Cyanobacteria Density Research Articles

Abiotic Factors and The Growth of Cyanobacteria in Surface Water Reservoirs in The State of Pernambuco

Objective: Analyze the relationship between physical-chemical and climatic abiotic factors in relation to the occurrence of cyanobacteria genera in surface water reservoirs used for public supply in the state of Pernambuco. Literature Review: Information is presented on cyanobacteria and the consequences of the release of untreated effluents on the eutrophication of surface waters with effects on the growth of cyanobacteria and consequences for aquatic organisms and humans and the climate in regions of Pernambuco where water reservoirs are located. Method: Quali-quantitative descriptive and exploratory approach to the analysis of abiotic variables (pH, C.E., Turbidity, Color, Calcium, Magnesium, Chlorides, Sulfate, Nitrogen, Phosphate, Alkalinity, Hardness, Iron, Manganese, Aluminum and rainfall) and biotic (Cyanobacteria density), collected from the Pernambuco Sanitation Company – COMPESA. The samples were from eutrophic freshwater reservoirs in Pernambuco collected between 2010 and 2020. Results and Discussion: The most frequent genus of cyanobacteria was Raphidiopsis/Cylindrospermopsis, found abundantly in all reservoirs, where the increase in color, turbidity and pH were positively correlated with the presence of Microcystis and Raphidiopsis/Cylindrospermopsis, and negatively with the increase in toughness. A positive correlation was also observed between hardness and the increase in Planktothrix density. Research Implications: Generate guidelines for drinking water supply services, presenting tools for understanding abiotic conditions that influence the growth of cyanobacteria, in order to outline control or mitigation strategies in ETAs. Originality/Value: Generate useful information in the evaluation of abiotic parameters and cyanobacteria density, observed over a long period (10 years), showing positive/negative correlations in surface waters used for human consumption.

Deep lakes support higher zooplankton functional diversity than shallow lakes: A case study in lacustrine environments affected by mining tailings (lower Doce River basin, Brazil)

Abstract Tragic incidents involving mine tailings spills have impacted many aquatic ecosystems around the world. The massive mine tailings dam collapse of Fundão, which occurred in Brazil in 2015, affected several aquatic ecosystems, including shallow and deep lakes in the lower Doce River basin. Until now, the effects of mine tailings on the functional diversity of zooplankton remain poorly understood. We investigated the functional diversity of zooplankton (functional groups, functional richness [FRic] and functional evenness [FEve]) in shallow and deep lakes, exploring the influence of environmental variables and metals. In addition, trends in functional redundancy and functional vulnerability were also assessed to understand patterns of resilience in mining‐impacted ecosystems. Surveys were performed monthly on three deep and three shallow lakes affected by the dam failure, from October 2018 to September 2019. In the deep lakes, the zooplankton community was dominated by smaller filter‐feeders and omnivorous species, associated with cyanobacteria density and chlorophyll‐a. Medium‐sized filters were associated to iron, suspended particulate organic matter and total organic carbon in shallow lakes. The smaller filter‐feeders and omnivorous trophic groups had a higher contribution to increasing the functional diversity of zooplankton than medium‐sized filter‐feeders in both deep and shallow lakes. FRic and FEve were higher in deep lakes than in shallow lakes. Shallow lakes were highly vulnerable to species loss and functional diversity was modulated by environmental changes and metal pollution. Tropical shallow lakes impacted by mining tailings should receive particular attention in conservation plans, as a consequence of their high level of pollutant retention in comparison with deep lakes. In addition, we highlight the importance of using a functional approach to better understand the ecosystem changes resulting from the impacts of mine tailings on aquatic environments.

Analysis of the Spatiotemporal Distribution of Algal Blooms and Its Driving Factors in Chaohu Lake Based on Multi-source Datasets

