High Total Phosphorus Concentrations Research Articles

An investigation of cyanobacteria, cyanotoxins and environmental variables in selected drinking water treatment plants in New Jersey

Harmful Algal Blooms (HAB) have the potential to impact human health primarily through their possible cyanotoxins production. While conventional water treatments can result in the removal of unlysed cyanobacterial cells and low levels of cyanotoxins, during severe HAB events, cyanotoxins can break through and can be present in the treated water due to a lack of adequate toxin treatment. The objectives of this study were to assess the HAB conditions in drinking water sources in New Jersey and investigate relationships between environmental variables and cyanobacterial communities in these drinking water sources. Source water samples were collected monthly from May to October 2019 and analyzed for phytoplankton and cyanobacterial cell densities, microcystins, cylindrospermopsin, Microcystis 16S rRNA gene, microcystin-producing mcyB gene, Raphidiopsis raciborskii-specific rpoC1 gene, and cylindrospermopsin-producing pks gene. Water quality parameters included water temperature, pH, dissolved oxygen, specific conductance, fluorescence of phycocyanin and chlorophyll, chlorophyll-a, total suspended solids, total dissolved solids, dissolved organic carbon, total nitrogen, ammonia, and total phosphorus. In addition to source waters, microcystins and cylindrospermopsin were analyzed for treated waters. The results showed all five selected New Jersey source waters had high total phosphorus concentrations that exceeded the established New Jersey Surface Water Quality Standards for lakes and rivers. Commonly found cyanobacteria were identified, such as Microcystis and Dolichospermum. Site E was the site most susceptible to HABs with significantly greater HAB variables, such as extracted phycocyanin, fluorescence of phycocyanin, cyanobacterial cell density, microcystins, and Microcystis 16S rRNA gene. All treated waters were undetected with microcystins, indicating treatment processes were effective at removing toxins from source waters. Results also showed that phycocyanin values had a significantly positive relationship with microcystin concentration, copies of Microcystis 16S rRNA and microcystin-producing mcyB genes, suggesting these values can be used as a proxy for HAB monitoring. This study suggests that drinking water sources in New Jersey are vulnerable to forthcoming HAB. Monitoring and management of source waters is crucial to help safeguard public health.

Management of eutrophication using combined the “flock & sink” mitigation technique and submerged plants restoration: a mesocosm study

Abstract Currently, the issue of eutrophication and cyanobacterial blooms persists in water bodies worldwide, prompting the exploration of various treatment methods. This study conducted a comparative analysis of eutrophic water bodies using ferric chloride-modified zeolite (FMZ) and calcium hydroxide-modified zeolite (CMZ) combined with Elodeanuttallii (E. nuttallii) for removal and purification effects. The results revealed that the addition of E. nuttallii had a sustained inhibitory effect on phosphorus release, maintaining stability with lower Turbidity(Tur) and stabilized pH within the range of 8.5-9. FMZ demonstrated rapid reduction in dissolved phosphorus concentration, achieving a removal rate of 96% within 3 days. The combined plant group of CMZ and FMZ exhibited synergistic effects with E. nuttallii, achieving an impressive total phosphorus (TP) removal rate of 80.13% and a total nitrogen (TN) removal rate of 48.77%. Additionally, chlorophyll a (Chl a) concentration decreased from 100.74 ± 24.72 μg/L to 49.96 ± 2.08 μg/L. The phytoplankton community composition indicated that diatoms thrived in low temperatures and high NH4 conditions. Under the same low Total Nitrogen to Total Phosphorus (TN:TP) ratio, high TP concentrations were associated with cyanobacteria dominance, while green algae dominated in other scenarios. This comprehensive approach demonstrates the potential efficacy of CMZ and FMZ combined with E. nuttallii in addressing eutrophic water bodies and mitigating cyanobacterial blooms.

