Nutrient Salts Research Articles

Assessment of pollutants in coastal waters, sediments, and biota of marine ecosystems in Algeria, North Africa

This study aims to assess the chemical and ecological quality of the marine ecosystem in Algerian central coastal zone (Bay of Algiers (AB) and Bou-Ismail Bay (BIB)) by examining several quality indicators of the marine ecosystem: water, sediment, and biota. Except for stations near the mouths of wadis and industrial and urban discharges released without prior treatment, the study of the physicochemical water quality in the different sampling stations revealed a more or less normal variation in temperature and salinity. According to nutrient salt analysis, all studied stations (in AB and BIB) have high nitrogen levels, such as ammonium and nitrate. However, low levels of phosphate were detected, indicating that this element is scarce in the Algerian coastal marine waters. Three trace metals were also analyzed in the sediments of both bays. Pb ranged from 21.15 to 52.69 μg g–1 dry weight (dw), Zn from 19.32 to 175.1 μg g–1 dw and Cd between 0.87 and 2.031 μg g–1 dw. Contamination factors ranged from 0.62 to 1.55 for Pb, 0.2 to 1.85 for Zn and 1.74 to 4.04 for Cd. Analysis of these three metals in sediment samples reveals their presence at most stations studied. The contamination index calculation shows a moderate anthropogenic intake that requires continuous monitoring to protect the study area’s ecosystem. Crucially, the analysis of fish products revealed a lack of chemical risk concerning trace metals, known for their detrimental health effects. However, this conclusion does not dismiss the potential for subtle contamination, warranting persistent environmental surveillance. Consequently, sustained efforts in environmental monitoring are imperative to ensure the preservation of the marine ecosystem amidst escalating anthropogenic pressures.

Mixed cropping enhances the nitrogen and phosphorus purification efficiency of sewage in wetland ecosystems

Although the water purification performance of individual species and their removal mechanisms have been thoroughly documented, the potential enhancement of sewage nitrogen and phosphorus removal rates through the combined effects of different plant species has yet to be comprehensively investigated. This study opted for Canna indica and Thalia dealbata, two characteristic wetland plants from the Three Gorges Reservoir Area, as the test subjects. The impact of cropping patterns (single-cropping and mixed-cropping) on the efficiency of nitrogen and phosphorus removal from sewage at varying concentrations was explored. The findings unveiled that the mixed-cropping pattern considerably heightened the total nitrogen (TN) absorption of plants in sewage environments, though it did not appreciably affect total phosphorus absorption. Moreover, sewage concentration influenced the nitrogen and phosphorus absorption patterns of plants, potentially exhibiting a threshold phenomenon. Mixed cropping significantly augmented the removal rates of sewage nitrogen and phosphorus. Under the single cropping arrangement, C. indica displayed superior pollutant removal performance in comparison to T. dealbata. Furthermore, the wetland plants significantly diminished the TN content of the soil matrix. The results indicated that the mixed planting pattern enhanced the purification efficiency of effluent nitrogen and phosphorus in the artificial wetland, probably due to the better purification by mixed species under competition for nutrients or the dilution effect of multiple species on effluent nitrogen and phosphorus nutrient salts following mixed planting. These results should guide planting selection for efficient and sustainable wastewater purification in wetland ecosystems.

Influence of influent C/N on sludge granulation process and nutrient removal pattern

Abstract In this paper, firstly, the relevant parameters of influent C/N quantification were selected, and then, on the basis of the relevant parameters, the apparent shear force formula was deduced, and the apparent shear force was used to reflect the hydraulic condition of the reactor. Next, the experimental device, operation method, influent water quality and analysis method were determined, and the influences of influent C/N on the sludge granulation process were derived from the influences of group I C/N ratio on anaerobic granular sludge and group II C/N ratio on anaerobic granular sludge. Then, the return sludge from the Guangzhou sewage treatment plant in Guangdong Province was selected as the experimental seed sludge, and the methanol concentration of 0.13g/L (COD=200mg/L) was used as the experimental water quality, and the influences of influent C/N on nutrient N2O denitrification were illustrated by the experimental analyses. The results showed that the NO2 − − N accumulation rate was maintained above 81% in all five water intake modes, and when the ratio of water intake (1:1) and (2:1), a higher concentration of NO2 − − N was accumulated in the first nitrification stage of 26.5 mg/L and 24.9 mg/L, respectively, which could give full play to the advantages of nitrifying bacteria to achieve nitrification rapidly and also reduce the production of nutrient salt N2O. This study combines macro-experiment and micro-analysis to provide a theoretical basis for granular sludge technology.

