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Evaluation of the use of eucalyptus to control algae bloom and improve water quality
... Finally, the eucalypt allelopathic properties were investigated to control algae bloom, which degrades water quality by producing the most potent toxins, which is a serious threat. Zhao et al. [50] was the first to study the effects of leaf extracts of Eucalyptus grandis × E. urophylla hybrids on the density of algae cells in mesocosm. Direct planting of eucalypts was significantly more effective, since, in addition to the isolation of allelochemicals, competitive absorption for macronutrients occurred as well. ...
... Direct planting of eucalypts was significantly more effective, since, in addition to the isolation of allelochemicals, competitive absorption for macronutrients occurred as well. At the same time, plants or extracts had no adverse effect on diversity or abundance of the microbial community [50]. ...
... Since juglone is synthesized in the phylloquinone pathway, green algae, cyanobacteria, or certain menaquinone-synthesizing bacteria can be used for its large-scale production [267]. Recent studies have shown activity of allelocochemicals of Ailanthus altissima [38], Cinnamomum camphora [309], Eucalyptus [50], and Juglans [195] against cyanobacteria that causes algae blooms, and, therefore, they can be potentially used as algaecides. ...
The use of natural products that can serve as natural herbicides and insecticides is a promising direction because of their greater safety for humans and environment. Secondary metabolites of plants that are toxic to plants and insects—allelochemicals—can be used as such products. Woody plants can produce allelochemicals, but they are studied much less than herbaceous species. Meanwhile, there is a problem of interaction of woody species with neighboring plants in the process of introduction or invasion, co-cultivation with agricultural crops (agroforestry) or in plantation forestry (multiclonal or multispecies plantations). This review describes woody plants with the greatest allelopathic potential, allelochemicals derived from them, and the prospects for their use as biopesticides. In addition, the achievement of and the prospects for the use of biotechnology methods in relation to the allelopathy of woody plants are presented and discussed.
... Cyanobacterial harmful algal blooms (CyanoHABs) have become a worldwide phenomenon, bringing serious consequences for lacustrine ecosystems and human health [1][2][3]. Microcystis is the most common bloom-forming cyanobacteria species due to its morphological and ecophysiological advantages [4,5]. In hypereutrophic shallow lakes such as Lake Taihu, Lake Dianchi and Lake Chaohu, Microcystis has usually been among the predominant species [6,7]. ...
... In hypereutrophic shallow lakes such as Lake Taihu, Lake Dianchi and Lake Chaohu, Microcystis has usually been among the predominant species [6,7]. Several measurements to control Microcystis populations, e.g., algaecides, photocatalysis and electron beam irradiation have been applied with relatively moderate success [3]. Notably, when Microcystis die off, the endogenous nutrients and microcystins are inevitably released into the aquatic environment [5,8]. ...
... Many countries and regions of the world are currently facing the problem of large-scale algal blooms caused by water eutrophication (Cao et al., 2016;Zhao et al., 2019a). Microcystis aeruginosa is the dominant algal species among eutrophic cyanobacteria in summer water (Ye et al., 2011), which seriously threatens ecological environmental safety (Dong et al., 2016). ...
... However, the TFL concentration used in this experiment is much lower than the lethal concentration to zebrafish, and thus the TFL + Fe 3+ conditions used in this experiment will effectively inhibit algae while having relatively little effect on fish. In addition, studies have shown that eucalyptus leaf extract exerts negligible effects on the species abundance and diversity of the microbial community (Zhao et al., 2019a) and that the rich nutrients in the eucalyptus leaf extract even increase the species diversity of the microbial community (Zhao et al., 2019b). Therefore, the use of eucalyptus tannins for algal suppression is an ecosystem-friendly and feasible method. ...
Microcystis aeruginosa is the competitively dominant algal species in eutrophic waters and poses a serious threat to the aquatic ecological environment. To investigate the effects of eucalyptus tannins (TFL) and black water in eucalyptus plantations on M. aeruginosa, this study exposed M. aeruginosa to different concentrations (0 (control), 20, 50, 80, 110, and 140 mg L–1) of tannic acid (TA; hydrolyzed tannins, HT; reagent tannin), epigallocatechin gallate (EGCG; condensed tannins, CT; reagent tannin), eucalyptus tannins (TFL, complex tannin) and mixed TFL + Fe3+ solution (tannin: Fe3+ molar ratio = 1:10). The cell density, chlorophyll-a (Chl-a) content, superoxide dismutase (SOD) activity, malondialdehyde (MDA) and soluble protein (SP) contents of algae under tannin stress were determined, and the algal cell density treated with under the combination of TFL and Fe3+ was determined. The results showed a reduction in the Chl-a content of algal cells, which inhibited photosynthesis; leading to membrane lipid peroxidation; and the complexation of soluble proteins resulting in blocked protein synthesis were the main mechanisms by which tannins inhibited the growth of M. aeruginosa. TFL achieved the same inhibition of algal cells as the tannin reagent at the same concentration. At 4 d, TFL at 80 mg L–1 and above could achieve more than 54.87 % algal density inhibition. The inhibition rate of 80 mg L–1 and above TFL + Fe3+ on algal density was more than 75 %, indicating that TFL + Fe3+ had a stronger inhibitory effect on algal density. The results may facilitate the resource utilization of eucalyptus harvesting residues, explorations of the potential application of eucalyptus tannins in the control of M. aeruginosa, and provide new ideas for ecological algal inhibition in eucalyptus plantations.
... It has been reported that water quality was closely linked to the diversities of different organisms, such as macrophytes, algae, insects and microbes (Beudert et al., 2015;Vymazal, 2013;Worm et al., 2006). Specifically, water quality could be improved due to increasing biodiversity either via removing nutrients or other chemical pollutants, or via reducing harmful pest loads (Finlayson et al., 2005); water quality could also decline due to decreasing diversity in algae (Tas et al., 2019;Worm et al., 2006;Zhao et al., 2019). However, there were still controversial opinions about the relationships between biodiversity and water quality (Cardinale, 2011;Onyenwe et al., 2018;Xu et al., 2016), and it is necessary to conduct further in-depth research to predict water quality changes under different biodiversity circumstances, especially in wetland ecosystems. ...
... Litter submergence can affect water quality both positively and negatively (Slack and Feltz, 1968;Pan et al., 2017). It has been reported that plant litter submergence might increase the concentrations of TN and TP in water, and hence increase the eutrophication of water (Dunck et al., 2015;Ferreira and Graca, 2016;Xiao et al., 2017;Zhao et al., 2019). However, litter decomposition might also decrease the nitrate nitrogen via increasing denitrification rates (Pan et al., 2017). ...
Plant litter plays an important role in affecting the water quality of wetland ecosystems. However, it is unknown whether litter decomposability and species traits might predict water quality changes during litter submergence. Here, we conducted a greenhouse experiment to examine the effects of four submerged plant species, together with two water sources (sampled from tourism and protected areas), and oxygen injection treatments on the changes of eight water quality parameters during litter submergence. Our results showed that litter submergence significantly affected water quality changes, and the observed effects changed through time and differed between two water sources, between oxygen injection and the control treatments, and among different litter species. Moreover, water electric conductivity (EC), total dissolved solids (TDS), water total nitrogen (TN), ammonium and nitrite nitrogen increased with increasing initial litter total carbon (TC), TN and total phosphorus (TP), but water dissolved oxygen (DO) decreased with increasing litter TC, TN and TP. Moreover, water EC, TDS and TN increased with the final mass losses after 10-week submergence. These results indicated that species traits (including decomposability) might be good predictors for the water quality changes during litter submergence, and such a trait-based approach might be a promising tool to link plant species diversity via plant functional traits to water quality or other wetland ecosystem services.
... Currently, an advantageous substitute for conventional methods is the use of organically acquired ingredients from floras, which is described to be an eco-friendly and promising method for regulating cyanobacterial blooms in water bodies. Several studies have been done on controlling cyanobacteria blooms using extracts from aquatic and terrestrial plants (Zhao et al., 2019). Due to its lower toxicity and reduced risk to the environment, this technique appears to offer a fresh and favorable alternative for controlling harmful algal blooms. ...
... On the other hand, algae blooms can reduce the concentration of dissolved oxygen in water, produce hepatotoxin microcystins and deteriorate water quality (Sandin and Johnson, 2000). These new environmental conditions, whether individually or combined, can directly or indirectly kill aquatic animals and cause a sharp decline in species diversity of local communities (Smith and Schindler, 2009;Zhao et al., 2019), as has been shown in our study for macroinvertebrates in subtropical floodplain lakes. ...
Anthropogenic disturbances have become one of the primary causes of biodiversity decline in freshwater ecosystems. Beyond the well-documented loss of taxon richness in increasingly impacted ecosystems, our knowledge on how different facets of α and β diversity respond to human disturbances is still limited. Here, we examined the responses of taxonomic (TD), functional (FD) and phylogenetic (PD) α and β diversity of macroinvertebrate communities to human impact across 33 floodplain lakes surrounding the Yangtze River. We found that most pairwise correlations between TD and FD/PD were low and non-significant, whereas FD and PD metrics were instead positively and significantly correlated. All facets of α diversity decreased from weakly to strongly impacted lakes owing to the removal of sensitive species harboring unique evolutionary legacies and phenotypes. By contrast, the three facets of β diversity responded inconsistently to anthropogenic disturbance: while FDβ and PDβ showed significant impairment in moderately and strongly impacted lakes as a result of spatial homogenization, TDβ was lowest in weakly impacted lakes. The multiple facets of diversity also responded differently to the underlying environmental gradients, re-emphasizing that taxonomic, functional and phylogenetic diversities provide complementary information on community dynamics. However, the explanatory power of our machine learning and constrained ordination models was relatively low and suggests that unmeasured environmental features and stochastic processes may strongly contribute to macroinvertebrate communities in floodplain lakes suffering from variable levels of anthropogenic degradation. We finally suggested guidelines for effective conservation and restoration targets aimed at achieving healthier aquatic biotas in a context of increasing human impact across the ‘lakescape’ surrounding the Yangtze River, the most important being the control of nutrient inputs and increased spatial spillover effects to promote natural metasystem dynamics.
