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The rapid increase in aquaculture over the last several decades has led to concerns about the environmental impact of fish feeds relying on marine resources for fishmeal (FM). We aim to assess Nannochloropsis sp. QH25 co-product as a viable and sustainable replacement for FM in juvenile rainbow trout, Oncorhynchus mykiss, feeds. We formulated four experimental diets: a reference (FM based), 33N, 66N, and 100N diet (33%, 66%, and 100% co-product replacement). Rainbow trout were randomly assigned to one of 16 tanks and randomly assigned an experimental diet to consume throughout the experiment (64 days total), with four replicate tanks per diet. We compared the phosphorus (P) and nitrogen (N) digestibility, emissions, and growth between diets and, compared six environmental impacts (biotic resource use (BRU), global warming potential (GWP), water use, land use, marine eutrophication potential (MEP), and freshwater eutrophication potential (FEP)) of each diet. Our results indicate that replacing FM with co-product did not significantly alter growth. P digestibility of the experimental and reference diets was comparable. BRU conversion ratio was significantly lower in the experimental diets. However, there were significantly higher water and land use conversion ratios but insignificantly higher results in GWP, MEP, and FEP between the reference and 100N diet.

A key control on the magnitude of coastal eutrophication is the degree to which currents quickly transport nitrogen derived from human sources away from the coast to the open ocean before eutrophication develops. In the Southern California Bight (SCB), an upwelling-dominated eastern boundary current ecosystem, anthropogenic nitrogen inputs increase algal productivity and cause subsurface acidification and oxygen (O 2 ) loss along the coast. However, the extent of anthropogenic influence on eutrophication beyond the coastal band, and the physical transport mechanisms and biogeochemical processes responsible for these effects are still poorly understood. Here, we use a submesoscale-resolving numerical model to document the detailed biogeochemical mass balance of nitrogen, carbon and oxygen, their physical transport, and effects on offshore habitats. Despite management of terrestrial nutrients that has occurred in the region over the last 20 years, coastal eutrophication continues to persist. The input of anthropogenic nutrients promote an increase in productivity, remineralization and respiration offshore, with recurrent O 2 loss and pH decline in a region located 30-90 km from the mainland. During 2013 to 2017, the spatially averaged 5-year loss rate across the Bight was 1.3 mmol m -3 O 2 , with some locations losing on average up to 14.2 mmol m -3 O 2 . The magnitude of loss is greater than model uncertainty assessed from data-model comparisons and from quantification of intrinsic variability. This phenomenon persists for 4 to 6 months of the year over an area of 278,40 km 2 ( ∼ 30% of SCB area). These recurrent features of acidification and oxygen loss are associated with cross-shore transport of nutrients by eddies and plankton biomass and their accumulation and retention within persistent eddies offshore within the SCB.

Eutrophication reduces the variability of the community composition of plankton. However, the mechanisms underlying the diversity and restructuring of eukaryotic algal communities remain unknown. This study analysed the diversity and compositional patterns of algal communities in shallow eutrophic lakes. It investigated how these communities were modified by key genera through mediating inter‐algal associations under the influence of abiotic factors. Inter‐algal associations explained more variance in algal communities than environmental variables, and variation in composition and diversity was primarily derived from Scenedesmus, Desmodesmus and Cryptomonas, rather than nutrients. Scenedesmus and Desmodesmus were positively correlated with the genera of Chlorophyta and formed the hub of the algal association network. When the relative abundance of Scenedesmus and Desmodesmus increased from 0.41% to 13.74%, communities enriched in biomarkers of Bacillariophyta, Chrysophyceae and Cryptophyta transitioned to communities enriched in biomarkers of Chlorophyta. Moreover, negative associations between the Chlorophyta hub genera and other non‐Chlorophyta genera increased. High concentrations of total phosphorus altered the composition of algal communities by increasing the abundance of Scenedesmus and Desmodesmus, which in turn had cascading effects through inter‐algal associations. Additionally, algal communities with higher abundances of Scenedesmus and Desmodesmus were more susceptible to the effects of total phosphorus. Our study suggested that inter‐algal associations, centred on Scenedesmus and Desmodesmus, had a greater influence on algal diversity and community structure than other factors. Nutrient levels were not a direct driver of algal diversity and community structure adjustments, but acted indirectly by enhancing the influence of Scenedesmus and Desmodesmus. [ABSTRACT FROM AUTHOR]

The presence of orthophosphate in streams stimulates eutrophication that brings negative implications to water quality and related economic sectors. This work was aimed at evaluating the removal of orthophosphate from water by iron-loaded adsorbents derived from coconut shells (CS). CS was carbonized and chemically activated with H3PO4 prior to ferric metals loading. The resultant adsorbents, CSA (coconut shell activated carbon), IC-CSA (ferric chloride-loaded), and IS-CSA (ferric sulfate-loaded) were characterized for physicochemical properties. Orthophosphate adsorption was studied under kinetic and equilibrium conditions considering the effects of concentration, solution pH, adsorbent dosage, and contact time. The modified adsorbents showed functional groups of –OH, C = C, and Fe–O, with IC-CSA exhibiting a greater specific surface of 722 m2/g. A maximum orthophosphate removal of 310 mg/g was recorded by IC-CSA in the pH range of 2–3. The Langmuir isotherm describes the equilibrium data well, while the adsorptive rate followed the pseudo-second-order model. Thermodynamic parameters indicate that the adsorption is spontaneous and exothermic. Adsorption was pH-dependent, and desorption was successfully accomplished by alkaline leaching. Iron-loaded coconut shell activated carbon is a promising adsorbent to abate eutrophication due to orthophosphate in water. [ABSTRACT FROM AUTHOR]

The ecological effects of eutrophication on estuaries and coastal ecosystems are significant worldwide. Based on data collected in 2019 from Hangzhou Bay and adjacent waters, this study employed biological traits analysis and RLQ/fourthcorner analysis methods to investigate the distribution patterns of macrobenthic assemblages along a eutrophication gradient and reveal the response patterns of their biological traits to eutrophication stress. The results showed that eutrophication had a significant structuring effect on the spatial distribution of macrobenthic community structure. As the level of eutrophication increased, the community abundance and number of macrobenthic biological traits decreased. The composition of macrobenthic community biological traits changed in response to eutrophication. In areas with high levels of eutrophication, larger body sizes became more dominant, reflecting a shift in dominant traits similar to the eutrophication gradient. Furthermore, the predominant species in this region were burrowers and tube dwellers, which preferred muddy sand and sandy mud substrates. The AMBI ecological group accurately reflects the degree of eutrophication disturbance, with tolerant species and second-order opportunistic species being common in eutrophic areas. [ABSTRACT FROM AUTHOR]

The impacts of environmental change on Lake Biwa have been explored for decades, with water monitoring and palaeolimnological studies revealing how environmental forcing, including climate warming, eutrophication, water level manipulation and human manipulation of fish populations, has influenced the food web of Lake Biwa. However, these studies have rarely accounted for microbial food‐web components. This knowledge gap is mostly due to the lack of time series spanning more than a couple of decades, coupled with the high taxonomical expertise required to identify organisms belonging to very diverse groups. The use of a sedimentary DNA approach allows for the reconstruction of past changes in the diversity, composition and structure of the microbial eukaryotic community of aquatic systems. The application of 18S metabarcoding has been proven successful to describe the response of unicellular eukaryotes (protists) and aquatic fungi in lake ecosystems, encompassing a large taxonomic and functional diversity such as phototrophs, heterotrophs and mixotrophs. We applied 18S metabarcoding to 31 sediment core samples from Lake Biwa, spanning the past 100 years and explored the response of microbial eukaryotic communities to changes in multiple environmental stressors, including nutrient levels, lake water level, climate, as well as fish and zooplankton biomass for the period 1973–2010. We found that the manipulation of the water level and changes in fish community composition were the primary factors impacting (indirectly) the structure of the lake microbial eukaryotic community with minor, but significant, effects of climate warming and phosphorus levels. Co‐occurrence network analysis highlighted the potential food web impacts on the microbial eukaryotic community, suggesting that organisms from this compartment were impacted by both bottom‐up and top‐down processes. [ABSTRACT FROM AUTHOR]

