Influence of salinity, nitrogen and phosphorus concentrations on the physiological and biochemical characteristics of two Chlorophyceae isolated from Fez freshwater, Morocco.

Microalgae are widely exploited for numerous biotechnology applications, including biofuels. In this context, Chlamydomonas debaryana and Chlorococcum sp. were isolated from Fez freshwater (Morocco), and their growth and lipid and carbohydrate production were assessed at different concentrations of NaCl, NaNO3, and K2HPO4. The results indicate a small positive variation in growth parameters linked to nutrient enrichment, with no considerable variation in carbohydrate and lipid levels in both algae. Moreover, a negative variation was recorded at increased salinity and nutrient limitation, accompanied by lipid and carbohydrate accumulation. Chlorococcum sp. showed better adaptation to salt stress below 200 mM NaCl. Furthermore, its growth and biomass productivity were strongly reduced by nitrogen depletion, and its lipid production reached 47.64% DW at 3.52 mM NaNO3. As for Chlamydomonas debaryana, a substantial reduction in growth was induced by nutrient depletion, a maximal carbohydrate level was produced at less than 8.82 mM NaNO3 (40.59% DW). The effect of phosphorus was less significant. However, a concentration of 0.115 mM K2HPO4 increased lipid and carbohydrate content without compromising biomass productivity. The results suggest that growing the two Chlorophyceae under these conditions seems interesting for biofuel production, but the loss of biomass requires a more efficient strategy to maximize lipid and carbohydrate accumulation without loss of productivity.

Distribution patterns and influential factors of pathogenic bacteria in freshwater aquaculture sediments.

Pathogenic bacteria, the major causative agents of aquaculture diseases, are a serious impediment to the aquaculture industry. However, the bioinformatics of pathogenic bacteria and virulence factors (VFs) in sediments, an important component of freshwater aquaculture ecosystems, are not well characterized. In this study, 20 sediment samples were collected from fish pond sediments (FPS), shrimp field sediments (SFS), fish pond sediment control (FPSC), and shrimp field sediment control (SFSC). Molecular biological information was obtained on a total of 173 pathogenic bacteria, 1093 virulence factors (VFs), and 8475 mobile genetic elements (MGEs) from these samples. The results indicated that (1) aquaculture patterns and sediment characteristics can affect the distribution of pathogenic bacteria. According to the results of the Kruskal-Wallis H test, except for Mycobacterium gilvum, there were significant differences (P < 0.05) among the four sediment types in the average abundance of major pathogenic bacteria (top 30 in abundance), and the average abundance of major pathogenic bacteria in the four sediment types followed the following pattern: FPS > SFS > FPSC > SFSC. (2) Pathogenic bacteria are able to implement a variety of complex pathogenic mechanisms such as adhesion, invasion, immune evasion, and metabolic regulation in the host because they carry a variety of VFs such as type IV pili, HSI-I, Alginate, Colibactin, and Capsule. According to the primary classification of the Virulence Factor Database (VFDB), the abundance of VFs in all four types of sediments showed the following pattern: offensive VFs > non-specific VFs > defensive VFs > regulation of virulence-related genes. (3) Total organic carbon (TOC), total phosphorus (TP), available phosphorus (AP), nitrite, and nitrate were mostly only weakly positively correlated with the major pathogenic bacteria and could promote the growth of pathogenic bacteria to some extent, whereas ammonia was significantly positively correlated with most of the major pathogenic bacteria and could play an important role in promoting the growth and reproduction of pathogenic bacteria. (4) Meanwhile, there was also a significant positive correlation between CAZyme genes and major pathogenic bacteria (0.62 ≤ R ≤ 0.89, P < 0.05). This suggests that these pathogenic bacteria could be the main carriers of CAZyme genes and, to some extent, gained a higher level of metabolic activity by degrading organic matter in the sediments to maintain their competitive advantage. (5) Worryingly, the results of correlation analyses indicated that MGEs in aquaculture sediments could play an important role in the spread of VFs (R = 0.82, P < 0.01), and in particular, plasmids (R = 0.75, P < 0.01) and integrative and conjugative elements (ICEs, R = 0.65, P < 0.05) could be these major vectors of VFs. The results of this study contribute to a comprehensive understanding of the health of freshwater aquaculture sediments and provide a scientific basis for aquaculture management and conservation.

