvement could facilitate the assessment of adopted alternative practices and help maintain mobilization among stakeholders. We evaluated the potential of the comet assay, a biomarker of genotoxic effects, using a freshwater mussel, Elliptio complanata, as a model animal. The frequency of DNA damage was assessed in hemocytes of mussels collected from a pristine habitat and caged for 8 weeks in the Pot au Beurre River, a tributary of the fluvial Lake St.-Pierre (Quebec, Canada) impacted by agricultural activities. We found that the level of DNA damage naturally induced in mussel hemocytes was low and showed very limited variations over time. Compared with these baseline levels and to laboratory controls, we observed a doubling in DNA alterations in mussels exposed to agricultural runoff in the third branch of the Pot au Beurre River. The genotoxic response was significantly lower in mussels caged in the first branch of the Pot au Beurre River, where longer stretches of shoreline have been restored as buffer strips. Glyphosate, mesotrione, imazethapyr, and metolachlor were the main discriminant pesticides between these two branches. Metolachlor was found in sufficient concentrations to induce DNA damage, but it is more likely that the observed genotoxicity was the result of a "cocktail effect," that is, the cumulative contribution of coexisting genotoxicants including the above-mentioned herbicides and ingredients in their formulation. Our findings suggest that the comet assay is a sensitive tool for the early detection of changes in water toxicity following the adoption of agricultural beneficial practices. Environ Toxicol Chem 2023;42:2201-2214. © 2023 Crown copyright and The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. This article is published with the permission of the Controller of HMSO and the King's Printer for Scotland.