Human‐induced nutrient eutrophication is a major threat to grassland biodiversity, because it promotes the dominance of fast‐growing plants. Negative impacts of fertilization on plant biodiversity may be offset by grazing by large vertebrate herbivores. However, whether grazers also mitigate impacts of nutrient addition on insects is less well understood. We use a field experiment to test how plant communities and abundances of pollinators and grasshoppers respond to nutrient addition and grazing by different assemblages of large herbivores, i.e. access by all herbivores (including cattle and horses), access by wild herbivores only (wild boar and deer), no access by large herbivores. Plant biomass increased, plant diversity decreased and community composition shifted towards lower forb cover in response to fertilization, but only in the absence of all herbivores. Flower visitation by Hymenoptera (bees and wasps), i.e. the most abundant pollinator group, was reduced by nutrient addition only in the absence of all herbivores and was positively related to flowering plant richness. In contrast, flower visitation by Diptera (e.g. hoverflies) was enhanced by fertilization, but not affected by grazing. Orthoptera (grasshopper) abundance was reduced by grazing and enhanced by nutrient addition, with positive impacts of fertilization tending to be stronger in plots with only wild or no herbivores. The abundance of grasshoppers was positively related to grass biomass. We conclude that vertebrate herbivores can offset impacts of fertilization on both plant and insect communities, making grazing by large mammals an essential tool to protect insects, particularly pollinators. Most responses to nutrient addition were only apparent in plots without any large herbivores, suggesting that wild herbivores alone could already mitigate nutrient impacts. We also show that insects with contrasting feeding guilds may be favoured by fertilized, ungrazed conditions. Therefore, creating a mosaic of patches grazed at different intensities will enhance overall insect biodiversity. [ABSTRACT FROM AUTHOR]

• Since the 1990s, the Po River has experienced a significant decline in N export. • River water is getting warmer and the number of warm days is increasing. • Higher temperature is likely to stimulates heterotrophic activity such as denitrification. • Climate change effects partially mitigate coastal eutrophication. Rivers worldwide are under stress from eutrophication and nitrate pollution, but the ecological consequences overlap with climate change, and the resulting interactions may be unexpected and still unexplored. The Po River basin (northern Italy) is one of the most agriculturally productive and densely populated areas in Europe. It remains unclear whether the climate change impacts on the thermal and hydrological regimes are already affecting nutrient dynamics and transport to coastal areas. The present work addresses the long-term trends (1992–2020) of nitrogen and phosphorus export by investigating both the annual magnitude and the seasonal patterns and their relationship with water temperature and discharge trajectories. Despite the constant diffuse and point sources in the basin, a marked decrease (-20%) in nitrogen export, mostly as nitrate, was recorded in the last decade compared to the 1990s, while no significant downward trend was observed for phosphorus. The water temperature of the Po River has warmed, with the most pronounced signals in summer (+0.13°C/year) and autumn (+0.16°C/year), together with the strongest increase in the number of warm days (+70%–80%). An extended seasonal window of warm temperatures and the persistence of low flow periods are likely to create favorable conditions for permanent nitrate removal via denitrification, resulting in a lower delivery of reactive nitrogen to the sea. The present results show that climate change-driven warming may enhance nitrogen processing by increasing respiratory river metabolism, thereby reducing export from spring to early autumn, when the risk of eutrophication in coastal zones is higher. [Display omitted] [ABSTRACT FROM AUTHOR]

Forest ground vegetation may serve as an early warning system for monitoring anthropogenic global-change impacts on temperate forests. Climate warming may induce a decline of cool-adapted species to the benefit of more thermophilous plants. Nitrogen deposition has been documented to potentially result in soil eutrophication or acidification, which can increase the proportion of species with higher nutrient requirements and species impoverishment caused by competitive exclusion. Abiotic forest disturbances are changing the light conditions in the forest understorey environment. In this resurvey study, we tested the magnitude and direction of change in alpha (species richness) and beta (within-site dissimilarity) diversity and composition of forest ground vegetation in forests of different types in Slovenia over fifteen years. Using plant-derived characteristics (Ellenberg-type indicator values) and by testing a priori predictions concerning expected effects of environmental drivers, we show that the magnitude and direction of forest ground vegetation diversity and floristic changes varies greatly between forest sites. Divergent responses at different sites resulted in low net change of alpha and beta diversity and a weak overall environmental signal. The largest decrease in species number was observed in lowland oak-hornbeam forests, which were also among the sites with the greatest compositional shifts. Changes in beta diversity did not show any consistent trend, and anticipated floristic convergence was not confirmed when all sites were considered. Thermophilization was mainly detected in montane beech sites and alpine spruce forests whereas eutrophication signal was most significant on nutrient-poor sites. Vegetation responses were strongly dependent on initial site conditions. Shrinkage of ecological gradients (process of ecological homogenization) suggests that sites positioned at the ends of the gradients are losing their original ecological character and are becoming more similar to mid-gradient sites that generally exhibit smaller changes. Our results point to the importance of local stand dynamics and overstorey disturbances in explaining the temporal trends in forest ground vegetation. Ground vegetation in Slovenian forests is changing in directions also dictated by multiple regional and global change drivers. [ABSTRACT FROM AUTHOR]

Under the background of increasingly serious global environmental pollution, ensuring the safety of drinking water has become one of the focuses of global attention. In this study, Meihu Reservoir, a drinking water source, was selected as the research object, and the main pollution problems and their sources were revealed through conventional water quality analysis, suitability evaluation of the drinking water source and eutrophication evaluation of the reservoir. Using modern water quality monitoring technology and methods, the paper monitors and analyzes various water quality parameters of the Meihu Reservoir. The results showed that the water quality indexes, except total nitrogen, met the class II–III standard of drinking water, and the comprehensive nutrient state index method (TLI) evaluated the reservoir, and its index met 30 ≤ TLI (∑) ≤ 50 , indicating that the reservoir belongs to the medium nutrition category. Therefore, the water quality of the reservoir has been affected by different degrees of agricultural, domestic and livestock pollution, mainly reflected in the serious excess of the total nitrogen index (the peak has reached 2.99 mg/L). The results of the on-site investigation showed that the main sources of nitrogen in the reservoir included agricultural non-point-source pollution, domestic sewage pollution, domestic garbage pollution and livestock and poultry pollution, accounting for 50.09%, 23.99%, 14.13% and 11.80% of the total load, respectively. On this basis, this paper puts forward some countermeasures for pollution control in order to provide a scientific basis and practical path for water quality protection and improvement of the Meihu Reservoir and other similar reservoirs. [ABSTRACT FROM AUTHOR]

Human activities have resulted in the eutrophication of rivers, leading to heightened concerns regarding the occurrence of filamentous algal blooms. With the increasing utilization of rivers by humans, the occurrence of these nuisance filamentous algae is expected to increase in frequency in the future. Blooms primarily occur due to energy congestion at the trophic level of primary producers, resulting from inefficient energy flow in both the bottom-up and top-down pathways. To investigate the mechanism underlying the outbreak of filamentous algae, two streams in the southern Taihang catchment with different nutrient conditions were selected for this study. The objective of this study was to understand the effects of nutrient levels and other potential factors on the distribution and succession of filamentous algae. Our findings revealed a positive correlation between nutrient conditions and the biomass of filamentous algae. Cladophora and Spirogyra were identified as the dominant species among filamentous algae, each exhibiting unique distribution patterns in the two streams. Spirogyra thrived predominantly in the Baligou stream, where lower nutrient levels and warmer temperatures prevailed. In contrast, Cladophora flourished in the nutrient-rich Nanping stream at colder temperatures. Results from the generalized linear model indicated that the biomass of Cladophora was influenced by nutrient concentration, water depth, water temperature, and macrobenthic biomass. The biomass of Spirogyra, on the other hand, was primarily determined by water temperature, nutrient concentrations, water depth, and velocity. The positive correlation between Cladophora and macrobenthos revealed a possible mutually beneficial relationship, suggesting that macrobenthos may promote the growth of Cladophora by inhibiting periphytic diatoms. In return, the macrobenthos benefit from a secure refuge and an environment conducive to foraging and reproduction. This study suggested that to alleviate energy flow congestion in the benthic food chain, it is advisable to address this issue by either reducing nutrient loadings in rivers or enhancing the presence of benthivorous fishes in streams. [ABSTRACT FROM AUTHOR]

The recovery of submerged macrophytes is crucial for lake restoration. However, Myriophyllum spicatum usually shows an overgrowth and inhibits the growth of Vallisneria denseserrulata via light shading in many restored shallow lakes after the plant transplantation. So far, harvesting M. spicatum is the primary method to alleviate these shading effects in post-restoration lakes. Nevertheless, the effects of harvesting on the growth of V. denseserrulata and water quality are poorly elaborated. In this study, we conducted a mesocosm experiment, including both monoculture and polyculture groups, to investigate the response of V. denseserrulata growth, light climate, and nutrient concentrations in the water with M. spicatum harvesting. Moreover, the growth and morphology of M. spicatum were also examined. We hypothesized that M. spicatum harvesting would enhance the growth of V. denseserrulata and improve both the light climate and water quality. Our results showed that harvesting M. spicatum in the polyculture mesocosms substantially enhanced the relative growth rate (RGR) of V. denseserrulata compared to the non-harvesting controls. Moreover, harvesting M. spicatum reduced the light attenuation coefficient at 30 cm depth; however, the concentrations of chlorophyll-a, total nitrogen, and total phosphorus did not change significantly. As for M. spicatum, harvesting inhibited the growth of main stem and root but did not significantly affect the cumulative weight and RGR of M. spicatum. In contrast, the presence of V. denseserrulata decreased cumulative weight and RGR while promoting the root parameters of M. spicatum. Our findings imply that harvesting overgrowth nuisance submerged macrophyte species (e.g., M. spicatum) can improve the light climate and reduce its root growth, thereby enhancing the growth of target macrophyte species like V. denseserrulata without changes in the water quality which provides valuable insights for post-restoration lake management. [ABSTRACT FROM AUTHOR]