Eutrophication and harmful algae blooms are one of the common ecological and environmental problems faced by freshwater lakes all over the world. As a typical inland freshwater lake, Chaohu Lake exhibits a high level of eutrophication and algae blooms year-round and shows a spatiotemporal difference in different regions of the lake. In order to understand the basic regularity of the development and outbreak of algal blooms in Chaohu Lake, the data from the comprehensive water observation platform and remote sensing were integrated to obtain the spatiotemporal distribution of algal blooms from 2015 to 2020. Then, an evaluation model based on Boosted Regression Trees (BRT) was constructed to quantitatively assess the importance and interactions of various environmental factors on algal blooms at different stages. The results indicated that:① The occurrence of algal blooms in Chaohu Lake exhibited significant seasonal variations, with the cyanobacteria beginning to recover in spring and bring about a light degree of algal blooms in the western and coastal areas of Chaohu Lake. The density of cyanobacteria reached its maximum in summer and autumn, accompanied by moderate and severe degrees of algal bloom outbreaks. ② During the non-outbreak period, the variation in the cyanobacteria density was greatly affected by physical and chemical factors, which explained 80.3% of the variance in the change in cyanobacteria density. The high concentrations of dissolved oxygen content in the water column and the weak alkalinity (7.2-7.6) and appropriate water temperature (about 3℃) provided a favorable environmental condition for the breeding and growth of cyanobacteria. In addition, the onset of algal blooms was closely related to the air temperature steadily passing through the threshold. According to the statistics, the date of first outbreak of algal blooms in Chaohu Lake was 11 days or so after the air temperature steadily remained above 7℃. ③ During the outbreak period, the occurrence of algal blooms was influenced by the combination of cyanobacterial biomass and meteorological conditions such as temperature, wind speed, and sunshine duration. The cumulative contribution ratio of the four factors was as high as 95%, and each factor had an optimal interval conductive to the outbreak of algal blooms. Furthermore, the results of multi-factor interaction analysis indicated a larger probability of the outbreak of algal blooms in Chaohu Lake under the combined effect of high cyanobacteria density, suitable temperature, and the breeze. This study analyzed and revealed the spatiotemporal characteristics and the dominant influencing factors of algal blooms in Chaohu Lake at different stages, which could provide the scientific basis for the prediction, early warning, and disposal of algal blooms under the context of climate change.

Vibrio Species and Cyanobacteria: Understanding Their Association in Local Shrimp Farm Using Canonical Correspondence Analysis (CCA).

In aquatic environments, Vibrio and cyanobacteria establish varying relationships influenced by environmental factors. To investigate their association, this study spanned 5 months at a local shrimp farm, covering the shrimp larvae stocking cycle until harvesting. A total of 32 samples were collected from pond A (n = 6), pond B (n = 6), effluent (n = 10), and influent (n = 10). Vibrio species and cyanobacteria density were observed, and canonical correspondence analysis (CCA) assessed their correlation. CCA revealed a minor correlation (p = 0.847, 0.255, 0.288, and 0.304) between Vibrio and cyanobacteria in pond A, pond B, effluent, and influent water, respectively. Notably, Vibrio showed a stronger correlation with pH (6.14-7.64), while cyanobacteria correlated with pH, salinity (17.4-24 ppt), and temperature (30.8-31.5 °C), with salinity as the most influential factor. This suggests that factors beyond cyanobacteria influence Vibrio survival. Future research could explore species-specific relationships, regional dynamics, and multidimensional landscapes to better understand Vibrio-cyanobacteria connections. Managing water parameters may prove more efficient in controlling vibriosis in shrimp farms than targeting cyanobacterial populations.

First monitoring of cyanobacteria and cyanotoxins in freshwater from fish farms in Rondônia state, Brazil

The main aimed of this study was to evaluate the physicochemical parameters, abundance and density of cyanobacteria, determine their blooms and the ecotoxicological risk of their cyanotoxins in fish ponds water. This study was conducted out in 20 fish farms in Rondônia state (Brazilian Amazon), samplings were carried out in the rainy and dry seasons. The experiment was developed in a completely randomized factorial design 20 × 3 x 3 (20 fish farms, 3 ponds and 3 replications). Regarding the composition of qualitative samples, horizontal and vertical hauls were carried out on the water surface, quantitative samples was obtained using a plankton net (50 μm mesh opening). Meanwhile, with the use of a multiparametric probe, physicochemical analyzes in fish ponds water were carried out. Furthermore, the cyanobacteria found were classified taxonomically and its blooms were recorded. Finally, blood was collected from 60 Colossoma macropomum. Concerning the higher averages in the rainy season 6.13 mg L⁻1 of dissolved oxygen, 40.02 cm of transparency, 0.35 NO31⁻ of nitrate, 0.15 NO21⁻ of nitrite, 44.55 mg L⁻1 CaCO3 of alkalinity and 50.10 mg L⁻1 CaCO3 of hardness, while higher averages of pH, phosphate and phosphorus were found in the dry season. A total of 15 families and 29 species of cyanobacteria were identified in the different seasons. The families that showed the highest densities (rainy and dry seasons) were Microcystaceae (356 and 760 cells mL⁻1), Leptolyngbyaceae (126 and 287 cells mL⁻1) and Microcoleaceae (111 and 405 cells mL⁻1). The species that showed the highest densities were Microcystis aeruginosa (356 and 697 cells mL⁻1), Planktolyngbya limnetica (98 and 257 cells mL⁻1) and Planktothrix sp. (111 and 239 cells mL⁻1). There were significant Pearson's correlations (r > 0.85; p < 0.05) between family abundances and cyanotoxin volume between physicochemical water variables and seasonality. A total of 20 cyanobacteria blooms were recorded, all of which in the dry season showed an ecotoxicological risk. Concerning the assessment mutagenicity in fish blood cells, a total of 78 abnormalities per slide were observed. In the dry season, the expected volume of cyanotoxins in the ponds from fish farms F1 and F4 were above the quantification limit (>QL). Abundance and density of cyanobacteria and their blooms and cyanotoxins can be used as bioindicators of eutrophication and/or water quality and ecotoxicological risk in fish ponds.

