Functioning Of Aquatic Ecosystems Research Articles

1 Million Turtles: empowering communities to save Australian freshwater turtles

ABSTRACT Australian freshwater turtle populations have declined substantially, with consequent losses to aquatic ecosystem functions. A leading hypothesis is that turtles have declined through lost recruitment caused by high nest predation by invasive foxes. The ‘fox hypothesis’ is supported by experiments showing that nest predation rates exceed 95% in many regions. Furthermore, population surveys have repeatedly found absences of juvenile turtles, and headstarting experiments have successfully replaced those juveniles in some species. We are currently leading a nationwide citizen science program, ‘1 Million Turtles’ (1millionturtles.com), to engage local communities to protect turtles from threats like nest predation using a suite of novel approaches. Our key innovation is to leverage community passion and interest for turtles to create positive conservation impacts via a nationwide support network. We provide a data collection tool and framework (TurtleSAT) and self-guided training in conservation methods. We assist with guidance for gaining licencing and permission, and applying for grants. We are evaluating our approach through both the impacts on turtle populations as well as through surveys of our engaged citizen scientists. Ultimately, we aim to create a science-supported, national grassroots conservation model where community champions can lead their own evidence-based approaches to help wildlife.

Interactive effects of drought and deforestation on multitrophic communities and aquatic ecosystem functions in the Neotropics-a test using tank bromeliads.

Together with the intensification of dry seasons in Neotropical regions, increasing deforestation is expected to exacerbate species extinctions, something that could lead to dramatic shifts in multitrophic communities and ecosystem functions. Recent studies suggest that the effects of habitat loss are greater where precipitation has decreased. Yet, experimental studies of the pure and interactive effects of drought and deforestation at ecosystem level remain scarce. Here, we used rainshelters and transplantation from rainforest to open areas of natural microcosms (the aquatic ecosystem and microbial-faunal food web found within the rainwater-filled leaves of tank bromeliads) to emulate drought and deforestation in a full factorial experimental design. We analysed the pure and interactive effects of our treatments on functional community structure (including microorganisms, detritivore and predatory invertebrates), and on leaf litter decomposition in tank bromeliad ecosystems. Drought or deforestation alone had a moderate impact on biomass at the various trophic level, but did not eliminate species. However, their interaction synergistically reduced the biomass of all invertebrate functional groups and bacteria. Predators were the most impacted trophic group as they were totally eliminated, while detritivore biomass was reduced by about 95%. Fungal biomass was either unaffected or boosted by our treatments. Decomposition was essentially driven by microbial activity, and did not change across treatments involving deforestation and/or drought. Our results suggest that highly resistant microorganisms such as fungi (plus a few detritivores) maintain key ecosystem functions in the face of drought and habitat change. We conclude that habitat destruction compounds the problems of climate change, that the impacts of the two phenomena on food webs are mutually reinforcing, and that the stability of ecosystem functions depends on the resistance of a core group of organisms. Assuming that taking global action is more challenging than taking local-regional actions, policy-makers should be encouraged to implement environmental action plans that will halt habitat destruction, to dampen any detrimental interactive effect with the impacts of global climate change.

Changes in submerged macrophyte diversity, coverage and biomass in a biosphere reserve site after 20 years: A plea for conservation efforts