Kelly, AG, Harris, TD. 2024. Watershed grassland fires drive nutrient increases in replicated experimental ponds. Lake Reserv Manage. 40:303–316. Forest and grassland fires have been increasing in frequency due to anthropogenic climate change and fire suppression-focused land management practices. Fire has frequently been observed in lake watersheds, yet links between fire ecology and limnology are not well understood, especially in grassland ecosystems. We conducted a 21-d replicated whole pond experiment to determine the effects of burning on lakes within grassland ecosystems. We examined physicochemical parameters and the phytoplankton concentration and community composition in control and treatment (burned) ponds. Total phosphorus, total dissolved phosphorus, soluble reactive phosphorus, and nitrate increased significantly following burning. The total nitrogen:total phosphorus and total dissolved nitrogen:total dissolved phosphorus ratios decreased significantly following burning. Increased nutrient inputs from burned material led to greater mean phytoplankton concentrations in the treatment ponds compared to the control ponds; however, no statistically significant changes were observed in phytoplankton concentration nor the community composition. Increases in nutrient concentrations in the treatment ponds were observed within the first half of the study and were short-lived, whereas increases in phytoplankton concentrations were not observed until experiment day 21. Our results indicate that increased prevalence of fire may worsen eutrophication issues in grassland water bodies, but more research is needed to understand the persistence of these impacts in pond ecosystems. [ABSTRACT FROM AUTHOR]

Hypoxia in coastal waters is a pressing ecological problem caused by continued eutrophication and climatic change that has widespread consequences for metazoan life and biogeochemical cycles. Numerous studies have investigated the controls on seasonal hypoxia formation and persistence in many of the world's large estuaries and coastal hypoxic zones, but far fewer studies have examined the controls on short-term oxygen variability that leads to diel-cycling hypoxia in shallow-water environments. We utilized a unique, comprehensive (181 stations) record of dissolved oxygen concentrations collected at shallow water sites (primarily < 2 m) at high frequency (15 min) throughout the estuarine complex of the Chesapeake Bay and its tributaries to quantify how internal and external variables co-varied with dissolved oxygen. We used a combination of time-series analysis, harmonic analysis, and machine learning (e.g., classification and regression trees (CART)) approaches to identify spatial patterns in major controls on oxygen variability and the duration of moderate hypoxia. We found that key controls on oxygen variability varied substantially over space. For example, photosynthetically active radiation (PAR) was a strong predictor of oxygen dynamics in the majority of mesohaline waters. In more fetch-exposed stations, wind strongly controlled hypoxic duration, but in eutrophic, inshore locations, chlorophyll a, or turbidity were often better predictors. Specifically, diel oxygen variability was muted in upstream regions characterized by high turbidity. The duration of low oxygen conditions, which we defined conservatively as less than 4.8 mg O2 L−1 (156 µM), was strongly controlled by temperature, and simple projections of regional warming and CART-derived oxygen thresholds suggest that the Bay could experience a 10% increase in this type of hypoxia duration by mid-to-late twenty-first century. The ratio of tidal to biological variability in oxygen was found to increase under conditions of higher turbidity, stronger wind, and lower salinity, but biological variability was typically a factor of two higher than tidal variability. Although chlorophyll-a generated high oxygen concentrations at some locations, those stations with exceptionally high chlorophyll a (> 30 µg L−1) were the most vulnerable to hypoxia. Because conventional water quality modeling frameworks are designed to capture hypoxia on relatively long time scales, these new insights can help inform updated oxygen models to support the management of shallow-water estuaries in the face of managed nutrient reductions and climate change. [ABSTRACT FROM AUTHOR]

Anthropogenic nutrient enrichment is one of the key global change pressures threatening the health of estuaries. This is evident at the persistently eutrophic Swartkops Estuary located along the warm temperate coast of South Africa. Augmented nutrient-rich baseflows (e.g., stormwater runoff, wastewater treatment work discharges) have resulted in the persistent growth of invasive alien aquatic plants (IAAPs), particularly water hyacinth (Pontederia crassipes), in the upper estuarine reaches. As such, the objective of this study was to investigate the temporal population dynamics of water hyacinth in the Swartkops Estuary to inform management options. Methods included five-weekly sampling campaigns in winter, spring, and summer, interspersed with monthly sampling over a year-long period. Physico-chemical variables and river inflow were measured in situ, while samples were collected for inorganic nutrients, phytoplankton biomass, and IAAP measurements (cover, biomass, and tissue nutrients). Model results indicated that increased water temperature and inorganic nitrogen (ammonium and NOx) levels promoted increased coverage of water hyacinth, while seasonal analysis highlighted reduced (p < 0.05) dissolved oxygen levels during the peak summer IAAP accumulation period. Notably, model results indicated declining IAAP tissue TN and TP concentrations with increasing water temperature, yet overall TN and TP storage was highest in summer due to the extensive water hyacinth cover observed during this period. Overall, the proportionally low and transient nature of nutrient storage by water hyacinth populations, together with the detrimental consequences they facilitate, highlights the need to integrate short-term control measures with catchment-scale management interventions geared towards mitigating the causative drivers. [ABSTRACT FROM AUTHOR]

Chironomids are keystone primary benthic consumers with semi‐aquatic life cycles. They support aquatic and terrestrial consumers at higher trophic levels by conveying dietary nutrients, such as fatty acids. In this study, we combined field sampling and laboratory experiments to examine the effects of environmental parameters, including diet, on fatty acid composition and metabolism in chironomid larvae and imagines. Results from 53 lakes showed that lake size, depth, dissolved organic carbon (DOC) concentrations, and trophic state had only marginal effects on the content of long‐chain polyunsaturated fatty acids (LC‐PUFA) in chironomids. Compound‐specific stable hydrogen isotope analyses confirmed that chironomids actively bioconvert dietary fatty acid precursors to LC‐PUFA in all lake types, independent of nutrient or DOC concentrations. Moreover, fatty acid‐specific stable carbon isotope data indicated that the diet of chironomids was subsidized, particularly in oligotrophic lakes in spring, by terrestrial C18 fatty acid precursors that were converted to LC‐PUFA. Data from feeding experiments further confirmed that decreased dietary availability of LC‐PUFA enhanced the conversion of dietary short‐chain precursors to LC‐PUFA. These results suggest that chironomids are PUFA regulators that can sustain LC‐PUFA levels under varying environmental conditions. Furthermore, our results indicate that they bioconvert terrestrial low‐quality material to high‐quality resources, which, via chironomid emergence, support terrestrial food webs. Chironomids are abundant and widespread, and thus, the trophic transfer of LC‐PUFA can have significant implications for the fitness and production of upper trophic level consumers in both aquatic and terrestrial ecosystems. [ABSTRACT FROM AUTHOR]

Introduction: Seagrass-associated microbial communities play a crucial role in the growth and health of seagrasses. However, like seagrass meadows, seagrassassociated microbial communities are often affected by eutrophication. It remains unclear how eutrophication influences the composition and function of microbial communities associated with different parts of seagrass. Methods: We employed prokaryotic 16S rRNA gene high-throughput sequencing combining microbial community structure analysis and co-occurrence network analysis to investigate variances in microbial community compositions, potential functions and complexities across sediment, seagrass leaves, and seawater within different eutrophic areas of two adjacent seagrass meadows on Hainan Island, China. Results: Our results indicated that microbial diversity on seagrass leaves was significantly lower than in sediment but significantly higher than in seawater. Both sediment and phyllosphere microbial diversity showed no significant difference between the highly eutrophic and less eutrophic sites in each lagoon. However, sediment microbial diversity was higher in the more eutrophic lagoon, while phyllosphere microbial diversity was higher in the less eutrophic lagoon. Heavy eutrophication increased the relative abundance of phyllosphere microorganisms potentially involved in anaerobic metabolic processes, while reducing those responsible for beneficial functions like denitrification. The main factor affecting microbial diversity was organic carbon in seawater and sediment, with high organic carbon levels leading to decreased microbial diversity. The co-occurrence network analysis revealed that heavy eutrophication notably reduced the complexity and internal connections of the phyllosphere microbial community in comparison to the sediment and seawater microbial communities. Furthermore, ternary analysis demonstrated that heavy eutrophication diminished the external connections of the phyllosphere microbial community with the sediment and seawater microbial communities. Conclusion: The pronounced decrease in biodiversity and complexity of the phyllosphere microbial community under eutrophic conditions can lead to greater microbial functional loss, exacerbating seagrass decline. This study emphasizes the significance of phyllosphere microbial communities compared to sediment microbial communities in the conservation and restoration of seagrass meadows under eutrophic conditions. [ABSTRACT FROM AUTHOR]