... There are many methods to solve HABs in recent years, such as chemical method (Zuo et al. 2021;Wang et al. 2021), physical method (Huang et al. 2020), and biological method (Zhao et al. 2019). These methods have been confirmed in the laboratory, but there were certain limitations because many factors were involved in the actual applications. ...
Harmful algal blooms have been a serious environmental problem. The flocculation of Microcystis aeruginosa by oyster shell powders prepared by aerobic calcination (CO), anaerobic calcination (CN), acidification anaerobic calcination (CAN), and deacetylation anaerobic calcination (CHN) was studied. The CO800 (100 mesh) and CN800 (160 mesh) presented the highest flocculation rate of 89.46% and 77.39% when they were stirred for 1 min with speed of 750 r/min and 250 r/min, respectively. The photosynthesis and viability of the algae cells flocculated by CO800 with particle size of 100 mesh were not significantly damaged. The phosphorus nutrient could be removed by CO800 and CN800 effectively due to the presence of Ca²⁺, which also limited Microcystis aeruginosa growth. The study showed that the processing of oyster shell powder could be used as an effective flocculating material.
Graphical Abstract
... Eucalypt leaf extracts reduce chlorophyll content in crops, related to possible poor photosynthesis and, as a result, poor plant growth [86]. Some allelopathic compounds from eucalypt have been used as inhibitors of photosynthetic activity in the control of algal blooms [87] and strongly limit the growth of other plant species around them [88]. Exposure to herbicides for long periods and in sunlight can lead to sustained or irreversible effects in photosynthetic organisms [89]. ...
Despite the reported allelopathic nature of the Eucalyptus genus, eucalypt leachates have unknown effects on the trophic base of stream green food webs. Eucalypt plantations have increased worldwide, including riparian ecosystems. We aimed to test whether short-term eucalypt leachates might alter water chemistry, periphytic algal biomass and diatoms, and herbivorous invertebrates’ (i.e., scrapers). We studied two oligotrophic and well-preserved headwaters from NW Spain. The experiment followed a before-after control-impact paired (BACIp) design, with weekly sampling before and after eucalypt leaves addition to streams. In the stream with lower discharge, the eucalypt treatments seemed to affect increases in biomass accrual (Chl-a) and diatom assemblages, disfavouring sensitive species (e.g., Eunotia minor and Achnanthidium pyrenaicum). Therefore, the ecological status was reduced from high to good. In the stream with higher discharge, invertebrate assemblages changed with scrapers having their abundances modified in comparison with the control (e.g., Habrophlebia sp. and Elmidae). Results suggest that eucalypt leaves leachates exert toxic effects on periphyton and on diatom and invertebrate assemblages, and this effect might be mediated by discharge. Alterations at the base of stream food webs may compromise their good ecological status. Further studies are necessary to identify whether this toxicity is due to allelopathic processes.
... It's difficult to assess the exact role of agriculture in eutrophication of lakes and rivers and their contamination. Different countries have reported how agriculture contributes to surface water pollution (Zhao et al., 2019) 32 . In 1960s Lake Erie was declared a 'dead lake' due to eutrophication and pollution from non-point sources. ...
... In recent years, eutrophication has caused Huangtai algal blooms in Lake Ulansuhai with severe adverse effects. Algal blooms covered the water surface and blocked sunlight projection into the lower water body (Zhao et al. 2019), further damaging the water environment and affecting the ecological safety of Lake Ulansuhai. To date, only a few studies on Huangtai algae have been conducted. ...
Huangtai algal blooms are key indicators of eutrophication and lake-ecosystem damage. Understanding the spatiotemporal heterogeneity of their growth is critical for preserving the ecological environment. The dimidiate pixel model is commonly used to estimate vegetation coverage; however, indices such as the normalized difference vegetation index have not been specifically constructed for the Huangtai algae spectrum and thus are not specific or sufficiently precise for use as indicators. Therefore, we propose a new dimidiate pixel model based on a novel additive vegetation index to calculate the Huangtai algal coverage for each pixel using Landsat multispectral satellite images with 30-m resolution. The results showed that the additive vegetation index with R² = 0.994 is a better indicator than the normalized difference vegetation index, enhanced vegetative index, and ratio vegetative index, with the accuracy of the new model reaching 86.61%. Monthly Landsat images from 2006 to 2016 were used to calculate the Huangtai algal coverage. Analysis of the inter-monthly variation indicated increased coverage from May to July, with an annual maximum and minimum of 14.43% and 0.33% in 2008 and 2013, respectively. This study provides a new reference map of Huangtai algal cover, which is important for monitoring and protecting the Lake Ulansuhai environment.
... Moreover, allelochemicals released by macrophytes could be used as natural biocides for ecological security to control various algae in rivers, lakes, and seas due to their characteristics including biodegradability, a natural origin, and less pollution than traditional algaecides [19,20]. In recent years, with the frequent occurrence of harmful algal blooms globally, the use of plant allelopathy to control algal blooms has attracted unique and widespread attention [19,21,22]. More than 20 types of plant allelochemicals have been discovered, including terpenes, fatty acids, phenolic acids, etc. [20,23]. ...
In recent years, with the frequent global occurrence of harmful algal blooms, the use of plant allelopathy to control algal blooms has attracted special and wide attention. This study validates the possibility of turning water dropwort into a biological resource to inhibit the growth of harmful Microcystis aeruginosa blooms via allelopathy. The results revealed that there were 33 types of allelopathic compounds in the water dropwort culture water, of which 15 were phenolic acids. Regarding water dropwort itself, 18 phenolic acids were discovered in all the organs of water dropwort via a targeted metabolomics analysis; they were found to be mainly synthesized in the leaves and then transported to the roots and then ultimately released into culture water where they inhibited M. aeruginosa growth. Next, three types of phenolic acids synthesized in water dropwort, i.e., benzoic, salicylic, and ferulic acids, were selected to clarify their inhibitory effects on the growth of M. aeruginosa and their mechanism(s) of action. It was found that the inhibitory effect of phenolic acids on the growth of M. aeruginosa increased with the increase of the exposure concentration, although the algae cells were more sensitive to benzoic acid than to salicylic and ferulic acids. Further study indicated that the inhibitory effects of the three phenolic acids on the growth of M. aeruginosa were largely due to the simultaneous action of reducing the number of cells, damaging the integrity of the cell membrane, inhibiting chlorophyll a (Chl-a) synthesis, decreasing the values of F0 and Fv/Fm, and increasing the activity of the antioxidant enzymes (SOD, POD, and CAT) of M. aeruginosa. Thus, the results of this study indicate that both culture water including the rich allelochemicals in water dropwort and biological algae inhibitors made from water dropwort could be used to control the growth of noxious algae in the future.
... If they exceed the environmental load standard, they cause environmental problems such as odour, water pollution, soil pollution, air pollution, etc. and negatively affect the human body and the natural ecosystem. In particular, because the overuse of compost and liquid fertilization of livestock excretions sprayed on farmlands is recognized as a major source for the generation of green algae in soil and rivers, environmental regulations such as revision of the Livestock Excretions Act are continuously being strengthened [3,4]. ...
Litter and compost were obtained at a cowshed of a livestock farm in Andong city in Korea. The morphological change of nitrogen and phosphorous from these samples were examined and suggested a more useful and realistic way for reducing them. Constituents and their content of sample were identified by XRF. The nitrite ion (NO2 −), nitrate ion (NO2 −) and phosphate ion (PO4 3−) and ammonium ion (NH4 +), total phosphorous (T-P) and total nitrogen (T-N) released from sample were analyzed using ion chromatograph and UV/Vis spectrometry. As the results of this study, the ammonia in the early stage of cow excretion is a need to make an ammonia gas state that can be immediately volatile by increasing the pH. Nitrogen and phosphorous, the main source of nutrition in green algal bloom can be reduced by transforming insoluble salts such as calcium phosphate (CaHPO4·3H2O) and struvite (NH4MgPO4·6H2O), respectively, with addition of Ca and Mg after stimulating fermentation of compost.
... Its spread to diverse production areas after the discovery of its economic value, showing fast diffusion and the ability to adapt to the most diverse climate conditions, from hot and dry, to humid and cold weather [2]. It presents a wide range of uses, including cellulose production, recovery of degraded areas, forests restoration, oils for pharmaceutical industries, ornamentation, windbreaks, firewood and charcoal production [3,4]. However, among the limiting factors to the crop, phytopathogenic agents, mainly fungi, can be present in different cycle stages, occurring in many places, species and seasons of the year, which can cause considerable reduction in the development and yield of eucalyptus [5]. ...