Water quality, microcystin-LR, and Cylindrospermopsin contamination status of spring and dug well water in CKDu high, low, and non-prevalent areas of Sri Lanka

Cyanotoxins, Microcystin LR (MC-LR) and Cylindrospermopsin (CYN) are hepato and nephro toxins and considered as one of the hypotheses for Chronic Kidney Disease of Unknown Etiology (CKDu) in Sri Lanka. Recent studies have revealed that significant number of dug wells in the North Central and Uva provinces where CKDu is prevalent are contaminated with cyanotoxins MC-LR and CYN. In the present study, cyanotoxin; MC-LR, CYN, and potential toxin-producing cyanobacteria were studied in 330 dug wells and 9 spring water samples collected from CKDu high prevalent areas in several Divisional Secretariats (DS) and Grama Niladhari (GN) divisions of Anuradhapura (Padaviya DS, Medawachchiya DS, Kebithigollewa DS), Polonnaruwa (Medirigiriya DS), Badulla (Girandurukotte GN) and Ampara (Dehiaththakandiya DS) districts, low prevalent areas in Anuradhapura district (Galnewa DS, Rajanganaya DS), non-prevalent areas in Angunakolapelessa DS of the Hambanthota district. General water quality parameters: temperature, pH, conductivity, Dissolved Oxygen (DO), Nitrate (N-NO3-), Nitrite (N-NO2-), Ammonia (N-NH3), Total Phosphorus (TP), and Total Hardness (TH) were determined using standard spectrophotometric and titrimetric methods. BACON test kits were used following manufactures instructions to quantify the CYN, and MC-LR concentrations by using the ELISA plate reader. Cyanobacteria density and species composition were determined under light microscopy following the standard algae and cyanobacteria keys. With the exception of Electrical Conductivity, all of the water quality parameters tested remained within the SLSI drinking water quality standard range. Microcystis spp. cell densities ranged from 14±3 to 1590±256 cells mL-1, where MC-LR concentration ranging from 0.04±0.01 to 3.89±0.02 µg L-1. At different CYN concentrations (0.04±0.01 to 3.59±0.05 µg L-1), Cylindrospermopsis spp. cell densities varied from 15 ±4 to 615±112 cells mL-1. Well water collected from Hambanthota district and spring water was collected Kebithigollewa DS, in Anuradhapura did not record cyanotoxins and cyanobacteria. The factor analysis classified well waters into three clusters of high, low, and non-prevalence areas with presence and absence of cyanobacteria and cyanotoxins. In contrast, springs were classified to a separate cluster. High concentrations of MC-LR and CYN were found in wells where CKDu high prevalent 85% of Padaviya DS and 80% of Medirigiriya DS, respectively. High Nitrate-N (3.01±0.56 mg L-1) and Nitrite-N (0.69±0.09 mg L-1) concentrations were recorded in well water collected from high CKDu prevalence areas. Thus, the results of the present study showed a relationship between cyanobacteria, cyanotoxins and CKDu records in the study area. Accordingly, further comprehensive studies are needed to be carried out to confirm the relationship between cyanotoxins and CKDu in Sri Lanka as cyanotoxin were listed in the WHO report as one of the possible reasons for CKDu.

Water quality and cyanobacterial blooms in the Piancó-Piranhas-Açu Watershed, Semi-arid Region of Northeastern Brazil: relationships with education toward sustainability