Due to coastal development expansion, an increasing influx of pollutants enters the sea through riverine input and land runoff, threatening coastal ecosystems and posing a risk of eutrophication. In this study, trace metals (Fe, Mn, Cu, and Zn), and nutrients (constituents of N, P, and Si) were assessed in the summer surface seawater of Yantai Sishili Bay (YSB), Northern China focusing on the determination of concentration, spatial-temporal distribution and sources identification, while exploring their correlations. It also aimed to clarify the eutrophication status and evaluate the linear relationships between eutrophication, trace metals, and nutrients in YSB. Over three years (2021-2023), the total dissolved concentrations of Fe, Mn, Cu, and Zn ranged from 4.79-26.71, 0.19-6.41, 0.26-1.53, and 0.74-13.12 µg/L, respectively. Concurrently, nutrient concentrations including NO2-, NO3-, NH4+, PO43-, and DSi exhibited a range of 0.37-11.66, 2.04-178.30, 1.69-70.01, 0.02-16.68, and 0.02-0.71 µg/L respectively. These concentrations revealed a gradual decrease from nearshore to offshore and the temporal variation also showed significant patterns from year to year, indicating distinct regional variations. The primary contributors to the trace metals and nutrients in the study region were recognized as external contributions stemming from natural, anthropogenic, and atmospheric deposition through correlation and principal component analysis. More specifically, riverine input and coastal farming contributed large amounts of nutrients to coastal waters, threatening a potential risk of eutrophication. The eutrophication evaluation expressed below the mild eutrophication level and was far lower than the other global and Chinese bays. The linear correlation between eutrophication and trace metals revealed a weak positive correlation but a significant correlation with nutrients. Despite the absence of significant eutrophication in the bay, potential risks were identified due to identifiable sources of nutrient and trace metal inputs. The findings provided insights to guide efforts in preventing and mitigating coastal eutrophication, as well as nutrient and trace metal pollution, in coastal cities. [ABSTRACT FROM AUTHOR]

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This research aims to propose management strategies to mitigate eutrophication caused by inefficient wastewater treatment plants in Colombia. The information analyzed was provided by environmental authorities such as IDEAM, CORANTIOQUIA, and CORNARE in Antioquia, where the average concentrations of phosphorus in wastewater from municipal, livestock, and industrial activities are 5.1, 30.6, and 29.1 mg P/L. The total nitrogen concentrations are 77, 143, and 121 mg N/L, respectively, surpassing the limit concentrations stated by the European Union, the United States, and Mexico, among others, while Colombia has not established its own limits. Including limitations for nutrient concentrations will align Colombia with the 2050 Sustainable Development Goals (SDGs), where microalgae species like Chlorella or Scenedesmus could be used in wastewater treatment systems for municipalities and industries. These microalgae can capture organic matter, nutrients, and greenhouse emissions and reduce the concentrations observed in natural water. They could also be an alternative for capturing heavy metals and some pollutants of emerging concern. In addition to the ecological and social benefits, the algal biomass could be valorized by transforming it into biological products such as fuels, fertilizers, and pigments when micropollutants are not present, reducing operational costs for treatment systems. [ABSTRACT FROM AUTHOR]

Sustainability requires understanding and respecting the ecosystem functioning to plan the use of its resources. Improvised planning plus economic benefits can stimulate unsustainable decisions that lead to complications and obscures the application of appropriate adaptations when a change is required. This paper is a historical review of a reservoir when the dam changes its use from hydroelectric to water supply and then tourism is superimposed on the ecosystem. Data collected from the literature are systematically analyzed to see the effects on basin-reservoir dynamics. The main effect was the increase in the hydraulic retention time of the reservoir that facilitates the accumulation of nutrients and eutrophication, aggravated by the increase in the fixed and floating population stimulated by tourism. The consequent cyanobacteria blooms deteriorate the landscape, become a health risk and cancels the use of the reservoir to tourism. The increase in emerging compounds detected in the treatment plant effluent discharged into the reservoir poses a risk to aquatic species and the water supply. These results are analyzed in light of the objectives and dimensions of Sustainability. Recommendations include modifying Goal 1 of SDO 8, because it is shown that an annual growth of 7% of GDP in developing countries threatens their natural resources. [ABSTRACT FROM AUTHOR]

Diatoms are key components of freshwater ecosystems and are regularly used for paleolimnological reconstructions, in which defining species optima and tolerances is fundamental for interpreting assemblage shifts in a sediment record. Here, we examined responses of diatoms across three major environmental gradients—dissolved inorganic carbon (range: 0.1–230.5 mg · L−1), total phosphorus (range: 3–326 μg · L−1), and maximum lake depth (range: 0.9–55.0 m)—taken from 158 lakes from across Canada. The lakes were sampled as part of the LakePulse Network, which conducted a standardized sampling of lakes spanning 12 Canadian ecozones. Hierarchical logistic regression was used to model the species responses of 37 common taxa, and species optima and tolerances were calculated with weighted average modeling. The most common response detected was the symmetrical unimodal model, suggesting we likely captured the full environmental ranges for many species, although skewed unimodal responses were also common. Indicator species analyses identified taxa with high predictive values and fidelities to particular ecozones, with high‐nutrient‐adapted taxa such as Stephanodiscus spp. and Cyclotella meneghiniana characteristic of the agriculturally productive Prairie region. The Prairies stood out in the dataset as the region with the most unique flora from the local contribution to beta diversity analysis. Overall, the autecological data provided by our study will allow for improved interpretations of paleolimnological records and other biomonitoring efforts, addressing management concerns and contributing to a better understanding of our changing environment. [ABSTRACT FROM AUTHOR]

Understanding spatio-temporal variability in the production of drift macroalgae is useful for monitoring and assessing the influence of local anthropogenic nutrient sources on coastal ecosystems. In this study we: (1) assessed how the drift macroalgal community composition and biomass have changed over a 22-year period in Port Phillip Bay (a large coastal embayment in Victoria, Australia); and (2) measured the amount of accumulated nitrogen in drift macroalgae and the contribution of anthropogenic nitrogen sources through isotopic analysis. The surveys revealed little overlap in species composition (<13%) and a significant decrease in standing stock biomass (from 631 to 49 g m-2) between surveys (1995/1996 and 2017/2018). This was associated with a high degree of turnover (β-diversity) at the genus level between surveys (mean – 0.53), resulting in distinct communities at all sites, particularly among red algal genera. In addition, the occurrence of ephemeral macroalgal blooms and a semi-perennial mat of the red macroalga Botryocladia sonderi at 10-15 m depth at locations close to nutrient sources indicate drift macroalgae are important nutrient accumulators in the bay. Isotopic analysis revealed a high contribution of anthropogenic-derived nitrogen (δ15N > 17‰ and ~ 3% N content) at depths and locations close to nutrient sources, particularly at times of the year when large wastewater discharges occur. Harvesting of drift macroalgae could be a cost-effective solution for offsetting nitrogen inputs from anthropogenic sources, but it will be important to first investigate whether harvesting results in negative impacts to associated fauna or nutrient cycling. [ABSTRACT FROM AUTHOR]

Because of the first observations in the 1900s of the oligotrophic and eutrophic states of lakes, researchers have been interested in the process that makes lakes become turbid because of high phytoplankton biomass. Definitions of eutrophication have multiplied and diversified since the mid‐20th century, more than for any other ecological process. Reasons for the high number of definitions might be that the former ones did not sufficiently describe their causes and/or consequences. Global change is bringing eutrophication more into the spotlight than ever, highlighting the need to find consensus on a common definition, or at least to explain and clarify why there are different meanings of the term eutrophication. To find common patterns, we analyzed 138 definitions that were classified by a multiple correspondence factor analysis (MCA) into three groups. The first group contains the most generic scientific definitions but many of these limit the causes to increased nutrient availability. A single definition takes into account all causes but would require additional work to clarify the process itself. Nutrient pollution, which is by far the primary cause of eutrophication in the Anthropocene, has generated a second group of environmental definitions that often specify the primary producers involved. Those definitions often mention the iconic consequences of nutrient pollution, such as increased algal biomass, anoxia/hypoxia and reduced biodiversity. The third group contains operational definitions, focusing on the consequences of nutrient pollution, for ecosystem services and therefore associated with ecosystem management issues. This group contains definitions related to regulations, mainly US laws and European directives. These numerous definitions, directly derived from the problem of nutrient pollution, have enlarged the landscape of definitions, and reflect the need to warn, legislate and implement a solution to remedy it. Satisfying this demand should not be confused with scientific research on eutrophication and must be based on communicating knowledge to as many people as possible using the simplest possible vocabulary. We propose that operational definitions (groups 2 and 3) should name the process "nutrient pollution," making it possible to refine (scientific) definitions of eutrophication and to expand on other challenges such as climate warming, overfishing, and other nonnutrient‐related chemical pollutions. [ABSTRACT FROM AUTHOR]