Effects of nutrient enrichment on freshwater macrophyte and invertebrate abundance: A meta-analysis.

External nutrient loading can cause large changes in freshwater ecosystems. Many local field and laboratory experiments have investigated ecological responses to nutrient addition. However, these findings are difficult to generalize, as the responses observed may depend on the local context and the resulting nutrient concentrations in the receiving water bodies. In this research, we combined and analysed data from 131 experimental studies containing 3054 treatment-control abundance ratios to assess the responses of freshwater taxa along a gradient of elevated nutrient concentrations. We carried out a systematic literature search in order to identify studies that report the abundance of invertebrate, macrophyte, and fish taxa in relation to the addition of nitrogen, phosphorus, or both. Next, we established mixed-effect meta-regression models to relate the biotic responses to the concentration gradients of both nutrients. We quantified the responses based on various abundance-based metrics. We found no responses to the mere addition of nutrients, apart from an overall increase of total invertebrate abundance. However, when we considered the gradients of N and P enrichment, we found responses to both nutrients for all abundance metrics. Abundance tended to increase at low levels of N enrichment, yet decreased at the high end of the concentration gradient (1-10 mg/L, depending on the P concentration). Responses to increasing P concentrations were mostly positive. For fish, we found too few data to perform a meaningful analysis. The results of our research highlight the need to consider the level of nutrient enrichment rather than the mere addition of nutrients in order to better understand broad-scale responses of freshwater biota to eutrophication, as a key step to identify effective conservation strategies for freshwater ecosystems.

Groundwater is a hidden global keystone ecosystem.

Groundwater is a vital ecosystem of the global water cycle, hosting unique biodiversity and providing essential services to societies. Despite being the largest unfrozen freshwater resource, in a period of depletion by extraction and pollution, groundwater environments have been repeatedly overlooked in global biodiversity conservation agendas. Disregarding the importance of groundwater as an ecosystem ignores its critical role in preserving surface biomes. To foster timely global conservation of groundwater, we propose elevating the concept of keystone species into the realm of ecosystems, claiming groundwater as a keystone ecosystem that influences the integrity of many dependent ecosystems. Our global analysis shows that over half of land surface areas (52.6%) has a medium-to-high interaction with groundwater, reaching up to 74.9% when deserts and high mountains are excluded. We postulate that the intrinsic transboundary features of groundwater are critical for shifting perspectives towards more holistic approaches in aquatic ecology and beyond. Furthermore, we propose eight key themes to develop a science-policy integrated groundwater conservation agenda. Given ecosystems above and below the ground intersect at many levels, considering groundwater as an essential component of planetary health is pivotal to reduce biodiversity loss and buffer against climate change.

Polystyrene nanoplastics alter the ecotoxicological effects of diclofenac on freshwater microalgae Scenedesmus obliquus.