Enhanced Treatment of Potato Starch Wastewater Using Chitosan-Modified Biochar Film Adsorption Coupled with Ultrafiltration

Potato starch wastewater, a byproduct of potato processing, is an escalating environmental concern due to its high concentrations of COD (chemical oxygen demand), ammonia nitrogen, and total phosphorus (TP). Addressing this challenge, this research introduced a novel method combining chitosan-modified biochar film (CBC) adsorption with subsequent ultrafiltration. SEM (scanning electron microscope), FTIR (Fourier transform infrared spectral), XRD (X-ray diffractometer), and BET (specific surface area) analyses validated CBC’s enhanced surface characteristics, confirming successful chitosan (CS) film impregnation. CBC exhibited superior adsorption capacities, especially 40%wt-CBC, optimizing COD removal at 79.8%, ammonia nitrogen at 93.3%, and TP at 91.2%. Kinetic studies associated the adsorption process with a pseudo-second-order model, highlighting chemical adsorption. Additionally, the Langmuir isotherm model suggested monolayer adsorption with no inter-adsorbate interactions. The treated effluent, post adsorption, was directed through an ultrafiltration membrane, ensuring water quality suitable for reuse. This integrative treatment not only offers an effective solution for potato starch wastewater management but also underscores the potential for sustainable water resource recovery in the food processing sector.

Removal and recovery of nutrients from septic tank wastewater using microalgae: Key factors and practical implications

Treatment of septic tank wastewater (STWW) with high concentrations of ammonium (NH4+) and total phosphorus (TP), is challenging in decentralized areas. Utilizing microalgae for STWW treatment can simultaneously recover nutrients in the form of high-value microalgal biomass. However, despite the potential benefits, microalgal treatment of STWW is rarely reported. Therefore, this work utilized bench-scale photobioreactors (PBR) to investigate different factors that could affect microalgal cultivation in STWW and treatment efficiency. Accordingly, it was observed that suspended solids present in STWW did not significantly affect the microalgae growth and nutrient removal efficiencies in bubble column PBR. On the other hand, the effect of endemic microorganism could not be verified in this study due to observed fungal contamination and change in nutrient profile of STWW after autoclave. Nevertheless, the highest microalgal growth and nutrient removal efficiencies of NH4+-N = 79.14% and TP = 41.11% were observed within 14 days of photoautotrophic cultivation in raw STWW. Further, 25 days of upscaled photoautotrophic cultivation in 4-L bubble column PBR was performed to study biomass yield, nutrient removal kinetics, and nutrient removal efficiency. Consequently, 0.75 g‧L−1 dry biomass was produced with improved removal efficiency of NH4+-N (96.16%), and TP (69.57%). Elemental analysis of biomass revealed that 62.99 ± 1.46 mg‧L−1 TN and 11.41 ± 1.42 mg‧L−1 TP were recovered. Further, 1.02 geq carbon dioxide (CO2) was bio-fixed with every liter of STWW treated. The findings of this study revealed that microalgae can be successfully utilized for the removal and recovery of nutrients from STWW.

Dynamic characteristics of total and microcystin-producing Microcystis in a large deep reservoir

Microcystis, one of the common cyanobacteria, often causes blooms in reservoirs, which has seriously threatened the safety of drinking water worldwide. To identify the growth characteristic of total and microcystin-producing Microcystis in large deep reservoirs, we used Quantitative PCR (qPCR) to measure the cell density of total and microcystin-producing Microcystis and monitored water quality in the water samples collected in Dongzhang Reservoir once a month. Microcystis blooms occurred in Dongzhang Reservoir in April 2017, which was composed of microcystin-producing and non-microcystin-producing Microcystis. Water temperature, dissolved oxygen, pH, and chlorophyll-a showed significant vertical stratification during Microcystis blooms. Total and microcystin-producing Microcystis grew rapidly under the high concentration of total phosphorus and rising water temperatures. Nitrate-nitrogen had a significant linear correlation with the abundance of microcystin-producing Microcystis. Our results indicated that nutrients and water temperature could be key triggers of Microcystis blooms and nitrate-nitrogen potentially regulates the competition between microcystin-producing and non-microcystin-producing Microcystis. This study improves our understanding of the characteristics of Microcystis blooms and the competition between microcystin-producing and non-microcystin-producing Microcystis in large deep reservoirs.