Seagrass recovery has been reported across the globe where previously eutrophied waters have become less nutrient‐rich. In the European Wadden Sea, different recovery trajectories were found after riverine nutrient loads decreased, namely full, temporary and no recovery. We compiled intertidal seagrass presence (Zostera noltei and Z. marina) and eutrophication data for 1930–2020, to relate the seagrass trajectories and regional eutrophication differences to riverine nutrient loads, and inferred prospects for seagrass recovery.Seagrass fully recovered in the less eutrophic North Frisian region. The recovery trajectory was tightly coupled to riverine nutrient load reduction. Relative seagrass area (meadow area/region area) dropped from 10% prior to eutrophication to 2% during the eutrophication peak, increased to 7% during the nutrient reduction period and subsequently expanded to 13%. Colonization of marginal habitats was observed, indicating propagule spillover from neighbouring meadows.The more eutrophic southern regions showed no or only temporary seagrass recovery. Prospects for (limited) recovery are good in only two out of four southern regions, provided that riverine nutrient loads are further reduced by ~40% (reference: 2010–2017). Without this reduction, seagrasses may only temporarily recover and will remain vulnerable to erratic disturbances like macroalgae accumulation or storms.Historical evidence and application of habitat suitability models suggest that the potential relative seagrass area in the southern regions is low: less than 0.2% in the western Dutch region and maximum 2.4% in the Ems‐Jade region.Synthesis and applications. Within a large seascape (15,000 km2) the least eutrophicated region showed seagrass recovery upon nutrient reduction. We translated the critical riverine nutrient loads for this recovery, via regional eutrophication indicators, to loads that may enable a sustained recovery in the other regions. This technique is applicable in other complex systems, provided sufficient historical data are available. Propagule spillover exerts a positive feedback at metapopulation scale leading to acceleration of recovery. Occupied and potential seagrass habitat (e.g. assessed by the maximum recorded area in the past) are thus important landscape selection criteria for restoration, particularly when eutrophication is not yet sufficiently reduced. [ABSTRACT FROM AUTHOR]

Global warming can affect biomass accumulation and the dynamics of periphytic communities, potentially altering their role in aquatic ecosystem functioning. We conducted a 38-day mesocosm experiment to investigate the effects of an increase in winter temperature on periphyton biomass accumulation under eutrophic conditions. We evaluated the warming effect on colonization phases, identifying the most affected phase. The experiment had two treatments (control: current winter temperature of 23.5 ℃, warming: + 5.7 ℃ under IPCC scenario). It was carried out in growth chambers under controlled temperature, light, and humidity. Periphyton and water samplings were performed on days 3, 6, 9, 13, 17, 21, 27, and 38. The increase in temperature did not affect the organic matter accrual rate of the periphyton. However, it negatively affected the net and gross accrual rate of the algal biomass. Ash-free dry mass and chlorophyll-a ratio in the periphyton increased at higher temperatures, indicating a decrease in autotrophic components in the periphyton in the warming treatment. We detected losses in algal biomass during the intermediate and advanced colonization phases. Our results showed a decrease in periphytic algal biomass with an increase in average temperature in winter. In conclusion, a warming scenario can negatively influence periphyton biomass in eutrophic ecosystems, where algal growth in the community is generally unfavorable. [ABSTRACT FROM AUTHOR]

Dissolved oxygen (DO) level at the sediment–water interface is one key factor controlling redox-sensitive processes, such as nutrient cycling. Microcosm experiments with sediment collected from three reservoirs were performed to quantify the influences of water column oxygenation (oxic, anoxic, oxygen fluctuation), sediment characteristics (grain size distribution, total nitrogen and total phosphorus contents, microbial activities), and their interactions on nutrient fluxes from sediments to the water column. Algal growth bioassays were also performed using water from the microcosms to determine which conditions produced the most favorable growth conditions. Anoxic conditions increased the release of dissolved inorganic nitrogen (DIN), mainly as ammonium and phosphates, compared to the other DO conditions. Such effects were likely due to an inhibition of the nitrification–denitrification coupling process for DIN and a reductive dissolution of Fe (III) oxides for phosphates. Following this increased nutrient availability, algal growth in the bioassays was the highest in water collected from microcosms exposed to anoxic conditions. Under both oxic and anoxic conditions, the percentage of fine sediment particles led to decreasing DIN and phosphates fluxes by reducing the nutrient diffusion rate from sediments to the water column. Finally, both DO and sediment grain size controlled the contribution of sediments to reservoir eutrophication. [ABSTRACT FROM AUTHOR]

Softwater ponds with Lobelia dortmanna (EU habitat type 3110) represent the rarest aquatic habitat in Belgium. As in many other European countries, its unfavourable conservation status necessitates restoration according to the EU Habitats Directive, which is compromised by a range of pressures and faces increasing social–economic opposition. To explore appropriate goals and remaining obstacles for its ecological rehabilitation, we investigated the environmental history of a pond, formerly renowned for the occurrence of this habitat. We complemented monitoring data with information inferred from diatoms analysed from old samples, herbarium specimens and surface sediments, vegetation records, physical–chemical analyses and additional observations. This indicated almost circumneutral, slightly buffered and nutrient-poor conditions for the first decades of the 20th century. Deposition of atmospheric pollutants caused gradual acidification from the early 1940s, intensifying into mineral-acidic conditions by the 1970s. More recently, a period of alkalinisation and eutrophication followed despite some restoration efforts. We discuss these changes in the contexts of general setting, external pressures and internal processes. Reflecting upon the prospects for restoring the pond's emblematic biodiversity, management implications for this and other softwater sites dealing with similar problems are discussed. A new combination in the diatom genus Iconella is proposed. [ABSTRACT FROM AUTHOR]

This article explores the role of the aquaculture industry as a research platform for studying the ecological impacts of nutrient enrichment on aquatic ecosystems. Cage culture farms, used for fish farming, provide controlled environments for studying the effects of inputs and measuring impacts. The industry has both positive and negative consequences, such as pollution and disease introduction, but it also contributes to global food demands, local economies, and sustainable development. The article highlights research opportunities in ecology, biogeochemistry, limnology, and oceanography, and emphasizes the need for collaboration between the industry and researchers. It also acknowledges the challenges of sustainability and calls for increased data sharing and equitable application of the research framework. The work was supported by the Simons Foundation and the National Science Foundation. [Extracted from the article]

The Delta do Parnaíba Environmental Protection Area (EPA) represents one of the largest deltaic systems in the Americas. This study investigated the spatiotemporal variability of phytoplankton communities and their correlation with environmental factors and assessed their trophic status and water quality across three mesotidal estuaries (Parnaíba-PRE, Comum-CRE, and Bom Gosto-BGRE) over a year-long sampling period. Multivariate analyses explored the interplay between environmental parameters, phytoplankton communities, and trophic indices. Salinity has emerged as a key determinant in these estuaries. Trophic components influence nutrient dynamics, with Redfield ratios indicating colimitation by orthophosphate (${\rm PO}_4^{3-}$ PO 4 3 − ) and silicate (${\rm SiO}_2^-$ SiO 2 − ). This study identified 355 taxa within the phytoplankton community, with Chlorophyta predominating in the PRE and diatoms dominating in estuaries with relatively high salinities (BGRE and CRE). Environmental drivers vary across estuaries, with temperature, dissolved oxygen (DO), total nitrogen (TN), chlorophyll-a (Chll-a), and the trophic index (TRIX) influencing the phytoplankton community in the PRE, while salinity, ${\rm PO}_4^{3-}$ PO 4 3 − , total phosphorus (TP), and TN affect the CRE, and salinity and Chll-a influence the BGRE. The Delta do Parnaíba EPA exhibits eutrophic to hypertrophic conditions, emphasising the need for comprehensive environmental monitoring, nutrient management, and conservation efforts to safeguard biodiversity, water quality, and ecosystem health. [ABSTRACT FROM AUTHOR]