The conservation of submerged vegetation is crucial in the functioning of aquatic ecosystems. We have assessed, by means of subaquatic quantitative sampling transects, the current status of the hydrophytic flora in 14 lakes in the Lagunas de Ruidera Natural Park, a Biosphere Reserve site in central Spain, surrounded by a semi-arid landscape. The conforming lakes have endured several anthropic pressures for decades (e.g., eutrophication, land-use changes, etc.). By comparing the current with the former status (20 years ago) of hydrophytes in the natural park, substantial negative (species richness loss, decrease in submerged meadow coverage, particularly in the upstream lakes) and positive (natural recovery of meadows after the cut-off of sudden disturbances caused by point pollution sources, improving of trophic state in some lakes, no presence of exotic hydrophytes) changes in the lakes were noticed. We have analyzed that the disappearance of all the hydrophyte (mainly charophytes) stands would represent the loss of ecosystem services. For example, up to 70 t CH4 might be released from the charophyte detritus, an internal pool of phosphorus (as high as 1400 mgP/m2) stored in the charophytes stands could be liberated. Some lakes require special measures, but overall, to preserve this lake complex, and other similar ones, we propose to study, in detail, the causes of submerged vegetation deterioration (focusing on the presence of pesticides –in water and sediments-, and other reasons) to assess the ecological risks, to protect the groundwater resources, preventing the lakes from receiving surficial point and non-point sources of pollution.

Disinfectant-induced ammonia oxidation disruption in microbial N-cycling process in aquatic ecosystem after the COVID-19 outbreak

Anthropogenic activities significantly impact the elemental cycles in aquatic ecosystems, with the N-cycling playing a critical role in potential nutrient turnover and substance cycling. We hypothesized that measures to prevent COVID-19 transmission profoundly altered the nitrogen cycle in riverine ecosystems. To investigate this, we re-analyzed metagenomic data and identified 60 N-cycling genes and 21 host metagenomes from four urban reaches (one upstream city, Wuhan, and two downstream cities) along the Yangtze River. Our analyses revealed a marked decrease in the abundance of bacterial ammonia monooxygenase genes, as well as in the host, ammonia-oxidizing autotrophic Nitrosomonas, followed by a substantial recovery post-pandemic. We posited that discharge of sodium hypochlorite (NaOCl) disinfectant may be a primary factor in the reduction of N-cycling process. To test this hypothesis, we exposed pure cultures of Nitrosomonas europaea to NaOCl to explore the microbial stress response. Results indicated that NaOCl exposure rapidly compromised the cell structure and inhibited ammonia oxidation of N. europaea, likely due to oxidative stress damage and reduced expression of nitrogen metabolism-related ammonia monooxygenase. Using the functional tagging technique, we determined that NaOCl directly destroyed the ammonia monooxygenase protein and DNA structure. This study highlights the negative impacts of chlorine disinfectants on the function of aquatic ecosystems and elucidates potential mechanisms of action.

Testing a Hyperspectral, Bio‐Optical Approach to Identification of Phytoplankton Community Composition in the Chesapeake Bay Estuary

AbstractThe multi‐to hyperspectral evolution of satellite ocean color sensors is anticipated to enable satellite‐based identification of phytoplankton biodiversity, a key factor in aquatic ecosystem functioning and upper ocean biogeochemistry. In this work the bio‐optical Phytoplankton Detection with Optics (PHYDOTax) approach for deriving taxonomic (class‐level) phytoplankton community composition (PCC, e.g. diatoms, dinoflagellates) from hyperspectral information is evaluated in the Chesapeake Bay estuary on the U.S. East Coast. PHYDOTax is among relatively few optical‐based PCC differentiation approaches available for optically complex waters, but it has not yet been evaluated beyond the California coastal regime where it was developed. Study goals include: (a) testing the approach in a turbid estuary including novel incorporation of colored dissolved organic matter (CDOM) and non‐algal particles (NAP), and (b) performance assessment with both synthetic mixture and field data sets. Algorithm skill was robust on synthetic mixtures. Using field data, cryptophyte and/or cyanophyte phytoplankton groups were predicted, but diatom and dinoflagellate detection was not conclusive. For one field data set, small but significant improvements were observed in predicted PCC groups when tested with incorporation of CDOM and NAP into the algorithm, but not for the second field data set. Sensitivity to three hyperspectral‐relevant spectral resolutions (1, 5, 10 nm) was low for all field and synthetic data. PHYDOTax can identify some phytoplankton groups in the estuary using hyperspectral, field‐collected measurements, but validation‐quality data with broad temporospatial coverage are needed to determine whether the approach is robust enough for science applications.