After long periods of storage, plant pathogen isolates lose their sporulation capacity. The objective of this study was to evaluate re-isolation methodologies for recovering sporulation of Pestalotiopsis grandis-urophylla isolates after subjection to a long period of storage. Isolates of P. grandis-urophylla were kept for 14 months on Petri dishes with PDA medium at 10°C. After this period, the isolate colonies showed reduced mycelial growth and no sporulation. The isolates were inoculated on healthy Eucalyptus grandis-urophylla leaves, and after ten days they were subjected to three re-isolation methods: scraping of the lesions (S) removing of injured plant tissue fragments, followed by disinfestation (D) and without disinfestation (WD). Then, the purified isolates were evaluated for the recovery of its sporulation ability. The different methods for re-isolation resulted in the occurrence of differences among the isolates, showing that sporulation is an isolate-dependent feature. The three methods (S, WD and D) allowed the sporulation recovery of P. grandis-urophylla, even after these isolates have been subjected to 14 months.
... Therefore, how to effectively control algal blooms is still one of the main tasks of water pollution control. At present, algal-bloom control mainly adopts physical disposal (Rajasekhar et al., 2012;Park et al., 2017;Kong et al., 2019;Wu et al., 2011), chemical treatment (Tsai et al., 2019;Chen et al., 2014;Shi et al., 2018;Silva et al., 2018a;Hamed et al., 2017;Chen et al., 2016), biological manipulation and ecological management (Zhao et al., 2019). Cu has been used to kill microalgae for several years. ...
Using copper (Cu) to treat algal blooms is a commonly accepted method worldwide. However, the release of Cu may cause environmental and health risk. It is required to exploit an efficient way to reduce the Cu concentration but improve the algicidal effectiveness. Here, a Cu ionization cell (CIC) was designed and utilized in a flow-through system for inactivation of two bloom-forming microalgae species, Chlorella vulgaris and Microcystis aeruginosa. The results showed that the in-situ Cu release in the CIC treatment cause efficient microalgae inactivation. The 96 h-growth inhibition for C. vulgaris and M. aeruginosa reached 98.5 ± 3.1% and 75.9 ± 2.0% at a flow rate of 5 mL/min with the effluent Cu concentration of 554 ± 9 μg/L and 613 ± 17 μg/L, respectively. The maximum quantum yield (Fv/Fm) inhibitions of C. vulgaris and M. aeruginosa were 37.0 ± 1.6% and 70.9 ± 2.1%. The electric field enhanced CIC treatment has a locally higher Cu level because of the in-situ release. The CIC improved the microalgae inactivation performance by increasing the microalgae cell membrane permeability with excessive Cu uptake. The energy consumption was only 16.8 J/L. The in-situ Cu treatment in this work provides a microalgae inactivation method with the more environment-friendly and cost-effective prospect.
... Various studies have also shown that algae can release a variety of neurotoxin toxins in aquatic sources. These toxins can affect the nervous system and can also be a risk factor for various cancers such as liver cancer 5 . ...
This article is a Letter to the Editor and does not include an Abstract.
... The water quality of rivers, lakes, and groundwater which are the main drinking water sources is getting worse compared to decades ago due to the development of industry and agriculture (Fu et al. 2019;Li et al. 2018). Especially, the eutrophication has become the main problem in rivers and lakes (Zhao et al. 2019). The general process in drinking water treatment includes coagulation, sedimentation, filtration, and disinfection. ...
Eutrophication has become great concern in recent years due to the fact that rivers, lakes, and reservoirs are the main drinking water source. Studies have been performed to enhance the removal of algae with ClO2 pre-oxidation, but there was high potential in the formation of chlorite and chlorate. In this study, ultra-sonication was employed to assist algae removal and control disinfection by-products formation in ClO2 pre-oxidation processes. It was found that solo ultra-sonication for 10 min (algae removal 86.11 ± 2.16%) could achieve similar algae removal efficiency as that with solo ClO2 (0.5 mg/L) pre-oxidation for 10 min (algae removal 87.10 ± 3.50%). In addition, no formations of chlorite and chlorate were detected in solo ultra-sonication process. Five-minutes ultra-sonication followed by 5-min 0.5 mg/L ClO2 treatment (total treatment time 10 min; algae removal 93.55 ± 3.22%) provided a better performance on algae removal compared to the solo ClO2 (0.5 mg/L) pre-oxidation for 10 min. Moreover, chlorite was undetectable. It suggests that the utilization of ultra-sonication in ClO2 pretreatment for algae removal has highly prevented the formations of chlorite and chlorate.
To better predict the timely variation of algal blooms and other vital factors for safer drinking water production, a new AI scanning–focusing process was investigated for improving the simulation and prediction of algae counts. With a feedforward neural network (FNN) as a base, nerve cell numbers in the hidden layer and the permutation and combination of factors, etc., were fully scanned to select the best models and highly correlated factors. All the factors involved in the modeling and selection included the date (year/month/day), sensor data (temperature, pH, conductivity, turbidity, UV254-dissolved organic matter, etc.), lab measurements (algae concentration) and calculated CO2 concentration. The new AI scanning–focusing process resulted in the best models with the most suitable key factors, which are named closed systems. In this case study, models with highest prediction performance are the (1) date–algae–temperature–pH (DATH) and (2) date–algae–temperature–CO2 (DATC) systems. After the model selection process, the best models from both DATH and DATC were used to compare the other two methods in the modeling simulation process: the simple traditional neural network method (SP), where only date and target factor as inputs, and a blind AI training process (BP), which considers all available factors as inputs. Validation results show that all methods except BP had comparable results for algae prediction and other water quality factors, such as temperature, pH and CO2, among which DATC displayed an obviously poorer performance through curve fitting with original CO2 data compared to that of SP. Therefore, DATH and SP were selected for the application test, where DATH outperformed SP due to the uncompromised performance after a long training period. Our AI scanning–focusing process and model selection showed the potential for improving water quality prediction by identifying the most suitable factors. This provides a new method to be considered in the enhancing of numerical prediction for the factors in water quality prediction and broader environment-related areas.
Natural capsaicin extracted from pungent plants can impede marine organisms and achieve antifouling effects, and it will not kill marine fouling organisms. Its derivatives inherit the good antifouling effects and toxicity. When it is introduced into an antifouling system, capsaicin can meet the environmental requirements of antifouling coatings. Using N-hydroxymethyl phthalimide and aromatic compounds as raw materials, six new active structural derivatives containing capsaicin were synthesized by the Friedel craft alkylation reaction, and their structures were determined by IR, NMR and MS. The antibacterial and algal inhibitory properties of the compound were tested, and the results revealed it had certain inhibitory effects on Marine bacteria and algae, with strong antibacterial and algal inhibitory properties observed of products D, E and F. The minimum inhibitory concentration was 0.1875 mg/mL, and the highest antibacterial rate of 3 mg/mL was 93.05%. The highest algae inhibition rate on the seventh day was 88.34%, the toxicity was low, and the toxicity grade was low. The compound as an antifouling agent added to marine antifouling coatings shows a good antifouling effect, thus laying a good foundation for research on environmentally friendly antifouling coatings.
An effective algicidal bacterium, Enterobacter hormaechei F2 , was isolated and identified using 16S rDNA sequencing. The increased production of algal catalases and peroxidases as well as the production of reactive oxygen species demonstrated the effective and distinctive algicidal activities of E. hormaechei F2. The comparative effects of different components of bacterial solutions suggested that indirect algicidal disruption was the major mechanism of E. hormaechei F2 performance. Dialysis of the extracellular material revealed that the molecular weight of the algicides was less than 3.5 kDa. These were inferred to be proteins, amino acids, and other small molecules. Gene enrichment analysis shows the pathways such as amino acid metabolism and Type n secretion systems involved in the algicidal process, which can predict that prodigiosin and signaling systems may play a role in the algicidal activity.
Purpose of Review
The aim of this review is to summarize the inactivation and removal technologies used for algal-bloom control and to serve the development of theories and technologies for algal bloom prevention and control in the future.
Recent Findings
The efficiency of inactivation and removal of algal blooms largely depends on the density of bloom-forming microalgae faced when the control measures are adopted. Locally enhanced electric field treatment technology has shown the most potential for low-density algal-bloom control, which could effectively inactivate algal cells with low energy consumption. Magnetic capture technology has outstanding advantages for the separation and capture of high-density algae blooms owing to its high efficiency, easy separation, and low cost.
Summary
This article reviews the physical, chemical, physicochemical, biological, and ecological methods of algal-bloom prevention and control. The key to effective prevention of algal blooms is to select the appropriate method based on the difference in microalgae density. For example, under low-density stages, if the inactivation of algae cells can be realized, the occurrence and development of high-density algal blooms may be prevented, and under high-density stages, if the capture of algae cells can be done effectively, the subsequent environmental hazards brought by algal blooms will be reduced or even eliminated. This paper will help in choosing appropriate methods of algal-bloom prevention and control based on the difference in microalgae density and providing suggestions for future research on algal-bloom control.