Due to various human activities, including intensive agriculture, traffic, and the burning of fossil fuels, in many parts of the world, current levels of reactive nitrogen emissions strongly exceed pre‐industrial levels. Previous studies have shown that the atmospheric deposition of these excess nitrogen compounds onto semi‐natural terrestrial environments has negative consequences for plant diversity. However, these previous studies mostly investigated biodiversity loss at local spatial scales, that is, at the scales of plots of typically a few square meters. Whether increased atmospheric nitrogen deposition also affects plant diversity at larger spatial scales remains unknown. Here, using grassland plant community data collected in 765 plots, across 153 different sites and 9 countries in northwestern Europe, we investigate whether relationships between atmospheric nitrogen deposition and plant biodiversity are scale‐dependent. We found that high levels of atmospheric nitrogen deposition were associated with low levels of plant species richness at the plot scale but also at the scale of sites and regions. The presence of 39% of plant species was negatively associated with increasing levels of nitrogen deposition at large (site) scales, while only 1.5% of the species became more common with increasing nitrogen deposition, indicating that large‐scale biodiversity changes were mostly driven by "loser" species, while "winner" species profiting from high N deposition were rare. Some of the "loser" species whose site presence was negatively associated with atmospheric nitrogen deposition are listed as "threatened" in at least some EU member states, suggesting that nitrogen deposition may be a key contributor to their threat status. Hence, reductions in reactive nitrogen emissions will likely benefit plant diversity not only at local but also at larger spatial scales. [ABSTRACT FROM AUTHOR]

Paleoenvironmental analyses have been widely used to infer the fluctuations in past environmental conditions of lakes and reservoirs due to either anthropogenic and/or climatic influences. The Siete Lomas shallow lake (37° 08′ S, 57° 38′ W) is located in an area with a long history of anthropogenic impacts in the Pampa plain, southeastern Argentina. Our aim was to reconstruct the paleoenvironmental history of the Siete Lomas shallow lake and to identify the main forcings of change during the last 1000 years. A multi-proxy analysis was performed including pollen and non-pollen palynomorphs, diatoms, fossil pigments, plant macrofossils and the associated fauna, Total Phosphorus (TP) and organic matter. Two main environmental stages (the latter including two substages) throughout the history of the Siete Lomas lake were recognized as a result of the action of natural variability and anthropogenic drivers. Stage I (1100–1880/1900 AD) recorded a pre-agricultural period when human impacts were negligible, and was considered as reference conditions. In this stage, a temporary, brackish and oligotrophic lake was inferred. Stage II was composed by two substages. Substage II-1 (1900–1945 AD) suggested the establishment of a permanent freshwater lake with higher pelagic primary production and an incipient eutrophication process, associated to increased anthropogenic activity and higher precipitation. Nutrient load and eutrophication processes controlled Substage II-2 (1945–2021), as a productive lake subject to increased eutrophication as a consequence of nutrient loadings from the surrounding catchment was identified. In particular, a highly productive, turbid-hypereutrophic and permanent lake related to the increase in agricultural activities was recognized for the period 2005–2021 AD. Overall, during the early period of the lake history, changes in dominant communities were mainly controlled by climate whereas after 1900 AD anthropogenic and natural forcing synergistically promoted the generalized degradation of the water quality of the Siete Lomas shallow lake. [ABSTRACT FROM AUTHOR]

This study is dedicated to the 300th anniversary of the Russian Academy of Sciences and the 80th anniversary of the establishment of the Institute of Limnology, Russian Academy of Sciences. The main results of studying Russian lakes in the Academy of Sciences over three centuries are presented. In the 18th century, the Academy of Sciences organized first "physical" expeditions for studying lakes, lake regions, as well as the Aral and Caspian seas. In 1916, a Commission for Studying Lake Baikal was set up at the Imperial St. Petersburg Academy of Sciences. After 1917, the studies of lakes expanded considerably because of the practical needs of the country's development. In 1928, the Presidium of the Academy of Sciences transformed the Baikal expedition into the Baikal Limnological Station. In 1944, the Laboratory of Limnology was created in Leningrad, and in 1971, the Institute of Limnology, of the USSR Academy of Sciences was created. In the 1970s–1980s, comprehensive studies of lakes and lake–river systems were carried out in the European part of the USSR along the design line of the redistribution of the water resources in the country. In 1970–1980, USSR Academy of Sciences participated in solving global problems of limnology—eutrophication, acidification, and pollution of lakes. In the late XX–early XXI centuries, special attention was paid to the assessment of the state and the development of forecasts of changes in the ecosystems of water bodies under various climatic and anthropogenic impacts. Monographs were published, generalizing the history of lakes studies in various parts of the country, and complex atlases of large lakes in Russia were compiled. The discovery of periglacial Lake Vostok in the Antarctic, and the obtained scientific results are outstanding scientific achievements in the late XX century. It is shown that lake studies by the Russian Academy of Sciences have contributed much to the basic science and to solving practical problems of the country's economy, and are significant for the development of problems of continental hydrology. [ABSTRACT FROM AUTHOR]

In this study, the results of hydrochemical measurement aboard the RV Kavoshgar Khalij Fars in the Persian Gulf (PG) in September 2018, May, and November 2019 are discussed. Nitrate, nitrite, ammonium, phosphate, and silicate concentrations, salinity, temperature, dissolved oxygen, and pH in the water column of a 1000-km transect in the PG were studied to determine the present status of nutrient regimes of this region. Nitrate, phosphate, and silicate were more concentrated at the bottom layer and showed a maximum just below the thermocline in summer and autumn. Seasonal distribution of nutrient ratios (N:P, N:Si, Si:P) indicates P limitation in autumn, N limitation in spring, P limitation and poor Si in summer throughout the upper layer. The results of this study do not infer eutrophication in the upper layer of the PG waters in autumn and summer. [ABSTRACT FROM AUTHOR]

The results of long-term studies of the dynamics of population parameters of the vendace Coregonus albula in Lake Syamozero in periods with different habitat conditions are presented. The vendace is the most abundant fish species in the lake and was the main object of commercial fishing for 39 years (1932–1970) (60% of the total catch). From 1971 until 2000, the input of nutrients into the lake increased significantly due to high human economic activity in the catchment area. This led to a change in the hydrochemical and hydrobiological regimes of the lake. As a result, favorable conditions were created for vendace feeding. The biomass of zooplankton which is the main component of its diet, increased fivefold from 1950 to 2000 (from 0.4 to 2.1 g/m3). However, the conditions of reproduction of vendace significantly worsened due to siltation of spawning grounds, which led to the mortality of eggs during a long period of its embryogenesis (6–7 months). The decrease in the vendace abundance in 1971–2000 was also caused by the accidental penetration of a new species, the European smelt Osmeruseperlanus into the lake. For a long time (about 15 years) vendace was not found either in catches or in the diet of predatory fish species of the lake. In recent years, as a result of a decrease in the impact of human activity on the lake and the disappearance of the smelt in 2015 due to its infection with the parasite, the vendace population has begun to recover. [ABSTRACT FROM AUTHOR]

The extracellular release of dissolved organic carbon (DOC) from marine macroalgae supports coastal ecosystem function by supplying photosynthetically fixed carbon to higher trophic levels via the microbial loop. Despite its widely acknowledged biogeochemical importance, DOC is not typically included in primary production estimates of coastal systems. Additionally, little is known about how changes in species composition and coverage will affect the supply of DOC to coastal systems. Within the context of the Baltic Sea, anthropogenic forces are driving a decline in habitat forming kelp species (Fucus vesiculosus) which is superseded by filamentous/turfing algal species, a pattern of change observed globally in numerous other aquatic systems. To evaluate how the drivers of this change may impact the flow of carbon within the Baltic Sea coastal system, the production of DOC by the filamentous algae (Ectocarpus siliculosus) was examined and its rate of release determined (0.095 mg C · g DW-1 · h-1 in light and 0.070 mg C · g DW-1 · h-1 in dark). In addition, bioassays were used to assess the short-term DOC use by bacteria as a proxy of the lability of the released products, with the majority (28.7% released in light and 18.6% released in dark) of the products remaining after 120 hours. This data was linked with long term macroalgae biomass and coverage surveys in order to assess changes in macroalgae community structure through time and to produce standing stock estimates of F. vesiculosus. DOC production as a metric of algal coverage was used to make a preliminary estimation of how changes in community structure may impact the flow of carbon within the system. Our results suggest that decreased levels of DOC released by filamentous algae relative to F. vesiculosus will act to reduce microbial activity. Our model estimates the presence of approximately 150,000 tonnes of F. vesiculosus (dry weight) within the Estonian coastal system translating to an annual release of 7,391 tonnes of DOC. Our study indicates that filamentous-dominated systems have likely altered carbon flow, impacting the broader ecology of the Baltic Sea. Consequently, the loss of kelp species and the expansion of filamentous algae may alter carbon dynamics, with important ecological consequences for other coastal systems globally. [ABSTRACT FROM AUTHOR]