Floods drive functional zooplankton diversity in a core area of the Brazilian Pantanal Biosphere Reserve

ABSTRACT Water dynamics in floodplains are fundamental in structuring aquatic communities. Our research investigated zooplankton communities in the Pantanal ecosystem. Different hydroperiod phases can influence the functioning of aquatic ecosystems, but an understanding of the taxonomic and functional diversity of zooplankton in these areas is lacking. Over 3 years (2018–2020), we assessed the zooplankton community in habitats along the Paraguay River at the Taiamã Ecological Station, considering the flood, ebb, drought, and inundation phases. We used indices such as Rao’s quadratic entropy (RaoQ), functional evenness (FEve), functional divergence (FDiv), community weighted means (CWM), and fourth-corner RLQ to investigate the potential relationships between the taxonomic and functional diversity of zooplankton and the hydroperiod phases and limnological variables. We identified 153 species of zooplankton, with greater richness in the families Lecanidae and Brachionidae (rotifers) and Chydoridae and Daphnidae (cladocerans). Species composition varied significantly between flood and drought phases. We observed positive relationships between chlorophyll a, total nitrogen/phosphorus, and species with larger body size, pelagic habitat, filter-feeding mode, and medium predator evasion capacity, whereas littoral species and those with low predator evasion capacity showed negative relationships. CWM exhibited differences in functional traits between hydroperiod phases. FDiv analysis indicated well-defined ecological functions among the community species, and the low FEve value during the flood phase indicated the dominance of certain functional attributes. These results emphasize the relationship between hydrological processes and the distribution of zooplankton communities, highlighting the importance of functional diversity in understanding ecological interactions.

A Review on Zooplankton Diversity with Reference to Physico-Chemical Parameters of Lentic Ecosystems in Maharashtra

Zooplanktons are diverse organisms, are found more or less in all water bodies. The plankton research is a highly helpful technique for determining the biotic potential of water bodies and adds to the overall calculation of their biotic nature and general economic potential.  Zooplanktons are microscopic, free-floating organisms that are essential to the functioning of aquatic ecosystems.  As the most crucial link in the energy transfer between phytoplankton and higher aquatic animals, zooplanktons are significant biotic components and play a significant role in the aquatic environment. The functioning of an aquatic ecosystem's food chains, food webs, energy flow, and nutrient cycling are all influenced by zooplankton. Zooplankton populations are excellent indicators of the stability of the food chain. Numerous environmental parameters, including pH, temperature, salinity, oxygen, and others, have an impact on zooplankton. The food chain and the flow of energy between the primary and tertiary trophic levels are both significantly influenced by zooplankton. They serve as indicators of the physical, chemical, and biological processes occurring in aquatic systems due to their high densities. Because they are highly sensitive to environmental change, changes in the abundance of certain species or in the makeup of certain communities can be used to gauge the health of the environment. An assessment of the literature on zooplanktons in Indian lentic water has been done in the current work, which has long been deemed necessary in this subject.              

Environmental heterogeneity at two spatial scales affects litter diversity-decomposition relationships.