Due to the escalating risk of plastic pollution, nanoplastics have attracted considerable attention in the recent past. They can co-exist and interact with other contaminants like pharmaceuticals in the aquatic environment. Therefore, it is pertinent to understand how these pollutants interact with one another in the ecosystem. The current study examined the individual and combined effects of fluorescent polystyrene nanoplastics (FNPs) and diclofenac (DCF) on Scenedesmus obliquus using a full factorial design. The toxicity of S. obliquus significantly increased in a dose-dependent manner upon exposure to pristine forms of DCF and FNPs. The major cause of individual toxicity of DCF and FNPs in S. obliquus was oxidative stress. In the combined toxicity tests when FNPs (0.01, 0.1, and 1 mg L-1) and DCF (1 mg L-1) were mixed, a synergistic effect was noted compared to the respective pristine FNPs. However, when the DCF concentration in the mixture was decreased to 0.25 mg L-1, the combined toxicity with FNPs (0.01, 0.1, and 1 mg L-1) reduced indicating an antagonistic effect. The independent action model also showed an antagonistic effect for low-dose combinations of DCF and a synergistic effect for high-dose combinations. The estimation of oxidative stress parameters, antioxidant enzyme activity, and photosynthetic pigment content in the algae further validated the cytotoxicity data. The mean hydrodynamic diameter and surface charge analyses further indicated that the colloidal stability of the FNPs in the medium was affected when they were combined with DCF. The key reason for differences in the cytotoxicity of combinations could be observed variations in the aggregation of FNPs and differential adsorption patterns of DCF on the FNPs. These factors efficiently altered cell-particle interactions in the mixture demonstrating a hormesis effect. Thus, this current study highlighted the hazardous nature of the nanoplastics and their co-exposure risks with pharmaceuticals on microalgae in freshwater environments.

Extraction of eutrophic and green ponds from segmentation of high-resolution imagery based on the EAF-Unet algorithm.

Inland ponds exhibit remarkable ubiquity across the globe, playing a vital role in the sustainability of global continental freshwater resources and contributing significantly to their biodiversity. Numerous ponds are eutrophic and experience recurrent seasonal or year-round algal blooms or persistent duckweed cover, conferring a characteristic green hue. Here, we denote these eutrophic and green ponds as EGPs. The excessive proliferation of algal blooms and duckweed within these EGPs poses a significant threat to the ecological functioning of these aquatic systems, which can lead to hypoxia or the release of microcystins. To identify these EGPs automatically, we constructed an Efficient Attention Fusion Unet (EAF-Unet) algorithm using Gaofen-2 (GF2) panchromatic and multispectral imagery. The attention mechanism was incorporated in Unet to help better detect EGPs. Using the first EGP labeled dataset, we determined the best input feature combination (RGB, NIR, NDVI, and Bright) and the most effective encoding (Rasnet50) for EAF-Unet for distinguishing EGPs from other ground cover types. The evaluation indices - Precision (0.81), Recall (0.79), F1-Score (0.80), and Intersection over Union (IoU, 0.67) - indicate that EAF-Unet can accurately and robustly extract EGPs from GF2 images without relying on pond water masks. Remote-sensing EGP products can assist in identifying ponds with severe eutrophication. Moreover, these products can serve as references for identifying high-risk areas prone to improper sewage discharge or inadequate sewer construction.

Fate, behaviour and microbial response of diluted bitumen and conventional crude spills in a simulated warm freshwater environment.

Diluted bitumen (DB), one of the most transported unconventional crude oils in Canada's pipelines, raises public concerns due to its potential spillage into freshwater environments. This study aimed to compare the fate and behaviour of DB versus conventional crude (CC) in a simulated warm freshwater environment. An equivalent of 10 L of either DB or CC was spilled into 1200 L of North Saskatchewan River (NSR) water containing natural NSR sediment (2.4 kg) in a mesoscale spill tank and its fate and behaviour at air/water temperatures of 18 °C/24 °C were monitored for 56 days. Oil mass distribution analysis showed that 42.3 wt % of CC and 63.6 wt% of DB resided in the oil slicks at the end of 56-day tests, consisting mainly high molecular weight (HMW) compounds (i.e., resins and asphaltenes). The lost oil contained mainly low molecular weight (LMW) compounds (i.e., light saturates and some aromatics) into the atmosphere, water column, and sediment through collective weathering processes. Notably, weathered CC emulsified with water and remained floating until the end, while the weathered DB mat started to lose its buoyancy after 24 days under quiescent conditions and resurfaced once waves were applied. Analysis of the microbial communities of water pre- and post-spills revealed the replacement of indigenous microbial communities with hydrocarbon-degrading species. Exposure to CC reduced the microbial diversity by 12%, while exposure to DB increased the diversity by 10%. During the early stages of the spill (up to Day 21), most dominant species were positively correlated with the benzene, toluene, ethylbenzene, and xylenes (BTEX) content or polycyclic aromatic hydrocarbon (PAH) content of the water column, while the dominant species at the later stages (Days 21-56) of the spill were negatively correlated with BTEX or PAH content and positively correlated with the total organic carbon (TOC) content in waters.

