Eutrophic Water Systems Research Articles

Enhancing phosphorus removal: the impact of alkaline environment in eutrophic water systems

Abstract Excessive phosphorus input leads to poor water quality and eutrophication. However, limited research has directly explored the influence of pH on phosphorous in actual aquatic systems. This study investigated the effect of pH on phosphorus removal in synthetic, eutrophic, and black-odorous water. The pH levels ranging from 3.5 to 12.0 were adjusted using H2SO4, NaOH, and cement with a 0.5 ± 0.03 interval, followed by a 25 ± 1 °C static water bath for 24 h. Results showed that NaOH-adjusted pH removed >65% TP from eutrophic water (pH ≥9.50) and black-odorous water (pH ≥11.0). Meanwhile, cement-adjusted pH removed >84%, >90%, and >82% TP from the synthetic solution (pH ≥11.0), eutrophic water (pH ≥9.5), and black-odorous water (pH ≥9.5), respectively. The alkaline environment enhanced the formation of Ca-P in eutrophic water and black-odorous water, and cement strengthened the chemical precipitation of phosphorus by providing additional Ca2+. This study lays the groundwork for pH adjustment strategies in eutrophic water, holding significant implications for water resource management and environmental protection.

Algal Extracellular Organic Matter Induced Photochemical Oxidation of Mn(II) to Solid Mn Oxide: Role of Mn(III)-EOM Complex and Its Ability to Remove 17α-Ethinylestradiol.

Photosensitizer-mediated abiotic oxidation of Mn(II) can yield soluble reactive Mn(III) and solid Mn oxides. In eutrophic water systems, the ubiquitous algal extracellular organic matter (EOM) is a potential photosensitizer and may have a substantial impact on the oxidation of Mn(II). Herein, we focused on investigating the photochemical oxidation process from Mn(II) to solid Mn oxide driven by EOM. The results of irradiation experiments demonstrated that the generation of Mn(III) intermediate was crucial for the successful photo oxidization of Mn(II) to solid Mn oxide mediated by EOM. EOM can serve as both a photosensitizer and a ligand, facilitating the formation of the Mn(III)-EOM complex. The complex exhibited excellent efficiency in removing 17α-ethinylestradiol. Furthermore, the complex underwent decomposition as a result of reactions with reactive intermediates, forming a solid Mn oxide. The presence of nitrate can enhance the photochemical oxidation process, facilitating the conversion of Mn(II) to Mn(III) and then to solid Mn oxide. This study deepens our grasp of Mn(II) geochemical processes in eutrophic water and its impact on organic micropollutant fate.

Aquatic phosphorus behaviour within a UK Ramsar wetland: Impacts of seasonality and hydrology on algal growth and implications for management

Fundamental to all life, phosphorus is an essential nutrient and, contrastingly, a significant threat to surface water biodiversity globally as one of the most common causes of eutrophication in surface waters worldwide. Freshwater wetland ditches affected by these conditions undergo a conversion from primarily submerged aquatic vegetation to algae or duckweed dominance, leading to anoxic conditions. However, macrophyte biomass harvesting in eutrophic water systems is a promising means of remediation and nutrient recycling. This study seasonally assesses spatial distribution and chemical fractionation of surface water phosphorus, as well as surface biomass abundance and total phosphorus content in the ditch systems at West Sedgemoor (Somerset, UK), a designated site of special scientific interest. Elevated phosphorus concentrations in the surface water were observed across the site, with all sites exceeding e hi the Common Standards Monitoring environmental quality standard value of 0.1 mg L−1 during summer and autumn Sites lacking hydrological flow connectivity with contaminated freshwater inputs, typically had lower surface water phosphorus concentrations than the rest of the moor, with localised hotspots associated with likely cattle related agricultural activity. Summer and autumn were determined as the dominant duckweed growth seasons, in which an estimated 39 kg of phosphorus could be removed via duckweed biomass harvesting, per harvest period.

Effect of different DOM components on arsenate complexation in natural water.