The cyanobacteria Microcystis flos-aquae can cause harmful algal blooms in waterbodies, which threaten the normal functioning of aquatic ecosystems and human health. The plant extracts are considered as the promising algaecides. In this study, the effects of ten plant extracts (Cinnamomum camphora, Ginkgo biloba, Firmiana platanifolia, Salix babylonica, Euphorbia humifusa, Erigeron annuus, Solidago canadensis, Alternanthera philoxeroides, Thalia dealbata and Eichhornia crassipes) against M. flos-aquae were investigated. The results showed that all ten plant extracts had a significant inhibitory effect on M. flos-aquae growth after 96 h (P < 0.01). The inhibition rates of S. babylonica, E. humifusa, S. canadensis and A. philoxeroides were over 70.00%. Furthermore, the E. humifusa extract had the best inhibitory effect on the photosynthesis of M. flos-aquae, with the effective quantum yield of photosystem II (YII) and maximal relative electron transport rate (rETRmax) decreasing by 97.50% and 97.00%, respectively, after 96 h. Additionally, the E. humifusa extract was found to be nontoxic to non-target organisms such as Brachydanio rerio and Vallisneria spiralis within 96 h. This study contributes to the existing knowledge and data of freshwater cyanobacteria blooms, and provides insights for their control and the restoration of freshwater systems affected by cyanobacteria blooms.
Locally enhanced electric field treatment (LEEFT) has been considered as a novel and promising technology for efficient microorganism inactivation in recent years. Previous studies were primarily conducted on bacteria and viruses. Here, polydopamine-protected copper-oxide-nanowire-modified copper mesh (PDA-CuONW-Cu) electrodes were fabricated and utilized in a flow-through LEEFT device to treat two microalgae species, Chlorella vulgaris and Microcystis aeruginosa. The results showed that the LEEFT achieved efficient microalgae inactivation and growth control. The inhibition of Fv/Fm were 46.7% and 34.3% for C. vulgaris and M. aeruginosa, respectively, after five LEEFT cycles at a flow rate of 1.2 mL/min and a 10 V alternating voltage with a frequency of 10⁴ Hz. The fluorescence staining and the flow cytometer measurement verified the inactivation of microalgae cells, with dead cell ratios increasing to 61.3% and 56.5% for C. vulgaris and M. aeruginosa, respectively. Both species could still grow after removing the electric field, indicating that the LEEFT is a physical treatment process without residual anti-microbial effects. Nevertheless, with five LEEFT cycles, the 96 h-growth inhibition reached 60.1% and 66.2% for C. vulgaris and M. aeruginosa, respectively. The LEEFT can still be a promising control method for microalgae blooms when the LEEFT electrodes are durable enough for long-term circular treatment.
The Microcystis aeruginosa (M. aeruginosa) blooms and Spartina alterniflora (S. alterniflora) invasion have caused serious damage to local ecological environment. This study validated the possibility of transforming the abandoned S. alterniflora into a biological resource to inhibit M. aeruginosa blooms through allelopathy. The results showed that the inhibitory effect became stronger with the increasing S. alterniflora concentration by decreasing chlorophyll a and weakening photosynthesis when S. alterniflora aqueous extract concentration was over 0.05 g/mL. The results of GC-MS showed that Cyclohexane, Heptane, 2-Cyclohexen-1-one, Hexadecanoic acid, 2,4-Di-tert-butylphenol and Hydrocinnamic acid may be the main allelochemicals. In addition, the S. alterniflora aqueous extract had little effect on the relative abundance and diversity of microbial communities in the culture system. This study provided a novel idea of controlling the M. aeruginosa blooms using the rapidly expanding S. alterniflora.
The forestry industry is known for negatively affecting stream quality when proper management is not applied. Nutrient retention by soils and streamside vegetation buffer strips could attenuate these impacts. We tested the response of different streams to the nutrients and sediments released by a) fertilization and b) clear-cutting of Eucalyptus globulus plantations growing on volcanic soils in southern Chile. We expected the exports to decrease as the remnant streamside native forest width (SNFW) increased. The response to fertilization was restricted to the days immediately after the nutrient addition. On the contrary, most of the nutrients analysed (nitrate, ammonium, dissolved organic nitrogen, phosphate, and total phosphorus) showed a long-term response to clear-cutting. The observed trends were not affected by the SNFWs included in this study (2.5-22 m). Regarding sediments, there were no differences compared to the control watershed, probably due to improvements in the implemented management practices. We conclude that a SNFW < 22 m is not sufficient to avoid the loss of nutrients released by clear-cutting, as it is for sediments. The analysed SNFWs were smaller than those established by Chilean regulations (maximum 30 m) and our results support claims for wider riparian widths in order to effectively filter the nutrients and sediments that influence streams.
Although areas planted with eucalyptus have increased under the subtropical conditions of southern Brazil, fertilization has followed practices from nearby tropical regions. The objective of this study was to determine the response of Eucalyptus urograndis to N, P, and K in two regions of Parana State (Jaguariaíva and Ventania) on a sandy oxisol following two harvest cycles of Pinus taeda. Site preparation prior to the new experiment included the application of rock phosphate (26.2 kg ha−1 of P) by in-row subsoiling. Five rates of N and P (0, 13, 26, 52, and 105 kg ha−1) and K (0, 29, 58, 116, and 232 kg ha−1) were separately tested. Treatment response was evaluated by determining maximum technical efficiency, height, and diameter at breast height (DBH) at 3, 6, 9, 12, 18, 24, 30, and 36 months after planting, and volume at 36 months. At all assessments, N additions did not influence growth parameters indicating that N demands were met by organic matter/litter mineralization. Phosphorus enhanced growth until the 18th month, with maximum gains at months 9 and 6 for Jaguariaíva and Ventania (56 and 59% of DBH for the 105 kg ha−1 P rate, respectively). Potassium improved growth only after the 24th month; maximum rate occurred at 166 kg ha−1 of K with a volume of 163 m3 ha−1 at the Jaguariaíva site at 36 months. In conclusion, findings indicated that Eucalyptus urograndis grown in southern Brazil could be responsive to P and K fertilization, but not to the addition of N fertilizer.
Existing models for predicting microcystin concentration in water body generally use chlorophyll or cyanobacteria concentration as input variables, although microcystins only originate from toxigenic strains of a few species. Moreover, the nonconcurrency between harmful algal growth and toxin release has yet to be quantified. Therefore, this study explored a new prediction method that considers these toxin production mechanisms for the eutrophic Yangcheng Lake, a large-scale drinking water source in China. The Lake was monitored weekly at six sampling sites from July to October in 2012, including the detection of toxigenic Microcystis (expressed as mcyA copy number) by qPCR. Compared with chlorophyll a, cyanobacteria, and total Microcystis abundance, toxigenic Microcystis concentration was more significant in predicting extracellular microcystin. Site-specific nonlinear regression models that link mcyA to microcystins were established. Parameters for toxin release delay (i.e., one or two weeks) were embedded in these models. Further analysis ascribed the different release timescale to NH3-N:TN and TN:TP ratios of approximately 0.015 and 9.2, respectively, which may decrease the delay in microcystin release. Model applications in determining mcyA monitoring frequency and its warning thresholds were discussed.
Germination bioassay was carried out to test the biological activity of Achillea santolina L. (ASAE), Artemisia monosperma Del. (AMAE), Pituranthus tortuosus L. (PTAE) and Thymus capitatus L. (TCAE) aqueous extracts (collected from Taif region, KSA) on germination percentage (GP), plumule (PL) and radicle (RL) lengths (mm) besides seedling dry weight (SDW) (mg/seedlings) of Medicago polymorpha L. The inhibitory effect of P. tortuosus was insignificant compared to the other three donor species which attained the strongest allelopathic potential in the following order: A. santolina > A. monosperma > T. capitatus. Growth experiment using crude powder of the four donor species was conducted to examine their effects on leaf area index (LAI), photosynthetic pigments, total available carbohydrates (TAC) and Total protein (TP).It is worth mention that each the four donor species crude powders mixed with clay loam soil appeared to have a great inhibitory allelopathic effect on LAI, total photosynthetic pigment and chlorophyll a (Chl. A.) while carotenoids exhibited a slight increase with the application of the four donor species crude powders. TAC and TP were significantly decreased with increasing the crude powder concentrations while a slight decrease was recorded for carbon/nitrogen (C/N) ratio. There is possibility of using these allelochemicals directly or as structural leads for the discovery and development of environment friendly herbicides to control weeds. The study recommended that these species must be phytochemically examined in future for their allelochemicals in order to provide information on the possibilities of using one or more of these species as bioherbicides.
Harmful cyanobacteria bloom contributes to economic loss as well as the threat to human health. Agricultural waste products, particularly straw, have been used to control bloom while arbor plant is the potential candidate for limiting antialgal activity. This study investigated the use of Dracontomelon duperreanum defoliation extract (DDDE) to inhibit the activity of Microcystis aeruginosa. The primary goal of the research was to explore the solution to control cyanobacterial bloom. The photosynthetic activity, cell morphology, membrane integrity, and esterase activity of M. aeruginosa were determined using phytoplankton analyzer pulse amplitude modulation (Phyto-PAM) and flow cytometry before and after exposure to DDDE. The inhibitory rate of M. aeruginosa was about 99.6 % on day 15 when exposed to 2.0 g L−1. A reduction of chlorophyll a (Chl-a) activity and changes in cell membrane suggested the algistatic property of DDDE. Inhibition of photosynthetic activity was reflected by changing mean Chl-a fluorescence intensity (MFI) which was about 52.5 % on day 15 when exposed to 2.0 g L−1 DDDE as well as relative electron transport rates (rETRs) of algal cell. These changes might contribute to the suppression of M. aeruginosa. Algal cell exposed to DDDE may lead to cell volume reduction or slow growth. This resulted in a decreased proportion of normal or swollen granular cells after DDDE treatment.