Computational modelling to advise and inform optimization for aeration and nutrient-dosing in wastewater treatment: Case study from pulp and paper mill in south-central Sweden

Sweden's pulp and paper sector accounts for a significant proportion of national energy usage, besides generating wastewater that causes eutrophication of nearby sinks. In this paper, the possibility of optimizing biological wastewater treatment at the Stora Enso Skoghall mill south of the city of Karlstad in central Sweden, with respect to electricity usage and the addition of nutrients, has been investigated. A computational model of the treatment process was developed, based on process data obtained from the said mill, and nine different scenarios were compared subsequently, with energy use, environmental impacts and operational expenses, as criteria. The most energy-efficient and cost-effective alternative was a combination of measures such as lowering the oxygen level in the MBBR (Moving Bed Bio-Reactor) from 3 mg/l to 2 mg/l and using the Hyperclassic aerator in the aerated lagoon. This arrangement yielded a 48.5 % reduction in operational expenses, and a 60 % decrease in the energy use, vis-à-vis the reference case, without affecting the efficiency of the treatment process. This also uncovered an opportunity to mitigate the annual global warming and eutrophication impacts, by approximately 100 tons CO2-eq. and 140 kg PO43−-eq. respectively. All attempts to optimise the use of resources and decrease the anthropogenic environmental footprint ought to be made to come closer to the targets set by the United Nations' sustainable development goals (SDGs). The authors' conclusion predicated on the results of the modelling and analysis done in this study is that the potential of seemingly small process modifications, such as lowering the oxygen level in the MBBR, and applying a more optimal dosage of nutrient salts, must not be overlooked by wastewater treatment plants in general (and those in pulp and paper mills in particular).

Response mechanism of sediment endogenous phosphorus release to functional microorganisms and its cyanobacterial growth and disappearance effects

Endogenous phosphorus (P) release from lake sediments is an important factor in the eutrophication of overlying waters, as P is the limiting nutrient salt affecting cyanobacterial growth. Microorganisms are also key to the evolution of cyanobacterial growth and disappearance, as they can influence the release of endogenous P. Meanwhile, endogenous phosphorus can also have an impact on microbial structure. However, there is a lack of studies on the response mechanisms between endogenous P release and microorganisms, as well as the exploration of endogenous P release on the whole cyanobacterial growth and disappearance evolution process. In this study, metagenome sequencing was used to characterize the microbial community structure at different times and to explain the P cycle from the perspective of functional genes. The results showed that the number of sediment microorganisms (genes) gradually increased with the P release capacity, and the outbreak with the strongest P release capacity possessed the most abundant microorganisms (genes). Proteobacteria with P solubilizing functions were consistently the most abundant phylum in all four periods and were positively correlated with P release potential assessment factors EPC0, EPC0F, and NAP. Functional genes affect the P cycle by acting primarily on inorganic P solubilization, organic P mineralization, and P transport. These P-functional genes are mainly found in Proteobacteria, Acidobacteria, Chloroflexi, and Actinobacteria microorganisms. In addition, the P form in the sediments was dominated by IP, with the highest concentration (704.86 mg/kg) occurring during the dormant period. Sediments from this period acted as a strong P “sink”, creating a precondition for cyanobacterial recovery and outbreaks to provide a source of P. The results of this study can provide a theoretical basis for controlling endogenous P release at the microscopic level of cyanobacterial growth and disappearance.

Analysis of the technology of electrochemical production of zirconium

To date, reactor-grade zircon is produced on an industrial scale using metallothermic and electrochemical methods. Electrolytic production of reactor-purity zirconium in a sealed electrolyzer is more cost-effective than metallothermic production, as it does not require iodide refining and the use of reducing metals (Na, Mg, and Ca). Despite the importance of this production, its features are not fully described in the literature. This study presents the results of industrial tests of the electrolysis process in a sealed electrolyzer with a current load of 10 kA from the molten electrolyte KCl–KF–K2ZrF6. Based on the achieved technological indicators, the current efficiencies of the main cathode and anode reactions were determined and the factors influencing them were evaluated. We analyzed the composition of nutrient salts and the mechanism of accumulation of potassium fluoride in the electrolyte, an increase in which concentration leads to an anode-destroying effect. We considered possible mechanisms of the electrochemical formation of freons and compiled material balances for all starting substances and reaction products. The change in the electrolyte density during electrolysis was calculated, which allowed justifying the volume of its daily drainage. Fine carbon and zirconium powder formed in the electrolyte due to the interaction with potassium metal are not separated and are removed for chemical redistribution, which reduces the productivity of the electrolysis process.

