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Remediation of water quality by stimulating algal photosynthesis using light-emitting diodes (LEDs) has attracted attention, but few studies have examined this in outdoor freshwater environments. To understand the effects of LED illumination on water quality, the dissolved oxygen (DO), temperature, pH, and electric conductivity were monitored over 5 months in three depressions with or without a red/blue LED light at the bottom of an experimental pond. The effects of the blue LED on water quality were evident in the period with less rainfall after the change of water quality to an equilibrium state; DO and pH were higher, and EC was lower for the blue LED than for the control. The diel changes of these variables were also lower for the blue LED. The effects of the red LED on DO and pH were also evident, but to a lesser extent compared to those of the blue LED. A vertical mixing of water associated with a nighttime cooling of the surface water was suggested by a rapid DO increase after a temperature decrease in the control. Such internal water circulation and an inflow of water after rainfall might have obscured the LED effects in the rainy period. The bottom water of the blue LED had a higher density and species richness of phytoplankton than that of the control at the end of the experiment. A lower density of phytoplankton and higher nutrient concentrations in the red LED might have been due to a higher density and feeding activity by zooplankton. Our results confirmed the applicability of LED illumination in stimulating algal photosynthesis, and in improving the oxygen condition of the bottom water in freshwater ponds.

Aims Vegetation classification consistent with the Braun‐Blanquet approach is widely used in Europe for applied vegetation science, conservation planning and land management. During the long history of syntaxonomy, many concepts and names of vegetation units have been proposed, but there has been no single classification system integrating these units. Here we (1) present a comprehensive, hierarchical, syntaxonomic system of alliances, orders and classes of Braun‐Blanquet syntaxonomy for vascular plant, bryophyte and lichen, and algal communities of Europe; (2) briefly characterize in ecological and geographic terms accepted syntaxonomic concepts; (3) link available synonyms to these accepted concepts; and (4) provide a list of diagnostic species for all classes. Location European mainland, Greenland, Arctic archipelagos (including Iceland, Svalbard, Novaya Zemlya), Canary Islands, Madeira, Azores, Caucasus, Cyprus. Methods We evaluated approximately 10 000 bibliographic sources to create a comprehensive list of previously proposed syntaxonomic units. These units were evaluated by experts for their floristic and ecological distinctness, clarity of geographic distribution and compliance with the nomenclature code. Accepted units were compiled into three systems of classes, orders and alliances (EuroVegChecklist, EVC) for communities dominated by vascular plants (EVC1), bryophytes and lichens (EVC2) and algae (EVC3). Results EVC1 includes 109 classes, 300 orders and 1108 alliances; EVC2 includes 27 classes, 53 orders and 137 alliances, and EVC3 includes 13 classes, 24 orders and 53 alliances. In total 13 448 taxa were assigned as indicator species to classes of EVC1, 2087 to classes of EVC2 and 368 to classes of EVC3. Accepted syntaxonomic concepts are summarized in a series of appendices, and detailed information on each is accessible through the software tool EuroVegBrowser. Conclusions This paper features the first comprehensive and critical account of European syntaxa and synthesizes more than 100 yr of classification effort by European phytosociologists. It aims to document and stabilize the concepts and nomenclature of syntaxa for practical uses, such as calibration of habitat classification used by the European Union, standardization of terminology for environmental assessment, management and conservation of nature areas, landscape planning and education. The presented classification systems provide a baseline for future development and revision of European syntaxonomy. This is the first comprehensive and critical account of the hierarchical syntaxonomic system of communities of vascular plants, bryophytes, lichens, and algae in Europe, synthesizing more than 100 years of research in classification of vegetation. It aims at documenting standardization of concepts and terminology of syntaxa and informing calibration of habitat classifications for environmental assessment, nature management, conservation, landscape planning, and education.