Assessment of nutrients and conductivity in the Wachusett Reservoir watershed: An investigation of land use contributions and trends

The quality of drinking water for the Boston Metropolitan Area, supplied by the Quabbin-Wachusett system, is impacted by environmental trends. The objectives of this study are to increase understanding of the role that small streams may play in degradation of reservoir quality by characterizing seasonal constituent patterns from 1998 to 2020 in the Wachusett Reservoir watershed and by developing enhanced modeling frameworks. Previous monitoring (1998–2012) exhibited increased loads due to increasing flows despite declining solute concentration. This present study analyzed seasonal nitrate (NO3) and total phosphorus (TP) concentration and load trends from 2012 to 2020 across 11 tributaries. Specific conductivity (SC) was also assessed to evaluate the impacts of road salt application. From 2012 to 2020, statistical results for mean nutrient concentrations suggest static or declining temporal trends, while SC in all tributaries exhibited increasing trends. Land use data suggest association with altered drainage landscapes as potential sources of increased constituent transport. Subbasins with the highest concentrations of TP, NO3, and SC have the largest percentage of impervious and cultivated areas, two to three times greater than other subbasins. Daily flows were modeled using the airGR hydrological model, subsequently used to calculate loads. Overall, flow magnitude was a more important load driver than long-term nutrient concentrations, thus, showing that stream discharge controlled load variability. On the other hand, persistently high SC levels controlled the increasing SC load trends. Finally, many nutrient reduction management strategies demonstrated an important impact from 1998 to 2020. Despite watershed programs aimed at reducing salt applications, concentrations in streams are increasing, indicating a long-term legacy of salt accumulation. Although smaller tributaries represent a modest portion of the system, addressing these sources has the potential to further reduce the long-term ecological impacts of reservoir constituent loading.

Total nitrogen and pH are key variables for functional structure of zooplanktonic communities in an agropastoral landscape

Changes in land use are one of the main impacts on aquatic ecosystems. The conversion of natural areas into agropastoral, such as pasture or monocultures, can affect the limnological characteristics of the water that in turn influence the structure of aquatic communities. But the impact is still unclear, particularly on zooplankton communities. The objective of this study was to evaluate the effect of water parameters from eight reservoirs inserted in an agropastoral landscape on the functional structure of zooplankton. The functional characterization of the zooplankton community was based on four traits: body size, feeding type, habitat type, and trophic group. Functional diversity indices (FRic FEve and FDiv) were estimated and modeled water parameters, using generalized additive mixed models (GAAM). The water parameters investigated were total nitrogen (TN) and total phosphorus (TP), dissolved oxygen (OD), temperature and pH. Moreover, we used RDA to analyze the influence of these environmental variables on the sharing of traits among the sample sites. FRic was high in the reservoirs with low TN concentration and low pH values. FEve was also high in low pH and high TP concentration. FDiv was high with unsharp increases of pH and high concentrations of TN and DO. Our analyses showed pH as a key variable for functional diversity, since it was related to the variation in all indices. Data also pointed out changes in diversity functional with small pH changes. The big and medium size, raptorial-cop and filtration-clad functional traits were positively associated with high concentrations of TN and alkaline pH. The small size and filtration-rot were negatively associated with high concentrations of TN and alkaline pH. Density of filtration-rot was lower in pasture landscapes. In conclusion, our study indicated that pH and TN are key variables for the functional structure of zooplanktonic communities in an agropastoral landscape.