Terpenoids are abundant in the foliage of Eucalyptus, providing the characteristic smell as well as being valuable economically and influencing ecological interactions. Quantitative and qualitative inter- and intra- specific variation of terpenes is common in eucalypts.
The genome sequences of Eucalyptus grandis and E. globulus were mined for terpene synthase genes (TPS) and compared to other plant species. We investigated the relative expression of TPS in seven plant tissues and functionally characterized five TPS genes from E. grandis. Compared to other sequenced plant genomes, Eucalyptus grandis has the largest number of putative functional TPS genes of any sequenced plant. We discovered 113 and 106 putative functional TPS genes in E. grandis and E. globulus, respectively. All but one TPS from E. grandis were expressed in at least one of seven plant tissues examined. Genomic clusters of up to 20 genes were identified. Many TPS are expressed in tissues other than leaves which invites a re-evaluation of the function of terpenes in Eucalyptus.
Our data indicate that terpenes in Eucalyptus may play a wider role in biotic and abiotic interactions than previously thought. Tissue specific expression is common and the possibility of stress induction needs further investigation. Phylogenetic comparison of the two investigated Eucalyptus species gives insight about recent evolution of different clades within the TPS gene family. While the majority of TPS genes occur in orthologous pairs some clades show evidence of recent gene duplication, as well as loss of function.
Predicting tree biomass and growth increments via allometric equations is routine in forestry, but this approach is problematic in old-growth forests unless equations are derived from trees spanning the full size range. Using intensive measurements of 27 standing Eucalyptus regnans trees 61.1–99.8 m tall and 80–430 years old in Tasmania, Victoria, and New Zealand, we develop allometric equations to predict aboveground attributes, including biomass and annual growth increments, of trees >60 m tall using ground-based measurements. Power functions of diameter underestimate biomass growth increments unless measurements are made above buttressing on the lower trunk. Growth anomalies apparent in several trees suggest that wounded E. regnans expend considerable energy to outgrow decay fungi and prevent structural collapse. Despite declining growth efficiency – defined as biomass growth per unit mass of photosynthetic tissues – with increasing tree size and age, biomass growth increments of E. regnans increase as trees enlarge with age until extrinsic forces cause mortality. The largest living E. regnans has an aboveground biomass of 215 Mg and a growth increment of 0.784 Mg year−1, not accounting for mass loss due to decay. An even larger E. regnans tree – killed by fire in 2003 – had an aboveground biomass of ∼270 Mg, an estimated growth increment of ∼1 Mg year−1, and was ∼480 years old at the end of its life. Prior to a stand-replacing fire in 2009, Australia’s tallest forest had a maximum aboveground biomass of 1504 Mg ha−1 and a maximum aboveground carbon mass of 706 Mg ha−1.
Here we draw attention to the potential for pelagic bloom-forming cyanobacteria to have substantial effects on nutrient cycling and ecosystem resilience across a wide range of lakes. Specifically, we hypothesize that cyanobacterial blooms can influence lake nutrient cycling, resilience, and regime shifts by tapping into pools of nitrogen (N) and phosphorus (P) not usually accessible to phytoplankton. The ability of many cyanobacterial taxa to fix dissolved N2 gas is a well-known potential source of N, but some taxa can also access pools of P in sediments and bottom waters. Both of these nutrients can be released to the water column via leakage or mortality, thereby increasing nutrient availability for other phytoplankton and microbes. Moreover, cyanobacterial blooms are not restricted to high nutrient (eutrophic) lakes: blooms also occur in lakes with low nutrient concentrations, suggesting that changes in nutrient cycling and ecosystem resilience mediated by cyanobacteria could affect lakes across a gradient of nutrient concentrations. We used a simple model of coupled N and P cycles to explore the effects of cyanobacteria on nutrient dynamics and resilience. Consistent with our hypothesis, parameters reflecting cyanobacterial modification of N and P cycling alter the number, location, and/or stability of model equilibria. In particular, the model demonstrates that blooms of cyanobacteria in low-nutrient conditions can facilitate a shift to the high-nutrient state by reducing the resilience of the low-nutrient state. This suggests that cyanobacterial blooms warrant attention as potential drivers of the transition from a low-nutrient, clearwater regime to a high-nutrient, turbid-water regime, a prediction of particular concern given that such blooms are reported to be increasing in many regions of the world due in part to global climate change.
Vegetation plays a key role in maintaining soil quality, but long-term
changes in soil quality due to plant species change and successive planting
are rarely reported. Using the space-for-time substitution method, adjacent
plantations of Pinus and first, second, third and fourth generations of
Eucalyptus in Guangxi, China were used to study changes in soil quality caused by
converting Pinus to Eucalyptus and successive Eucalyptus planting. Soil chemical and biological
properties were measured and a soil quality index was calculated using
principal component analysis. Soil organic carbon, total nitrogen, alkaline
hydrolytic nitrogen, microbial biomass carbon, microbial biomass nitrogen,
cellobiosidase, phenol oxidase, peroxidase and acid phosphatase activities
were significantly lower in the first and second generations of
Eucalyptus plantations compared with Pinus plantation, but they were significantly higher
in the third and fourth generations than in the first and second
generations and significantly lower than in Pinus plantation. Soil total and
available potassium were significantly lower in Eucalyptus plantations (1.8–2.5 g kg−1
and 26–66 mg kg−1) compared to the Pinus plantation (14.3 g kg−1 and
92 mg kg−1), but total phosphorus was significantly higher
in Eucalyptus plantations (0.9–1.1 g kg−1) compared to the Pinus plantation (0.4 g kg−1). As an integrated indicator, soil quality index was highest in
the Pinus plantation (0.92) and lowest in the first and second generations
of Eucalyptus plantations (0.24 and 0.13). Soil quality index in the third and
fourth generations (0.36 and 0.38) was between that in Pinus plantation and in
first and second generations of Eucalyptus plantations. Changing tree
species, reclamation and fertilization may have contributed to the change
observed in soil quality during conversion of Pinus to Eucalyptus and successive
Eucalyptus planting. Litter retention, keeping understorey coverage, and reducing soil
disturbance during logging and subsequent establishment of the next rotation
should be considered to help improving soil quality.
These past years have seen an enormous development of the area of natural antioxidants and antimicrobials. Eucalyptus globulus is widely cultivated in subtropical and Mediterranean regions in intensive short rotation coppice plantations. In the Portuguese context, E. globulus is the third species in terms of forest area. The stump is the basal part of the tree, including the near-the-ground stem portion and the woody roots that remain after stem felling. The purpose of this work was to study the phytochemical profile and to evaluate the antioxidant and antimicrobial properties of several crude stump wood and stump bark extracts of E. globulus, comparing it with similar extracts of E. globulus wood (industrial chips). The results showed the presence of high concentrations of total phenolic compounds (>200 mg GAE/g extract) and flavonoids (>10 mg QE/g extract) in E. globulus stump extracts. Generally the stump wood extracts stands out from the other ones, presenting the highest percentages of inhibition of linoleic acid oxidation. It was also possible to conclude that the extracts were more active against Gram-positive bacteria, presenting low MIC values. This study thus provides information supporting the economic valorization of E. globulus stump wood.
To take advantage of affordable high-throughput next-generation sequencing technologies to characterize microbial community composition often requires the development of improved methods to overcome technical limitations inherent to the sequencing platforms. Sequencing low sequence diversity libraries such as 16S rRNA amplicons has been problematic on the Illumina MiSeq platform and often generates sequences of suboptimal quality.
Here we present an improved dual-indexing amplification and sequencing approach to assess the composition of microbial communities from clinical samples using the V3-V4 region of the 16S rRNA gene on the Illumina MiSeq platform. We introduced a 0 to 7 bp "heterogeneity spacer" to the index sequence that allows an equal proportion of samples to be sequenced out of phase.
Our approach yields high quality sequence data from 16S rRNA gene amplicons using both 250 bp and 300 bp paired-end MiSeq protocols and provides a flexible and cost-effective sequencing option.
The ecosystem of the highly eutrophic Lake Taihu (China) is seriously affected by recurrent cyanobacterial blooms, but little is known about the contribution made by cyanobacteria to the food web. In this study, we investigated the fate of detritus of the cyanobacterium Microcystis in the food web of Lake Taihu through a 19-day mesocosm experiment using stable-isotopic tracers of carbon (13C) and nitrogen (15N). 13C- and 15N-labeled Microcystis detritus was added to the mesocosm tanks and tracked through different elements of the food web. We found clear enrichment with both 13C and 15N in some zooplankton species, including Daphnia, Diaphanosoma, and Sinocalanus, which suggests that these zooplankters can utilize cyanobacterial detritus as a food source. Benthic animals, chironomid larvae and Limnodrilus, also showed pronounced increases in 13C and 15N, but the isotope increase was relatively smaller in the gastropods, Radix sp. and Bellamya sp., implying that they either exploited this food source differently or responded slower than the zooplankton, which apparently grew faster than the snails. Our study suggests that cyanobacterial detritus, originating almost wholly from the bloom-forming Microcystis, is an important food source for both planktonic and benthic food webs in eutrophic lakes such as Lake Taihu.