Greater emphasis has been attached to aquatic ecosystems in recent decades, as these are associated with indicators determinant of sustainability indices. The environmental impacts of these ecosystems with potential risk to human health in the semi-arid region of the state of Rio Grande do Norte have been frequently observed. This study aimed at evaluating the cyanobacteria density, and the indices that indicate the Piancó-Piranhas-Açu Watershed quality. It also targeted to identify the factors that impact most the blooming of these aquatic organisms. The sampling design consisted of 12 collections in different seasonal periods from 2009 to 2016, carried out by the Água Azul Program on 6 points along the basin. Environmental variables were used to analyze the Water Quality Index (WQI), Trophic State Index (TSI), and Cyanobacteria Density (CD). The mean WQI indicated ‘Regular’ water status for points PPA3 and PPA4, while PPA1, PPA2, PPA5 and PPA6 resulted in ‘Good’. As for the TSI, the levels indicate average degree of eutrophication (mesotrophy) on three sampling points, high degree of eutrophication (eutrophy) on two points, and low degree of eutrophication (oligotrophy) on one point. In this sense, human activities - especially diffuse polluting sources - around the spring seemed to worsen these scenarios. The density of potentially toxic cyanobacteria was high, exceeding CONAMA Resolution 357/2005 that recommends a maximum value of 50,000 cells/mL, and the Ministry of Health Ordinance 2914/2011 that recommends a threshold of 20,000 cells/mL. Regarding the general correlation between CD and seasonality we found significant influence (p &lt; 0.05), with greater proliferation of these organisms directly related to periods of drought. We concluded that although the WQI indicated that dams’ waters are suitable for multiple uses, the TSI had limitations, considering the excessive primary productions associated with the presence of cyanobacteria and, thus, the potential occurrence of cyanotoxins ensuing from pollutant loads. The study led us to conclude that the adoption of education practices toward sustainability would help environmental preservation and local social development. It would also enable the establishment of effective priority public policies on mitigation of water pollution.

Phytoplankton, with emphasis on potentially toxic cyanobacteria, from Amor Island, Alter do Chão (Santarém, Pará, Brazil)

Amor Island (Alter do Chão, Santarém, Pará, Brazil) is considered a region of great natural beauty and a national and international tourist attraction. The aim of this study was to determine the composition and density of the phytoplankton of the Amor Island, with emphasis on heterocytous cyanobacteria. Water samples for phytoplankton were collected and analyzed at seven points in October 2021. Filaments of heterocytous cyanobacteria were cultured and analyzed, measuring the cells of the first 30 trichomes. The abundance, diversity and evenness of phytoplankton species were calculated and balneability of beach in relation to algal blooms was evaluated. 106 generic and infrageneric taxa were identified, highlighting the Chlorophyta. Phytoplankton density was higher at Verde Lake (145.6 ± 22.0 org.L-1), diversity and evenness were higher at point 03 (Lake Verde) with 3.0 bits.cell-1 and 0.47, respectively. The most abundant species were: Aphanothece minutissima, Ankistrodesmus sp., Aphanothece sp., Aphanizomenon sp., Mougeotia sp., Merismopedia sp. and Quadrigula sp. The average density of cyanobacteria was higher in the Tapajós River (517.0 cell.mL-1). No algal and cyanobacterial blooms were identified, indicating water appropriate for bathing. Through morphological and morphometric description, the cultivated species were identified as Aphanizomenon gracile and Cylindrospermopsis/Raphidiopsis raciborskii, cited among the cyanobacteria with the highest occurrence of toxic blooms in the world. The region deserves phytoplankton monitoring studies, due to reports of cyanobacterial blooms, and greater knowledge of its planktonic biodiversity, since it is a threatened region.

Water quality for triathlon and open water swimming competitions in Brazilian freshwaters

Abstract In high-performance competitive activities, there can be intense and prolonged exposure to water during swimming components of the competition. Therefore, water quality assessments with reference to standards are desirable to ensure athletes’ health. We evaluated whether the official criteria established for primary contact recreation in Brazilian freshwaters (CONAMA Directive 274/2000), and an integrated index of bathing conditions in Brazil (ICB), are consistent with the water quality standards stipulated by the International Triathlon Union (ITU). The water quality of Lake of Ingleses, an important venue for triathlon and open water swimming near Belo Horizonte, Minas Gerais, Brazil, was assessed between 2003 and 2019. Results for E. coli, cyanobacteria density, and pH were favorable for contact recreation and competitions at the lake. Of the variables considered, only turbidity, used as a proxy indicator of visual water clarity, was unsuitable during part of the monitoring period. The ICB agreed with the ITU standards for Very Good and Excellent quality classes and is recommended as a tool for screening sites considered for competitions in Brazilian freshwaters. However, the Brazilian national criteria for contact recreation only present standards for E. coli and pH, which is insufficient coverage of attributes affecting primary contact suitability of water in high-performance sports activities.

Co-occurrence of multiple cyanotoxins and taste-and-odor compounds in the large eutrophic Lake Taihu, China: Dynamics, driving factors, and challenges for risk assessment