Acute and subchronic effects of petroleum on the freshwater fish Hoplias aff. malabaricus / Efeitos agudo e subcrônico do petróleo no peixe de água doce Hoplias aff. malabaricus

Abstract Petroleum water soluble fraction (WSF) impairs organisms, but damages may vary among cell and tissue levels. The aim of the present study was to evaluate the acute (24 h, 48 h, 72 h) and subchronic effects (36 days) of WSF (0%, 25% and 100%) in juveniles of the Neotropical top predator fish Hoplias aff. malabaricus. The effects of WSF were evaluated at a molecular level using the comet assay and micronucleus test for genome damage; and at a morphological level through histological identification of liver pathologic lesions. In both acute and subchronic exposure we found low levels of DNA damage (< 10% of comet tail) and non-significant frequency of micronucleus in WSF exposed fish. The most significant liver lesions in WSF exposed fish were fatty vacuolization, hypertrophy and focal necrosis. Since these tissue injuries were progressive and persistent, their irreversibility may negatively affect fish recruitment, even in a such resistant top predator.

Resumo A fração solúvel de petróleo (WSF) prejudica os organismos, porém os danos podem variar entre os níveis celular e tecidual. O objetivo do presente estudo foi avaliar o efeito agudo (24 h, 48 h e 72 h) e subcrônico (36 dias) da WSF (0%, 25% e 100%) em juvenis do peixe neotropical predador topo Hoplias aff. malabaricus. Os efeitos da WSF foram avaliados no nível molecular utilizando o ensaio do cometa e o teste do micronúcleo para o dano genômico e no nível morfológico através da identificação histológica de lesões patológicas no fígado. Em ambas exposições (aguda e subcrônica) encontramos baixos níveis de dano no DNA (< 10% de DNA na cauda do cometa) e frequência de micronúcleos não significativa em peixes expostos a WSF. As lesões mais significativas no fígado dos peixes expostos a WSF foram a vacuolização lipídica, hipertrofia e focos de necroses. Como estas lesões foram progressivas e persistentes, sua irreversibilidade pode afetar negativamente o recrutamento dos peixes, mesmo sendo um predador topo resistente.

Plant based synthesis of silver nanoparticles, antimicrobial efficiency, and toxicological assessment using freshwater fish (Cyprinus carpio).

Silver nanoparticles (AgNPs) are widely used and have various applications, including medicine, electronics, and textiles. However, their increasing use raises concern about their potential environmental impact, particularly on aquatic organisms, such as fish, which are the primary consumers of aquatic environments and can be exposed to AgNPs through various routes. For this purpose, the leaves of the plant species Bellis perennis were used as a reductive agent to convert silver nitrate into AgNPs, to assess its toxicity against fish. Well-dispersed and undersized AgNPs were obtained and confirmed using analytical techniques, including Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Moreover, the AgNPs have shown significant antibacterial activity against Aeromonas hydrophila (25.71 ± 0.63) and Vibrio harveyi (22.39 ± 0.29). In addition, the toxicity of the obtained AgNPs was assessed by exposing Cyprinus carpio to various concentrations, including 0.06, 0.1, and 0.2 mg/L. The findings revealed that the AgNPs were significantly accumulated in the intestine, followed by the gills, liver, muscles, kidney, and brain. This bioaccumulation led to histological alterations and destruction in the villi of the intestine, regeneration of liver cells, and degeneration of the gill lamella. RESEARCH HIGHLIGHTS: Plants based synthesis of AgNPs is mostly considered as eco-friendly A significant antibacterial activity was obtained The plant mediated AgNPs were found less toxic The AgNPs was profoundly accumulated and causes histological alterations.

