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Biomanipulation has been widely used in the ecological restoration of eutrophic lakes for decades. However, biomanipulation is prone to failure if external nutrient loads are not reduced. In order to explore the importance of filter‐feeding fish and bivalves on algal control, an outdoor mesocosm experiment was conducted using different nutrient concentrations. Four treatments simulating daily loads of nutrients in Lake Taihu were studied: current, two times, and three times average daily loads of nutrients with both fish (Aristichthys nobilis) and Asian clam (Corbicula fluminea) and as a control current daily loads without fish or bivalves. Results showed that stocking of filter‐feeding fish and bivalves (80 g m−3 bighead carp; 200 g cm−2 clams) at two times daily nutrient loads could effectively control water column Chl a concentrations and phytoplankton biomass. At higher nutrient concentrations (TN ≥ 260 μg L−1 d−1; TP ≥ 10 μg L−1 d−1), top‐down control of filter‐feeding fish and bivalves was less effective and bottom‐up effects resulted in significant increases of Chl a concentration. Thus, as phytoplankton biomass in freshwater ecosystems is determined by both the top‐down effects of predators and the bottom‐up effects of nutrients, external loadings should be controlled when filter‐feeding fish and bivalves are used for algal control to ensure the efficacy of biomanipulation. [ABSTRACT FROM AUTHOR]

Abstract Biomanipulation has been widely used in the ecological restoration of eutrophic lakes for decades. However, biomanipulation is prone to failure if external nutrient loads are not reduced. In order to explore the importance of filter‐feeding fish and bivalves on algal control, an outdoor mesocosm experiment was conducted using different nutrient concentrations. Four treatments simulating daily loads of nutrients in Lake Taihu were studied: current, two times, and three times average daily loads of nutrients with both fish (Aristichthys nobilis) and Asian clam (Corbicula fluminea) and as a control current daily loads without fish or bivalves. Results showed that stocking of filter‐feeding fish and bivalves (80 g m−3 bighead carp; 200 g cm−2 clams) at two times daily nutrient loads could effectively control water column Chl a concentrations and phytoplankton biomass. At higher nutrient concentrations (TN ≥ 260 μg L−1 d−1; TP ≥ 10 μg L−1 d−1), top‐down control of filter‐feeding fish and bivalves was less effective and bottom‐up effects resulted in significant increases of Chl a concentration. Thus, as phytoplankton biomass in freshwater ecosystems is determined by both the top‐down effects of predators and the bottom‐up effects of nutrients, external loadings should be controlled when filter‐feeding fish and bivalves are used for algal control to ensure the efficacy of biomanipulation.

Montmorillonite modified lime-ceramic sand-lake sediment (LC-sediments) was synthesized and its algae removal efficiency was investigated in this study. Montmorillonite not only improved the morphology and surface area of original LC-sediments, but also promoted the algal removal rate due to its inherent properties such as accumulating an electric charge, acting as a flocculant, and displaying a local bridging effect. Based on parameter optimization including the ratio of raw materials, agent dosage, initial algae density, pH and a determination of overlying water, the effect of hydrodynamic conditions on the algal removal process was researched. Under the optimal condition, the removal rates of turbidity, algae density and chlorophyll a could reach 86, 88 and 68%, respectively. As verified with a response surface model, it was shown that low disturbance (stirring) of the algae could promote algal removal by montmorillonite modified LC-sediment. Furthermore, a water column was utilized to approximatively simulate the flocculation and algae control in shallow lakes. This study solved the problem of reducing the dosage of lake sediment and improving the removal efficiency of algae without causing secondary pollution to the environment. It was expected to provide a certain theoretical basis for clay flocculation-based algae control in a real environment. HIGHLIGHTS Hydrodynamic conditions on algal removal process were studied.; Montmorillonite improved algal control efficiency of modified lake sediment.; Water column was utilized to simulate the state of natural lakes.; The removal rates of turbidity and algae reached 86 and 88%, respectively.;

A problem with the use of chemical oxidants for algae control in water treatment processes is an incomplete destruction of algal cells, leading to the clogging of the filter media. Ozone, with its high oxidizing power, can be used not only for treating many types of organic contaminants but also for destroying microorganisms. This study investigated the effect of ozone in controlling an algal population. The sample for the study, obtained from a raw water reservoir of the MWA Bangkhen Water Treatment plant (Thailand), was cultured in Bold’s Basal medium and used as a study population. Morphological identification of algae in raw water sample and cultured sample (study population) revealed that the predominant organisms were Chlorophyta, Cyanophyta and Bacillariophyta. Identification by PCR-DGGE and DNA sequencing of Cyanophyta in raw water and in the study population showed that the predominant algae were Oscillatoria sp. (99% similarity), Limnothrix sp. (99% similarity) and Merismopedia sp. (93% similarity). Ozonation was conducted using ozone gas from a corona discharge type generator, generated at the rate of 3.7 mg/min. The results showed that ozone successfully destroyed algae. With 15.4 mg O3/L, the initial population of 1,021 μg chlorophyll-a/L was reduced by 72.4%. This was equivalent to the removal rate of 47μg chlorophyll-a/mg O3. The re-culturing of the ozonated algae population, both in supernatant and sludge, yielded no change in chlorophyll-a content. Also no presence of a cyanophyta DNA fingerprint was observed on agarose gel. This indicated that regrowth did not occur and ozonation completely destroyed all the algae.

Phaeocystis globosa is a harmful algal bloom (HAB) species worldwide. Using modified clay (MC) to control HABs and to mitigate their adverse effects is currently a commonly used method in China. In this paper, the effects of oxidized composite modified clay (OXI-MC) on P. globosa were studied from different perspectives. The results show that the OXI-MC could effectively remove P. globosa and inhibit both the growth of residual algal cells and the formation of new colonies. The P. globosa algal biomass removal efficiencies after 3 h reached 90% at a dose of 0.1 g/L, and the number of colonies with different particle sizes was greatly reduced. Compared with those of the control, the superoxide dismutase (SOD) activity, catalase (CAT) activity, and malondialdehyde (MDA) content of the residual algae significantly increased, indicating that OXI-MC caused oxidative stress in the algal cells. In addition, we evaluated the effects of OXI-MC on the photosynthesis of residual microalgae and found that the maximal photochemical efficiency of photosystem II (PSII) under dark adaptation (Fv/Fm) and actual photochemical efficiency of PSII (ΦPSII) decreased, severely damaging the photosynthesis efficiency, implying that OXI-MC effected the photosynthesis system of P. globosa. The results of this study clarify that OXI-MC could remove the most of algal cells and break up the colonies of P. globosa by collision, flocculation, and releasing active substances, as well as inhibit effectively the growth and colony formation of residual P. globosa by causing oxidative stress, reducing photosynthesis activity, accelerating the degradation of polysaccharides, and inhibiting the formation of colonies. [ABSTRACT FROM AUTHOR]