Cyanobacterial blooms producing toxic metabolites occur frequently in freshwater, yet the environmental behaviors of complex cyanobacterial metabolites remain largely unknown. In this study, the seasonal and spatial variations of several classes of cyanotoxins (microcystins, cylindrospermopsins, saxitoxins) and taste-and-odor (T&O) compounds (β-cyclocitral, β-ionone, geosmin, 2-methylisoborneol) in Lake Taihu were simultaneously investigated for the first time. The total cyanotoxins were dominated by microcystins with concentrations highest in November (mean 2209 ng/L) and lowest in February (mean 48.7 ng/L). Cylindrospermopsins were abundant in May with the highest content of 622.8 ng/L. Saxitoxins only occurred in May (mean 19.2 ng/L) and November (mean 198.5 ng/L). Extracellular T&O compounds were most concentrated in August, the highest being extracellular β-cyclocitral (mean 240.6 ng/L) followed by 2-methylisoborneol (mean 146.6 ng/L). Environment variables play conflicting roles in modulating the dynamics of different groups of cyanotoxins and T&O compounds. Total phosphorus (TP), total nitrogen (TN), chlorophyll-a and cyanobacteria density were important factors affecting the variation of total microcystins, β-cyclocitral and β-ionone concentrations. In contrast, total cylindrospermopsins, 2-methylisoborneol and geosmin concentrations were significantly influenced by water temperature and TP. There was a significant and linear relationship between microcystins and β-cyclocitral/β-ionone, while cylindrospermopsins were positively correlated with 2-methylisoborneol and geosmin. The perceptible odors may be good indicators for the existence of cyanotoxins. Hazard quotients revealed that potential human health risks from microcystins were high in August and November. Meanwhile, the risks from cylindrospermopsins were at moderate levels. Cylindrospermopsins and saxitoxins were first identified in this lake, suggesting that diverse cyanotoxins might co-occur more commonly than previously thought. Hence, the risks from other cyanotoxins beyond microcystins shouldn't be ignored. This study also highlights that the necessity for further assessing the combination effects of these complex metabolites.

Analysis of cyanobacteria outbreak effects in southern offshore area of Taihu lake

The eutrophication of lake water bodies has been emphasized for decades in our country due to its severe environmental effects. Indeed, 85.4% of lakes have met the eutrophication standard, and 40.1% of the lakes have met the severe eutrophication standard in China nowadays. Taihu lake, as the most important freshwater lake in eastern China, has been embarrassed because of the serious cyanobacteria outbreak problem every year. In this study, a statistic analysis of cyanobacteria outbreak in the offshore area of Taihu lake is conducted. Both the satellite image and field monitoring data are cited and analyzed. As a result, it is confirmed that the cyanobacteria outbreak effects are serious in spring and summer due to the high temperature and the high ratio of TN/TP. Additionally, the variations of TN/TP and cyanobacteria density are both computed and compared to show the environmental issues close to the Taihu lake.

Diazotrophic Cyanobacteria are Associated With a Low Nitrate Resupply to Surface Waters in Lake Tanganyika

In Lake Tanganyika, blooms of nitrogen-fixing (diazotrophic) cyanobacteria emerge, when the upper water column re-stratifies after a period of upwelling and convective mixing. During this seasonal transition, diazotrophic cyanobacteria exploit the abundant phosphate and fix nitrogen after other phytoplankton taxa have consumed the available nitrate. However, it remains less clear, which mechanisms favour diazotrophic cyanobacteria under more heavily stratified conditions with lower levels of excess phosphate and persistent nitrate-depletion. Here, we collected profiles of physicochemical parameters, nutrients and photo-pigments, as well as the medium- to large-sized phytoplankton community during two lake-wide cruises to elucidate to what extent the abundance of diazotrophic cyanobacteria in Lake Tanganyika may be controlled by the nitrate resupply through the thermocline into the euphotic zone. At stations where nitrate was depleted, but phosphate remained available near the surface, high densities of diazotrophic cyanobacteria were associated with a low nitrate supply to surface waters. Our data provide first support for two conceptual scenarios, where the relative position of the thermocline and the euphotic depth may create a functional niche for diazotrophic cyanobacteria: when the upward transport of nitrate into the euphotic zone is reduced by a subjacent thermocline, diazotrophic cyanobacteria, comprising Dolichospermum and Anabaenopsis, are key players in the medium-to large-sized phytoplankton community. By contrast, a thermocline located within the euphotic zone allows for a rapid vertical transport of nitrate for a thriving nitrate-assimilating phytoplankton community that evidently outcompetes diazotrophic cyanobacteria. This study highlights that, under nitrogen-depleted conditions, diazotrophic cyanobacteria can also grow in response to a reduced nutrient resupply to the productive surface waters.