Land-use change and climate variability have the potential to alter river flow and groundwater resources dramatically, especially by modifying actual evapotranspiration. Seven catchments with intermittent flow dominated by either winter-active perennial pastures (4 catchments) or Eucalyptus globulus plantations (3 catchments), located in 3 geologic settings of southeastern Australia, were studied for over 6 years to determine the primary controls on water resources. Groundwater levels in the pasture sites were stable through the 2011–2016 study period, while levels in the plantations declined in the same period. Streamflow occurred mainly during winter. Annual streamflow showed no difference clearly attributable to pasture versus plantation land use. The presence of grass buffers along streams enhances groundwater recharge and saturation-dependent overland flow, reducing the impacts of the plantations on streamflow. Site water balances indicated that the average annual actual evapotranspiration was 87–93% of precipitation for pasture catchments and 102–108% of precipitation for plantation catchments. Actual evapotranspiration greater than precipitation at the plantations was attributed to uptake of groundwater by the root system in parts of the catchments. Thus, change to groundwater storage is a critical component in the water balance. Actual evapotranspiration from pasture catchments was higher than previously estimated from global pasture and cropping data, instead matching global precipitation versus actual evapotranspiration curves for treed catchments.
Allelopathy and resource competition are considered to be two primary mechanisms responsible for loss of biodiversity in plantations of Eucalyptus species. However, these two processes are usually studied separately, and they have been rarely tested on native woody species. In this study, we used a bioassay to assess sensitivities of twenty broad-leaved tree species on roots, stem growth and seed germination to leaf aqueous extracts of Eucalyptus urophylla S.T. Blake and categorized them into two types: inhibited and uninhibited (including stimulated and unaffected). To compare the relative importance of allelopathy and resource competition, we planted these two species groups into the E. urophylla plantation separately and treated with three gradients of irrigation-nutrients. The results showed that the allelopathic effects of aqueous extract of E. urophylla were species-specific and could be inhibitory, neutral or stimulatory. Compared to the inhibited species, the uninhibited species grew faster and survived better after they were planted in an E. urophylla plantation for approximately 10 years, suggesting that allelopathy from E. urophylla is an important restraining factor on native woody communities. Individuals from both species groups grew faster following higher resource treatment at the early but not the late stage of growth. Saplings did not vary in their survival rates across resource gradients. This indicates that resource competition between E. urophylla and native woody species has only a limited role in reducing the diversity of native species in an E. urophylla plantation. We conclude that allelopathy is more important than resource competition in mediating the reduction in plant biodiversity in E. urophylla plantations. Our study suggests that mixing certain types of species (e.g. Helicia cochinchinensis, Pterospermum lanceaefolium, Cinnamomum burmanni, Machilus chinensis, Acmena acuminatissima and Castanopsis chinensis) in E. urophylla plantations can mitigate against plant diversity loss.
Algaecides can be sued to effectively control a rise in cyanobacteria population. However, too high of a concentration or long-term applications can pose detrimental effects on the ecosystem. This work investigated the potential of a copper-based algaecide to effectively manage the cyanobacteria population in a public water system when applied at a lower concentration. The cyanobacteria population (via phycocyanin) and chlorophyll-a concentration were tracked with optical probes over 14 days. The cyanobacteria population responded to the treatment within 2 days with the largest declines observed deeper in the water column and only marginal changes at the surface. The lowest cyanobacteria population was observed after 7 days for all depths in the water column with at 53% decrease at the surface. However, the cyanobacteria population increased by 14-days after treatment. The population at the 1 m depth had increased by 151%; surpassing the initial population. There were notable differences between cyanobacteria and chlorophyll-a data. For example, from 7 to 14-days chlorophyll-a at the surface decreased by 26% whereas cyanobacteria had exhibited an 74% increase. This may be highlighting a shift to cyanobacteria dominance in the phytoplankton community. This work produced strong evidence that algaecide application was successful in suppressing the in-situ cyanobacteria population. However, it cannot be determined if the treated population rebounded or if new cyanobacteria entered the treatment area due to external environmental conditions such as flow and/or wind conditions. Careful application of lower algaecide concentrations may yield effective control of HABs with minimal harm to the surrounding ecosystem.
The extensive use of 2,4-dichlorophenoxiacetic acid (2,4-D) in agriculture is an important source of pollution to water and soil. Toxicity of commonly used herbicides to non-target, planktonic photosynthetic organisms has not been described completely yet. Therefore, we determined the effect of subinhibitory 2,4-D concentrations on the Chlorophycean alga Ankistrodesmus falcatus and on a toxigenic strain of the cyanobacterium Microcystis aeruginosa. Population growth, photosynthetic pigments, macromolecular biomarkers (carbohydrates, lipids, and protein), and antioxidant enzymes (catalase [CAT], glutathione peroxidase [GPx], and superoxide dismutase [SOD]) were quantified, and the integrated biomarker response (IBR) was calculated. Scanning electron microscope (SEM) and transmission electron microscope (TEM) observations were also performed. The 96-h median inhibitory concentration (IC50) for 2,4-D was 1353.80 and 71.20mgL(-1) for the alga and the cyanobacterium, respectively. Under 2,4-D stress, both organisms increased pigments and macromolecules concentration, modified the activity of all the evaluated enzymes, and exhibited ultrastructural alterations. M. aeruginosa also increased microcystins production, and A. falcatus showed external morphological alterations. The green alga was tolerant to high concentrations of the herbicide, whereas the cyanobacterium exhibited sensitivity comparable to other phytoplankters. Both organisms were tolerant to comparatively high concentrations of the herbicide; however, negative effects on the assessed biomarkers and cell morphology were significant. Moreover, stimulation of the production of cyanotoxins under chemical stress could increase the risk for the biota in aquatic environments, related to herbicides pollution in eutrophic freshwater ecosystems.
Annually occurred cyanobacterial bloom aggravated eutrophication situation and changed the lacustrine ecosystem components. Recently, high concentration of bloom cyanobacteria had been found to accelerate total nitrogen (TN) removal. However, the contribution of cyanobacterial bloom to TN removal remained unclear. In this study, microcosms with different density of bloom cyanobacteria were constructed and quantitative PCR and structural equation modelling (SEM) were used to analyze the microbes, environmental variables and the causal relationship to TN removal. Total bacteria, ammonia-oxidizing archaea and nirS gene abundances were indirectly influenced by cyanobacteria biomass and all of them had a direct effect on TN removal. SEM confirmed that cyanobacteria made a direct contribution to ammonium‑nitrogen (NH4⁺-N) level in water and induced nitrification activity, which favored the process of denitrification by supplying substrate and aggravating the anoxic status. These results strongly suggested that an increased cyanobacteria biomass had strong impacts on mineralization, nitrification and denitrification by mediating TN, dissolved organic carbon and dissolved oxygen directly and subsequently influenced the nitrifiers and denitrifiers.
Submerged macrophytes and filter-feeding aquatic animals have been widely used in ecological engineering to control eutrophic pollution. However, the use of filter-feeding aquatic animals to control eutrophic water bodies remains debatable. As such, more work is needed to understand the combined effects of submerged macrophytes and aquatic animals on the restoration of eutrophic water bodies. In this study, we first conducted a mesocosm experiment to evaluate the combined effects of submerged macrophytes and aquatic animals on water body restoration, and then applied these results in the field. We found that silver carp (Hypophthalmichthys molitrix) deteriorated water quality by increasing nutrient and total suspended solid concentrations, and decreased the biomass of submerged macrophytes. However, triangle sail mussels (Hyriopsis cumingii) promoted the establishment of a clear-water state by grazing on phytoplankton and detritus, and stimulating submerged macrophyte growth. In practical ecological engineering, we suggest that silver carp can be used at low density (20 g/m³) as a biomanipulation tool, despite their potential to deteriorate water quality. Furthermore, stocking mussels in nets at a biomass of 150 g/m³ can be effectively used to restore eutrophicated water bodies. Finally, Hydrilla verticillata and Potamogeton malaianus, in combination with filter-feeding aquatic animals, are suitable submerged macrophyte species for the restoration of eutrophicated lakes.
Eucalyptus is one of the most important plantation species in South China. Alternate applications of plantation grown hardwood such as eucalyptus need to be developed due to decreased demands of fibers for pulp and paper industry. The feasibility of manufacturing three-layer cross-laminated timber (CLT) using fast-grown small diameter eucalyptus wood (Eucalyptus urophylla × Eucalyptus grandis) was evaluated in this study. L9 (3³) orthogonal tests with three factors and three levels were adopted to study the effects of adhesive spread rate, pressure, and pressing time duration on the block shear strength (BSS), wood failure percentage (WFP), and rate of delamination (RD) of CLT via block shear tests and cyclic delamination tests. The results indicated that the optimal pressing parameters were adhesive spread rate of 160 g/m², pressing pressure of 0.8 MPa, and pressing time duration of 200 min with one-component polyurethane adhesive used. The values of modulus of elasticity (MOE) and modulus of rupture (MOR) in the major and minor strength directions of CLT were 11,466 MPa, 24.5 MPa, 681 MPa, and 8.6 MPa, respectively. The values of transverse shear moduli and interlaminar shear strength in the major and minor strength directions of CLT were 91.8 MPa, 1.3 MPa, 241.6 MPa, and 0.5 MPa, respectively. The mechanical properties of eucalyptus CLT were equivalent to those of commercially available softwood CLT. These results indicate CLT panels manufactured from fast-grown small diameter eucalyptus lumber is promising for structural applications.