Urban lakes play an important role in drainage and water storage, regulating urban microclimate conditions, supplying groundwater, and meeting citizens’ recreational needs. However, geographical patterns of algal communities associated with urban lakes from a large scale are still unclear. In the present work, the geographical variation of algal communities and water quality parameters in different urban lakes in China were determined. The water quality parameters were examined in the samples collected from north, central, south, and coastal economic zones in China. The results suggested that significant differences in water quality were observed among different geographical distribution of urban lakes. The highest total phosphorus (TP)(0.21 mg/L) and total nitrogen (TN) (3.84 mg/L) concentrations were found in XinHaiHu (XHH) lake, it also showed highest the nitrate nitrogen (NO3−-N) (0.39 mg/L),total organic carbon(TOC) (9.77 mg/L), and COD Mn (9.01 mg/L) concentrations among all samples. Environmental and geographic factors also cause large differences in algal cell concentration in different urban lakes, which ranged from 4700 × 104 to 247,800 × 104cell/L. Through light microscopy, 6 phyla were identified, which includes Chlorophyta, Bacillariophyta, Cyanophyta, Dinophyta, Euglenophyta, and Cryptophyta. Meanwhile, the heat map with the total 63 algal community composition at the genus level profile different urban lakes community structures are clearly distinguishable. Further analyses showed that the dominant genera were Limnothrix sp., Synedra sp., Cyclotella sp., Nephrocytium sp., Melosira sp., and Scenedesmus sp. among all samples. The integrated network analysis indicated that the highly connected taxa (hub) were Fragilaria sp., Scenedesmus sp., and Stephanodiscus sp. The water quality parameters of NO3−-N and NH4+-N had significant impacts on the structural composition of the algal community. Additionally, RDA further revealed distinct algal communities in the different urban lakes, and were influenced by NO2−-N, Fe, and algal cell concentrations. In summary, these results demonstrate that the pattern of algal communities are highly correlated with geographic location and water quality on a large scale, and these results also give us further understanding of the complex algal communities and effectively managing eutrophication of urban lakes.

【Objective】 This study delves into the successional interrelationship between algal communities and environmental factors to uncover the mechanisms behind water bloom outbreaks in Shanzai Reservoir. 【Method】 Utilizing redundancy analysis and correlation analysis, we investigated the temporal variations in water temperature, pH, dissolved oxygen (DO), transparency, and dominant algal species in Shanzai Reservoir from 2020 to 2021. We explored the seasonal succession and vertical distribution of the algal community. A machine learning approach was used to establish the relationship between pertinent environmental factors and chlorophyll a. 【Result】 The average total nitrogen (TN) and total phosphorus (TP) concentrations in Shanzai Reservoir measured in the studied period were (0.675±0.137) mg/L and (0.021±0.006) mg/L, respectively. Water quality in the reservoir was Class III grade. The dominant algal species in the reservoir are diatoms and cyanobacteria. Diatom blooms were prevalent from May to July, particularly under moderate temperature and reduced light conditions. In contrast, cyanobacteria proliferated from July to September, leading to a reduction in pH, DO and water quality. The cyanobacterial outbreaks had a significant positive correlation with water temperature, pH, water turbidity, and TP, with their R2 being 0.71, 0.77, 0.65, and 0.74, respectively. Diatoms were negatively correlated to water temperature, pH, turbidity, and TP, with their R2 ranging from -0.43 to -0.37. Using machine learning algorithms can improve the R2 to 0.852 6. 【Conclusion】 There were differences in outbreak timings between different algae species in Shanzai Reservoir due to the difference in their underlying mechanism. Machine learning model has a good applicability and can be used for accurate analysis of algal blooms in Shanzai Reservoir.

Harmful algal blooms (HABs) in freshwater produce toxins that pose a threat to public health and aquatic ecosystems. Although algal communities have been studied globally to understand the characteristics of HABs, the occurrence of toxic cyanobacteria in freshwater ecosystems is rarely understood. Unlike abiotic factors, the effects of biotic factors (e.g., interaction, dominance, and variability) on the occurrence of toxic cyanobacteria were overlooked due to the intricate interaction of microorganisms under different environmental conditions. To address this problem, a comprehensive ecological concept stability, which encompasses variations in species or communities due to changing biological interactions or environmental fluctuations, was applied in this study. The algal communities in six river-connected lakes in the North Han River, South Korea, were classified into high and low stability groups. The algal species belonging to diatoms and green algae groups played a major role in the interaction within the algal community in highly stable lakes, but the frequency of Microcystis led the interaction within the algal community at the center of the network in low-stability lakes. These results indicate that the interaction within the cluster is easily changed by Microcystis, where the abundance explosively increases in lakes with low algal community stability. Water quality is more strongly associated with the occurrence of toxic cyanobacteria (Microcystis and Dolichospermum). In low-stability lakes, more diverse water quality indicators are correlated with the development of toxic algae than in high-stability lakes. This paper is the first report on the importance of algal community stability in freshwater in the occurrence of toxic cyanobacteria and offers a new perspective on Microcystis monitoring and management.