Predicting high resolution total phosphorus concentrations for soils of the Upper Mississippi River Basin using machine learning

Predicting high resolution total phosphorus concentrations for soils of the Upper Mississippi River Basin using machine learning

Soil management effects of extensive pastures, intensive pastures and sugarcane crops on the availability of metals and nutrients in freshwater: A realistic mesocosm approach

Changes in land use have led to important modifications in aquatic ecosystems around the world. In Brazil, extensive pastures are being converted to sugarcane crops to avoid deforestation, while the remaining pastures are being intensified to compensate for the loss of area. In this study, the hypothesis that conventional soil management practices conducted on intensive pasture and sugarcane crops increase the availability of contaminants in freshwater was tested. Thirteen mesocosms embedded in extensive pasture (EP), intensive pasture (IP), and sugarcane crops (C) systems were monitored for 392 days. The monitoring included the measurement of in situ parameters (pH, dissolved oxygen, electrical conductivity, turbidity, and chlorophyll), nutrients (total nitrogen, nitrite, nitrate, ammonium ion, total phosphorus, total dissolved phosphorus, inorganic phosphorus, and silicate), and metals (aluminum, cadmium, copper, manganese, nickel, lead, potassium, and zinc). Soil management practices were performed in IP and C treatments at full-scale (tillage, application of fertilizers, vinasse and pesticides, and cattle pasture). The patterns observed for each treatment were obtained developing Principal Component Analysis over time. The mesocosms in the EP treatment did not experience large variations in water quality over time since no soil management was performed in this treatment. However, we found that fertilizer and vinasse application was the major precursor to the deterioration of water quality over time. After the first fertilizer application, we found eight and 16 times higher concentrations of total phosphorus, and seven and 45 times higher concentrations of total nitrogen in the IP and C treatments, respectively, in comparison to their concentration in the EP treatment. The application of vinasse in sugarcane crop increased water conductivity, potassium, and manganese concentrations in mesocosms. Dissolved oxygen and pH values decreased over time in all treatments. Overall, soil management practices resulted in greater deterioration of water quality in the sugarcane treatment than in the intensive pasture.

IMPACT OF ARTISANAL PERMA GOLD MINING ON GROUNDWATER QUALITY

The artisanal exploitation of gold in Perma is not without impact on the environment and even the quality of groundwater. For this, three gold panning sites were selected. Samples of water (surface and underground) and sediments were taken during the rainy season between the months of August and September 2021. The results from the physico-chemical analyzes show that the waters are slightly acidic (6 < pH < 7.42), weakly mineralized and conductive (21 < EC < 448 µS/cm) the water temperature varies between 27.7 °C and 30.8 °C. The concentrations of cyanides and zinc vary respectively from 0 µg/L and 30 µg/L and from 0.01 and 0.5 mg/L. With regard to the sediments, the physico-chemical analyzes show the following results: the water pH is close to neutral [6.79 6.98] and the KCl pH is slightly acidic [6.42 6.53]. Sediments from the Kouaterna site record high concentrations of total phosphorus 7934.00 meq/kg, total carbon 1.1094%, NTK 1200 mg/kg and organic matter 1.91%. As for the exchangeable K and the cation exchange capacity, they evolve respectively between 0.0859 meq/kg and 0.1791 meq/kg and 4.360 meq/kg < CEC < 6.160 meq/kg. Groundwater in the area is weakly mineralized, of good quality and has no impact on consumption, unlike unsuitable surface water.

Changes in water chemical composition in Lake Vedlozero and one of its bays as a result of anthropogenic eutrophication

Lake Vedlozero is an accumulating system of a variety of anthropogenic impacts. Since the 1970s, significant changes have occurred in the landscape structure of stream catchments in the southeastern and western parts of the lake’s drainage basin. Deforestation, conversion to arable land and drainage have enriched the lake water with nutrients and organic matter. The northeastern bay of the lake receives substantial amounts of wastewater from the village of Vedlozero and water from the River Vokhtozerka, affected by agriculture in the catchment. High average annual concentrations of total phosphorus (47–173 μg/l) in the water of the bay cause continuous blooming during the open water period. Blooming intensively in the bay, blue-green algae (cyanobacteria) release toxic substances (neuro-, hepato-, and dermatotoxins) dangerous for humans and animals. Massive development of cyanobacteria in the northeastern bay of Lake Vedlozero in summer now causes skin disorders, specifically allergic dermatitis, in Vedlozero village inhabitants (especially children) who swim in the lake.