Potentials of Aloe barbadensis inclusion in fish feeds on resilience to Aeromonas hydrophila infection in freshwater fish Labeo rohita.

Aquatic bacterial pathogens can cause severe economic loss in aquaculture industry. An opportunistic pathogen, Aeromonas hydrophila is responsible for Motile Aeromonas Septicemia, leading to high mortality rates in fish. The present study was focused on the efficacy of Aloe barbadensis replacing fishmeal diets on hematological, serum biochemical, antioxidant, histopathological parameters, and disease resistance against A. hydrophila infection in Labeo rohita. Isonitrogenous fishmeal replaced diets (FMR) were prepared with varying levels of A. barbadensis at D1 (0%) (control), D2 (25%), D3 (50%), D4 (75%) and D5 (100%) then fed to L. rohita. After 60 days of post-feeding, the experimental fish were challenged with A. hydrophila. Blood and organs were collected and examined at 1- and 15-days post infection (dpi). The results demonstrated that on 1 dpi, white blood cells (WBC), total protein, cholesterol and low-density lipoprotein (LDL) levels were significantly increased in D3 diet fed groups. The D2 and D3 diet fed group showed decreasing trends of serum glutamic pyruvic transaminase (SGPT) and antioxidant enzymes activity on 15 dpi. The histopathological architecture results clearly illustrated that the D3 diet fed group had given a higher protective effect by reducing the pathological changes associated with A. hydrophila infection in liver, intestine and muscle. Higher percentage of survival rate was also observed in D3 diet fed group. Therefore, the present study suggested that the dietary administration of A. barbadensis up to 50% fishmeal replacement (D3 diet) can elicit earlier antioxidant activity, innate immune response and improve survival rate in L. rohita against A. hydrophila infection.

Consumer-driven nutrient recycling of freshwater decapods: Linking ecological theories and application in integrated multitrophic aquaculture.

The Metabolic Theory of Ecology (MTE) and the Ecological Stoichiometry Theory (EST) are central and complementary in the consumer-driven recycling conceptual basis. The understanding of physiological processes of organisms is essential to explore and predict nutrient recycling behavior, and to design integrated productive systems that efficiently use the nutrient inputs through an adjusted mass balance. We fed with fish-feed three species of decapods (prawn, anomuran, crab) from different families and with aquacultural potential to explore the animal-mediated nutrient dynamic and its applicability in productive systems. We tested whether body mass, body elemental content, and feeds predict N and P excretion rates and ratios within taxa. We also verified if body content scales allometrically with body mass within taxa. Finally, we compared the nutrient excretion rates and body elemental content among taxa. N excretion rates of prawns and anomurans were negatively related to body mass, emphasizing the importance of MTE. Feed interacted with body mass to explain P excretion of anomurans and N excretion of crabs. Body C:N content positively scaled with body mass in prawns and crabs. Among taxa, prawns mineralised more N and N:P, and less P, and exhibited higher N and C body content (and lower C:N) than the other decapods. Body P and N:P content were different among all species. Body content and body mass were the main factors that explained the differences among taxa and influence the role of crustaceans as nutrient recyclers. These features should be considered to select complementary species that efficiently use feed resources. Prawns need more protein in feed and might be integrated with fish of higher N-requirements, in contrast to crabs and anomurans. Our study contributed to the background of MTE and EST through empirical data obtained from decapods and it provided insightful information to achieve more efficient aquaculture integration systems.

An integrated assessment of ecological and human health risks of per- and polyfluoroalkyl substances through toxicity prediction approaches.