The surface waters of the Mediterranean Sea are extremely poor in the nutrients necessary for plankton growth. At the same time, the Mediterranean Sea borders with the largest and most active desert areas in the world and the atmosphere over the basin is subject to frequent injections of mineral dust particles. We describe statistical correlations between dust deposition over the Mediterranean Sea and surface chlorophyll concentrations at ecological time scales. Aerosol deposition of Saharan origin may explain 1 to 10% (average 5%) of seasonally detrended chlorophyll variability in the low nutrient-low chlorophyll Mediterranean. Most of the statistically significant correlations are positive with main effects in spring over the Eastern and Central Mediterranean, conforming to a view of dust events fueling needed nutrients to the planktonic community. Some areas show negative effects of dust deposition on chlorophyll, coinciding with regions under a large influence of aerosols from European origin. The influence of dust deposition on chlorophyll dynamics may become larger in future scenarios of increased aridity and shallowing of the mixed layer.

Algae exert great impact on soil formation and biogeochemical cycling. However, there is no full understanding of the response of soil algal community structure to the seasonal fluctuations in temperature and moisture and changes of soil physicochemical properties across different forests. Here, based on 23S rRNA gene sequencing, we analyzed soil algal community structure in four different forest plantations in two seasons and examined soil physiochemical properties. The results showed the significantly seasonal variation in soil algal community structure, with the higher overall diversity in summer than in winter. In addition, there existed significant correlations between soil algae (species composition, relative abundance, diversity index) and physicochemical properties (pH, total phosphorus, organic matter and nitrate nitrogen), suggesting that edaphic characteristics are also largely responsible for the variation in soil algal community. Nevertheless, the seasonal variation in algal community structure was greater than the variation across different forest plantations. This suggest temperature and moisture are more important than soil physicochemical properties in determining soil algal community structure. The findings of the present study enhance our understanding of the algal communities in forest ecosystems and are of great significance for the management and protection of algal ecosystem.

A number of studies evidenced the impact of human activities on aquatic environments worldwide. The availability of nutrients in lakes is strongly influenced by watershed land use patterns depending on the share of forestry, agriculture and urbanization level. Nearly all the previous studies, which examined the relationships between the phytoplankton community and the land use pattern on the watershed of lakes or reservoirs were performed on a taxonomic basis. In this study, 78 lakes were sampled to analyse how the different land use types affect their phytoplankton functional group compositions. Our results concluded that land use is a complex driver, and it cannot provide an unequivocally straightforward forecast, which could result in the selection of a specific functional group or taxa. Thus, land use alone is a weak predictor, but the shared effects may structure the phytoplankton assemblage composition.

Located within the subpolar front (SPF) zone, the eastern coast of Korea is subject to frequent environmental changes on both spatial and temporal scales. In this study, we analyzed seasonal changes in the algal community structure and related environmental factors at two sites, Chodo (CD) and Sageunjin (SG), which were influenced by cold and warm-water masses, respectively, in the SPF zone. Sea surface temperature (SST) exhibited greater seasonal change in CD, whereas significant wave height was higher in SG. The salinity and nutrient concentrations decreased during summer and increased in winter at both sites. Seasonal shifts in the dominant species were distinct, with turf species positively correlated with SST dominating the intertidal zone of SG during winter, and canopy species were associated with nutrient concentrations dominating the intertidal zone of CD. Bryopsidales, which was positively correlated with the N:P ratio, dominated the SG subtidal zone in summer, whereas Fucales, which was positively correlated with the SST, dominated the CD subtidal zone. These results enhance our understanding of seaweed responses to environmental changes in SPF zones and provide a basis for predicting future changes in coastal ecosystems.

Balaton is the largest shallow lake in Central Europe. It is one of the few lakes where eutrophication processes have been successfully reversed. The creation of a wetland area on the lower part of the main inflow river played a major role in the re-oligotrophication processes. After several decades of operation and multiple transformations, an attempt was made to explore the microbial community of the water reservoir and its relationship with algal groups and environmental parameters. In the main inflow river, floods had the greatest effect on the microbial community composition, while in the open water areas of the wetland system, the algae production that develops due to external nutrient load was the main driver of the bacterial community. In the high-macrophyte-covered areas, the decomposition processes of the dying algae biomass were the most decisive. Finally, in the large open water areas of Lake Balaton, the external and internal nutrient loads together determined the algal production and thus the bacterial community composition.