Phosphorus (P) is a fundamental element for life, playing an integral role in cellular metabolism including energy transfer, nucleic acid synthesis, and membrane structure. This nutrient is critical to the physiological ecology in all photosynthetic organisms including eukaryotic microalgae and cyanobacteria. The review, here presented, delves into the intricate mechanisms governing phosphorus acquisition from the environment, its utilization in plant metabolism, and regulation in these photosynthetic microorganisms. Furthermore, it comprehensively explores the strategies employed by microalgae to cope with phosphorus limitation, such as the activation of high-affinity phosphate transporters and the synthesis of phosphorus storage compounds. On the other hand, the ability to consume abundant phosphate makes microalgae exploitable organisms for environmental remediation processes. The knowledge synthesized in this review contributes to the broader understanding of microalgal physiology, offering insights into the ecological and biotechnological implications of phosphorus assimilation in these microorganisms. [ABSTRACT FROM AUTHOR]

The primary energy source in developing countries, including Indonesia, is fossil energy. Therefore, evaluating the environmental impact of coal-fired steam power plants is crucial, but limited. Comprehensive scientific analysis is required to develop appropriate alternative measures. This research aims to analyze the life cycle impact of the coal power plant at the gate, including the coal yard, coal crusher, boiler, turbine, and generator, with the functional unit of 1 kWh of electricity produced. This research provides clear recommendations for mitigating emissions from the main contributing units. The analysis reveals the highest impact in the climate change potential category (1.40 × 10-1 kg CO2 eq/kWh), while the smallest impact was recorded in the Eutrophication potential category (7.55 × 10-4 kg PO4 eq/kWh), with no impact on ozone depletion in the stratosphere. The operation of boiler and generator units (gate hotspots) are the main contributors to climate change impacts, including carbon dioxide (9.25 × 10-2 kg CO2), sulfur dioxide (8.21 × 10-3 kg SO2), and nitrogen dioxide (7.55 × 10-4 kg PO4). Alternative programs that may be implemented to reduce emissions include co-firing and installation of flue gas desulfurization and low NOx burner. The findings of this research provide guidance for developing a policy framework to promote more environmentally friendly coal power plants, thereby achieving greater energy sustainability. [ABSTRACT FROM AUTHOR]

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In the riparian zone of the Yangtze River, using polders to impound flood water with high sediment content probably brings eutrophication. A nutrient (nitrogen and phosphorus) release experiment was conducted to reveal the risk. Bare soil and arable soil were used as underlying soils. Overlying water with two sediment concentrations (formed 1 cm and 4 cm thickness layer after deposited, respectively) was used to simulate reserved floods. Higher nutrient content in arable soil led to faster nutrient release into overlying water (16–21 and 0.32–1.32 mg/d·cm2 for TN and TP, respectively) relative to bare soil (5–13.5 and 0.25–1.26 mg/d·cm2 for TN and TP, respectively), suggesting that bare land with lower nutrient content is better than arable land for storing flood water. Nutrient content in sediment deposit layer relative to in original underlying soil determined whether deposited sediment accelerated or mitigated the release of nutrients into overlying water. Because sediment has higher nutrient content than bare soil, the preferred time to impound flood is at the end of flood seasons when sediment load steeply decreases. It is more likely to suffer eutrophication in the initial stage of flood impounding, when overlying water was abundant in both nitrogen and phosphorus and N/P ratio (10–23) was fit for phytoplankton growth. This study helps to identify the risk of eutrophication due to reserving turbid flood water in polders. [ABSTRACT FROM AUTHOR]

Although somewhat debated, it is generally agreed in Europe that small water bodies comprise lentic ecosystems that are shallow (less than 20 m) and have a surface area of a few hectares (less than 10 ha). In Albania, 84 glacial lakes constitute a substantial portion of the aquatic ecosystems that sustain high levels of biodiversity, metabolic rates, and functionality. This paper discusses the integration of ecological sustainability into ecosystem services (i.e., cultural, regulatory, and sustaining services) and the national ecological networks of protected sites. This integration is particularly important in light of recent advancements regarding European integration. It is also important due to the catchment continuum, which addresses biodiversity values and gradients that, in this work, are considered using rotifer communities and aquatic plant species. The main causes of the stressors on small ecosystems are inappropriate land use, water pollution, altered habitats, non-native species introduction, resource mismanagement in basins, inadequate planning, and a lack of sector integration. The glacial lakes reflect climate change elements through: an increased number of dried glacial lakes, so only 84 remain functioning; the water level is slowly being reduced; the oscillation of the water level is steadily increasing; and the eutrophication process is rapidly advancing. [ABSTRACT FROM AUTHOR]

A pilot ichthyological index was developed for use within the Water Framework Directive in the area of Central and Eastern Europe for dam reservoirs, which are heavily modified water bodies. This is the first approach to assessing this water body type based on ichthyofauna in Poland. Various fishing gear types were used. The tested dam reservoirs were scattered throughout the country, from lowland to mountainous areas, with very diverse hydrological and morphological characteristics and pressure ranges based on the TSI index. In preliminary work, a correlation matrix with the TSI index's pressure indicator was tested based on the abundance or biomass of fish species, fish families present, fishing gear used, and fishing depth range for a total of 588 cases. As a result of the tests carried out, the preliminary indicator was based on the ratio of the number of the two families Cyprinidae and Percidae. The correlation between the developed indicator and the pressure index was strong (r = 0.77; p < 0.001). The Percidae family exhibited a strong correlation with the most connections in the matrix. Based on the obtained results, the principle of using already confirmed relationships, such as the ratio between Cyprinidae and Percidae fish families, in the assessment of eutrophication was confirmed to be effective, guaranteeing the effective initial assessment of ecological potential. [ABSTRACT FROM AUTHOR]

In southwest Florida, the Caloosahatchee River flows from Lake Okeechobee into a biologically productive tidal estuarine system. A combination of excess water during the wet season, insufficient fresh water in the dry season, and poor quality of the river water are damaging the estuarine ecosystem. To better control the quality and quantity of the water entering the estuary, reservoirs are being constructed to store excess, poor quality water during the wet season and return it to the river for discharge into the estuary at an appropriate time. This stored water is enriched in nutrients and organic carbon. Because of the subtropical nature of the climate in southwest Florida and potential increases in temperature in the future, the return flow of water from the reservoirs must be treated before it can be returned to the river. Hence, an experimental water treatment system was developed and operated to compare biological treatment processes consisting of solely wetland plants versus adding some engineered processes, including slow sand filtration and a combination of slow sand filtration and ultraviolet (UV) treatment. These three treatment trains were operated and monitored through a seasonal cycle in 2021–2022. All three treatment methods significantly reduced the concentrations of nutrients and total organic carbon. While the enhanced engineered wetlands' treatment trains did slightly outperform the wetland train, a comparison of the three process trains showed no statistically significant difference. It was concluded that upscaling of the slow sand filtration and UV process could improve the treatment efficiency, but this change would have to be evaluated within a framework of long-term economic benefits. It was also concluded that the Caloosahatchee River water quality is quite enriched in nutrients so that reservoir storage would increase the organic carbon concentrations, making it imperative that it be treated before being returned to the river. It was also discovered that the green alga Cladophora sp. grew rapidly in the biological treatment tubs and will present a significant challenge for the treatment of the reservoir discharge water using the currently proposed alum treatment. [ABSTRACT FROM AUTHOR]

Sulfide in sediment porewaters, is toxic to rooted macrophytes in both marine and freshwater environments. Current research on sulfide stress in seagrasses primarily focuses on morphological and physiological aspects, with little known about the molecular response and resistance mechanisms. This study first investigated the damage caused by sulfide to eelgrass (Zostera marina L.) using transcriptomic, metabolomic, and other physiological and biochemical indicators and explored the potential resistance of eelgrass at molecular level through laboratory simulated and in‐situ sulfide stress experiments. Comprehensive results showed that sulfide stress severely inhibited the growth, photosynthesis, and antioxidant enzyme activities of eelgrass. Importantly, transcriptome analysis revealed significant activation of pathways related to carbohydrate and sulfur metabolism. This activation served a dual purpose: providing an energy source for eelgrass stress response and achieving detoxification through accelerated sulfur metabolism—a potential resistance mechanism. The toxicity of sulfide increased with rising temperature as evidenced by a decrease in EC50. Results from recovery experiments indicated that when Fv/Fm reduced to about 0 under sulfide stress, the growth and photosynthesis of eelgrass recovered to normal level after timely removal of sulfide. However, prolonged exposure to sulfide resulted in failure to recover, leading ultimately to plant death. This study not only enhances our understanding of the molecular‐level impacts of sulfide on seagrasses but also provides guidance for the management and ecological restoration of seagrass meadows under sulfide stress. [ABSTRACT FROM AUTHOR]