The effects of biodiversity on ecological processes have been experimentally evaluated mainly at the local scale under homogeneous conditions. To scale up experimentally based biodiversity-functioning relationships, there is an urgent need to understand how such relationships are affected by the environmental heterogeneity that characterizes larger spatial scales. Here, we tested the effects of an 800-m elevation gradient (a large-scale environmental factor) and forest habitat (a fine-scale factor) on litter diversity-decomposition relationships. To better understand local and landscape scale mechanisms, we partitioned net biodiversity effects into complementarity, selection, and insurance effects as applicable at each scale. We assembled different litter mixtures in aquatic microcosms that simulated natural tree holes, replicating mixtures across blocks nested within forest habitats (edge, interior) and elevations (low, mid, high). We found that net biodiversity and complementarity effects increased over the elevation gradient, with their strength modified by forest habitat and the identity of litter in mixtures. Complementarity effects at local and landscape scales were greatest for combinations of nutrient-rich and nutrient-poor litters, consistent with nutrient transfer mechanisms. By contrast, selection effects were consistently weak and negative at both scales. Selection effects at the landscape level were due mainly to nonrandom overyielding rather than spatial insurance effects. Our findings demonstrate that the mechanisms by which litter diversity affects decomposition are sensitive to environmental heterogeneity at multiple scales. This has implications for the scaling of biodiversity-ecosystem function relationships and suggests that future shifts in environmental conditions due to climate change or land use may impact the functioning of aquatic ecosystems.

Comparative foraging behavior of 3 heron species in small standing-water ecosystems in the arid zone of Oman

Abstract The composition of assemblages, diet and behavior of waterbird species with similar ecological features are important aspects in the functioning of aquatic ecosystems. Closely related animal species often share resources such as space and food in ways that reduce competition, but if the diets of different species strongly overlap, interspecific competition may intensify. This analysis examined behavioral data relating to Great Egret, Little Egret, and Squacco Heron to explore their foraging efficiencies in rich aquatic habitats in an arid zone during post-breeding movements. The fieldwork was carried out in small estuaries of a Wadi on the southern coast of Oman. The frequency of interactions was the highest in Squacco Heron and the lowest in Great Egret. However, the differences in the numbers of inter- and intra-specific interactions between the 3 species were significant. Activity indices calculated for a 5-min period, i.e., the number of interactions (interaction index) and times of flying and walking (movement index) differed among the 3 species. The number of successful attacks was the highest in Squacco Heron, while the foraging effectiveness of Great Egret and Little Egret was similar. GLM analysis showed that only the movement index was significant, as it had a positive impact on individual foraging success. Great Egret caught more fish than the other 2 heron species which, in turn, caught a greater number of smaller prey items, mostly invertebrates. This study shows that heron species in the same rich habitat employ different foraging tactics. In comparison to the other two heron species, the foraging tactics of Squacco Heron seem to be the most susceptible to competition. However, its greater mobility and using different foraging tactics, enhance its foraging success.

Cross-domain diversity effects: linking diatom species richness, intraspecific richness, and biomass production to host-associated bacterial diversity

Abstract Interactions between bacteria and microalgae are important for the functioning of aquatic ecosystems, yet interactions based on the biodiversity of these two taxonomic domains have been scarcely studied. Specifically, it is unclear whether a positive biodiversity-productivity relationship in phytoplankton is largely facilitated by niche partitioning among the phytoplankton organisms themselves, or whether associated bacterial communities play an additional role in modifying these diversity effects. Moreover, effects of intraspecific diversity in phytoplankton communities on bacterial community diversity have not been tested. To address these points, we factorially manipulated both species and intraspecific richness of three diatoms to test effects of diatom species/strain diversity on biomass production and bacterial diversity in algae-bacteria communities. The results show that diatom intraspecific diversity has significant positive effects on culture biomass and the diversity of the associated free-living bacterial community (0.2-3 μm size fraction), which are comparable in magnitude to species diversity effects. However, there were little to no effects of diatom diversity on host-associated bacterial diversity (>3 μm size fraction), or of bacterial diversity on biomass production. These results suggest a decoupling of bacterial diversity from the diatom diversity-productivity relationship and provide early insights regarding the relations between diversity across domains in aquatic ecosystems.

Diverse winter communities and biogeochemical cycling potential in the under-ice microbial plankton of a subarctic river-to-sea continuum.