The Thores Lake proglacial system: remnant stability in the rapidly changing Canadian High Arctic

We describe limnological data sets from Thores Lake, a large ice-contact proglacial lake in northern Ellesmere Island, Nunavut (82.65°N), including longitudinal and cross transects (vertical resolution 0.03 m, horizontal resolution 100–200 m). The lake is formed due to damming by Thores Glacier at its northwest margin, has multi-year ice cover and a cold (<1.54 °C) fresh water column with a bottom layer of <0 °C, high-conductivity water in the deepest basin. Thores Lake is ultraoligotrophic, with low nutrient and phytoplankton stocks. Accessory pigment data and metagenomics were used to describe the eukaryotic microbial community. Diversity and taxonomic composition in the water column were homogeneous down to a depth of 40 m, consistent with density profiles. Surface water at the glacier interface was characterized by high turbidity and total phosphorus concentrations, and a distinct phytoplankton community dominated by chlorophytes, whereas the lake water column had higher relative abundances of chrysophytes and photosynthetic dinoflagellates. Thores Lake has a contracted pelagic food web, with the highest trophic level occupied by phytoplankton-feeding rotifers, and no crustacean zooplankton; profiles showed that omega-3 fatty acids (FAs) ranged from <1% (glacier interface) to 3.6% (central lake) of total seston FAs. Given the stability of the Thores Glacier ice dam and the persistence of cold water capped by perennial ice, Thores Lake provides a baseline to assess the impact of climate change on far northern lakes.

Water Quality in a Small Lowland River in Different Land Use

The paper describes water quality in the Raszynka River based on selected chemical parameters dependent on different land use. The research was carried out in the Raszynka River catchment, characterized by a small surface area (75.9 km2) and length (17.14 km). The river is a right tributary of the Utrata River. It is located in the Piaseczno and Pruszkow districts in the Mazowieckie voivodship. The dominant type of land use in the basin is agricultural land. Water samples were collected from 2017 to 2019 from previously designated research points at similar distances along the river. Selected physicochemical indicators examined in the samples include total alkalinity, electrolytic conductivity (EC), pH, and chemical oxygen demand (COD). Moreover, the concentration of selected substances was determined, including nitrogen compounds: NO3− (nitrates) and NH4+ (ammonium), TP (total phosphorus), and Cl− (chlorides). The results showed that the values of some of the examined indicators do not meet the standards set for first-class surface water quality. Indicators significantly exceeding the limit included ammonium, chlorides, and pH. The highest concentration of chlorides, ammonium, and nitrate was found in urbanized areas. The highest concentrations of total phosphorus and COD were determined in agricultural areas and total alkalinity in meadows.

The spatial organization of CAFOs and its relationship to water quality in the United States

• Applied Nearest Neighbor Index and Moran’s I to quantify the spatial pattern of AFOs. • Watersheds with higher AFO NNI were associated with elevated nutrient levels. • Clustering of smaller farms (less regulated) also corresponded to high nutrients. • Results help to inform management of AFOs and other pollutant sources. Large animal operations in the United States (US) have expanded in recent decades as a solution for meeting increasing food demand. These operations can release large amounts of organic matter and nutrients into the environment, potentially impacting water quality conditions of nearby waterbodies. Often referred to as animal feeding operations (AFOs) or CAFOs (concentrated AFOs) based on nomenclature in federal regulations, these operations are usually clustered in space, which may intensify the impacts observed. However, the influence of the known spatial aggregation of CAFOs on water quality conditions has not been evaluated. This study investigates the spatial organization of CAFOs and its relationship to water quality conditions. We hypothesized that watersheds with clustered CAFOs are likely to be associated with higher concentrations of Total Phosphorus (TP) and Total Nitrogen (TN) in the US. We gathered and digitized CAFO locations in 16 US states and used TP and TN concentration data to evaluate our hypothesis. We calculated the flow-weighted mean concentration of TN and TP from 2005 to 2014 and averaged those values per season. We used the nearest neighbor index (NNI) to determine the spatial pattern (i.e., clustering or dispersed) of CAFOs per watershed and its significance level. Additionally, for states with animal number information per farm, we performed a Local Moran’s I analysis to understand if the clustering of CAFOs with a low or high number of animals relates to the TP and TN concentrations of each nearest water quality station. Overall, we found that watersheds with significant clustering patterns were associated with higher TP and TN levels. Seasonally, this finding also held principally during spring and summer seasons, when manure tends to be land applied. Our Local Moran’s I analysis also revealed that the clustering of smaller and medium-sized farms, usually less regulated, is associated with elevated TP and TN concentrations. This reveals that the small, yet potentially unregulated farms could be highly impactful to the environment, which warrants further study. Given the lack of information on the influence of CAFO clustering (and other pollutant source clustering) on water quality and that most states do not regulate emitters based on this aspect, our outcomes advance the knowledge of how these entities may be driving changes to the environment. This study also brings insights into new water quality modeling approaches and supports future policy decisions.