A simplified stochastic control model for optimization of logistic dynamics with the control-dependent carrying capacity, which is motivated by a recent algae population management problem in the river environment, is presented. Solving the optimization problem reduces to finding a solution to a non-local first-order differential equation called tt–Jacobi–Bellman (HJB) equation. It is shown that the HJB equation has a unique viscosity solution and that the solution can be approximated with a finite difference scheme. Asymptotic estimates of the solution and the optimal control are derived and compared with numerical solutions. Finally, parameter dependence of the optimal control is examined numerically with implications to river environmental management. [ABSTRACT FROM AUTHOR]

Goldfish (Carassius auratus) have been reported as a method to keep water tanks clean; however, little information exists on this approach. The objectives were to evaluate the efficacy of goldfish on maintaining water quality in tanks and to evaluate the frequency that this method is used. The first objective was completed during June through October 2017 in St. Paul, MN, using plastic and metal 379 L stock tanks, each with and without goldfish in a drylot that housed six adult horses. The stocking rate was 5 goldfish per tank. Daily readings of total dissolved solids (TDS) and water turbidity (NTU), and weekly samples to measure chlorophyll a were taken. At the end of each 28-day period, tanks were cleaned and rotated. Plastic tanks had lower TDS than metal tanks (P <.001); however, metal tanks had lower NTU and chlorophyll a (P ≤.008). Adding goldfish resulted in lower TDS (P <.001); however, there was no effect on NTU or chlorophyll a (P ≥.097). No parameters had an impact on horse preference (P ≥.108). The second objective was completed using an online survey that was open from October 31 until December 15, 2018. Of the 672 completed surveys, 56% had not tried using goldfish in water tanks, 26% had utilized goldfish in the past, and 18% currently used goldfish. The inclusion of goldfish in water tanks did not affect all water quality parameters; however, 44% of survey respondents had tried, or were currently using, this management method. • Goldfish do not improve water quality parameters except for total dissolved solids. • Metal tanks had lower turbidity and chlorophyll a than plastic tanks. • Total dissolved solids and turbidity increased as water temperature increased. • Frequent cleaning is important, especially in warm months and with plastic tanks. • Fifty six percent of respondents never used fish, 26% used fish before, and 18% currently used fish. [ABSTRACT FROM AUTHOR]

A problem with the use of chemical oxidants for algae control in water treatment processes is an incomplete destruction of algal cells, leading to the clogging of the filter media. Ozone, with its high oxidizing power, can be used not only for treating many types of organic contaminants but also for destroying microorganisms. This study investigated the effect of ozone in controlling an algal population. The sample for the study, obtained from a raw water reservoir of the MWA Bangkhen Water Treatment plant (Thailand), was cultured in Bold's Basal medium and used as a study population. Morphological identification of algae in raw water sample and cultured sample (study population) revealed that the predominant organisms were Chlorophyta, Cyanophyta and Bacillariophyta. Identification by PCR-DGGE and DNA sequencing of Cyanophyta in raw water and in the study population showed that the predominant algae were Oscillatoria sp. (99% similarity), Limnothrix sp. (99% similarity) and Merismopedia sp. (93% similarity). Ozonation was conducted using ozone gas from a corona discharge type generator, generated at the rate of 3.7 mg/min. The results showed that ozone successfully destroyed algae. With 15.4 mg O3/L, the initial population of 1,021 μg chlorophyll-a/L was reduced by 72.4%. This was equivalent to the removal rate of 47μg chlorophyll-a/mg O3. The re-culturing of the ozonated algae population, both in supernatant and sludge, yielded no change in chlorophyll-a content. Also no presence of a cyanophyta DNA fingerprint was observed on agarose gel. This indicated that regrowth did not occur and ozonation completely destroyed all the algae. [ABSTRACT FROM AUTHOR]

Natural allelochemicals are considered as a source of algaecides. To uncover the anti-algal activity of Cinnamomum camphora fallen leaves and promote their usage as algaecides, the composition of their water and methanol extracts was analyzed, and the inhibitory effects of extracts on the growth of Microcystis aeruginosa and Chlamydomonas reinhardtii, and chlorophyll (Chl) content and photosynthetic abilities in C. reinhardtii were investigated. Twenty-five compounds were detected in the water extracts, mainly including terpenoids, esters, alcohols, and ketones. Compared to water extracts, there were more compounds and higher concentration in methanol extracts. Both water and methanol extracts inhibited the growth of the two algae, and 15 mg·ml-1 methanol extracts killed the algal cells after 48 h. The levels of Chl a and Chl b, as well as maximum quantum yield of photosystem II photochemistry (Fv/Fm) in C. reinhardtii cells reduced gradually with increasing the concentration of extracts, while the maximum quantum yield of nonphotochemical de-excitation (φDO) increased gradually. At the same concentration, methanol extracts showed stronger inhibitory effects than water extracts, due to their higher number of compounds and higher concentration. Therefore, C. camphora fallen leaves have a potential value as an algaecide [ABSTRACT FROM AUTHOR]

The effects and mechanism of phycocyanin removal from water by high-frequency ultrasound treatment were studied. The efficiency of sonication treatment in removing proteins derived from algal cells was investigated, and the factors influencing the process, including the effects of coagulation, were also studied. In addition, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), the three-dimensional fluorescence spectrum, and mass spectrum were used to illustrate the removal mechanism. The results indicated that phycocyanin can be degraded to the point where it is barely detectable in water samples after 180 min of high-frequency sonication. While the total nitrogen (TN) concentration remained consistent during the entire sonication process (240 min), about 78.9% of the dissolved organic nitrogen (DON) was oxidized into inorganic nitrogen. The sonication effect was greatly influenced by the ultrasound frequency, with 200 kHz having the highest removal performance due to the large production of hydroxyl (HO ) radicals. Coagulation was adversely influenced by sonication in the first 60 min due to the cross-linking reaction between protein molecules caused by the sonication. The influence of sonication weakened with sonication time due to the further degradation of the proteins by ultrasound. The variation of the TN, DON, and inorganic nitrogen indicated that the main mechanism occurring during the high-frequency sonication of the phycocyanin was the direct oxidation of the radicals, which was totally different from of the mechanism occurring during ultrasound with low frequency. [ABSTRACT FROM AUTHOR]

Ultrasound is a well-established technology, but it has been applied only recently to control algal blooms. The main purpose of this study is to determine the appropriateness of field measurements for evaluating the performance of an ultrasonic algae control system using an artificial neural network (ANN) in the Dogancı Dam Reservoir (Bursa, TURKEY). Within this study, data were obtained using the NeuroSolutions 5.06 model. Each sample was characterized using ten independent variables (time, total organic carbon (TOC), pH, water temperature (Twater), dissolved oxygen (DO), suspended solids (SS), the Secchi disc depth (SDD), open-water evaporation (E), heat flux density (H), air temperature (Tair), and one dependent variable (chlorophyll-a (Chl-a)). The correlation coefficients between the neural network estimates and field measurements were as high as 0.9747 for Chl-a. The results indicated that the adopted Levenberg–Marquardt back-propagation algorithm yields satisfactory estimates with acceptably low mean square error (MSE) values. [ABSTRACT FROM AUTHOR]