FIRST EVIDENCE OF POTENTIAL TOXIC CYANOBACTERIA IN THE WATER-SEDIMENT INTERFACE OF A TROPICAL DRINKING WATER RESERVOIR

The Nostocales and Chroococcales cyanobacteria can produce potent cyanotoxins and survive in deep zones of aquatic ecosystems by the formation of morphologically distinguishable resistance structures and temporarily latent colonies in sediments. The purpose of this study was to determine the presence and density of Nostocales and Chroococcales with toxic potential in the water-sediment interface. During four samplings in three locations of the drinking water reservoir Riogrande II, some physical and chemical variables and chlorophyll a concentration of different spectral groups were measured, density of cyanobacteria was established by conventional microscopy, and mcyD and mcyE genes were detected by PCR. The environmental factors correlated with the abundance of cyanobacteria in the water-sediment interface were pH, total phosphorus, and iron. The highest chlorophyll concentration was provided by Chlorophyceae, while chlorophyll from the cyanobacteria spectral group fluctuated between 0.07 and 3.6 mg/L in field samples. About 86 % of the total cells number corresponded to the Microcystis complex while the Nostocales represented just 3.35 %. It was possible to find evidence for cyanobacteria with toxic potential in the three sampling points through the detection of the mcyD and mcyE genes. The presence of these cyanobacteria is possibly related to their life cycle and the resuspension processes caused by the way river water enters the reservoir. Additionally, this is the first evidence that demonstrates the importance of the water-sediment interface as a reservoir of cyanobacteria with toxic potential, since they can recolonize the water column in ecosystems that supply drinking water.

Characteristic Study of Briquette Cyanobacteria as Fuel in Chemical Looping Combustion with Hematite as Oxygen Carrier

Due to the more and more serious cyanobacteria bloom problem, it is particularly urgent to find a technology suitable for large-scale disposal and the efficient recovery of abundant nitrogen and phosphorus resources in cyanobacteria. The combination of chemical looping combustion (CLC) and biomass densification technology is thought to be a promising utilization selection. Based on the experimental results, the mechanical strength and energy density of briquette cyanobacteria are evidently increased with the compressive load; whereas, 10% is the optimal moisture content in the densification process. A higher heating rate in TGA would result in the damage of the internal structure of the briquette cyanobacteria, which are conducive to the carbon conversion efficiency. The presence of a hematite oxygen carrier would enhance the carbon conversion and catalyzed crack liquid products. CO2 yield is increased 25 percent and CH4 yield is decreased 50 percent at 900 °C in the CLC process. In addition, the lower temperature and reduction atmosphere in CLC would result in a lower NO emission concentration. The reactivity and porous property of hematite OC in CLC also increased during 10 redox cycle experiments. The CLC process accelerates the generation of CaH2P2O7 and CaHPO4 in cyanobacteria ash, which is more conducive to phosphorus recovery.

Species Diversity of Cyanobacteria and Desmids of a Drinking Water Source under Anthropogenic Pressure, and Their Implication in Toxin Production and Water Quality in Sub-Saharan Africa (Burkina Faso, Western Africa)

Drinking water sources in many African countries have been progressively degraded over the past decades. This degradation due to human activities leads to the proliferation of algae, especially toxin-producing cyanobacteria. The presence of toxigenic algae in water has adverse consequences on human and animal health. This study aimed to determine the diversity and density of Cyanobacteria and Desmids and to identify toxin-producing cyanobacteria and environmental variables that influenced the structure of these groups of microalgae in the Loumbila reservoir in Burkina Faso located in the western part of Africa. Algal samples were collected and physico-chemical parameters were measured. Plankton species were observed under a light microscope and identified using standard methods. Species density was determined by cell counting using a Fuchs-Rosenthal chamber. Kruskal Wallis and Pearson correlation tests were performed using R software. A canonical analysis was performed using CANOCO software. In total, 205 algal species were inventoried, of which 83 species composed of 37 species of Cyanobacteria and 46 species of Desmids were identified. Microcystis aeruginosa, Staurodesmus convergens and Cosmarium connatum var africanum had the highest presence index respectively (100%, 83.333% and 77.77%). Among cyanobacteria species, toxin-producing species (30 species) and microcystin-producing species (28 species) had the highest number. In terms of species density, Microcystis aeruginosa was the most abundant species. The density of toxin-producing cyanobacteria was positively correlated (p < 0.05) with temperature, pH, dissolved oxygen, transparency, nitrates, and orthophosphates. However, at p < 0.05, desmids community was only correlated with dissolved oxygen, transparency, and conductivity. Furthermore, canonical analysis showed that temperature, dissolved oxygen, transparency, and orthophosphates influenced the density of both cyanobacteria and Desmids. These results reveal the high occurrence of toxin-producing cyanobacteria and certainly high toxins produced in the drinking water source. Basic tools should be developed for monitoring of cyanotoxins in drinking water sources and drinking water supplied to population to consider cyanotoxins during water treatment.