Dissolved organic matter (DOM) and dissolved ions are two integral parameters to affect the environmental fate of As in different ways. Numerous studies chose surrogate of DOM, humic substances (HSs), to investigate the As complexation behavior. However, microbial secretion (protein and polysaccharide) was also considered for a great proportion in surface aquatic system, and its effect was still not fully understood. The present research distinguished the As complexation behavior with different DOM components (HSs, protein, polysaccharide and synthetic organic matter) in natural and simulated water samples. The results indicated that different DOM components exhibited various binding capacities for As. HSs showed the strongest affinity for As, followed by long-chain compounds (polysaccharide and synthetic organic matter) and proteins. In water source, HSs were probably the primary parameter for As complexation. In eutrophic water system, however, polysaccharide maybe the main DOM component to bind As. Cationic bridge function was prone to occur in the presence of HSs, but not observed in the presence of protein. PO43- competed for binding sites with As, consequently decreasing the As complexation with all the DOM components. The research implied that a comprehensive and meticulous analyses of DOM fractions and coexist ions are the prerequisite to understanding the behavior of As (or other pollutants) in different natural aquatic systems.

Warming and eutrophication effects on the phytoplankton communities of two tropical water systems of different trophic states: An experimental approach

AbstractBoth global warming and eutrophication are predicted to promote cyanobacterial blooms. At the same time, how tropical phytoplankton communities exhibiting different trophic state systems will respond to temperature variations is less clear. To investigate the effects of temperature changes and nutrient additions on phytoplankton communities, and gain insights regarding possible resistance to these effects, the present study focused on testing the hypothesis that temperature variations and nutrient additions will have a stronger effect on cyanobacteria dominance in eutrophic water system than in oligo‐mesotrophic water systems. Experiments were conducted with phytoplankton communities from two aquatic ecosystems exhibiting different trophic states. To this end, water samples from a eutrophic and oligo‐mesotrophic system were collected and incubated at 25 and 30ºC. Samples receiving additional surplus nitrogen (N) and phosphorus (P) inputs were included to serve as eutrophication treatments. The study results indicated that temperature variations alone did not promote cyanobacteria in water from either the oligo‐mesotrophic or eutrophic water system. However, nutrient enrichment of the water from the eutrophic system significantly boosted the cyanobacteria, with the biomass increasing by factor of 10 for both the 25°C and 30°C treatments. In contrast, eutrophication of the water from the oligo‐mesotrophic system did not change the relative contribution of phytoplankton groups, with the response ratios being much lower than those for the water from the eutrophic system. Although based on a simple experimental design, the results of the present study suggest that cyanobacteria dominance is favoured by further nutrient additions for eutrophic water systems, independently of any direct temperature effects, and that more pristine environments possess some resistance against eutrophication effects. Since global warming is assumed to indirectly intensify eutrophication symptoms, the results of the present study underscore the importance of nutrient control.

Responses of daphnids and other zooplankton populations to massive fish kill in Lake Suwa

AbstractIn 2016, a massive fish kill of the planktivorous pond smelt Hypomesus nipponensis occurred in Lake Suwa, Japan. Pond smelt, which is important fish species from commercial and cultural perspectives, influences the zooplankton community in the lake. Following the massive fish kill, Daphnia galeata appeared and their population density increased to previously unseen levels by summer 2017. To help recover the fish population, larval pond smelt were released into the lake. Consequently, D. galeata has rarely appeared in Lake Suwa since summer 2017, except for a low‐density population observed in May–June 2018. These phenomena indicated that fish predation is a possible primary factor for suppressing daphnid populations in shallow eutrophic lake. Zooplankton populations showed species‐specific responses to the alterations in predation pressure. When the D. galeata population peaked after the fish kill event, rotifers, which are small‐sized competitors of daphnids, and calanoids tended to decrease in density. Rotifers then increased with the decrease in the daphnid populations due to the recovery of fish. Alternatively, cyclopoids, which demonstrated a similar population density following the fish kill event, tended to decrease when the fish population recovered. The population densities of Leptodora cf. kindtii/richardi and Bosmina spp. did not significantly differ between before the massive kill event and after pond smelt recovery. It is believed that the changes in zooplankton population densities observed in the present study may provide insights for further monitoring of aquatic food webs in eutrophic water systems, including Lake Suwa, where re‐oligotrophication is occurring and biological interactions are changing.