To evaluate the effect of ultrasound on the release of heavy metals in sediments during the ultrasonic algae inhibition and elimination process, low-frequency and low-power ultrasound at 35 kHz, 0.105 W/cm2 was used to irradiate a simulated water body for 60 min. Water samples were extracted at 10 min intervals to detect the concentration changes of Cu, Zn, Pb, and Cr. Samples from the sediment surface and 10 cm below the surface were extracted to determine the changes of total amounts for the four heavy metals, as well as the corresponding concentration changes of exchangeable, carbonate binding, Fe-Mn binding, organic binding, and residue states. The test results showed that the concentrations of the four heavy metals in water increase rapidly during the first 20 min of ultrasonic treatment, decreasing thereafter. The concentrations approach a stable level after 50 min. The concentrations of all the four metals increased by over 80%. During the first 20 min of ultrasonic treatment, the release rates of Cu, Zn, Pb, and Cr at the sediment surface were 27%, 24%, 29%, and 29%, respectively, while the concentrations of the Fe-Mn binding state and exchangeable state decreased by 25% and 47%, 22% and 43%, 29% and 28%, and 29% and 29%, respectively. The release rate of the four heavy metals at 10 cm below the surface was 34%, 34%, 32%, and 39%, respectively. Meanwhile, the concentrations of the Fe-Mn binding state of Cu, Zn, and the Fe-Mn binding state and organic bonding state of Pb and Cr decreased significantly. After 50 min of ultrasonic treatment, the total amount of heavy metals and the five states approached a stable level. These findings suggest that ultrasonic treatment can accelerate the release of metal elements from sediments to the water body; thus the ultrasonic algae inhibition technology is not sufficiently safe and reliable, involving the risk of secondary pollution. [ABSTRACT FROM AUTHOR]

Song, M.-S.; Yun, H.-S.; Kim, T.-W., and Cho, J.-M., 2017. Algae inflow monitoring using satellite images for the process control of the Gijang desalination plant in Busan, South Korea. In: Lee, J.L.; Griffiths, T.; Lotan, A.; Suh, K.-S., and Lee, J. (eds.), The 2nd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 79, pp. 159-163. Coconut Creek (Florida), ISSN 0749-0208. Climate change has recently been taking place due to the sudden rise of water temperature resulting from global warming and the red tides adversely affected the seawater desalination plant directly or indirectly every year. Harmful Algal Blooms (HABs) occur if the perishable organic pollutants, minerals, and growth stimulating substances are abundantly dissolved in the water and if solar radiation, water temperature, salinity, and other environmental conditions are met. Once the algae are agglomerated by the wind and tide, high-density red tide occurs. This may also cause damages to the desalination plants. RO membrane in the main process cannot be cleaned by the chlorination for membrane cleaning because the material of RO membrane is polyamide. Therefore, the algae and microorganisms contained in seawater have a negative impact on membrane fouling. Accordingly, pre-treatment method for blocking the inflow of algae by monitoring the occurrence of HABs is more effective than post-processing method that is used for cleaning after the membrane is already contaminated. In this study, algae inflow monitoring was carried out through satellite image analysis looking for an appropriate analysis algorithm of chlorophyll- a concentration by using the Geostationary Ocean Color Imager (GOCI) Data Processing System (GDPS) for the process control of Gijang desalination plant. Accordingly, the chlorophyll- a concentration analyzed by OC2 algorithm for algae inflow monitoring is the most suitable algorithm. [ABSTRACT FROM AUTHOR]

[Display omitted] • g-C 3 N 4 doping significantly increased the antialgal activity and microcystin degradation ability of Cu-MOF. • g-C 3 N 4 doping enhanced the heteroaggregation between Cu-MOF with algal cells. • 10 wt% g-C 3 N 4 /Cu-MOF exhibited a great visible light utilization ability and hydrostability. • O 2 – and ·OH were the primary free radicals in photocatalytic degradation of microcystin by 10 wt% g-C 3 N 4 /Cu-MOF. In this work, g-C 3 N 4 /Cu-MOF nanocomposites were prepared to inactivate Microcystis aeruginosa and degrade microcystin under visible light irradiation. Doping with g-C 3 N 4 statistically enhanced the photocatalytic efficiency of Cu-MOF, and followed the order of 10 wt% g-C 3 N 4 /Cu-MOF > 20 wt% g-C 3 N 4 /Cu-MOF > 2 wt% g-C 3 N 4 /Cu-MOF. Specially, the performance of 10 wt% g-C 3 N 4 /Cu-MOF was 1.86- and 2.93-fold of Cu-MOF in photocatalytic antialgal activity and degradation of microcystin. Mechanistically, 1) heteroaggregation between algal cells and photocatalyst is a primary prerequisite for eliminating harmful algae by photocatalyst, g-C 3 N 4 /Cu-MOF nanocomposites exhibited greater ability of heteroaggregation with algal cells than Cu-MOF; 2) g-C 3 N 4 doping increased the visible light utilization of Cu-MOF, with subsequent enhancing its free radicals generation ability; 3) the presence of g-C 3 N 4 elevated the hydrostability of Cu-MOF, and then enhanced the sustainable free radicals production ability of Cu-MOF. The higher performance of 10 wt% g-C 3 N 4 /Cu-MOF as compared with 20 wt% g-C 3 N 4 /Cu-MOF was because that the excess g-C 3 N 4 doping in 20 wt% g-C 3 N 4 /Cu-MOF enhanced the recombination rate of electron-hole pairs, inhibiting the generation of free radicals. O 2 – and ·OH were main free radicals inducing algal inactivation and microcystin degradation. Two possible photocatalytic degradation pathway of microcystin was identified. The findings provide new insight into enhancing the photocatalytic efficacy of Cu-MOF and the obtained g-C 3 N 4 /Cu-MOF nanocomposites have high potential in harmful algal blooming control. [ABSTRACT FROM AUTHOR]

Small ponds often suffer from the overgrowth of harmful algae (including cyanobacteria), and few safe methods exist for the rapid suppression of these harmful algae blooms in situ. Since laboratory studies indicated that cyanobacteria could be inhibited by Acorus calamus roots extracts, we evaluated the application of the extracts in natural water column. Besides, we also considered the shifts of algal community structures in extracts-treated enclosures. There were 65 algal species existed in pond before the addition of extracts, which belonged to six phyla: Cyanophyta, Chlorophyta, Cryptophyta, Xanthophyta, Bacillariophyta and Euglenophyta. The water bloom belonged to Microcystis bloom because the algal community was dominated by Microcystis aeruginosa with the abundance of 23.3 × 10 4 cells mL −1 . After A. calamus roots extracts addition, The total algal biomass decreased sharply. In the 20, 50 and 100 mg L −1 extracts-treated enclosures, the removal percentages of the algae were 64.5%, 92.7% and 94.6% after 3 days, respectively. The total algal biomass and Chl a concentration decreased more than 90% for 7 days, and the decrease ratios lasted till the end of 30 days experiment. And at the end of 30 days experiment, the Simpson index (D), Shannon-Weaver index (H’) and Pielou index (E) of the algae community in three treatments were all higher than that of calculated in the controls. The predominant species in algal community shifted from cyanobacteria to Chlorophyta and Bacillariophyta in the extracts-treated enclosures. Furthermore, the biomass of cyanobacteria did not recover, while the Chlorophyta and Bacillariophyta showed slight recovery. During the first week, the COD Mn increased obviously in the extracts-treated and control 2 (with ethanol) enclosures. Moreover, the concentration of TN increased slightly in the 50 and 100 mg L −1 extracts-treated enclosures in the 1 st day. And in the end of the experiment, the concentrations of TN and I Mn in the three extracts-treated enclosures tended to be consistent with two controls. The initial slight negative effects of the extracts on the water quality eliminated over time. Overall, the antialgal-activity of the extracts showing in pond is encouraging from the applied perspective of using A. calamus roots extracts as natural agent(s) to manage harmful cyanobacteria (Microcystis) blooms. [ABSTRACT FROM AUTHOR]