Per- and polyfluoroalkyl substances (PFAS) are also known as "forever chemicals" due to their persistence and ubiquitous environmental distribution. This review aims to summarize the global PFAS distribution in surface water and identify its ecological and human risks through integrated assessment. Moreover, it provides a holistic insight into the studies highlighting the human biomonitoring and toxicological screening of PFAS in freshwater and marine species using quantitative structure-activity relationship (QSAR) based models. Literature showed that PFOA and PFOS were the most prevalent chemicals found in surface water. The highest PFAS levels were reported in the US, China, and Australia. The TEST model showed relatively low LC50 of PFDA and PFOS for Pimephales promelas (0.36 and 0.91 mg/L) and high bioaccumulation factors (518 and 921), revealing an elevated associated toxicity. The risk quotients (RQs) values for P. promelas and Daphnia magna were found to be 269 and 23.7 for PFOS. Studies confirmed that long-chain PFAS such as PFOS and PFOA undergo bioaccumulation in aquatic organisms and induce toxicological effects such as oxidative stress, transgenerational epigenetic effects, disturbed genetic and enzymatic responses, perturbed immune system, hepatotoxicity, neurobehavioral toxicity, altered genetic and enzymatic responses, and metabolism abnormalities. Human biomonitoring studies found the highest PFOS, PFOA, and PFHxS levels in urine, cerebrospinal fluid, and serum samples. Further, long-chain PFOA and PFOS exposure create severe health implications such as hyperuricemia, reduced birth weight, and immunotoxicity in humans. Molecular docking analysis revealed that short-chain PFBS (-11.84 Kcal/mol) and long-chain PFUnDA (-10.53 Kcal/mol) displayed the strongest binding interactions with human serum albumin protein. Lastly, research challenges and future perspectives for PFAS toxicological implications were also discussed, which helps to mitigate associated pollution and ecological risks.

Nutritional values of wild edible freshwater macrophytes.

Background: The social acceptability of wild freshwater macrophytes as locally consumed vegetables is widespread. Freshwater macrophytes have several uses; for example, they can be used as food for humans. This study determined the proximate composition and mineral content of three freshwater macrophyte species, i.e., Eichhornia crassipes, Limnocharis flava, and Neptunia oleracea. Methods: Young shoots of E. crassipes, L. flava, and N. oleracea were collected from shallow channels of Puchong (3°00'11.89″N, 101°42'43.12″E), Ladang 10, Universiti Putra Malaysia (2°58'44.41″N, 101°42'44.45″E), and Kampung Alur Selibong, Langgar (06°5'50.9″N, 100°26'49.8″E), Kedah, Peninsular Malaysia. The nutritional values of these macrophytes were analysed by using a standard protocol from the Association of Official Analytical Chemists. Eight replicates of E. crassipes and L. flava and four replicates of N. oleracea were used for the subsequent analyses. Results: In the proximate analysis, N. oleracea possessed the highest percentage of crude protein (29.61%) and energy content (4,269.65 cal g-1), whereas L. flava had the highest percentage of crude fat (5.75%) and ash (18.31%). The proximate composition trend for each species was different; specifically, all of the species possessed more carbohydrates and fewer crude lipids. All of the species demonstrated a similar mineral trend, with high nitrogen and potassium and lower copper contents. Nitrogen and potassium levels ranged from 12,380-40,380 mg kg-1 and from 11,212-33,276 mg kg-1, respectively, and copper levels ranged from 16-27 mg kg-1. The results showed that all three plant species, i.e., E. crassipes, N. oleracea, and L. flava are plant-based sources of macro- and micronutrient beneficial supplements for human consumption.

Phosphorus storage and utilization strategies of two bloom-forming freshwater cyanobacteria.