THE BEHAVIOUR OF PHOSPHORUS IN AN OLD PARALLEL CHANNEL SLAŇÁKY IN THE POODŘÍ (CZECH REPUBLIC)

Within the Poodří nature reserve and the Odra River old parallel channel, Slaňáky, various forms of phosphorus were investigated due to increased high concentrations of total phosphorus (Ptot) in the surface water. Surface water samples were subjected to chemical analyses using absorption spectrophotometry (Ptot and P-PO43- ) and accompanying parameters (t, O2, pH, Cond, TSS ) were measured. Next, grain size analysis of the sediment and sediment analyses using X-ray fluorescence were carried out (P, Fe, Al, Ca, Si, K, Mn, S, etc.). The seasonality of Ptot concentrations in the water was not confirmed, the reservoir behaved as a pool. The concentrations of the dissolved inorganic form P- PO43- were low when compared to Ptot, thus suspended phosphorus prevailed. This may be related to the low depth of the given water body, where stratification does not occur in contrast to deep water bodies. However, sediment resuspension is frequent, and phosphorus largely accumulates. The concentrations of Ptot in the sediment ranged around 4900 mg/kg, where the inorganic form prevailed (87.24 – 93.73 %) over the organic (6.27 – 12.76 %). At the same time, the sediment samples were abundant for sand fractions (2 – 0.03 mm), 47.86 – 60.89 %, and finest silt and clay (< 0.063 mm), 33.07 – 44.60 %.

RESPONSE OF TAXONOMIC AND FUNCTIONAL BENTHIC MACROFAUNA RICHNESS TO LAND USE AND LAND COVER AT BRAZILIAN RESERVOIRS DURING EXTREME DROUGHT

Introduction: Reservoirs are artificial aquatic ecosystems created by damming rivers, and are influenced by different sorts of impacts. Anthropic land use and occupation are one of the main causes of the loss of environmental quality and biological diversity in aquatic ecosystems. The objective of this work was to evaluate the effects of land use and occupation on the taxonomic and functional richness of benthic macroinvertebrates in reservoirs in the Brazilian semiarid region during a period of extreme drought. Material and methods: The study was conducted in six reservoirs located in the semiarid region from Brazilian Northeast (Paraíba and Rio Grande do Norte states): Sabugí, Passagem das Traíras, Cruzeta, Cordeiro, Sumé and Poções. The collections of benthic macrofauna, physical and chemical variables of water and the mapping of land use and occupation were performed for the years 2014 and 2019, in June and September. The sampling period was characterized as the most severe drought in the last 50 years in this study area. The land use and occupation were verified through the semi-supervised classification method of images captured by the Landsat 8 satellite, within 100 meters of the reservoir margin. The diversity of benthic macrofauna was analyzed through the taxonomic richness and functional richness, according to five functional characteristics: feeding trophic groups, breathing mode, voltinism, body size and body protection. To check for significant differences in physical and chemical water variables and taxonomic and functional richness among land use and land cover categories we performed PERMANOVA test. Results and Discussion: Seven land use and land cover categories were found in the reservoirs studied in the years 2014 and 2019, these are: water, agriculture, pasture, exposed soil, human occupation, open vegetation (native and exotic species of small/medium size with continuous spacing) and tree/shrub vegetation (native and exotic species of medium/large size with associated herbaceous stratum and predominance of semi-continuous dorsel). In all reservoirs the prevalent-use was pasture. Physical and chemical variables of water varied significantly among land use and land cover types, they were soluble reactive phosphate (p=0.02), total phosphorus (p=0.002) and water volume (p=0.01). The highest concentrations of total phosphorus were associated with predominant human occupation and soluble reactive phosphate with agriculture. The highest percentage of water volume was associated with a predominant use of tree/shrub vegetation. In reservoirs of semiarid regions with low connectivity due to intermittent rivers and extreme drought periods, adjacent anthropic activities such as agriculture, pasture and human occupation are the main external sources of nutrients. The taxonomic and functional richness of benthic macrofauna was higher in areas of open vegetation, however, it did not vary significantly between land use and land cover categories. Conclusions: Our results show that the effects of anthropic use and occupation in reservoirs associated with water scarcity lead to the homogenization of the macrobenthic community, which can generate negative consequences in processes sustained by the community.