Microbiomes vary over multiple timescales, with short- and long-term changes in the physico-chemical environment. However, there is a scarcity of data and understanding about the structure and functioning of aquatic ecosystems during winter relative to summer. This is especially the case for seasonally ice-covered rivers, limiting our understanding of these ecosystems that are common throughout the boreal, subpolar, and polar regions. Here, we examined the winter under-ice microbiome of a Canadian subarctic river and its entry to the sea to characterize the taxonomic and functional features of the microbial community. We found substantial diversity in both composition and functional capabilities, including the capacity to degrade complex terrestrial compounds, despite the constraints imposed by a prolonged seasonal ice-cover and near-freezing water temperatures. This study indicates the ecological complexity and importance of winter microbiomes in ice-covered rivers and the coastal marine environment that they discharge into.

Dissolved organic matter (DOM) is independently stratified in thermally stratified water bodies

Thermal stratification often occurs in deep-water bodies, including oceans, lakes, and reservoirs. Dissolved organic matter (DOM) plays a critical role in regulating the dynamics of aquatic food webs and water quality in aquatic ecosystems. In the past, thermal stratification boundaries have been sometimes used exclusively to analyze the vertical distribution of DOM in thermally stratified water bodies. However, the validity of this practice has been challenged. Currently, there is limited understanding of the formation mechanism and stratification of the vertical distribution of DOM in thermally stratified water bodies, which hinders the analysis of the interactions between DOM and vertical aquatic ecological factors.To address this gap, we conducted a comprehensive study to extensively collect the vertical distribution of DOM in thermally stratified water bodies and identify the primary factors influencing this distribution. We found that DOM was independently stratified in thermally stratified water bodies (including two cases in unstratified water bodies), and that the formation mechanisms and statuses of DOM stratification were different from those of thermal stratification. The boundaries and numbers of DOM stratification were generally inconsistent with those of thermal stratification. Therefore, it is more accurate to divide DOM into different layers according to its own vertical profile, and analyze DOM characteristics of each layer based on its own stratification instead of thermal stratification. This study sheds light on the relationship between DOM and thermal stratification and provides a novel approach for analyzing DOM vertical distribution characteristics and their impact on aquatic ecosystems. This finding also holds significant implications for the design and implementation of environmental management programs aimed at preserving the health and functionality of aquatic ecosystems.

Shrinkage and desiccation: evaluating the streambed bacterial responses to intermittent water deficit

Hydrological drought, characterized by a significant deficiency in rainfall events, promotes natural desiccation processes. The reduction in water recharge and the loss of freshwater ecosystems pose urgent challenges in the face of increasing global population and the escalating demand for water resources. The variability in the duration of no-flow periods can have profound implications for ecosystem functioning, specifically impacting the microbiota residing in streambed sediments and the vital processes they perform. The streambed serves as an ecotone where microorganisms form biofilms, playing critical roles in in-stream biogeochemical cycles and greenhouse gas emissions. Consequently, prolonged desiccation periods and subsequent rewetting episodes can disrupt, limit, or alter the functions and structure of microbial communities, thereby compromising the overall functioning of aquatic ecosystems. Understanding how streambed microbial communities respond to prolonged desiccation events is crucial. This revision manuscript provides a synthesis of recent empirical and experimental studies that have explored various aspects of streambed microbial communities in the context of diverse drying-rewetting periods. A special focus is placed on highlighting key microbial community structural and functional responses that could be used as endpoints of responses to desiccation. In particular, we showed the greater expression of the phenol-oxidase activity among the intermittent streambeds submitted to long-term drought. This result suggested a potential begin of transition from freshwater to terrestrial systems. Additionally, we observed a tendency of decreasing bacterial diversity in the dry conditions together with a change in the relative abundance of certain microbial taxa and a general shift from Gram-negative to Gram-positive bacteria. All of these evidences strengthened the similarity between the dry streambed systems studied and a (dry)-soil environment, suggesting that prolonged and unusual dry periods could boost the terrestrial transition of the aquatic intermittent ecosystem. By summarizing these findings, we aim to enhance our understanding of the responses exhibited by streambed microbiota in the face of desiccation events. The synthesized results may further provide potential diagnosis and/or management tools for intermittent freshwater ecosystems functioning.