Ecological risk assessment of selected contaminants in seawater, sediment and some fish species from Alexandria beaches, South-Eastern Mediterranean Sea, Egypt

The present study aims to investigate the hydrographical characteristics, nutrient salts, and heavy metals (HM) to estimate the contamination status of selected coastal beaches along the Alexandria coastal area in the southeast Mediterranean Sea. Water and sediment samples were collected from 8 beaches along the cost of Alexandria, while 122 fish samples representing 10 species were collected from 2 beaches representing two ports at Alexandria city. All samples were subjected to specific analyses to assessment of ecological risks at study area. The study indicated that the seawater quality of the investigated beaches varied between medium to good based on the Water Quality Index (WQI = 0.233–0.713). Moreover, the highest average concentration in water was observed for Fe (33.624 μgl−1) and the lowest was detected for Cd (0.050 μgl−1). HM in sediment have the same trend of these HM in water. The most of beaches’ sediments were classified as non-contaminated (PI < 1) with all examined HM. Hazard Quotient and Hazard Index (HQ &HI < 1) this indicated that the lack of non-carcinogenic impacts for children and adults due to dermal contact with sediments of all beaches. The most abundance HM in fish were Fe and Zn. Bioaccumulation factors (BAF) in fish muscles was evaluated. MPI (Metal Pollution Index) of HM in the investigated species ranged from (0.381–2.216) in Pomatomus saltatrix and Scomberomorus commerson species respectively. HQ, HI, EDI (Estimated Daily Intake), and TR (Target Risk) values showed that the examined species are still safe for human consumption.

Variations in bacterial diversity and community structure in the sediments of an alkaline lake in Inner Mongolia plateau, China.

Alkaline lakes are a special aquatic ecosystem that act as important water and alkali resource in the arid-semiarid regions. The primary aim of the study is to explore how environmental factors affect community diversity and structure, and to find whether there are key microbes that can indicate changes in environmental factors in alkaline lakes. Therefore, four sediment samples (S1, S2, S3, and S4) were collected from Hamatai Lake which is an important alkali resource in Ordos' desert plateau of Inner Mongolia. Samples were collected along the salinity and alkalinity gradients and bacterial community compositions were investigated by Illumina Miseq sequencing. The results revealed that the diversity and richness of bacterial community decreased with increasing alkalinity (pH) and salinity, and bacterial community structure was obviously different for the relatively light alkaline and hyposaline samples (LAHO; pH < 8.5; salinity < 20‰) and high alkaline and hypersaline samples (HAHR; pH > 8.5; salinity > 20‰). Firmicutes, Proteobacteria and Bacteriodetes were observed to be the dominant phyla. Furthermore, Acidobacteria, Actinobacteria, and low salt-tolerant alkaliphilic nitrifying taxa were mainly distributed in S1 with LAHO characteristic. Firmicutes, Clostridia, Gammaproteobacteria, salt-tolerant alkaliphilic denitrifying taxa, haloalkaliphilic sulfur cycling taxa were mainly distributed in S2, S3 and S4, and were well adapted to haloalkaline conditions. Correlation analysis revealed that the community diversity (operational taxonomic unit numbers and/or Shannon index) and richness (Chao1) were significantly positively correlated with ammonium nitrogen (r = 0.654, p < 0.05; r = 0.680, p < 0.05) and negatively correlated with pH (r = -0.924, p < 0.01; r = -0.800, p < 0.01; r = -0.933, p < 0.01) and salinity (r = -0.615, p < 0.05; r = -0.647, p < 0.05). A redundancy analysis and variation partitioning analysis revealed that pH (explanation degrees of 53.5%, pseudo-F = 11.5, p < 0.01), TOC/TN (24.8%, pseudo-F = 10.3, p < 0.05) and salinity (9.2%, pseudo-F = 9.5, p < 0.05) were the most significant factors that caused the variations in bacterial community structure. The results suggested that alkalinity, nutrient salt and salinity jointly affect bacterial diversity and community structure, in which one taxon (Acidobacteria), six taxa (Cyanobacteria, Nitrosomonadaceae, Nitrospira, Bacillus, Lactococcus and Halomonas) and five taxa (Desulfonatronobacter, Dethiobacter, Desulfurivibrio, Thioalkalivibrio and Halorhodospira) are related to carbon, nitrogen and sulfur cycles, respectively. Classes Clostridia and Gammaproteobacteria might indicate changes of saline-alkali conditions in the sediments of alkaline lakes in desert plateau.