This paper considers a significant problem in biological control of algae issue in ecological environment. A four-dimensional dynamic model is carefully formulated to characterize the interactions among phytoplankton, submerged macrophyte, zooplankton, and general fish class in a lake ecosystem. The predation relationship is modeled by Beddington-DeAngelis functional responses derived from the classical Holling time budget arguments. Qualitative analyses of the global dynamics show that the system can generate very rich dynamics with potentially 10 different equilibria and several bistable scenarios. We perform analysis on the existence and local stability of equilibria and explore the refuge effect of macrophyte on the zooplankton with numerical simulations on aquatic ecosystems. We also discuss effective methods of biological control used to restrain the increase of phytoplankton. Our study shows the proposed model could have rich and complex dynamics including but not limited to bistable and chaotic phenomenon. Numerical simulation results demonstrate that both the refuge constant and the density of the macrophytes are two key factors where refuge effects take place. In addition, the intraspecific competition between the macrophyte and the phytoplankton can also affect the macrophyte's refuge effect. Our analytical and simulation results suggest that macrophytes provide structure and shelter against predation for zooplankton such that it could restore the zooplankton population, and that planting macrophyte properly might achieve the purpose of controlling algae growth. [ABSTRACT FROM AUTHOR]

The feasibility of using O3pre-oxidation and polyaluminum chloride (PAC)-enhanced coagulation for treating slightly polluted algae-containing raw water of the Pearl River was investigated. Results demonstrated that O3pre-oxidation and PAC-enhanced coagulation have greatly increased the removal of algae, turbidity, and natural organic material compared with PAC coagulation only. Specifically, the greatest removal of chlorophyll-a(chl-a) and TOC attained 97.67% and 32.29%, respectively, at the O3concentration of 1.0 mg/L and a PAC dose of 6.0 mg/L. 1.0 mg/L O3pre-oxidation reduces the 60% PAC dose when the residual turbidities reached 0.99 NTU. 2.0 mg/L O3pre-oxidation increased the UV254removal from 16.97 to 57.28% at a PAC dose of 6.0 mg/L. [ABSTRACT FROM AUTHOR]

In 1970s, barley straw has been known to be capable of controlling algal growth.In vitroandin situexperiments were performed to investigate the effects of barley straw on algal growth inhibition substances. In addition, its ecotoxicity and the algal growth inhibition substances extracted from barley straw were examined. In thein vitroexperiment, barley straw and retinaspora leaf treatment groups caused significant decreases (pvalue < 0.05) in the number of cells inAnabaena affinis,Microcystis aeruginosa, andScenedesmus quadricaudacompared with the control group. However, the treatment group, which applied 0.2 g of barley straw, showed a tendency of increasing the number of cells inS. quadricaudacompared with the control group. It reveals that types of algae and proper applications of barley straw are important to inhibit algal growth. In addition, the barley straw showed almost no ecotoxicities in ecotoxicity experiments while the retinaspora leaf showed a certain degree of ecotoxicity (Toxicity unit >36). In thein situexperiment, algal growth was inhibited by barley straw. In particular, diatoms exhibited a tendency of decreasing the number of algal cells compared with blue-green algae. It shows that the barley straw does not inhibit the growth of all algae and shows different effects according to types of algae. The algal growth inhibition substances were extracted from the barley straw and tested. It was found that a ferulic acid in various phenol compounds affected the algal growth most. [ABSTRACT FROM PUBLISHER]

Controlling the growth of algae is a major issue, wherever there is adequate light, moisture and simple nutrients sustain. The main objective of the current research was to carry out treatability studies to control the growth of algae using barley, rice and ragi straws and a comparison was made between straws by varying its dosages. This study revealed the fact that decomposing straw is effective in controlling the growth of algae. Barley straw at a dosage of 5 g/L was found to be more effective in controlling the growth of algae with 80% reduction in chlorophyll 'a' concentrations when compare with control tray, at an average temperature 29° C, light intensity of 562 μ mol-2s-1 photon flux and pH of 7.9. However, barley 2 g/L and rice 5 g/L were also found to control the growth of the algae. ANOVA results express barley 5 g/L was highly significant when compared with the control tray with 99% confidence level. Simulation of Kembalu water treatment plant was done to study the effect of bed surface on the growth of algae. Surface study give an insight about role of surface on the growth rate of algae. In the present study it was observed that growth of Chlorophyace and Euglenophyceae were predominant on concrete surface compared Bacillariophyceae, however ceramic surface promoted the growth of Bacillariophyceae. Higher biomass of Cyanophyceae was found on brick surface. [ABSTRACT FROM AUTHOR]

Golden alga ( Prymnesium parvum) is a harmful alga that has caused ecological and economic harm in freshwater and marine systems worldwide. In inland systems of North America, toxic blooms have nearly eliminated fish populations in some systems. Modifying nutrient profiles through alterations to land or water use may be a viable alternative for golden alga control in reservoirs. The main objective of this study was to improve our understanding of the nutrient dynamics that influence golden alga bloom formation and toxicity in west Texas reservoirs. We examined eight sites in the Upper Colorado River basin, Texas: three impacted reservoirs that have experienced repeated golden alga blooms; two reference reservoirs where golden alga is present but nontoxic; and three confluence sites downstream of the impacted and reference sites. Total, inorganic, and organic nitrogen and phosphorus and their ratios were quantified monthly along with golden alga abundance and ichthyotoxicity between December 2010 and July 2011. Blooms persisted for several months at the impacted sites, which were characterized by high organic nitrogen and low inorganic nitrogen. At impacted sites, abundance was positively associated with inorganic phosphorus and bloom termination coincided with increases in inorganic nitrogen and decreases in inorganic phosphorus in late spring. Management of both inorganic and organic forms of nutrients may create conditions in reservoirs unfavorable to golden alga. [ABSTRACT FROM AUTHOR]