Aquatic Mercury Pollution from Artisanal and Small-Scale Gold Mining in Sub-Saharan Africa: Status, Impacts, and Interventions

Mercury (Hg) pollution remains an environmental global concern due to its non-degradable and toxic nature. Natural and anthropogenic sources of Hg adversely affect the functioning of aquatic ecosystems and biological processes. In sub-Saharan Africa (SSA), unregulated artisanal and small-scale gold mining (ASGM) contributes up to 20% of global gold production and uses 205–496 tonnes/yr of Hg. Despite being a vital economic driver for 20–30 million people, ASGM threatens the health of aquatic systems from Hg pollution, presenting a complex challenge that demands urgent interventions. This review seeks to (1) establish the current status of aquatic Hg pollution, (2) explore the environmental impacts of aquatic Hg, and (3) highlight the proposed interventions for aquatic Hg pollution in SSA. We examined publications and institutional reports between 2000 and 2023 addressing aquatic Hg pollution, impacts, and interventions in the ASGM of SSA. Results indicate a rise in aquatic Hg pollution due to the expansion and intensification of ASGM. West Africa remained the highest contributor (50.2%), followed by Central Africa (39.6%), Southern Africa (9.6%), and Eastern Africa (<1%). Contamination of freshwater ecosystems, toxicity to aquatic biota, and environmental health risks to humans were evident. Alternative Hg-free ASGM technologies, including physical, metallurgical, and pyrometallurgical, were investigated from case studies and recommended for adoption.

How do different modalities of land use practices impact the environmental features and macroinvertebrates? An assessment of mountain streams from Patagonia, Argentina

Agricultural intensification is a significant process, transforming the land and modifying stream water quality and biodiversity. Land-use practices are associated with substantial changes in vegetation structure, significant inputs of nutrients, erosion, and increased sedimentation, all of which profoundly impact aquatic biota and ecosystem functioning. The effect of different agricultural practices (horticulture, extensive and intensive livestock) on stream water quality was compared in terms of physicochemical features, bacteria, habitat condition, riparian ecosystem, and macroinvertebrate variables in a temperate rural landscape (Patagonia). The main objective was to identify which variables related to land use were determinants in the configuration of biotic communities. Significantly higher values in water temperature, conductivity, nutrients, and bacteria were found at intensively developed sites than at reference ones. The quality of the habitat and the riparian ecosystem had been profoundly modified. A multidimensional scaling analysis revealed that macroinvertebrate assemblages also differed among land use categories, with the variables: total phosphorous, total nitrogen, bacteria (E. coli, mesophilic and total coliforms), water temperature, and oxygen having the highest predictive power. Macroinvertebrate metrics (richness of EPT (Ephemeroptera+Plecoptera+Trichoptera), Plecoptera, shredders and scrapers, and the percentage of scrapers and collectors) proved appropriate bioindicators for discriminating intensive land use impacts and highlighted a trend of biodiversity loss. Plecoptera richness, a taxa group with a high level of endemism, responded significantly to habitat condition degradation. These results confirm that the intensification of land use leads to increased nutrient levels and suppressed aquatic-terrestrial interactions involved in the provision of allochthonous detrital input, shade, and habitat structure for larval stages and adults. The Habitat Condition Index appears to be a useful tool for rapid stream assessment and providing early warnings. Several ecological services are threatened in these Patagonian agroecosystems. Restoring riverbank heterogeneity and improving management practices that ameliorate nutrient and sediment inputs are crucial to enhance biodiversity.

Trophic cascades within and across ecosystems: The role of anti-predatory defences, predator type and detritus quality.