四川丘陵区水库浮游植物群落结构与蓝藻水华风险——基于优势种生态位与种间联结研究

为了解四川丘陵区中小型水库浮游植物群落结构周年变化，掌握其演替规律并预测其发展方向，于2016年-2017年分季节对该地区10个典型水库进行了周年研究。结果显示：共检出浮游植物9门104属188种，其中优势种4门16属16种，以湖泊假鱼腥藻（Pseudanabaena linmnetica）优势度指数为最高；蓝藻密度在各季节、各水库中均占据优势，尤其是夏季。优势种生态位宽度和生态位重叠度在存在明显的季节差异性，并受到水温、营养条件等环境因子的显著影响；优势种可分为3个类别，竞争力相对较强的7个种中有5种蓝藻；全年发展性最强的种类也多为蓝藻，特别是湖泊假鱼腥藻等具有产毒潜力的种类，其优势度存在进一步扩大的风险。种间联结性检验结果显示，群落种间大致表现出净的正联结，优势种种对间正负关联比大于1，该类水库群落结构较为稳定且存在正向演替的趋势，可能会导致夏季间断性产毒蓝藻水华的风险。研究结果可为四川丘陵区中小型水库浮游植物群落演替研究以及蓝藻水华预警提供基础资料。;Sichuan is known as a province with thousands of rivers and numerous reservoirs which play an important role in production and life. There is a general problem of pollution in small and medium-sized reservoirs in this area, which may affect the structure, function and utilization of aquatic ecosystem. Aiming to explore the annual changes and succession rules of phytoplankton community structure in small and medium-sized reservoirs in hilly regions of Sichuan Province and to predict its development direction, this study conducts an annual survey on 10 typical reservoirs in specific regions in different seasons from 2016 to 2017. The survey identifies a total of 188 species of phytoplankton in 104 genera of 9 phyla, including 16 species (9 species are cyanobacteria) of 16 genera of 4 phyla which are identified as dominant species. In particular, the dominance index of Pseudoanabaena linmnetica is the highest, and the density of cyanobacteria is dominant in all seasons and reservoirs, especially in summer. Furthermore, the improved Levins formula and Petraitis index are applied to determine the niche metrics of the phytoplankton dominant species. The results show that the niche breadth and niche overlap of each dominant species vary seasonally and are significantly affected by water temperature and nutrient. Based on their niche breadth in different seasons, the dominant species are classified into three categories, two of which are relatively competitive. These two categories include 7 species, of which there are 5 species of cyanobacteria, including P. linmnetica. The dominant species in four seasons are mostly in a state of developing, and the most promising species throughout the year are mainly cyanobacteria. In particular, species with the potential to produce toxins such as P. linmnetica have the risk of further expansion of their dominance. The results of interspecific association show a positive correlation among the community species throughout the year, indicating that the community structure in these reservoirs is relatively stable and there is a positive succession trend. In such a trend, intermittent toxic cyanobacteria bloom which affects the quality and function of water may occur in these reservoirs in summer, especially in reservoirs with simple dominant species composition.This paper provides research background for the study of phytoplankton community succession and the early warning of cyanobacteria blooms in small and medium-sized reservoirs in hilly regions of Sichuan Province. To prevent possible filamentous cyanobacteria bloom outbreak, water quality of the reservoirs should be effectively managed and immediately repaired under the dual promotion of high nutritional level and global warming.

Cyanobacteria Growth in Nitrogen- &amp;amp; Phosphorus-Spiked Water from a Hypereutrophic Reservoir in Kentucky, USA

Cyanobacteria may adversely impact aquatic ecosystems through oxygen depletion and cyanotoxin production. These cyanotoxins can also harm human health and livestock. In recent years, cyanobacterial blooms have been observed in several drinking water reservoirs in Kentucky, United States. In Kentucky, the paradigm is that phosphorous is the limiting nutrient for cyanobacteria growth. To explore this paradigm, an indoor microcosm study was conducted using hypereutrophic Guist Creek Lake water. Samples were collected and spiked with various combinations of locally used agricultural grade fertilizers, including ammonium nitrate, urea, and triple phosphate (calcium dihydrogen phosphate). Samples were incubated indoors for the photoperiod-specific to the time of the year. Cyanobacteria density, measured by phycocyanin, did not demonstrate increased growth with the addition of phosphate fertilizer alone. Cyanobacteria growth was enhanced in these conditions by the combined addition of ammonium nitrate, urea, and phosphorus fertilizer. Growth also occurred when using either ammonium nitrate or urea fertilizer with no additional phosphorus input, suggesting that phosphorus was not limiting the cyanobacteria at the time of sample collection. The addition of both nitrogen fertilizers (ammonium nitrate and urea) at the concentrations used in this study, in the absence of phosphorus, was deleterious to both the Chlorophyta and cyanobacteria. The results suggest further studies using more robust experimental designs are needed to explore lake-specific dual nutrient management strategies for preventing cyanobacterial blooms in this phosphorus-rich hypereutrophic lake and possibly other hypereutrophic lakes.