This study identifies and quantifies the operational advantages of covering agricultural water reservoirs (AWRs) for irrigation by means of Suspended Shade Cloth Covers (SSCCs) in comparison with other traditional management practices: Casual Chemical Treatment (CCT) and Systematic Chemical Treatment (SCT). The operational advantages, including the cost-effectiveness, were analysed by carrying out filtering trials at ten sites in south-eastern Spain, where the effect of each technique on algae presence and filtering requirements for microirrigation was evaluated. The results evidenced that AWR management can significantly affect the quality of stored water, with SSCC being the most effective practice in controlling algae presence. Filtering trials corroborated the extraordinary performance of SSCCs since they presented much higher volumes of treated water until filter saturation, two and three orders of magnitude higher than the CCT and SCT management practices, respectively. This result would imply a total annual reduction in operational costs due to the SSCC installation ranging from 359.6 to 598.0 € y when comparing with the CCT, and of 403.2 € y in the case of SCT. Therefore the effect on filtering requirements is an essential consideration in the SSCCs cost-effectiveness assessment. [ABSTRACT FROM AUTHOR]

Hydrodynamic properties of rivers and streams are primary controls on the abundance and structure of algal communities. In Florida, USA, filamentous macroalgal proliferation in spring-fed rivers has largely been attributed to nitrogen enrichment; however, changes in hydrodynamics and other potential mechanisms have not been thoroughly evaluated. This study tested whether macroalgal abundance (primarily Lyngbya wollei) was related to hydrodynamics in Gum Slough, a sub-tropical Florida spring-fed river. Flow velocities and macroalgal cover were measured at three transects bimonthly between June 2010 and January 2013, a period during which river discharge fluctuated in response to a drought and a tropical storm. Temporal variation in macroalgal cover was significantly inversely related to flow velocity, excluding fall/winter sampling events when light limitation was likely. The results indicate a velocity threshold below which macroalgal cover increased substantially, and a lower threshold below which complete cover frequently occurred. Local differences in channel morphology and substrate type (i.e., aquatic plant beds) seemed to affect the relationship between macroalgal cover and velocity at each transect. Nitrogen and phosphorus concentrations and other water chemistry parameters were not associated with variation in macroalgal cover. Overall, this study suggests that hydrodynamics can strongly control filamentous macroalgae in Florida spring-fed rivers. [ABSTRACT FROM AUTHOR]

The effects of five natural products on the growth of three harmful algae species including Chattonella marina Hara et Chihara, Alexandrium tamarense Balech and Karenia mikimotoi ( Miyake & Kominami ex Oda) G. Hansen & Ø. Moestrup were observed. Four products including ε-polylysine, betaine, stachydrine and berberine exhibited selectively inhibitory effects against the three algae. However, the other product chitosan had no obvious inhibition against the above algae. Berberine and ε-polylysine exhibited relatively higher inhibitory capability against C. marina, and betaine had the highest inhibitory effect against A. tamarense. While only berberine could effectively inhibit the growth of K. mikimotoi with LC50, 120 at 3.1 mg/L. The fast inhibitory effect against K. mikimotoi and environmental safety of berberine suggested that it might be a potential algaecide against K. mikimotoi. [ABSTRACT FROM AUTHOR]

To suppress the occurrence of phytoplankton blooms dominated by cyanobacteria, control measures were implemented during the bottleneck stages of algal succession, overwintering and pre-recruitment, using a combination of chemical and biological algicides. First, water and sediment samples were incubated in the laboratory to determine the threshold temperature for cyanobacteria recruitment. Second, the functional characteristics of candidate algicides were screened. Third, an in situ pilot experiment was conducted to test the feasibility of this method. Our results indicated that (1) the recruitment of cyanophytes was initiated at 15°C, (2) H202 and rice straw were the optimum algicides and their optimal concentrations were 10 mg/L and 1 g/L, respectively, and (3) following the combined application of H202 and rice straw during overwintering and pre-recruitment, the biomass of cyanobacteria decreased by 27.1% during recruitment and by 53.2% during the first algal bloom. These results suggested that the combined application of H202 and rice straw, during the bottleneck stages of algal cycling, suppressed the recruitment of cyanobacteria and decreased the magnitude of algal blooms, thus offering a promising choice for prevention of cyanobacterial blooms. [ABSTRACT FROM AUTHOR]

This study represents for the first time a comprehensive assessment of functionality and environmental impacts of metallic silver nanoparticles (Ag-NP) compared to conventional organic biocides. Four different transparent, hydrophobic coatings of wooden outdoor façades were tested during one year outdoor weathering. The total silver release from products with Ag-NP was proportional to the overall erosion of the coating. The results indicate that the Ag-NPs are likely transformed to silver complexes, which are considerably less toxic than ionic silver. The protective effect of the silver containing coatings against mold, blue stain and algae was insufficient, even in immaculate and non-weathered conditions. The release of organic biocides from conventional coatings was dependent on the weather conditions, the type of biocide and the use in the base or top coat. The conventional coating showed a good overall performance free from mold, blue stain and algae until the end of the test period. [Copyright &y& Elsevier]

A universal environmental friendly method was developed to turn sand into effective flocculants for mitigating harmful algal blooms (HABs) in marine and freshwater systems. The isoelectric point of sand was largely increased from pH 4.5 to 10.5 after been modified by Moringa oleifera coagulant (MO) abstracted form MO seeds. However, when sand was modified by MO alone, maximum removal efficiencies of 80% and 20% for Amphidinium carterae (A.C.) and Chlorella sp. (C.S.) in seawater and 60% for Microcystis aeruginosa (M.A.) in fresh water were achieved in 30 min. The limited removal improvement was due to the form of only small floes (20-100 μm) by surface charge modification only. Large floes (270-800 μm) and high removal rate of 96% AC. and C.S. cells in seawater and 90% of MA cells in fresh water were achieved within 30 min when the small MO-algae-sand floes were linked and bridged by chitosan. High HAB removal rate is achievable when the sand is modified by the bicomponent mechanism of surface charge and netting-bridging modification using biodegradable modifiers such as MO and chitosan. The optimized dosage of modified sand depends on the property of algal cells and water conditions [ABSTRACT FROM AUTHOR]

Abstract: An effective and benign approach to mitigating fish-killing Prymnesium parvum blooms in small impoundments has yet to be identified. The aquatic herbicide flumioxazin (Clipper®, Valent Corp., Walnut Creek, CA), however, shows promise as it suppresses P. parvum while having little effect on other plankton. Its influence on fish has yet to be evaluated. Here, we investigated potential effects of flumioxazin on growth, survival and feed conversion ratio of a non-target organism, bluegill sunfish (Lepomis macrochirus) in a laboratory experiment. We exposed fish to several herbicide concentrations that spanned the manufacturer''s recommended dosage (0, 25, 50, 100, 200 and 400μgL−1). The duration of the experiment was six weeks with weekly re-application of flumioxazin to specified tanks. No significant differences were found in average fish weight gain (p =0.76), percent survival of fish (p =0.83) or the feed conversion ratio (p =0.89). These findings provide further evidence that flumioxazin application may be an effective and benign approach to P. parvum mitigation. [Copyright &y& Elsevier]