The inter-relationships between cellular phosphorus (P) storage, dissolved inorganic P (DIP) uptake affinity, alkaline phosphatase activity (APA) and dissolved inorganic nitrogen (DIN) concentrations were studied in two ubiquitous diazotrophic freshwater cyanobacteria, Raphidiopsis raciborskii (six strains) and Chrysosporum ovalisporum (two strains). DIP uptake kinetics were measured using rates of incorporation of the radio-isotope, 33P and APA as a proxy for DOP-ester utilization. The study showed that DIP uptake of individual strains followed Michaelis-Menten kinetics (modified in our study to incorporate cellular P quotas), but differed with DIN and P availability, and between growth stages. High-affinity DIP uptake and APA were activated below a P quota threshold of approximately 0.01 µg P µg-1 C across the species and strains. C. ovalisporum had significantly higher APA and P quotas (per unit C and cell) but lower uptake affinity than R. raciborskii. Demand for DIP by C. ovalisporum increased when N fixation occurred, but typically not for R. raciborskii. Our results indicate that cyanobacterial species and strains differ in their strategies to P limiting conditions, and highlight the interplay between N and P. Physiological adaptations like APA and diazotrophy of cyanobacteria adapting to low DIP and/or DIN conditions may occur simultaneously and drive species dominance in oligotrophic environments.

Expanding non-invasive approaches for fish-health monitoring: A survey of the epidermal mucous metabolomes of phylogenetically diverse freshwater fish species.

There is a pressing need for more-holistic approaches to fisheries assessments along with growing demand to reduce the health impacts of sample collections. Metabolomic tools enable the use of sample matrices that can be collected with minimal impact on the organism (e.g., blood, urine, and mucus) and provide high-throughput, untargeted biochemical information without the requirement of a sequenced genome. These qualities make metabolomics ideal for monitoring a wide range of fish species, particularly those under protected status. In the current study, we surveyed the relative abundances of 120 endogenous metabolites in epidermal mucus across eight freshwater fish species belonging to seven phylogenetic orders. Principal component analysis was used to provide an overview of the data set, revealing strong interspecies relationships in the epidermal mucous metabolome. Normalized relative abundances of individual endogenous metabolites were then used to identify commonalities across multiple species, as well as those metabolites that showed notable species specificity. For example, taurine was measured in high relative abundance in the epidermal mucus of common carp (Cyprinus carpio), northern pike (Esox lucius), golden shiner (Notemigonus crysoleucas), rainbow trout (Oncorhynchus mykiss), and rainbow smelt (Osmerus mordax), whereas γ-amino butyric acid (GABA) exhibited a uniquely high relative abundance in flathead catfish (Pylodictis olivaris). Finally, hierarchical cluster analysis was used to evaluate species relatedness as characterized by both the epidermal mucous metabolome (phenotype) and genetic phylogeny (genotype). This comparison revealed species for which relatedness in the epidermal mucous metabolome composition closely aligns with phylogenetic relatedness (e.g., N. crysoleucas and C. carpio), as well as species for which these two measures are not well aligned (e.g., P. olivaris and Polyodon spathula). These, and other findings reported here, highlight novel areas for future research with fish, including development of epidermal mucous-based markers for non-invasive health monitoring, sex determination, and hypoxia tolerance.

No lukewarm diatom communities-the response of freshwater benthic diatoms to phosphorus in streams as basis for a new phosphorus diatom index (PDISE).

In the present study, we developed a new Swedish phosphorus diatom index (PDISE) to improve the poor fit of existing indices to match the needs of water managers to detect and mitigate eutrophication. We took advantage of a large amount of data (820 Swedish stream sites) collected in recent years. During our work, we found an unexpected bimodal response of the diatom assemblages to phosphorus. The taxa clustered either into an assemblage with a low or with a high site-specific averaged TP optimum (a calculated value comprised of the diatom taxa-specific optima). We could not find a characteristic diatom assemblage for sites with intermediate site-specific averaged TP optima. To our knowledge, this bimodal community response has not been shown earlier. The PDISE correlated more strongly than the currently used TDI to changes in TP concentrations. Thus, the PDISE should replace the TDI in the Swedish standard method. The modeled TP optima (expressed as categories) were different compared to the TDI for most of the taxa included in the index, indicating that the realized niche for these morphotaxa was different between Sweden and the UK where the TDI was developed originally. With a r2 of 0.68, the correlation of the PDISE to TP is among the highest reported for other diatom nutrient indices globally; thus, we believe that it might be worth to test it for other bioregions with similar geography and climate.