Species in one ecosystem can indirectly affect multiple biodiversity components and ecosystem functions of adjacent ecosystems. The magnitude of these cross-ecosystem effects depends on the attributes of the organisms involved in the interactions, including traits of the predator, prey and basal resource. However, it is unclear how predators with cross-ecosystem habitat interact with predators with single-ecosystem habitat to affect their shared ecosystem. Also, unknown is how such complex top-down effects may be mediated by the anti-predatory traits of prey and quality of the basal resource. We used the aquatic invertebrate food webs in tank bromeliads as a model system to investigate these questions. We manipulated the presence of a strictly aquatic predator (damselfly larvae) and a predator with both terrestrial and aquatic habitats (spider), and examined effects on survival of prey (detritivores grouped by anti-predator defence), detrital decomposition (of two plant species differing in litter quality), nitrogen flux and host plant growth. To evaluate the direct and indirect effects each predator type on multiple detritivore groups and ultimately on multiple ecosystem processes, we used piecewise structural equation models. For each response variable, we isolated the contribution of different detritivore groups to overall effects by comparing alternate model formulations. Alone, damselfly larvae and spiders each directly decreased survival of detritivores and caused multiple indirect negative effects on detritus decomposition, nutrient cycling and host plant growth. However, when predators co-occurred, the spider caused a negative non-consumptive effect on the damselfly larva, diminishing the net direct and indirect top-down effects on the aquatic detritivore community and ecosystem functioning. Both detritivore traits and detritus quality modulated the strength and mechanism of these trophic cascades. Predator interference was mediated by undefended or partially defended detritivores as detritivores with anti-predatory defences evaded consumption by damselfly larvae but not spiders. Predators and detritivores affected ecosystem decomposition and nutrient cycling only in the presence of high-quality detritus, as the low-quality detritus was consumed more by microbes than invertebrates. The complex responses of this system to predators from both recipient and adjacent ecosystems highlight the critical role of maintaining biodiversity components across multiple ecosystems.

Accurate and Rapid Extraction of Aquatic Vegetation in the China Side of the Amur River Basin Based on Landsat Imagery

Since the early 1950s, the development of human settlements and over-exploitation of agriculture in the China side of the Amur River Basin (CARB) have had a major impact on the water environment of the surrounding lakes, resulting in a decrease of aquatic vegetation. According to the United Nations Sustainable Development Goals, a comprehensive understanding of the extent and variability of aquatic vegetation is crucial for preserving the structure and functionality of stable aquatic ecosystems. Currently, there is a deficiency in the CARB long-sequence dataset of aquatic vegetation distribution in China. This shortage hampers effective support for actual management. Therefore, the development of a fast, robust, and automatic method for accurate extraction of aquatic vegetation becomes crucial for large-scale applications. Our objective is to gather information on the spatial and temporal distribution as well as changes in aquatic vegetation within the CARB. Utilizing a hybrid approach that combines the maximum spectral index composite and Otsu algorithm, along with the integration of convolutional neural networks (CNN) and random forest, we applied this methodology to obtain an annual dataset of aquatic vegetation spanning from 1985 to 2020 using Landsat series imagery. The accuracy of this method was validated through both field investigations and Google Images. Upon assessing the confusion matrix spanning from 1985 to 2020, the producer accuracy for aquatic vegetation classification consistently exceeded 87%. Further quantitative analysis unveiled a discernible decreasing trend in both the water and vegetation areas of lakes larger than 20 km2 within the CARB over the past 36 years. Specifically, the total water area decreased from 3575 km2 to 3412 km2, while the vegetation area decreased from 745 km2 to 687 km2. These changes may be attributed to a combination of climate change and human activities. These quantitative data hold significant practical implications for establishing a scientific restoration path for lake aquatic vegetation. They are particularly valuable for constructing the historical background and reference indices of aquatic vegetation.

The use of copper as plant protection product contributes to environmental contamination and resulting impacts on terrestrial and aquatic biodiversity and ecosystem functions.