The temporal and spatial variation of chlorophyll a concentration in the China Seas and its impact on marine fisheries

Marine chlorophyll a is a key molecule for photosynthesis of marine plants and some plankton, which is important in marine ecosystems. This study utilized the chlorophyll a concentration data product observed by the MODIS sensor (MODerate resolution Imaging Spectroradiometer) to construct a long-term sequence of chlorophyll a concentration dataset by processing the raw data. Based on this, the multi-time-scale chlorophyll a concentration data was synthesized, and it was used to analyze the spatial and temporal variation characteristics of chlorophyll a concentration in China Seas. In addition, several oceanographic variables, including sea surface temperature, nutrients (phosphate, nitrate, silicate), partial pressure of seawater carbon dioxide, net primary productivity of the ocean, physical dynamics of seawater processes (mixed layer), were analyzed to ascertain their potential influence on chlorophyll a concentration. Finally, we analyzed the effects of changes in chlorophyll a concentration on marine fisheries. The result showed that: The average value of chlorophyll a concentration in China Seas from 2002 to 2022 was 0.874 mg/m3, with the highest concentration observed in the Bohai Sea area (4.547 mg/m3) and the lowest in the South China Sea area (0.288 mg/m3). The spatial variation of chlorophyll a concentration revealed an overall decrease of 0.0095 mg/m3 in China Seas from 2002 to 2022. From the perspective of time changes, the concentration of chlorophyll a in China’s Bohai Sea area showed a downward trend from 2002 to 2022, while the Yellow Sea area showed an upward trend. The concentration remained relatively stable in the East China Sea area, whereas a significant declining trend was observed in the South China Sea area. The relationship between temperature and chlorophyll a concentration was non-linear, and chlorophyll a concentration showed some fluctuation or threshold effect with the change of seawater temperature. The three nutrient salts studied have a promoting effect on chlorophyll a, among which phosphate has the most obvious promoting effect on chlorophyll a. Chlorophyll a was negatively correlated with pCO2 and positively correlated with ocean net primary productivity. Seasonal changes in the mixed layer had a significant effect on changes in the upper marine nutrients, which in turn affected changes in chlorophyll a concentration. Six of the eight types of algae studied show a trend toward deeper sea depths, which may have implications for the food availability of marine fish at different levels and pose new challenges for marine fisheries development.

Distribution, sources, and potential health risks of fluoride, total iodine, and nitrate in rural drinking water sources of North and East China

Small-scale water sources serving villages and towns are the main source of drinking water in rural areas. Compared to centralized water sources, rural water sources are less frequently monitored for water quality and have poor post-treatment facilities, making them vulnerable to drinking health risks. To reveal the hydrochemical characteristics, contaminant sources, and health risks in rural water sources, 189 water samples were collected from lakes and reservoirs, rivers, and groundwater in North and East China for major ions, nutrient salts, microelements, and stable isotope analysis. Statistical analysis and isotopic tracing were performed, as well as human health risk assessment. The exceeding threshold rates for fluoride (F−) and nitrate (NO3−) in surface water were 1.8 % and 9.1 %, respectively. For groundwater, the exceeding threshold rates were 20.9 % for F−, 15.7 % for total iodine (TI), and 4.5 % for NO3−. F− and TI were mainly derived from the leaching of fluoride- and iodine-containing minerals by cationic exchange, and NO3− is mainly derived from nitrogen in the soil (31.7–43.9 %), the use of ammonia fertilizers (24.3–36.1 %), and the discharge of manure and sewage (19.4–31.9 %). Nitrogen in the soil can be an important source of nitrate in the aquatic environment, and soils with higher clay content have a greater retention effect on the migration of nitrogen pollutants from the surface to the groundwater. F− in water sources contributes most to human health risks for drinking, followed by NO3− and TI, and a higher proportion of groundwater (37 %) present health risks for drinking than surface water (14 %) for children. Authorities should give high priority to optimizing the choice of water sources and technology for water treatment, and rational measures should be taken to protect water sources from the threats of anthropogenic pollution.

Simulation of suitable habitats for typical vegetation in the Yellow River Estuary based on complex hydrodynamic processes