Spatial and Temporal Variation of Phytoplankton Community Structure and Its Influencing Factors in Shanghai River Channels

In order to explore the spatial and temporal characteristics of the phytoplankton community structure and its influencing factors in Shanghai rivers, the water quality and phytoplankton community structure at 44 river channel sites in a central urban area, new town area, and rural area in Shanghai were investigated from September to October 2018 (autumn) and July to August 2019 (summer). The results showed that:① Chlorophyta was the dominant phyla during the autumn and summer, and was followed by Cyanobacteria and Bacillariophyta. Cyanobacteria dominated the phytoplankton community in terms of density. The number of species and density of phytoplankton were 24% and 2.77 times higher, respectively, than those during the summer and autumn. The dominance of Microcystis sp. was obvious during the autumn (Y=0.16), but there was no absolute dominant species during the summer. ② The difference in the number of phytoplankton species among the three regions was not significant, and the density of the total phytoplankton and cyanobacteria species showed a similar spatial pattern:rural area > new town area > central urban area. Additionally, no significant difference was observed in the total phytoplankton and Cyanobacteria density among the three regions during the autumn (P>0.05), whereas it was 1.82 and 1.93 times higher, respectively, in the rural area in comparison to the central urban area during the summer (P<0.05). Montecarlo test results revealed that the main factors affecting the phytoplankton community structure during the autumn were secchi disk transparency (SD), total phosphorus (TP), total nitrogen (TN), and turbidimetry (Turb), whereas these were TN, Turb, SD, and pH during the summer. ③ The results of a redundancy analysis (RDA) indicated that during the autumn, the phytoplankton in the rivers of the new town area were mainly affected by Turb, TN, and TP, while the rural rivers were mainly affected by SD. During the summer, the phytoplankton in the rivers of the new town and rural areas were mainly affected by TN and Turb. The influencing factors in the central urban area were complex.

Usage and Effects of Algaecide in Kurtboğazı Dam Lake

In recent years, the increased density and incidence of cyanobacteria, also known as blue-green algae, in water resources has become a growing global problem in consequence of the increasing temperature associated with climate change. The growth of cyanobacteria in dam lakes causes algae blooms and deteriorates water quality. Since it contains Methyl-Isoborneol, Geosmin and toxins, taste and odour problems in water occur and those threatens public health. Rising density of algae causes an increase in the total amount of organic carbon in water, which increases the amount of disinfection by-products. In this study, algae control applications were performed during the summer period kesin tarih parantez içinde verilmelidir. The water samples were taken before and after the algaecide application, and total organic carbon, pH, chlorophyll-a, dissolved oxygen, copper, turbidity, orthophosphate phosphorus and total nitrogen were analysed. In order to calculate the amount and depth of the algaecide application, we determined which cyanobacterial species would be used. Copper ethanolomine is the main constituent of the algaecide so copper contamination in water has been investigated. In general, the density of cyanobacteria in bay and stagnant waters was increase before its application. According to the results of the study, appropriate doses and times are supporters to prevent algae blooms and to control sudden increases in the number of algae. In accordance with the results of the analysis, permanent copper pollution does not occur at different depths or at different points. However, a smallamount of increase in the samples taken during the algaecide effect time can be seen from time to time.

Phytoplankton community characteristics in rice paddy fields under different nitrogen fertiliser applications

Community characteristics of phytoplankton in the surface water of paddy fields under four nitrogen fertiliser (NF) treatments were studied in the Yangtze River Delta, China. The results were as follows: (1) in total, 65 species, belonging to six phytoplankton phyla and 50 genera were detected; their average total density was 1.25 × 106/L. Number of species and diversity of phytoplankton were higher in the control treatment (0 kg N/ha; CK) than in the NF treatments at later experimental times; (2) there was a significant positive correlation between phytoplankton density and total N; however, total density of phytoplankton was higher in CK than in NF treatments; (3) during the transplanting and rehabilitation stage, under high N treatments, phytoplankton mainly comprised Chlorophyta, among which the dominant species was Volvox aureus, while under low N treatments, the main phyla were Chlorophyta and Cryptophyta, with Chlamydomonas reinhardtii and Chroomonas acuta forming the dominant species. During the rice tillering stage, the dominance of Chlorophyta was partially replaced by Cryptophyta and Bacillariophyta in all NF treatments, while the proportion of Cyanobacteria in CK increased significantly; (4) species and density of Cyanobacteria were higher in CK than in NF treatments, accompanied by the dominance of nitrogen-fixing species such as Anabaena spp. at later experimental times. The results indicate that NF application changed the phytoplankton community. Low N conditions can promote competition for photosynthesis and nutrients among phytoplankton in paddy fields, while low N application rates can induce growth of some algae with nitrogen-fixing abilities.