Large-scale variation in phytoplankton community composition of >1000 lakes across the USA

Although environmental impacts on the biodiversity and species composition of lakes have been studied in great detail at local and regional scales, unraveling the big picture of how lake communities respond to environmental variation across large spatial scales has received less attention. We performed a comprehensive analysis to assess how the phytoplankton community composition varies among >1000 lakes across the conterminous United States of America. Our results show that lake-to-lake similarity in species composition was low even at the local scale, and slightly decreased with geographical distance. Analysis of the compositional data by Dirichlet regression revealed that the geographical variation in phytoplankton community composition was best explained by total phosphorus (TP), water temperature, pH, and lake size. High TP concentrations were associated with high relative abundances of cyanobacteria and euglenophytes at the expense of other phytoplankton groups. High lake temperatures stimulated cyanobacteria, dinoflagellates, desmids and euglenophytes, whereas cryptophytes, golden algae and diatoms were relatively more abundant in colder lakes. Low lake pH correlated with high dissolved CO2 concentrations, which may explain why it benefitted phytoplankton groups with inefficient carbon concentrating mechanisms such as golden algae and euglenophytes. Conversely, the relative abundance of cyanobacteria showed a pronounced increase with lake pH. Large lakes showed higher relative abundances of cyanobacteria and diatoms, whereas small lakes showed higher relative abundances of chlorophytes, desmids and euglenophytes. Biodiversity increased with lake temperature, but decreased at high TP concentrations and pH. The key environmental variables identified by our study (high phosphorus loads, warm temperature, low pH) are associated with anthropogenic pressures such as eutrophication, global warming and rising atmospheric CO2 concentration. Hence, our results provide a comprehensive illustration of the major impact of these anthropogenic pressures on the biodiversity and taxonomic composition of lake phytoplankton communities.

Hydrological Regime and Fish Predation Regulate the Zooplankton Community Size Structure in a Tropical Floodplain Lake

Floodplain ecosystems are characterised by alternating flood and drought periods that can affect the structure of the aquatic community. Dynamic changes in the hydrological regimes from flooding to dry periods influence the migration and dispersal of aquatic fauna and the exchange of particulate matter and nutrients. Riverine floodplains are among the most productive ecosystems; however, increasing pressure from anthropogenic activities has altered the hydrological regimes, threatening aquatic biodiversity. In this study, we examined the temporal patterns of zooplankton community size structure and fish density during three distinct hydrological events in a tropical floodplain lake, Lake Tempe, Indonesia. We included fish density data and three contrasting hydrological conditions, moderate-, high-, and low-water periods, as the environmental factors regulating zooplankton community structure. In high- and low-water conditions, the ecosystem heterogeneity was characterised by high chlorophyll-a, total nitrogen, and total phosphorus concentrations; high fish density; and high zooplankton abundance and biomass. During the early flood period, the ecosystem was characterised by lower concentrations of trophic indicators and significant decreases in zooplankton abundance and biomass, as well as decreased fish density. While there was no clear association between hydrological conditions and zooplankton size structure, our findings indicate that fish predation probably suppressed zooplankton size diversity in Lake Tempe, shown by the dominant contribution of small-sized zooplankton towards total abundance and biomass under all hydrological conditions. Our results indicate that the patterns of environmental variables, zooplankton community, and fish density are affected by hydrological conditions, highlighting the role of water level fluctuation as the driving factor for zooplankton community structure. Our results also indicated that fish predation led to the development of a small-sized population of zooplankton in Lake Tempe.