Estuarine ecosystems are influenced by the combination of freshwater runoff and ocean tides, and the natural environment is intricate and complex, with special natural environmental conditions and biological habitat characteristics. The Yellow River is characterized by high sediment-bearing water flow, and the estuary forms a unique clear and turbid confluence. The Water and Sand Regulation (WSRS) from the Xiaolangdi Reservoir to the estuary and nearshore has had significant impacts on the environmental conditions of water, sediment and nutrients, further affecting the growth and development of vegetation in the nearshore zone. In recent years, more studies have focused on the effects of climate change and ocean tides on vegetation in the Yellow River Estuary; however, few studies have been conducted on the effects of the WSRS on klysmoeionion. In this study, we investigated the influence of water flow, sediment and nutrients on klysmoeionion based on long-term field monitoring and indoor control experiments; constructed a three-dimensional hydrodynamic water quality model to simulate the hydrodynamic characteristics, sediment transport patterns and nutrient salt distribution in the Yellow River Estuary under the combined influence of tides and riverine water and sediment; and further combined the growth competition model of typical vegetation (including the native species Zostera japonica and invasive species Spartina alterniflora) to construct a suitable habitat simulation model for typical vegetation communities in the Yellow River Estuary. Habitat and biomass changes in Z. japonica and S. alterniflora in the Yellow River Estuary were simulated under the influence of the WSRS and climate change. The results showed that the distribution of suitable habitats for Z. japonica and S. alterniflora in the Yellow River Estuary and offshore was characterized by a zonal distribution along both sides of the estuary, with an increasing trend of suitable habitat area from the estuary to both sides of the estuary; due to environmental conditions and inter- and intra-species competition, the biomass of Z. japonica and S. alterniflora was mainly distributed in the estuary and near the northern and southern shores, with the southern shore have the most distribution. In contrast, S. alterniflora was mainly distributed in the northern shore away from the estuary and in Laizhou Bay. During the WSRS period, the suitable habitat area of Z. japonica decreased by 25%, and the biomass decreased by 50%, while the suitable habitat and biomass of S. alterniflora were not significantly affected. The growth of Z. japonica was severely affected by the dual effects of global warming and the WSRS, while the biomass of S. alterniflora showed an increasing trend. The WSRS can further consider the growth pattern of vegetation to protect the resources of Z. japonica and to curb the expansion of the invasive S. alterniflora.

Vertical distribution analysis and total mass estimation of nitrogen and phosphorus in large shallow lakes

Analysing the vertical distribution of nutrient salts and estimating the total mass of lake nutrients is helpful for the management of lake nutrient status and the formulation of drainage standards in basins. However, studies on nitrogen (N) and phosphorus (P) in lakes have focused on obtaining measures of N and P concentrations, but no understanding exists on the vertical distribution of N and P in the entire water column. The present study proposes algorithms for estimating the total masses of N/P per unit water column (ALGO-TNmass/ALGO-TPmass) for shallow eutrophic lakes. Using Lake Taihu as an example, the total masses of nutrients in Lake Taihu in the historical period were obtained, and the algorithm performance was discussed. The results showed that the vertical distribution of nutrients decreased with increasing depth and exhibited a quadratic distribution. Surface nutrients and chlorophyll-a concentrations play important roles in the vertical distribution of nutrients. Based on conventional surface water quality indicators, algorithms for the vertical nutrient concentration in Lake Taihu were proposed. Both algorithms had good accuracy (ALGO-TNmass R2 > 0.75, RMSE <0.57; ALGO-TPmass R2 > 0.80, RMSE ≤0.50), the ALGO-TPmass had better applicability than the ALGO-TNmass, and had good accuracy in other shallow lakes. Therefore, deducing the TPmass using conventional water quality indicators in surface water, which not only simplifies the sampling process but also provides an opportunity for remote sensing technology to monitor the total masses of nutrients, is feasible. The long-term average total mass of N was 11,727 t, showing a gradual downward trend before 2010, after which it stabilised. The maximum and minimum intra-annual total N masses were observed in May and November, respectively. The long-term average total mass of P was 512 t, showing a gradual downward trend before 2010, and a slow upward trend thereafter. The maximum and minimum intra-annual total masses of P occurred in August and February or May, respectively. The correlation between the total mass of N and meteorological conditions was not obvious, whereas some influence on the total mass of P was evident, particularly water level and wind speed.

Water quality assessment for Northern Egyptian lakes (Bardawil, Manzala, and Burullus) using NSF-WQI Index