Copper-based plant protection products (PPPs) are widely used in both conventional and organic farming, and to a lesser extent for non-agricultural maintenance of gardens, greenspaces, and infrastructures. The use of copper PPPs adds to environmental contamination by this trace element. This paper aims to review the contribution of these PPPs to the contamination of soils and waters by copper in the context of France (which can be extrapolated to most of the European countries), and the resulting impacts on terrestrial and aquatic biodiversity, as well as on ecosystem functions. It was produced in the framework of a collective scientific assessment on the impacts of PPPs on biodiversity and ecosystem services in France. Current science shows that copper, which persists in soils, can partially transfer to adjacent aquatic environments (surface water and sediment) and ultimately to the marine environment. This widespread contamination impacts biodiversity and ecosystem functions, chiefly through its effects on phototrophic and heterotrophic microbial communities, and terrestrial and aquatic invertebrates. Its effects on other biological groups and biotic interactions remain relatively under-documented.

Ecological Implications on Aquatic Food Webs Due to Effects of Pesticides on Invertebrate Predators in a Neotropical Region.

Predation presents specific behavioral characteristics for each species, and the interaction between prey and predator influences the structuring of the food web. Concerning insects, predation can be affected in different ways, such as exposure to chemical stressors, e.g., pesticides. Therefore, analyses were carried out of the effects of exposure to insecticide fipronil and the herbicide 2,4-D on predation, parameters of food selectivity, and the swimming behavior of two neotropical predatory aquatic insects of the families Belostomatidae (giant water bugs) and larvae of Libellulidae (dragonfly). These predatory insects were exposed for 24 h to a commercial formulation of the chlorophenoxy herbicide, 2,4-D at nominal concentrations of 200, 300, 700, and 1400μgL-1, and to a commercial formulation of the phenylpyrazole insecticide, fipronil at nominal concentrations of 10, 70, 140, and 250µgL-1. In a control treatment, the insects were placed in clean, unspiked water. At the end of the exposure, the maximum swimming speed of the predators was evaluated. Afterward, the predators were placed in clean water in a shared environment for 24 h with several prey species, including the cladoceran Ceriodaphnia silvestrii, larvae of the insect Chironomus sancticaroli, the amphipod Hyalella meinerti, the ostracod Strandesia trispinosa, and the oligochaete Allonais inaequalis for 24 h. After this period, the consumed prey was counted. The results reveal that predators from both families changed prey consumption compared with organisms from the control treatment, marked by a decrease after exposure to fipronil and an increase in consumption caused by 2,4-D. In addition, there were changes in the food preferences of both predators, especially when exposed to the insecticide. Exposure to fipronil decreased the swimming speed of Belostomatidae individuals, possibly due to its neurotoxic effect. Exposure to the insecticide and the herbicide altered prey intake by predators, which could negatively influence the complex prey-predator relationship and the functioning of aquatic ecosystems in contaminated areas.

The effects of silver particle size on bacterioplankton community and potential function in aquatic environment

Silver nanoparticles (AgNPs), known for their antimicrobial properties, are increasingly being recognized as a water pollutant, with their physicochemical properties varying based on particle size. However, there is a lack of research on whether presence of AgNPs and their particle size affect bacterial communities in water bodies. In this study, the water from Chaohu Lake was collected and spiked with AgNPS of different particle sizes of (5 nm, 50 nm, and 100 nm) to stimulate the microbial response. Our findings revealed that the presence of AgNPs could significantly disrupt bacterial community structure and strengthen the associations between certain bacteria, with significant impacts observed on nitrifying and denitrifying processes. Different particle sizes of AgNPs had various effects on bacterial community structure, with small-sized AgNPs affecting the bacterial community the most. Moreover, the presence of AgNPs and their varying particle sizes were observed to significantly affect the nitrogen cycle, carbon cycle, and respiration, thus imposing significant impacts on other ecological functions of aquatic ecosystems. This study provides a baseline study on the aquatic ecotoxicological effects of AgNPs.