Environmental impacts and sustainability of low-value roach fish when used as food

One of the major global environmental challenges is the overuse of nutrients and related eutrophication problems. Specifically in Finland, the roach fish population is rapidly increasing in eutrophic water systems. Currently roach fish does not have economic value, and it is mainly composted despite the fact that it could provide a direct protein source for human needs. This paper assumes that new business could be established by removing roach fish from eutrophic water systems and using them as a protein source for human consumption. Removing roach fish directly removes nutrients and indirectly impacts the vicious cycle of eutrophication. This paper assesses different environmental sustainability perspectives of roach fish removal and utilization. It also aims to present different environmental impacts on the planetary boundary framework. The research is carried out using life cycle assessment methodology.Based on the results, the use of roach fish as a protein source would help in returning to a safe operational zone in biochemical flows. Phosphorous removal with roach fish is 5.8 (1.9–10.3) g kg−1 while nitrogen removal is 28.4 (26.4–30.4) g kg−1. However, the production has also climate change impacts which are 2.9–5.2 kgCO2eq kg−1 roach protein. Nevertheless, the climate change impacts are 12–57 times lower than positive impacts on eutrophication.Different environmental impacts are assessed regarding whether or not they help to avoid crossing planetary boundaries. Roach fish should be marketed especially for green consumers, and creating new markets for roach fish could also help in eutrophic lake restoration projects. Additionally, new business could be created from nutrient offsetting by roach fish removal.Roach removal from eutrophic water systems and use as food helps in returning to a safe operational zone in biochemical flows and the positive impacts are far greater than the negative impacts on climate change from fishing and fish processing.

Harvesting Environmental Microalgal Blooms for Remediation and Resource Recovery: A Laboratory Scale Investigation with Economic and Microbial Community Impact Assessment.

A laboratory based microflotation rig termed efficient FLOtation of Algae Technology (eFLOAT) was used to optimise parameters for harvesting microalgal biomass from eutrophic water systems. This was performed for the dual objectives of remediation (nutrient removal) and resource recovery. Preliminary experiments demonstrated that chitosan was more efficient than alum for flocculation of biomass and the presence of bacteria could play a positive role and reduce flocculant application rates under the natural conditions tested. Maximum biomass removal from a hyper-eutrophic water retention pond sample was achieved with 5 mg·L−1 chitosan (90% Chlorophyll a removal). Harvesting at maximum rates showed that after 10 days, the bacterial diversity is significantly increased with reduced cyanobacteria, indicating improved ecosystem functioning. The resource potential within the biomass was characterized by 9.02 μg phosphate, 0.36 mg protein, and 103.7 μg lipid per mg of biomass. Fatty acid methyl ester composition was comparable to pure cultures of microalgae, dominated by C16 and C18 chain lengths with saturated, monounsaturated, and polyunsaturated fatty acids. Finally, the laboratory data was translated into a full-size and modular eFLOAT system, with estimated costs as a novel eco-technology for efficient algal bloom harvesting.

Naturally occurring phytopathogens enhance biological control of water hyacinth (Eichhornia crassipes) by Megamelus scutellaris (Hemiptera: Delphacidae), even in eutrophic water

Insect biological control agents directly damage target weeds by removal of plant biomass, but herbivorous insects have both direct and indirect impacts on their host plants and can also facilitate pathogen infection. Megamelus scutellaris Berg (Hemiptera: Delphacidae) was recently released into South Africa to help control invasive water hyacinth (Eichhornia crassipes, Pontederiaceae). We compared the impact of fungicide surface-sterilised and unsterilised M. scutellaris individuals and water hyacinth leaves on growth of the weed at two nutrient levels. The survival and reproduction of adult M. scutellaris was not reduced by sterilisation. Under high nutrient conditions, unsterilised M. scutellaris with unsterilised leaves reduced water hyacinth daughter plant production by 32%, length of the second petiole by 15%, chlorophyll content by 27% and wet weight biomass by 48%, while also increasing leaf chlorosis 17-fold, in relation to control plants under the same nutrient regime. Surface sterilisation of the insect and/or plant surfaces led to a general reduction in these impacts on water hyacinth growth and health. This contrast was less evident under low nutrient conditions. Megamelus scutellaris facilitated infection by fungal and other pathogens, thus its biology is compatible with pathogens that could be developed into mycoherbicides. This integrated approach may be ideal for management of infestations of water hyacinth in eutrophic water systems where control has been problematic, both in South Africa and elsewhere.