Egyptian Lakes are received different organic and inorganic pollutants from treated and untreated drainage effluent. Forty-five surface water samples from 15 locations were collected in June 2018 from Bardawil, Manzala, and Burullus lakes in northern Egypt. The collected samples measured nutrient salts (NH3, NO2, NO3, and PO4) and some metal ions (Cd, Pb, Cu, and Zn). Furthermore, several instruments are used for managing and organizing data on the total quality of water bodies with risk factors related to heavy metal pollution. This research aimed to apply the National Science Foundation’s WQI (NSF-WQI) and metal pollution index (MPI) to estimate water quality status and degree of pollution in three Northern Lakes in Egypt. The results indicated that Manzala Lake had the greatest concentration of nutritional salts (7.0, 3.8, 3.2 and 5.6 mg/L) for NH4, NO2, NO3 and PO4, respectively. Furthermore, the same order recorded for the mean levels of metal ions (Cd, Pb, Cu, and Zn) were (1.69, 0.29, 3.58 and 20.38 μg/l). In contrast, Bardawil Lake had the lowest values. Trophic Status Index TSIs of Bardawil Lake revealed that it is eutrophic with mean values (69.73), whilst those of Manzala and Burullus Lakes revealed that they are hypertrophic with mean values (90.68–86.20). WQI of Bardawil Lake was assessed as a good rating (92.01) and Excellent by NSF-WQI (95.18) according to WHO. On the other hand, Manzala and Burullus Lakes were rated as very bad and unfit. Manzala Lake was deemed unsafe for human consumption because it tested higher on pollution indices (MI, PI and MPI > 1 are polluted with slightly affected than Bardawil and Burullus lakes. This was due to the enormous quantities of human, animal, and industrial wastes dumped into Manzala Lake.

Enrichment and ecological risks of microplastics in mangroves of southern Hainan Island, China

Mangroves have recently been identified as one of the most threatened ecosystems by microplastics (MPs) pollution from terrestrial and marine sources, while little is known regarding the MPs enrichment, influencing factors and associated ecological risks in mangroves. The present investigation aims to evaluate the accumulation, characteristics, and ecological risks of MPs in various environmental matrices from three mangroves of southern Hainan Island during dry and wet seasons. The results revealed the prevalence of MPs pollution in the surface seawater and sediment from all studied mangroves during two seasons, where the highest MPs abundance was observed at Sanyahe mangrove. The abundance of MPs varied considerably in surface seawater by seasons and were distinctly modulated by rhizosphere effect. The characteristics of MPs also exhibited some pronounced variations across mangroves, seasons and environmental compartments, but the detected MPs were dominated by fiber-shaped, transparent-colored, and smaller-sized (100–500 μm) MPs. The most prevalent polymer types were polypropylene, polyethylene terephthalate and polyethylene. Further analyses revealed positive correlations between MPs abundance and contents of nutrient salts in surface seawater but negative relationships between MPs abundance and water physicochemical properties, including temperature, salinity, pH and conductivity (p < 0.05). The joint use of three evaluation models indicated MPs posed varying degrees of ecological risks to all studied mangroves, whereas Sanyahe mangrove exhibited the highest ecological risk of MPs pollution. This study provided new insights into the spatial-seasonal variations, influencing factors and risk assessment of MPs in mangroves, which would be helpful for source tracing, pollution monitoring and policy formulation.

A numerical study on the responses of coastal water quality to river runoff after heavy rainfall in the case of a complex coastline with two artificial islands

Heavy rainfall causes large volumes of freshwater and nutrient salts to flow from rivers into the sea. This leads to major changes in the ecological environment of estuarine waters in a short period of time. The responses of the estuarine hydro-environment become more complex with the concentrated construction of artificial structures, which is a major cause of marine ecological disasters. This paper considers the Tang Estuary in Qinhuangdao, where artificial structures (e.g., ports, artificial islands, and bridges) are concentrated, as a prototype with the weak tidal dynamic environment. A nested prototype of hydrodynamics and water quality was established using a Delft3D model, with coupled waves and flows. The model was used to simulate the spatial and ephemeral characteristics of the short-term responses of ecological environmental factors, such as dissolved inorganic nitrogen (DIN), nitrate-nitrogen (i.e., NO3-N), ammonium-nitrogen (NH4-N), and orthophosphate (i.e., PO4-P), to an episode of heavy rainfall in August 2022. The results showed that concentrations of DIN and NO3-N in the source areas remain high after the flooding process. The concentration recovered to normal values approximately 5.5 days after the flooding process. In contrast, NH4-N and PO4-P showed a response with ephemeral correspondence with the flooding process, and concentration recovery took only approximately 1 day. This paper proposes two short-term response modes of pollutant diffusion, which provide help in exploring the role of hydro-environmental changes in offshore algal hazards and the effect of permeable buildings on pollutant dispersion. This additionally provides possibilities with the forecasting of red tide and green tide, and for their prevention in the future.