Spatially eutrophication potential and policy implication of nitrogen emission for surface water: A case study in Guangzhou city, China.

Understanding the spatial distribution and path tracing of eutrophication caused by nitrogen (N) enrichment in urban freshwater is crucial for whole-process and precise damage effect control. This study constructed a site-specific life cycle impact assessment (LCIA) model, covering the overall cause-effect chain from source emission to endpoint effect, to assess N-induced eutrophication potential at the species damage level. Applied to Guangzhou city, China, marked spatial disparities in eutrophication potential were derived, with higher values in the downtown areas driven by anthropogenic disturbances, such as wastewater discharge. Spatially differentiated measures were provided through eutrophication hotspot identification and driver tracking. This study offers a necessary complement for eutrophication impact category indicators in LCIA methodology and lays a scientific foundation for potential hotpots diagnosis and targeted mitigation policy-making.

Cable bacteria regulate sedimentary phosphorus release in freshwater sediments.

Previous studies have demonstrated that e-SOx can regulate the sedimentary release of phosphorus (P) in brackish and marine sediments. When e-SOx is active, an iron (Fe) and manganese (Mn) oxide rich layer is formed near the sediment surface, which prevents P release. When e-SOx becomes inactive, the metal oxide layer is reduced via sulfide-mediated dissolution, and P is subsequently released to the water column. Cable bacteria have been shown to also occur in freshwater sediments. In these sediments, sulfide production is limited, and the metal oxide layer would thus dissolve less efficiently, leaving the P trapped at the sediment surface. This lack of an efficient dissolution mechanism implies that e-SOx could play an important role in the regulation of P availability in eutrophied freshwater streams. To test this hypothesis, we incubated sediments from a eutrophic freshwater river to investigate the impact of cable bacteria on sedimentary cycling of Fe, Mn and P. High-resolution depth profiling of pH, O2 and ΣH2S complemented with FISH analysis and high-throughput gene sequencing showed that the development of e-SOx activity was closely linked to the enrichment of cable bacteria in incubated sediments. Cable bacteria activity caused a strong acidification in the suboxic zone, leading to the dissolution of Fe and Mn minerals and consequently a strong release of dissolved Fe2+ and Mn2+ to the porewater. Oxidation of these mobilized ions at the sediment surface led to the formation of a metal oxide layer that trapped dissolved P, as shown by the enrichment of P-bearing metal oxides in the top layer of the sediment and low phosphate in the pore and overlying water. After e-SOx activity declined, the metal oxide layer did not dissolve and P remained trapped at the surface. Overall, our results suggested cable bacteria can play an important role to counteract eutrophication in freshwater systems.

Toxicological effect of endocrine disrupting insecticide (deltamethrin) on enzymatical, haematological and histopathological changes in the freshwater iridescent shark, Pangasius hypothalamus.

This study investigated the deltamethrin (DMN) induced harmful effects on Pangasius hypophthalmus using enzymatic activity, haematological, and histopathological changes. LC50 value was 0.021 mg/L at 96 h, and sublethal toxicity was tested for 45 days at two `concentrations (i.e., 1/5th and 1/10th of LC50). Haematological parameters and enzymatic activities significantly changed between DMN-exposed and control groups (p < 0.05). Histopathologically, both DMN doses induced liver hyperemia, hepatic cell rupture, necrosis, hypertrepheoid bile duct, shifting nuclei, vascular haemorrhage, and hepatocyte degeneration, while in gill, secondary lamellae destruction, a fusion of adjacent gill lamellae, hypertrophy, hyperplasia, adhesion, and fusion were noticed. Kidney developed melanomacrophages, increased periglomerular and peritubular space, vacuolation, decreased glomerulus, hyaline droplets in tubular cells, loss of tubular epithelium, distal convoluted segment hypertrophy, and granular layer in brain pyramid and Purkinje cell nucleus. But, limiting pesticide impacts on freshwater fish and their habitat requires a holistic, cradle-to-grave approach and toxicological studies.