This study was focused on the phosphorus mobility among sediments, water and cyanobacteria in eutrophic Lake Dianchi. Four conditions lake water, water and algae, water and sediments, and three objects together were conducted to investigate the effects of cyanobacteria growth on the migration and transformation of phosphorus. Results showed a persistent correlation between the development of cyanobacterial blooms and the increase of soluble reactive phosphorus (SRP) in the lake water under the condition of three objects together. Time-course assays measuring different forms of phosphorus in sediments indicated that inorganic phosphorus (IP) and NaOH-P were relatively more easier to migrate out of sediment to the water and cyanobacteria. Further studies on phosphorus mobility showed that up to 70.2% of the released phosphorus could be absorbed by cyanobacteria, indicating that sediment is a major source of phosphorus when external loading is reduced. Time-course assays also showed that the development of cyanobacterial blooms promoted an increase in pH and a decrease in the redox potential of the lake water. The structure of the microbial communities in sediments was also significantly changed, revealed a great impaction of cyanobacterial blooms on the microbial communities in sediments, which may contribute to phosphorus release. Our study simulated the cyanobacterial blooms of Lake Dianchi and revealed that the cyanobacterial blooms is a driving force for phosphorus mobility among sediments, water and cyanobacteria. The outbreak of algal blooms caused deterioration in water quality. The P in the sediments represented a significant supply for the growth of cyanobacteria.
Harmful algal blooms in Lake Taihu, China, are getting plagued due to excess nutrients loads. Despite several recent strict nutrient management strategies, especially to reduce the external nutrient loads, Lake Taihu still receives large amounts of nutrients from its tributaries. As a result, frequency and intensity of algal blooms have not abated as expected. In this study, a three-dimensional eutrophication model was used to identify the limiting factors for algal growth and the effect of external nutrient loads reduction on water quality. The modeling results showed that the limiting factor for the dominant algae (cyanobacteria) depended on seasonality and location. Water temperature affected algal growth in winter, while light was important for deeper water columns in all seasons. Phosphorus (P) and Nitrogen (N) impacted algal growth from spring to autumn. Results showed that Chlorophyll a (Chl-a) concentrations only decreased about 38%, 26% and 24% in Meiliang Bay, Zhushan Bay and Northwest Zone, respectively when implementing high nutrient reduction scenario (external N and P inputs reduced up to 80% and 50%). External nutrient reduction for both N and P is a prudent and likely most practical solution for reducing bloom potentials and overall trophic state of this currently hypereutrophic system. However, achieving observable algal control is not likely in the short term and other ecological restoration tools will be required to battle with the legacy of several decades of nutrient over-enrichment.
Terrestrial and aquatic ecosystem degradation is widely recognized as a major global environmental and development problem. Although great efforts have been made to prevent aquatic ecosystem degradation, the degree, extent and impacts of this phenomenon remain controversial and unclear, such as its driving mechanisms. Here, we present results from a 17-year field investigation (1998–2014) of water quality and a 12-year remote sensing mapping (2003–2014) of the aquatic vegetation presence frequency (VPF) in Eastern Lake Taihu, a macrophyte-dominated bay of Lake Taihu in China. In the past 17 years, nutrient concentrations and water level (WL) have significantly increased, but the Secchi disk depth (SDD) has significantly decreased. These changes were associated with increased lake eutrophication and a degraded underwater light climate that further inhibited the growth of aquatic vegetation. In Eastern Lake Taihu, increased nutrients, chlorophyll a and WL, and a decreased SDD were all significantly correlated with a decreased VPF. NH4+-N concentration and SDD/WL were the most important controlling factors for VPF. Therefore, increased anthropogenic nutrient inputs and a degraded underwater light climate surely result in a decreased VPF. These results elucidate the driving mechanism of aquatic vegetation degradation and will facilitate Lake Taihu ecological restoration.
Coastal hypoxia is an increasingly recognized environmental issue of global concern to both the scientific community and the general public. We assessed the relative contributions from marine and terrestrially sourced organic matter that were responsible for oxygen consumption in a well-studied seasonal coastal hypoxic zone, the East China Sea off the Changjiang Estuary. Our fieldwork was conducted in August 2011 during reinstatement of a subsurface hypoxia, when we observed a continuous decline of dissolved oxygen along with production of dissolved inorganic carbon resulting from organic carbon remineralization. Based on a three end-member mixing model and determinations of the stable isotopic compositions of dissolved inorganic carbon (δ13CDIC), the end product of particulate organic carbon (POC) degradation, we quantified the δ13C value of the remineralized organic carbon (δ13COCx), which was -18.5±1.0‰. This isotopic composition was very similar to the δ13C of marine sourced POC produced in situ (-18.5±0.3‰) rather than that of the terrestrially sourced POC (-24.4±0.2‰). We concluded that marine sourced organic matter, formed by eutrophication-induced marine primary production was the dominant oxygen consumer in the subsurface hypoxic zone in the East China Sea off the Changjiang Estuary.
We investigated the effects of allelochemical ferulic acid (FA) on a series of physiological and biochemical processes of blue-green algae Microcystis aeruginosa, in order to find sensitive diagnostic variables for allelopathic effects. Algal cell density was significantly suppressed by FA (0.31-5.17 mM) only after 48 h exposure. Inhibitions of photosynthetic parameters (Fv/Fm and Fv'/Fm') occurred more rapidly than cell growth, and the stimulation of non-photochemical quenching was observed as a feed-back mechanisms induced by photosystem II blockage, determining by PAM fluorometry. Inhibitions on esterase activity, membrane potential and integrity, as well as disturbance on cell size, were all detected by flow cytometry with specific fluorescent markers, although exhibiting varied sensitivities. Membrane potential and esterase activity were identified as the most sensitive parameters (with relatively lower EC50 values), and responded more rapidly (significantly inhibited only after 8 h exposure) than photosynthetic parameters and cell growth, thus may be the primary responses of cyanobacteria to FA exposure. The use of PAM fluorometry and flow cytometry for rapid assessment of those sensitive variables may contribute to future mechanistic studies of allolepathic effects on phytoplankton.
Ethnopharmacological relevance:
Traditional herbal medicine has become an important issue on the global scale during the past decade. Among drugs of natural origin, special place belongs to essential oils, known as strong antimicrobial agents that can be used to combat antibiotic-resistant bacteria. Eucalyptus camaldulensis leaves are traditional herbal remedy used for various purposes, including treatment of infections. The aim of this study was to determine antimicrobial potential of two E. camaldulensis essential oils against multi-drug resistant (MDR) Acinetobacter baumannii wound isolates and to examine possible interactions of essential oils with conventional antimicrobial agents.
Materials and methods:
Chemical composition of essential oils was determined by gas chromatography-mass spectrometry analysis (GC-MS). MIC values of essential oils against A. baumannii strains were estimated by modified broth microdilution method. The components responsible for antimicrobial activity were detected by bioautographic analysis. The potential synergy between the essential oils and antibiotics (ciprofloxacin, gentamicin and polymyxin B) was examined by checkerboard method and time kill curve.
Results:
The dominant components of both essential oils were spatulenol, cryptone, p-cimene, 1,8-cineole, terpinen-4-ol and β-pinene. The detected MICs for the E. camaldulensis essential oils were in range from 0.5 to 2μl mL-1. The bioautographic assay confirmed antibacterial activity of polar terpene compounds. In combination with conventional antibiotics (ciprofloxacin, gentamicin and polymyxin B), the examined essential oils showed synergistic antibacterial effect in most of the cases, while in some even re-sensitized MDR A. baumannii strains. The synergistic interaction was confirmed by time-kill curves for E. camaldulensis essential oil and polymyxin B combination which reduced bacterial count under detection limit very fast, i.e. after 6h of incubation.
Conclusions:
The detected anti-A. baumannii activity of E. camaldulensis essential oils justifies traditional use of this plant. The proven E. camaldulensis essential oil synergistic interactions with conventional antibiotics could lead to the development of new treatment strategies of infections caused by MDR A. baumannii strains in the term of antibiotic dose reduction.
The frequency of freshwater cyanobacterial blooms is at risk of increasing as a consequence of climate change and eutrophication of waterways. It is increasingly apparent that abiotic data are insufficient to explain variability within the cyanobacterial community, with biotic factors such as heterotrophic bacterioplankton, viruses and protists emerging as critical drivers. During the Australian summer of 2012-2013, a bloom that occurred in a shallow ephemeral lake over a 6-month period was comprised of 22 distinct cyanobacteria, including Microcystis, Dolichospermum, Oscillatoria and Sphaerospermopsis. Cyanobacterial cell densities, bacterial community composition and abiotic parameters were assessed over this period. Alpha-diversity indices and multivariate analysis were successful at differentiating three distinct bloom phases and the contribution of abiotic parameters to each. Network analysis, assessing correlations between biotic and abiotic variables, reproduced these phases and assessed the relative importance of both abiotic and biotic factors. Variables possessing elevated betweeness centrality included temperature, sodium and operational taxonomic units belonging to the phyla Verrucomicrobia, Planctomyces, Bacteroidetes and Actinobacteria. Species-specific associations between cyanobacteria and bacterioplankton, including the free-living Actinobacteria acI, Bacteroidetes, Betaproteobacteria and Verrucomicrobia, were also identified. We concluded that changes in the abundance and nature of freshwater cyanobacteria are associated with changes in the diversity and composition of lake bacterioplankton. Given this, an increase in the frequency of cyanobacteria blooms has the potential to alter nutrient cycling and contribute to long-term functional perturbation of freshwater systems.The ISME Journal advance online publication, 4 December 2015; doi:10.1038/ismej.2015.218.