Abstract: The present study aims to identify the effect of installing Suspended Shade Cloth Covers (SSCCs) on the water quality of Agricultural Water Reservoirs (AWRs) for irrigation. Four AWRs located in the irrigated coastal plane of the Segura River Basin (south-eastern Spain) were monitored for 1 year. Two of them were covered with a black polyethylene SSCC, whereas the two others remained uncovered during the trial. The main physical, chemical and microbiological water quality parameters were monthly monitored with a multi-parametric instrument OTT-DS5 and water samples analysis. Additionally, a laboratory experiment replicating covered and uncovered AWR conditions was carried out to analyze the influence of water temperature and light intensity on the evolution of bacteria populations. The low transmitted solar radiation of the SSCC dramatically reduced the photosynthesis activity, limiting the algal bloom in covered AWRs. Despite this photosynthesis restriction and the lack of turbulence, the oxygen levels remained close to saturation in the covered AWRs as a result of the frequent water inflows. The installation of the cover also led to a reduction of 82% in Escherichia coli and faecal coliforms, partly due to the reduction of organic matter (mainly algae) and partly because of the lower water temperature. Data from the laboratory experiment confirmed the field results. Overall, the results show the implementation of SSCCs in AWRs produces significant effects in the stored water quality, which are mainly beneficial for irrigation purposes, especially in drip irrigation systems and when reclaimed water is reused. [Copyright &y& Elsevier]

In China, mechanical collection of cyanoblooms followed by soil-based treatments has been widely used as emergency strategies in many eutrophicated freshwaters. This study was to evaluate both efficiencies and potential risks of typical soil-based technologies. Results from this study indicated that over 90% of cyanobacterial biomass and 96% of dissolved microcystins (MCs) could be restrained in soils via three-level systems, which were much better than single-level systems. High concentrations of MCs, ranged from 65 to 276 ng g-1 and from 2.12 to 6.6 ng g-1, were found in soils around treatment systems and croplands, respectively. In the soil solutions, MCs ranged from 0.35 to 2.0 μg L-1, showing a potentially high leaching risk. In the samples from shallow groundwater near the treatment systems, MC concentrations were detected as high as 1.2 μg L-1. Moreover, bioaccumulations of MCs varied between 22 and 365 μg kg-1, and 19-222 μg kg-1 were found in 13 kinds of crops and 7 kinds of wild grass, respectively. Our results indicated for the first time that current soil-based technologies were effective but could pose potential environmental, ecological, and public health risks. Further improvements of these technologies were also proposed based on our findings. [ABSTRACT FROM AUTHOR]

Abstract: Known as Golden Algae in popular media, the harmful algal bloom causing organism Prymnesium parvum secretes increased amounts of toxic chemicals called prymnesins when stressed, resulting in major fish kills in Texas. Although many options exist for mitigation of blooms, a feasible protocol for control of blooms on large-scale impoundments has yet to be identified. Chemical control of P. parvum using six different enzyme inhibiting aquatic herbicides was explored in laboratory experiments. Of the six chemicals screened, one (flumioxazin) was selected for further study due to a significant decrease in P. parvum cell numbers with increasing chemical concentration. It was applied to natural plankton communities during in-situ experiments (Lake Granbury, Texas). The first experiment was conducted during a period of P. parvum bloom initiation (March) and the second experiment conducted during a post bloom period (April). Experiments were carried out in 20 L polycarbonate carboys covered in 30% shade cloth to simulate natural light, temperature and turbulence conditions. Through cell counts via light-microscopy, the chemical flumioxazin was found to cause significant decreases in P. parvum, but no significant differences in zooplankton abundance during the period of bloom initiation. However, significant decreases in adult copepods were observed during the post bloom period, with no significant decreases in P. parvum most likely due to decreased light penetration and inhibition of the photosensitive mode of action. [Copyright &y& Elsevier]

It is well established that the drinking water treatment has several disadvantages such as it may rupture the algae, thereby releasing the taste- and odour-producing oils before the whole algae are removed from the treatment system. This review aims to present the concept of algae recovery instead of its removal in drinking water treatment plant. Control of algae in water supplies and some coagulation/flocculation and electrolysis experiments as harvesting methods are discussed. In fact, algae recovery instead of its removal in water treatment plant is a promising perspective and a suitable issue when the surface water comes from dams where algae blooms occur frequently. Micro-algae are a sustainable energy resource with great potential for CO2 fixation. The micro-algae could be grown in photo-bioreactors or in open ponds. A new interesting field of research would be fast and simultaneous algal biodiesel production with drinking water treatment in the biodiesel production/water treatment plant without chemicals. However, the fact that algal cultivation needs light and space would be very difficult challenge. [ABSTRACT FROM AUTHOR]

Brown tide algal blooms, caused by the excessive growth of Aureococcus anophagefferens, recur in several northeastern US coastal bays. Direct bloom control could alleviate the ecological and economic damage associated with bloom outbreak. This paper explored the effectiveness and safety of natural chemical biocide hydrogen peroxide (H2O2) for brown tide bloom control. Culture studies showed that H2O2 at 1.6 mg L-1 effectively eradicated high density A. anophagefferens within 24-hr, but caused no significant growth inhibition in the diatoms, prymnesiophytes, green algae and dinoflagellates of >2-3 µm cell sizes among 12 phytoplankton species tested over 1-week observation. When applied to brown tide bloom prone natural seawater in a microcosm study, this treatment effectively removed the developing brown tide bloom, while the rest of phytoplankton assemblage (quantified via HPLC based marker pigment analyses), particularly the diatoms and green algae, experienced only transient suppression then recovered with total chlorophyll a exceeding that in the controls within 72-hr; cyanobacteria was not eradicated but was still reduced about 50% at 72-hr, as compared to the controls. The action of H2O2 against phytoplankton as a function of cell size and cell wall structure, and a realistic scenario of H2O2 application were discussed. [ABSTRACT FROM AUTHOR]

The article discusses a study that researched the increase in green algae in coastal areas of Bretagne, France, and the various means used to control it. Topics mentioned include Breton attitudes towards the problem, the possible effect of urban-rural discrimination on algae control programs, and technical details about algae recycling programs.