Characterization of phosphorus sorption and microbial community in lake sediments during overwinter and recruitment periods of cyanobacteria.

The release of endogenous phosphorus from lacustrine sediment is a key element of freshwater eutrophication. The microbes in sediments may affect phosphorus migration and transformation during the growth of cyanobacteria, which may lead to the release of phosphorus from sediments and contribute to water eutrophication. To study phosphorus sorption and the microbial community structure in the overlying water and the vertical depth of sediments, samples in Meiliang Bay were collected during the dormancy and resuscitation phases of cyanobacteria. The results showed that there were high total phosphorus (TP) concentrations in the overlying water and sediment, with maximum values reached 0.24 mg L−1 and 1059 mg kg−1, respectively. Fitting by modified Langmuir model indicated that the partitioning coefficients (KP) was, from greatest to least: bottom sediment (maximum of 0.923 L g−1) > middle sediment (0.571 L g−1) > surface sediment (0.262 L g−1). During the cyanobacteria resuscitation stage, the relative abundance of Proteobacteria (18.37%–33.56%), Chloroflexi (9.57%–17.76%), Cyanobacteria (0.38%–2.62%), and the Nitrospirota phylum Thermodesulfovibrionia (4.61%–10.14%) were higher than the dormant period of cyanobacteria, and bacteria with phosphorus-solubilizing (27.27%–52.01%) accounted for the majority. The redundancy analysis (RDA) found that the structure of the microbial communities in sediments was significant correlation with organic phosphorus (OP) (P = 0.002) during recruitment period of cyanobacteria, which would accelerate the conversion of OP into soluble inorganic phosphorus and then gets released from sediment to water. The most predominant phylum among phosphorus-solubilizing bacteria (PSB) is Proteobacteria, followed by Actinobacteriota, which were positively correlated with equilibrium phosphorus concentration (EPC0) (P < 0.05) during the cyanobacterial resuscitation phase. The sediments from the cyanobacteria resuscitation phase had phosphorus release risk and highlighted the significant role of the bacterial community.

Potential metal phytoremediation in peri-urban wetlands using rooted macrophytes

The pollution of natural water bodies and peri-urban wetlands is frequent in the Middle Paraná River (Argentina). This work evaluates the potential use of different rooted macrophytes for metal phytoremediation in peri-urban wetlands. Macrophytes, water and sediment were collected in the study sites. Cr, Ni, Zn, Pb, total phosphorus (TP) and total Kjeldahl nitrogen (TKN) were determined in water, sediment, and different plant tissues. Industrial Park and RECU (water dump) showed the highest Cr concentrations. The highest Ni water concentration was observed in Rincón. Industrial Park showed the highest Zn water concentration. The highest Pb water concentration was observed in Industrial Park followed by Rincón. The highest Cr and Zn concentrations in sediment were registered in Industrial Park and Leyes (lake). The sites that showed the highest Ni concentrations in sediment were Industrial Park, RECU (water dump), and Leyes (lake). The high TP concentration measured in the sediment of RECU (water dump) was quite remarkable. Regarding plant tissues, the roots of Pontederia rotundifolia (Leyes, lake). showed the highest Pb concentration. Typha domingensis showed the highest concentrations of Cr, Ni and Zn, in agreement with the highest concentration in sediment. Plants presenting high biomass, such as T. domingensis, are needed to obtain an efficient metal removal from water in peri-urban wetlands. Studies focused on different rooted species will extend the knowledge about metal phytoremediation, management of peri-urban wetlands that receive pollution, and the use of treatment wetlands as nature-based solutions.