Eucalyptus are of tremendous economic importance being the most planted hardwoods worldwide for pulp and paper, timber and bioenergy. The recent release of the Eucalyptus grandis genome sequence pointed out many new candidate genes potentially involved in secondary growth, wood formation or lineage-specific biosynthetic pathways. Their functional characterization is, however, hindered by the tedious, time-consuming and inefficient transformation systems available hitherto for eucalypts. To overcome this limitation, we developed a fast, reliable and efficient protocol to obtain and easily detect co-transformed E. grandis hairy roots using fluorescent markers, with an average efficiency of 62%. We set up conditions both to cultivate excised roots in vitro and to harden composite plants and verified that hairy root morphology and vascular system anatomy were similar to wild-type ones. We further demonstrated that co-transformed hairy roots are suitable for medium-throughput functional studies enabling, for instance, protein subcellular localization, gene expression patterns through RT-qPCR and promoter expression, as well as the modulation of endogenous gene expression. Down-regulation of the Eucalyptus cinnamoyl-CoA reductase1 (EgCCR1) gene, encoding a key enzyme in lignin biosynthesis, led to transgenic roots with reduced lignin levels and thinner cell walls. This gene was used as a proof of concept to demonstrate that the function of genes involved in secondary cell wall biosynthesis and wood formation can be elucidated in transgenic hairy roots using histochemical, transcriptomic and biochemical approaches. The method described here is timely because it will accelerate gene mining of the genome for both basic research and industry purposes.
The underlying mechanisms and consequences of competition and diversity are central themes in ecology. A higher diversity of primary producers often results in higher resource use efficiency in aquatic and terrestrial ecosystems. This may result in more food for consumers on one hand, while, on the other hand, it can also result in a decreased food quality for consumers; higher biomass combined with the same availability of the limiting compound directly reduces the dietary proportion of the limiting compound. Here we tested whether and how interspecific competition in phytoplankton communities leads to changes in resource use efficiency and cellular concentrations of nutrients and fatty acids. The measured particulate carbon : phosphorus ratios (C:P) and fatty acid concentrations in the communities were compared to the theoretically expected ratios and concentrations of measurements on simultaneously running monocultures. With interspecific competition, phytoplankton communities had higher concentrations of the monounsaturated fatty acid oleic acid and also much higher concentrations of the ecologically and physiologically relevant long-chain polyunsaturated fatty acid eicosapentaenoic acid than expected concentrations based on monocultures. Such higher availability of essential fatty acids may contribute to the positive relationship between phytoplankton diversity and zooplankton growth, and may compensate limitations by mineral nutrients in higher trophic levels.
The use of allelochemicals has been proved an environmentally friendly and promising method to control harmful algal blooms. This study was conducted to explore the application potential of Ailanthus altissima (A. altissima) extracts in Microcystis aeruginosa (M. aeruginosa) control for the first time. Four treatments with A. altissima extractions (25mgL(-1), 50mgL(-1), 100mgL(-1), and 200mgL(-1) respectively) and a control group were built to investigate the effects of A. altissima on the growth, cellular microstructure and cell viability, physiological changes, and release of extracellular matters. Results showed that the cell density of M. aeruginosa was effectively inhibited by A. altissima extract, and the inhibition rates were dose-dependent within 5d. Especially for the treatment with 200mgL(-1) of extract, the inhibitory rates remains above 90% after 5d exposure. In addition, A. altissima effectively decreased the amount of extracellular cyanotoxin microcystins and destroyed the photosynthesis-related structure of algae cell during the experimental period. The results demonstrated the A. altissima extracts can be used as an effective and safe algicide to control algal blooms. However, it must be noted that specific compounds responsible for algicidal effect should be isolated and identified to explore inhibition mechanism of A. altissima in future study.
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Microcystis aeruginosa, the most common toxic cyanobacterial bloom, could cause severe environmental problem by producing and releasing lethal cyanobacterial toxins to water body. This study investigated the electron beam irradiation for the inactivation of M. aeruginosa. The treatment process was monitored via the measurement of chlorophyll a concentration, optical density, photosynthesis, and antioxidant enzymes. At low electron beam irradiation dose (1.0 kGy), its performance is not desirable. High dosage of electron beam irradiation (2.0-5.0 kGy) can dramatically decrease chlorophyll a concentration, optical density, and photosynthesis rate and affect activities of antioxidant enzymes. The transmission electron microscopy measurement indicates that electron beam irradiation treatment cause significant damages on integrity and morphology. Our results demonstrate that electron beam irradiation is a promising technique for quick and efficient inactivation of M. aeruginosa in aqueous solution.
Dissolved organic nitrogen (DON) is now considered as one of the most important precursors of nitrogenous disinfection byproducts(N-DBPs), and the algae cells were the main source of DON in eutrophic water sources. In this study, the characterizations of DON (especially proteins) in intracellular organic matter (IOM) were investigated. In addition, the DON removal by using sunlight/immobilized TiO2 was also studied. The results showed that in algae cells, about 185 kinds of proteins were found and isoelectric pH was mostly in acidic side. Apo-α-phycocyanin and Apo-β-phycocyanin are the two main components, whose concentration were 0.187mg/L and 0.136mg/L, respectively. The removal rate of DON by sunlight/TiO2 system was about 29% after 7 hours’ irradiation, moreover, the system altered the molecular weight ranges of 30kD~80kD to the range of 20kD~30kD. Furthermore, proper photo-catalytic oxidation enhanced the coagulation efficiency significantly due to the direct removal and change of proteins.
The effects of the flocculant composed of autoclaved fly-ash brick and chitosan for algae Microcystis aeruginosa removal were investigated. The results showed that when 1 mL flocculant was added in 25 mL algae suspension, which initial density was 106 cells/mL, the removal rate of algae reached 88.4%. In order to enhance the removal efficiency, pre-oxidation with KMnO4 was studied. The results indicated that it could improve algae coagulation removal by 9.44% when it was pre-oxidized by KMnO4 with the concentration of 0.9 mg/L. The cells of M. aeruginosa sunk quickly, thus the algal cells were removed completely. In conclusion, the combined flocculant owns the advantages of low concentration, short reaction time, and could be employed for algae control.
An effective measure to cope with eutrophication of lakes is to remove nutrients that can cause algal blooming by taking advantage of natural water purification processes. Here, the term "purification" is defined, in a wide sense, as the potential role of a water body to contribute to the reduction of pollutants and thus controlling eutrophication. Also regarded as a kind of ecological regulating services, biological purification involves various processes concerning seasonal nutrient fixation, such as uptake by aquatic macrophyte, biofouling onto foliage substrates, feeding by organisms in higher trophic level, and eternal loss or removal of substance from the water. In order to evaluate the water purification ability, a numerical lake ecosystem model (EcoTaihu) was developed and applied to Lakes Taihu. The model includes the biological interactions between pelagic compartments (phytoplankton and zooplankton, detritus, dissolved organic matter, fish, and nutrients). Under dynamic forcing of meteorological and hydrological parameters, the model was run over years to evaluate the annual nutrient cycles and purification functions. The reproducibility of the model was validated for water body by comparison with the field data from the water quality monitoring campaign. Numerical results revealed that self-purification capacity of nitrogen of Lake Taihu in years 2006, 2008, and 2010 is 4.00 × 10(4), 4.27 × 10(4), and 4.11 × 10(4) ton, respectively, whereas self-purification capacity of phosphorus of Lake Taihu in years 2006, 2008, and 2010 is 1.56 × 10(3), 1.80 × 10(3), and 1.71 × 10(3) ton, respectively.
Combined toxicity of spiramycin and amoxicillin was tested in Microcystis aeruginosa. The respective 50% effective concentrations (EC50mix) expressed in toxic unit (TU) values were 1.25 and 1.83 for spiramycin and amoxicillin mixed at 1:7 and 1:1, suggesting an antagonistic interaction at the median effect level. Deviations from the prediction of concentration addition (CA) and independent action (IA) models further indicated that combined toxicity of two antibiotics mixed at 1:1 varied from synergism to antagonism with increasing test concentration. Both the EC50mix of 0.86 (in TU value) and the deviation from two models manifested a synergistic interaction between spiramycin and amoxicillin mixed at 7:1. At an environmentally relevant concentration of 800 ng L−1, combined effect of mixed antibiotics on algal growth changed from stimulation to inhibition with the increasing proportion of higher toxic component (spiramycin). Chlorophyll-a content and expression levels of psbA, psaB, and rbcL varied in a similar manner as growth rate, suggesting a correlation between algal growth and photosynthesis under exposure to mixed antibiotics. The stimulation of microcystin-production by mixed antibiotics was related with the elevated expression of mcyB. The mixture of two target antibiotics with low proportion of spiramycin (<50%) could increase the harm of M. aeruginosa to aquatic environments by stimulating algal growth and production and release of microcystin-LR at their current contamination levels.
Impact of sustained discharge of treated wastewater effluent on wetland water quality
- Saint-Fort
Saint-Fort, R., 2018. Impact of sustained discharge of treated wastewater effluent on wetland water quality. Int. J. Envron. Sci. Nat. Res. 10, 1-11.