Abstract: We analyzed small subunit ribosomal rRNA gene (SSU rDNA) in single-cell isolated strains of “Alexandrium tamarense”, “Alexandrium fundyense” and “Alexandrium catenella” (Atama complex) by both direct and clone-based sequencing, and found 42–50 intragenomic SSU rDNA polymorphic sites (High IRP) in some of the strains but none or one (No/Low IRP) in others. Clone sequencing of the High-IRP amplicons revealed numerous variants with 0–3.5% nucleotide differences. Phylogenetic analyses including reported and new Atama complex SSU rDNA data divided this complex into two major well-separated clades. All the High-IRP sequences obtained in this study were grouped in Clade I (High-IRP clade), which also contained strains of Atama complex previously reported from northern Asia. Clade II (No/Low-IRP clade), with no evidence of IRP except for the one polymorphic site found in one of the strains, contained a subclade (IIC) exclusively of “A. catenella” from various geographic locations and several other subclades (IIA, IIB) predominantly of “A. tamarense”. Clade I corresponded to Group I in the large subunit (LSU) rDNA-based phylogenetic tree (), and subclades in our Clade II corresponded to the LSU-based Groups II–V. Our IRP information further unites the many seemingly different genotypes into a coherent group (Clade I) and provides delineating boundary between this and other genotypes (Clade II) in Atama complex. Based on the currently available data, we propose that Clade I and subclade IIC represent two distinct species, while the rest of Clade II represents another one or more species. Clade I should be considered one species because (1) intragenomic rDNA variants dispersed across strains in the phylogenetic tree uniting the many different genotypes to same or closely related populations, (2) their expressed SSU rDNAs (i.e. rRNAs) are almost identical (1 out of 1700nt, 0.06% difference), and (3) the corresponding Group I in the LSU-based tree also appears to be a coherent group. Subclade IIC should be considered another species because it has a long distance from the rest of Clade II as well as Clade I. Whether the rest of Clade II (mainly European “A. tamarense” subclades) represents another one or more species requires further study. Our results show that the three original morphospecies designations are invalid, and the strains do not group based on geographic locations or whether they are toxic in general, although some subclades are predominated by part of a morphotype from a region. Applying the IRP-guided analysis to a toxic Alexandrium bloom in Long Island Sound revealed that although some undocumented Alexandrium-related and other dinoflagellate lineages co-existed, the majority of the “diverse” SSU sequences detected belonged to one single population identical to “A. fundyense” in Gulf of Maine. Our result suggests that negligence of IRP could lead to incorrect recognition of the intragenomic SSU rDNA variants as distinct genotypes, thus overestimating strain diversity of a bloom of this species complex and possibly other HAB lineages. [Copyright &y& Elsevier]

Abstract: The influences of spiramycin and amoxicillin on the algal growth, production and release of target microcystins (MCs), MC-LR, MC-RR and MC-YR, in Microcystis aeruginosa were investigated through the seven-day exposure test. Spiramycin were more toxic to M. aeruginosa than amoxicillin according to their 50 percent effective concentrations (EC50) in algal growth, which were 1.15 and 8.03μg/l, respectively. At environmentally relevant concentrations of 100ng/l–1μg/l, spiramycin reduced the total MC content per algal cell and inhibited the algal growth, while exposure to amoxicillin led to increases in the total MC content per algal cell and the percentage of extracellular MCs, without affecting the algal growth. Toxicity of MCs in combination with each antibiotic was assessed in the luminescent bacteria test using the toxic unit (TU) approach. The 50 percent effective concentrations for the mixtures (EC50mix ) were 0.56TU and 0.48TU for MCs in combination with spiramycin and amoxicillin, respectively, indicating a synergistic interaction between MCs and each antibiotic (EC50mix <1TU). After seven-day exposure to 100ng/l–1μg/l of antibiotics, spiramycin-treated algal media and amoxicillin-treated algal media showed significantly lower (p<0.05) and higher (p<0.05) inhibition on the luminescence of Photobacterium phosphoreum, respectively, compared with the untreated algal medium. These results indicated that the toxicity of MCs were alleviated by spiramycin and enhanced by amoxicillin, and the latter effect would increase threats to the aquatic environment. [Copyright &y& Elsevier]

Abstract: The antibacterial property of silver has long been known and used in various applications due to its high toxicity to bacteria and low toxicity to humans. Excessive algae growth has been a common problem for landscape water in many urban areas in China. In this study, silver oxide in the form of tetrasilver tetroxide coated on pebbles was used to investigate its effect on inhibiting algae growth. Experiment results showed that a rapid and long-lasting algaeinhibiting effect was produced by the tetrasilver tetroxide-coated pebbles, provided that the water depth was less than a certain value. The first-three-days algae removal rates all reached above 50%, and the 90-day algae removal rates stabilized above 90% for experiments with water depths of 0.4 and 0.7 m. No algae-inhibiting effect was found when the water depth was increased to 1 m. [Copyright &y& Elsevier]

Abstract: Recycling of greenhouse irrigation water in hydroponic tomato production requires a water remediation process to reduce the risk of pathogen proliferation and the accumulation of other chemical compounds. The dissolution of ozone into bulk irrigation solutions is an effective technology for reducing chemical contaminant and pathogen levels in greenhouse irrigation water. Greenhouse managers utilizing ozonation typically remove residual ozone prior to distribution to the crop. Removal of the active compound in this treatment process has been deemed a prudent measure intended to prevent ozone-based plant damage. This said, although atmospheric ozone has been extensively studied with respect to its phytotoxicity, there are very few studies available on ozone in the aqueous phase in which evidence to support the removal of ozone (on the basis of phytotoxicity) is provided. Furthermore, removal limits the overall efficacy of the treatment as the ozone is not available to treat distribution lines and emitters. The purpose of this study was to determine if aqueous ozone impacts tomato (Lycopersicon esculentum Mill. cv Matrix F1) productivity when applied directly to a mineral wool growth substrate via drip irrigation. At the highest aqueous ozone treatment level (3.0mgL−1) significant increases in leaf area, shoot dry matter, and stem thickness were observed. There were no differences across all treatments in terms of net CO2 assimilation rate, stomatal conductance, internal leaf CO2 concentration, chlorophyll content index, and fruit production. A qualitative assessment of algae growth on the substrate surface was conducted. Both ozone treatments resulted in a visually discernible reduction in algae prevalence on the substrate surface. The results of this study do not support the removal of aqueous ozone (at the concentrations examined) prior to distribution when the solution is applied via drip irrigation in mineral wool hydroponic tomato production. [Copyright &y& Elsevier]

Abstract: The SOLAS Air–Sea Gas Exchange (SAGE) experiment was conducted in Sub-Antarctic waters off the east coast of the South Island of New Zealand in the late summer of 2004. This mesoscale iron enrichment experiment was unique in that chlorophyll a (chl a) and primary productivity were only 2× OUT stations values toward the end of the experiment and this enhancement was due to increased activity of non-diatomaceous species. In addition, this enhancement in activity appeared to occur without a significant build up of particulate organic carbon. Picoeukaryotes (<2μm) were the only members of the phytoplankton assemblage that showed a statistically significant increase, a doubling in biomass. To better understand the controls of phytoplankton growth and biomass, we present results from a series of on-deck perturbation experiments conducted during SAGE. Results suggest that the pico-dominated phytoplankton assemblage was only weakly inhibited by iron. Diatoms with high growth rates comprised a small (<1%) fraction of the phytoplankton assemblage, were likely iron limited, and potentially further limited by silicic acid and therefore did not significantly contribute to bloom dynamics. On deck experiments and comparison of SAGE with other iron addition experiments suggested that neither light availability nor deep mixed layers limited phytoplankton growth. Although no substantial increase in grazing rate or specific phytoplankton growth rate was detected, microzooplankton biomass doubled over SAGE as a result of an increase in cell size. The importance of microzooplankton grazing was highlighted by the fact that they were capable of consuming 15–49% of the total phytoplankton production per day. Removal was highest on eukaryotic picophytoplankton production with a mean value of 72% (29–143%). Patch dilution played an important role during SAGE; the mean patch net algal growth:dilution rate, 1.13 (0.4–2.2) was the lowest reported for a mesoscale iron enrichment experiment. Phytoplankton biomass, estimated by chlorophyll a, only accumulated when phytoplankton growth exceeded grazing and when net algal growth exceeded dilution rate. The SAGE results highlight the function of the smallest phytoplankton size fraction described by the ecumenical Iron Hypothesis. Thus, adding iron to HNLC-low silicic acid regions during certain times of the year may simply transfer more carbon through the microbial food web. A primary implication of this study is that any iron-mediated gain in fixed carbon with this set of environmental conditions has a high probability of being recycled in surface waters. [Copyright &y& Elsevier]