Effects of biodegradation, biotoxicity and microbial community on biostimulation of sulfolane

To evaluate the effectiveness of biostimulation in remediating soil-free groundwater and groundwater with soil, experiments were conducted using soil and groundwater samples that were contaminated with sulfolane. The main objective was to characterize the differences in sulfolane removal efficiency and biotoxicity between in situ soil-free groundwater and groundwater with soil and different concentrations of dissolved oxygen (1 mg/L and 5 mg/L) and various nutrient salts (in situ and spiked). Optimizing the nutrient salt conditions improved the removal efficiency of sulfolane by 1.8–6.5 that under in situ nutrient salt conditions. Controlling the dissolved oxygen concentration enhanced the efficiency of removal of sulfolane by 1.5–4.5 times over that at the simulated in situ dissolved oxygen concentration, suggesting that the degradation of sulfolane by indigenous microorganisms requires nutrient salts more than it requires dissolved oxygen. Biotoxicity data showed that the luminescence inhibition of Aliivibrio fischeri by sulfolane was lower in the biostimulated samples than in the pre-treated samples. Biostimulation reduced the biotoxicity of the treated samples by 42−51%, revealing that it was effective in removing sulfolane and reducing biotoxicity. Microbial community analysis showed that the biostimulation did not change the dominant species in the original in situ community, and increased the proportion of sulfolane-degraders. The outcome of this study can be used to set parameters for the remediation of groundwater that is contaminated by sulfolane in oil refineries.

Study on Spatial and Temporal Distribution of Nutrient Salts in Typical Seaward Rivers in Hainan Island

Hainan Island, China’s second largest island, is located in the tropics and its rivers are significantly affected by precipitation. With the construction of free trade port with Chinese characteristics, Hainan Island’s industry, agriculture, tourism and urbanization have developed in an all-round way. With the rapid development of economy, water environment ecology has been destroyed. Based on the two seasons of drought and rain, this paper took Ningyuan River and Wanquan River as the research object to study the spatial and temporal distribution of nitrogen and phosphorus nutrients in the rivers entering the sea in Hainan, and found that the concentration of nutrients in Ningyuan River was higher than that in Wanquan River. The total nitrogen pollution in dry season was higher than that in rainy season, and that in tributaries was higher than that in main stream. The maximum nitrogen content in Ningyuan River reached 2.99 mg/L and 2.37 mg/L in the dry season and rainy season, and human activities were the main reason for the increase of nutrient concentration.

Metabolic mechanism and function of cyanobacterial polyphosphate in lakes

大规模蓝藻水华暴发对湖泊水生态系统健康和饮用水安全产生巨大危害，而湖泊水体磷是影响蓝藻水华暴发程度的重要生源要素。应对水体不同磷酸盐浓度，蓝藻高效运行磷酸盐转运系统和磷酸盐特殊转运系统，并合成多聚磷酸盐（聚磷）。蓝藻胞内存在颗粒态、胶体态和可溶态3种形态的聚磷，且不同形态的聚磷分布位置不同。不同蓝藻合成聚磷颗粒的大小、数量和合成期均有所差异。多聚磷酸盐激酶、多聚磷酸盐外切酶、多聚磷酸盐内切酶和P-AMP-磷酸转移酶分别催化聚磷的合成与分解。多聚磷酸盐是二价阳离子的螯合剂，也是磷酸盐及高能磷酸键的储藏库，为细胞生存提供阳离子、磷酸盐和能量，满足蓝藻生命活动过程中生理生化活动所需，具有抵御高温、高pH、紫外线和营养盐缺乏等环境胁迫的生理功能，提升其在不利环境中的生存能力。同时，在蓝藻水华持续暴发、湖泊藻型生境稳态和磷生物地球化学循环过程中聚磷发挥重要的生态功能。因此，蓝藻合成聚磷的分子生物学机制及生态功能研究能够阐明聚磷的存在如何改变湖泊水体-沉积物磷分配、食物网中磷传递等。而开展调控聚磷合成的技术研究，通过控制蓝藻合成聚磷来减轻蓝藻水华暴发规模，将为湖泊水体良性生态系统的重构提供新方法。;Cyanobacterial blooms pose a huge harm to lake aquatic ecosystems health and drinking water safety, and the high phosphorus concentration of lake water bodies is an important inducement for the frequent outbreak of cyanobacterial blooms in lakes. The efficient operation of cyanobacterial intracellular inorganic phosphate transport system and the phosphate special transport system and polyphosphate (polyP) synthesis in cyanobacteria ensures the absorption of phosphate and its survival in phosphorus fluctuating environment. Three forms of polyP including granular, colloidal and soluble polyP, appear in cyanbacterial cells. The subcellular locations of different polyP forms are varied. The size, quantity and the growth period of polyP synthesized are different in different cyanobacterial species. The synthesis and decomposition of polyP are catalyzed by polyphosphate kinase, polyphosphate exonuclease, polyphosphate endonuclease and P-AMP-phosphate transferase, respectively. PolyP is also a chelating agent of divalent cations and a reservoir of phosphate and high-energy phosphate bonds, providing cations, phosphate and energy for cell survival. Cyanobacterial synthesizing polyP is a response to environmental stresses such as high temperature, peroxidation, and nutrient salt deficiency, which improves the viability of cyanobacteria. Therefore, the synthesis of polyP is required for physiological and biochemical activities in the life activities of cyanobacteria. In addition, the synthesis of polyP plays an important ecological function in the continuous outbreak of cyanobacterial blooms and the maintenance of the homeostasis of algal eco-environments. Therefore, it should strengthen the research on the molecular biological mechanism and the ecological function of cyanobacterial polyP synthesis. How the presence of polyphosphorus changes the phosphorus distribution in lake water-sediment and phosphorus transfer in food webs should also be elucidated. The techniques to control large-scale outbreaks of cyanobacterial blooms by controlling the synthesis of polyP in cyanobacteria may provide new methods to reconstruct benign ecosystems in lake waters.