In situ removal of dissolved and suspended contaminants from a eutrophic pond using hybrid sand-filter

In this study, in situ hybrid sand filters were designed to remove dissolved and suspended contaminants from eutrophic pond. Currently, there are no attempts made to eradicate dissolved as well as suspended contaminants from eutrophic water system in a single step. Monitoring studies revealed that examined pond contain high chlorophyll-a content (101.8 μg L−1), turbidity (39.5 NTU) and total dissolved solids concentration (0.04 g L−1). Samples were further exposed to extensive water quality analysis, which include examining physicochemical parameters (pH, conductivity, total dissolved solids, salinity, turbidity and chlorophyll-a), metals (Na, K, Ca, Mg, Al, Fe, Cu, Cd, Pb, Zn, Cr, and Ni) and anions (NO3, NO2, PO4, SO4, Cl, F and Br). To tackle pollutants, filtration system was designed to comprise of several components including fine sand, coarse sand/sorbent mix and gravel from top to bottom loaded in fiberglass tanks. All the filters (activated carbon, Sargassum and zeolite) completely removed algal biomass and showed potential to decrease pH during entire operational period of 20 h at 120 L h−1. To examine the efficiency of filters in adverse conditions, the pond water was spiked with heavy metals (Cu, Cd, Pb, Zn, Cr, and Ni). Of the different filter systems, Sargassum-loaded filter performed exceedingly well with concentrations of heavy metals never exceeded the Environmental protection agency regulations for freshwater limits during total operational period. The total uptake capacities at the end of the fifth event were 24.9, 20.5, 0.58, 5.2, 0.091 and 2.8 mg/kg for Cr, Ni, Cu, Zn, Cd and Pb, respectively.

Detailed study of cyanobacterial microcystins using high performance tandem mass spectrometry.

Microcystins (MC) are a large group of toxic cyclic peptides, produced by cyanobacteria in eutrophic water systems. Identification of MC variants mostly relies on liquid chromatography (LC) combined with collision-induced dissociation (CID) mass spectrometry. Deviations from the essential amino acid complement are a common feature of these natural products, which makes the CID analysis more difficult and not always successful. Here, both CID and electron capture dissociation (ECD) were applied in combination with ultra-high resolution Fourier transform ion cyclotron resonance mass spectrometry to study a cyanobacteria strain isolated from the Salto Grande Reservoir in Sao Paulo State, Brazil, without prior LC separation. CID was shown to be an effective dissociation technique for quickly identifying the MC variants, even those that have previously been difficult to characterize by CID. Moreover, ECD provided even more detailed and complementary information, which enabled us to precisely locate metal binding sites of MCs for the first time. This additional information will be important for environmental chemists to study MC accumulation and production in ecosystems.

Effect of water trophic level on the impact of the water hyacinth moth Niphograpta albiguttalis on Eichhornia crassipes

Eutrophication contributes to the proliferation of alien invasive weed species such as water hyacinth Eichhornia crassipes. Although the South American moth Niphograpta albiguttalis was released in South Africa in 1990 as a biological control agent against water hyacinth, no post-release evaluations have yet been conducted here. The impact of N. albiguttalis on water hyacinth growth was quantified under low-, medium- and high-nutrient concentrations in a greenhouse experiment. Niphograpta albiguttalis was damaging to water hyacinth in all three nutrient treatments, but significant damage in most plant parameters was found only under high-nutrient treatments. However, E. crassipes plants grown in high-nutrient water were healthier, and presumably had higher fitness, than plants not exposed to herbivory at lower-nutrient levels. Niphograpta albiguttalis is likely to be most damaging to water hyacinth in eutrophic water systems, but the damage will not result in acceptable levels of control because of the plant's high productivity under these conditions. Niphograpta albiguttalis is a suitable agent for controlling water hyacinth infestations in eutrophic water systems, but should be used in combination with other biological control agents and included in an integrated management plan also involving herbicidal control and water quality management.