Abstract: The present study aimed to design the liposomal delivery system for TD53, a novel algicial drug in order to improve the delivery properties of TD53 and evaluate its algicidal effects as well as selectivity against harmful and non-harmful algae. Liposomes of TD53 were prepared with 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) by a lyophilization, resulting in relatively small size vesicles (234±38nm) and narrow size distribution (PI=0.130±0.027). The drug leakage from the liposome was negligible in the F/2 media (<2% during 96h incubation). Subsequently algicidal activity of liposomal TD53 against harmful and nonharmful algae was evaluated at various concentrations. The IC50 values of TD53 in liposome against harmful algae such as Chattonella marina, Heterosigma akashiwo and Cocholodinium polykrikoides were 2.675, 2.029, and 0.480μM, respectively, and were reduced by approximately 50% compared to those obtained from non-liposomal TD53. In contrast, the algicidal effect of liposomal TD53 was insignificant against non-harmful algae including Navicula pelliculosa, Nannochloropsis oculata and Phaeodactylum EPV. Those results suggested that liposomal delivery systems might be effective to enhance the efficacy of TD53 while maintaining the selectivity to harmful algal species. [ABSTRACT FROM AUTHOR]

Abstract: The harmful alga Prymnesium parvum can be controlled with chemicals that also can kill non-target organisms including fish. Currently, there is no ecologically safe and sustainable method for controlling this alga. Therefore, we evaluated SolarBee® solar powered water circulation (SPC) for efficacy in controlling P. parvum blooms and ichthyotoxicity. We hypothesized that SPC can alter the ecological niche that promotes P. parvum blooms and toxicity, and thereby control this alga. Ecological niche variables considered were inorganic phosphorus (P) and nitrogen (N), conductivity, pH, temperature, and cations. The effects of SPC on total algal biomass and community structure and zooplankton were also investigated. The study was conducted in six 0.4ha plastic-lined fish hatchery ponds from September 2007 to March 2008. Three ponds received SPC and another three without SPC served as control. Variables tested were P. parvum cell density and ichthyotoxicity, total algal density, algal population diversity, chlorophyll a, P, N, pH, water temperature, dissolved oxygen, conductivity, calcium, magnesium, potassium, and sodium. The algal community consisted of 69 taxa (genera and species) from eight divisions, including Haptophyta and Chlorophyta, and two unidentified algae. The SPC suppressed the chlorophytes population and otherwise had no effect on any of the tested variables. The SPC was unable to alter water quality and nutrient levels in hatchery ponds and thus failed to control P. parvum. [Copyright &y& Elsevier]

This paper investigates a dynamic mathematical model of fish algae consumption with an impulsive control strategy analytically. It is proved that the system has a globally asymptotically stable algae-eradication periodic solution and is permanent by using the theory of impulsive equations and small-amplitude perturbation techniques. Numerical results for impulsive perturbations demonstrate the rich dynamic behavior of the system. Further, we have also compared biological control with chemical control. All these results may be useful in controlling eutrophication. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this study was to compare the coagulation and flotation of different algae species with varying morphology and algogenic organic matter (AOM) composition in order to link physical and chemical algae characteristics to treatment. Microcystis aeruginosa (cyanobacteria), Chlorella vulgaris (green algae), Asterionella formosa and Melosira sp. (diatoms) were treated by coagulation with aluminium sulphate and flotation. The AOM was extracted and treated separately. Analyses included cell counts, dissolved organic carbon, aluminium residual and zeta potential. Removal efficiencies in the range 94–99% were obtained for each species. Cells, AOM and aluminium were concurrently removed at a coagulant dose that was related on a log–log basis to both cell surface area and total charge density, although the relationship was much stronger for the latter. This was attributed to a significant proportion of the coagulant demand being generated by the AOM. The implications of such findings are that relatively simple charge measurements can be used to understand and control coagulation and flotation of algae. [Copyright &y& Elsevier]

Cyanobacteria are photosynthetic bacteria with some characteristics of algae. Some cyanobacteria produce toxins that have been shown to be hazardous to both animals and humans. Previous research has demonstrated power ultrasound can provide a suitable method to control algae blooms although the optimum ultrasonic parameter settings have not been determined to ensure an effective and energy efficient treatment. In this work the effect of ultrasound on suspensions of Microcystis aeruginosa has been investigated at the following frequencies 20, 40, 580, 864 and 1146 kHz. Results showed that the reduction in algal numbers is dependent on both frequency and intensity. In order to quantify the effect we have defined the efficiency of the ultrasonic control of algae at a specific frequency as: (% inactivation of the algae) / (ultrasonic intensity applied). When this is applied to the results at different frequencies the order of efficiency for algae reduction is 20 < 1146 < 864 < 580 kHz. This suggests that ultrasound can offer a suitable method for algae inactivation or control but the sonication conditions must be taken into account. [ABSTRACT FROM AUTHOR]

Algal blooms are a significant problem in the UK, particularly in water sources that supply potable water treatment works. A wide range of methods to control algae have been tested and, whilst many are effective, they all have disadvantages. The use of barley straw to control algal growth in reservoirs is one option that is gaining popularity, but little is known about its mode of action. One suggested mechanism is that, as the straw is broken down, algastatic chemicals such as phenolics are released. Here we have used an algae inhibition test to evaluate the effect of chemicals reported to be released from straw on three common algal species: Chlorella vulgaris, Microcystis aeruginosa and Scenedesmus subspicatus. It was shown that, of the chemicals assessed, many produced an algastatic effect on the growth of the three algal species tested, with 2 phenyl-phenol being the most effective, whilst p-cresol and benzaldehyde were shown to be effective at concentrations similar to those that have been reported downstream of rotted straw. Scenedesmus subspicatus proved to be much more resistant to the chemicals tested than the other species. [ABSTRACT FROM AUTHOR]

One strain of algicidal bacterium which can inhibit Harmful algal blooms (HABs), FDT5, was isolated from activated sludge and found to have good algicidal effects on Microcystis aeruginosa. It was revealed that: The FDT5 was a Gram-negative bacterium and identified as Ochrobactrum sp.; The greater the initial bacterial cell density, the faster the degradation of chlorophyll a.; The algicidal efficiency was evaluated at the most favorable conditions which were a temperature of 30-35°C, a pH of 7.6 and complete darkness; The FDT5 strain lysed Microcystis aeruginosa not directly but by secreting metabolites which could withstand high temperatures and pressure. [ABSTRACT FROM AUTHOR]