In aquatic ecosystems with low nutrient levels, organic aggregates (OAs) act as nutrient hotspots, hosting a diverse range of microbial species compared to those in the water column. Lake eutrophication, marked by intensified and prolonged cyanobacterial blooms, significantly impacts material and energy cycling processes, potentially altering the ecological traits of both free-living (FL) and particle-attached (PA) bacteria. However, the extent to which observed patterns of FL and PA bacterial diversity, community assembly, and stability extend to hypereutrophic lakes remains understudied. To address this gap, we investigated bacterial diversity, composition, assembly processes, and stability within hypereutrophic Lake Xingyun. Our results revealed that FL bacterial communities exhibited higher α-diversity than PA counterparts, coupled with discernible taxonomic compositions. Both bacterial communities showed distinct seasonality, influenced by cyanobacterial bloom intensity. Environmental factors accounted for 71.1% and 54.2% of the variation among FL and PA bacteria, respectively. The assembly of the PA bacterial community was predominantly stochastic, while FL assembly was more deterministic. The FL network demonstrated greater stability, complexity, and negative interactions, indicative of competitive relationships, while the PA network showed a prevalence of positive correlations, suggesting mutualistic interactions. Importantly, these findings differ from observations in oligotrophic, mesotrophic, and eutrophic lakes. Overall, this research provides valuable insights into the interplay among bacterial fractions, enhancing our understanding of nutrient status and cyanobacterial blooms in shaping bacterial communities. [ABSTRACT FROM AUTHOR]

Constructed wetlands (CWs) are a widely used technology for the treatment of wastewater, with Free Water Surface Constructed Wetlands (FWS CWs) being the simplest configuration. However, there is currently no consensus on the Hydraulic Retention Time (HRT) that optimizes P removal efficiency. To address this issue, this study conducted a bibliometric review of 85 scientific articles published between 1997 and 2021 that investigated the relationship between P removal and the HRT in FWS CWs. Scientometric maps were constructed to identify key topics, and bibliometric surveys were used to refine and explore the relationship between P removal and HRT. The analysis found a high correlation between P removal and HRT across all scales of the FWS CW systems, ranging from moderate to very strong. Specifically, the regressions between P removal efficiency and HRT were 73%, 70%, and 67% for lab-scale, pilot-scale, and real-scale systems, respectively. Overall, the FWS CWs demonstrated strong P removal efficiency, with removal rates reaching 95%, making them a promising technology for the tertiary treatment of effluents with a focus on nutrient removal and recovery. Future studies that focus on the many parameters of CW, especially on how macrophytes management affects the nutrient removal performance of these systems, are necessary to enrich our knowledge of CWs and optimize the application of this technology to wastewater treatment. [ABSTRACT FROM AUTHOR]

Background: Protists, single-celled eukaryotic organisms, are critical to food web ecology, contributing to primary productivity and connecting small bacteria and archaea to higher trophic levels. Lake Mendota is a large, eutrophic natural lake that is a Long-Term Ecological Research site and among the world's best-studied freshwater systems. Metagenomic samples have been collected and shotgun sequenced from Lake Mendota for the last 20 years. Here, we analyze this comprehensive time series to infer changes to the structure and function of the protistan community and to hypothesize about their interactions with bacteria. Results: Based on small subunit rRNA genes extracted from the metagenomes and metagenome-assembled genomes of microeukaryotes, we identify shifts in the eukaryotic phytoplankton community over time, which we predict to be a consequence of reduced zooplankton grazing pressures after the invasion of a invasive predator (the spiny water flea) to the lake. The metagenomic data also reveal the presence of the spiny water flea and the zebra mussel, a second invasive species to Lake Mendota, prior to their visual identification during routine monitoring. Furthermore, we use species co-occurrence and co-abundance analysis to connect the protistan community with bacterial taxa. Correlation analysis suggests that protists and bacteria may interact or respond similarly to environmental conditions. Cryptophytes declined in the second decade of the timeseries, while many alveolate groups (e.g., ciliates and dinoflagellates) and diatoms increased in abundance, changes that have implications for food web efficiency in Lake Mendota. Conclusions: We demonstrate that metagenomic sequence-based community analysis can complement existing efforts to monitor protists in Lake Mendota based on microscopy-based count surveys. We observed patterns of seasonal abundance in microeukaryotes in Lake Mendota that corroborated expectations from other systems, including high abundance of cryptophytes in winter and diatoms in fall and spring, but with much higher resolution than previous surveys. Our study identified long-term changes in the abundance of eukaryotic microbes and provided context for the known establishment of an invasive species that catalyzes a trophic cascade involving protists. Our findings are important for decoding potential long-term consequences of human interventions, including invasive species introduction. BaNPxYigHXA7H5uqkH8sry Video Abstract [ABSTRACT FROM AUTHOR]

Long Island Sound (LIS) is a highly urbanized estuary that receives high inputs of nitrogen pollution leading to summertime hypoxia in the bottom waters of its western region. Though LIS hypoxia has been well-studied for decades, there is a paucity of information regarding eutrophication-induced acidification due to the challenges of obtaining high-precision observations of the marine carbonate system. In this work, we established a time-series of carbon dioxide (CO2) system observations in LIS through measurements of dissolved inorganic carbon (DIC) and total alkalinity (TA) during thirteen sampling events between March 2020 and August 2022. This time span captured both seasonal and interannual variation, including the contrast between two historic drought years (2020 and 2022) and one high-freshwater flow year with significant tropical storm activity (2021). Observations revealed reduced acidification in western LIS (WLIS) (minimum aragonite saturation state, Ωar > 1.5) during the high-river discharge summer of 2021, corresponding to a decrease in the DIC/TA ratio of the Housatonic River. By contrast, LIS bottom water DIC and DIC/TA were higher during the drought summers of 2020 and 2022 (bottom DIC/TA = 0.9-1.0 and 0.85-0.9 in 2020 and 2021, respectively), leading to more acidified conditions and persistent aragonite undersaturation (minimum Ωar <1.0 and 1.1 in 2020 and 2022, respectively). Increased river discharge mitigated respiration-induced acidification in WLIS, likely due to a combination of decreased estuarine residence time and reduced riverine DIC/TA. These results motivate future studies of the carbonate chemistry of LIS and its freshwater endmembers in relation to hypoxia dynamics, with consideration of climate related shifts in physical and biological dynamics of the estuary with time. [ABSTRACT FROM AUTHOR]

Freshwater biodiversity has been declining in urban areas, which may threaten ecosystem functions. Although many studies have demonstrated a positive correlation between biodiversity and ecosystem functioning (BEF) in terrestrial and marine ecosystems, little is known about the BEF relationship in freshwater environments, especially in highly urbanized regions where water pollution is a major concern. Eutrophication in urban water bodies may trigger algae blooms, decreasing the evenness or functional divergence (FDiv) of phytoplankton communities, thus negatively affecting ecosystem functioning. Through an annual field investigation, we clarified the relationship between phytoplankton diversity and ecosystem functioning, represented as resource use efficiency (RUE), in an urban river in northern China. Results indicated that evenness in the phytoplankton community contributes most to driving ecosystem functioning compared to environmental factors. The relative abundance of dominant Bacillariophyta was positively correlated with the resource use efficiency of phytoplankton (RUEpp) but negatively correlated with the resource use efficiency of zooplankton (RUEzp). Both phytoplankton evenness and functional divergence were negatively linked to RUEpp but positively to RUEzp. Our findings suggest that the reduction of phytoplankton evenness and functional divergence may seriously threaten resource use efficiency (RUE), and its potential mechanism can provide a crucial reference for water quality protection and sustainable water resource utilization in the basin. [ABSTRACT FROM AUTHOR]

Harmful algae blooms are a rare phenomenon in rivers but seem to increase with climate change and river regulation. To understand the controlling factors of cyanobacteria blooms that occurred between 2017 and 2020 over long stretches (> 250 km) of the regulated Moselle River in Western Europe, we measured physico-chemical and biological variables and compared those with a long-term dataset (1997–2016). Cyanobacteria (Microcystis) dominated the phytoplankton community in the late summers of 2017–2020 (cyano-period) with up to 110 µg Chlorophyll-a/L, but had not been observed in the river in the previous 20 years. From June to September, the average discharge in the Moselle was reduced to 69–76% and water temperature was 0.9–1.8 °C higher compared to the reference period. Nitrogen (N), phosphorus (P) and silica (Si) declined since 1997, albeit total nutrient concentrations remained above limiting conditions in the study period. Cyanobacterial blooms correlated best with low discharge, high water temperature and low nitrate. We conclude that the recent cyanobacteria blooms have been caused by dry and warm weather resulting in low flow conditions and warm water temperature in the regulated Moselle. Under current climate projections, the Moselle may serve as an example for the future of regulated temperate rivers. [ABSTRACT FROM AUTHOR]