Investigation of the Levels of Bio-Indicator Bacteria in the Kınalıada Coastal Area, Istanbul, Turkey

Coastal areas have an important place in island ecosystems. These areas, which may be fragile depending on the impact of human activities exposed and other environmental factors and in addition to domestic, agricultural and industrial activities, it hosts intensive touristic use in spring and summer. In this study, the closest contact with the shores of a mainland like Istanbul, among the Prince Islands in the Marmara Sea which is under the influence of the vast majority of the pollution load Kınalıada has been selected as a research area. Total heterotrophic aerobic bacteria (HAB) levels were analyzed using spreading plate method. The levels of fecal coliform (FC), total coliform (TC) and intestinal streptococci (IS) examined using Membrane Filtration Technique in the surface water samples. Variable environmental parameters (dissolved oxygen, pH, salinity, temperature) were recorded periodically using the Multiparameter (YSI 556 MPS) with seawater samples. Nutrient salts (nitrite nitrogen, nitrate nitrogen, ammonium nitrogen, phosphate phosphor), trophic level indicator Chlorophyll-a were analyzed using spectrophotometric methods. While the highest TC, FC and IS level detected as 96x103 CFU/100 ml, 49x103 CFU/100 ml, 82x103 CFU/100 ml, respectively. The highest HAB level was determined as 92x1011CFU /ml .Variable environmental parameters recorded for seawater temperature between 25.7-6.89˚C, pH 11.55 -3.60, dissolved oxygen 19.98 -1.66 mg /l and salinity ‰ 29.11-21.18 during the study period. Nutrient salts; nitrite nitrogen detected to be 0.21-0.01 mg/l; nitrate nitrogen detected to be 9.90-0.13 mg/l; ammonium nitrogen detected to be 4.80-0.02 mg/l; phosphate phosphor detected to be 22.45-0.01 mg/l. The levels of FC, TC and IS determined in Kınalıada coastal area fluctuate depending on the seasons, but these levels are determined above the legal limits. The presence of bio-indicator bacteria detected above the border throughout the sampling shows that it poses a serious risk for ecosystem health and public health.

Highly Efficient Genetic Transformation Methods for the Marine Oleaginous Diatom Fistulifera solaris.

The oleaginous diatom Fistulifera solaris is a promising producer of biofuel owing to the high content of the lipids. A genetic transformation technique by microparticle bombardment for this diatom was already established. However, the transformation efficiency was significantly lower than those of other diatoms. Devoting efforts to advance the genetic modifications of this diatom is crucial to unlock its full potential. In this study, we optimized the microparticle bombardment protocol, and newly established a multi-pulse electroporation protocol for this diatom. The nutrient-rich medium in the pre-culture stage played an essential role to increase the transformation efficiency of the bombardment method. On the other hand, use of the nutrient-rich medium in the electroporation experiments resulted in decreasing the efficiency because excess nutrient salts could hamper to establish the best conductivity condition. Adjustments on the number and voltage of the poring pulses were also critical to obtain the best balance between cell viability and efficient pore formation. Under the optimized conditions, the transformation efficiencies of microparticle bombardment and multi-pulse electroporation were 111 and 82 per 108 cells, respectively (37 and 27 times higher than the conventional bombardment method). With the aid of the optimized protocol, we successfully developed the transformant clone over-expressing the endogenous fat storage-inducing transmembrane protein (FIT)-like protein, which was previously found in the genome of the oleaginous diatom F. solaris and the oleaginous eustigmatophyte Nannochloropsis gaditana. This study provides powerful techniques to investigate and further enhance the metabolic functions of F. solaris by genetic engineering.