A STUDY ON THE FLUX, SPECIATION, AND BUDGET OFMERCURY IN CONTROLLED EXPEEIMENTAL ECOSYSTEMS

The lowest addition of mercury (0.1 ug Hg 1-1) was used in CEEs for research on mercury flux, speciation and budget. The removal behavior of mercury by phytoplankton in water columns of CEEs can be described by first order kinetic equations for total and particulate mercury in the CEE spiked by mercury. The removal rate of mercury in water columns depends on the size and productivity of phytoplanton in a water column to which mercuric ions were added. A 4.4 day half-life time and a 2.8 day half-life time for total and particulate mercury respectively was obtained in diatom bloom. During microflagellate bloom a 30 day total mercury half-life time was estimated with increase of particulate mercury in the water column. The 0.010 ug Hg cm-2y-1 mercury flux rate that was attained in the control bag agreed with the values from field measurements in Saanich Inlet where the bags Were launched.The proportion of total mercury to dissolved and particulate mercury depended also on the size, productivity, and concen     

Fast adsorption of microcystin-LR by Fe(Ⅲ)-modified powdered activated carbon

Microcystins(MCs) are cyclic hepatotoxic peptides produced by the bloom-forming cyanobacterium Microcystis and present a public health hazard to humans and livestock. The removal of MCs from contaminated water with powdered activated carbon(PAC) has been employed as a simple and economic treatment strategy. In this study, PAC-Fe(Ⅲ) was prepared and utilized for the fast and efficient removal of MCs from water. PAC-Fe(Ⅲ) exhibited superior microcystin-LR(MC-LR) removal capacity and efficiency compared to the unmodified PAC. The MC-LR removal efficiency of PAC-Fe(Ⅲ) increased with decreasing p H within the pH range of 4.3 to 9.6. PAC-Fe(Ⅲ) could be reused for 3 times by methanol elution while the MC-LR removal efficiency was still over 70 percent. The removal efficiency was positively correlated to the ionic strength of water and negatively correlated to alkalinity. Natural organic matter(NOM) such as humic acid(HA) and salicylic acid(SA) generated low interference with MC-LR adsorption by PAC-Fe(Ⅲ). The complexation reaction between Fe~(3+) in PAC-Fe(Ⅲ) and the functional groups of MCLR was suggested as the key mechanism of MC-LR removal by PAC-Fe(Ⅲ). The results suggest that Femodified PAC is a promising material for the treatment of MC-contaminated waters.     

Performance of wuxi WWTP in china

In Wuxi Wastewater Treatment Plant, the Anaerobic, anoxic and oxic (A2/O) process was employed to remove the nitrogen and phosphorus, which exhibited the positive results of the high removal efficiency for phosphorus with a range of 67.7% to 89.9% and an average value of 78.0. The effluent of phosphorus met the national discharge standard. The removal of TN was effected by both BOD variation of influent and wastewater temperature. TN removal was in the range of 28.5% to 55.8% with an average value of 39.4%. The energy cost was 0.15 kWh(m3d)-1 or 1.35 kWh(kgBOD·d)-1. The annual average sludge production was 46.3 m3d-1, the annual average dosage for the dewatering was 40 kgd-1.     

Biosorption and desorption of Cd^2＋ from wastewater by dehydrated shreds of Cladophorafascicularis

The adsorption and desorption of algae Cladophora fascicularis and their relation with initial Cd^2＋ concentration, initial pH, and co-existing ions were studied. Adsorption equilibrium and biosorption kinetics were established from batch experiments. The adsorption equilibrium was adequately described by the Langmuir isotherm, and biosorption kinetics was in pseudo-second order model. The experiment on co-existing ions showed that the biosorption capacity of biomass decreased with an increasing concentration of competing ions. Desorption experiments indicated that EDTA was efficient desorbent for recovery from Cd^2＋. With high capacities of metal biosorption and desorption, the biomass of Cladophora fascicularis is promising as a cost-effective biosorbent for the removal of Cd^2＋ from wastewater.     

Optimized water vapor permeability of sodium alginate films using response surface methodology

The water vapor permeability （WVP） of films is important when developing pharmaceutical applications. Films are frequently used as coatings, and as such directly influence the quality of the medicine. The optimization of processing conditions for sodium alginate films was investigated using response surface methodology. Single-factor tests and Box-Behnken experimental design were employed. WVP was selected as the response variable, and the operating parameters for the single-factor tests were sodium alginate concentration, carboxymethyl cellulose （CMC） concentration and CaClz solution immersion time. The coefficient of determination （R2） was 0.97, indicating statistical significance. A minimal WVP of 0.389 8 g-mm/（m^2.h.kPa） was achieved under the optimum conditions. These were found to be a sodium alginate concentration, CMC concentration and CaCl2 solution immersion time at 8.04%, 0.13%, and 12 min, respectively. This provides a reference for potential applications in manufacturing film-coated hard capsule shells.     

The extraction of pigments from fresh <Emphasis Type="Italic">Laminaria japonica</Emphasis>

The pigments in Laminariajaponica was extracted with six organic solvents and analyzed in spectroscopy analysis. The extractions conditions were screened by an orthogonal test and the quantity of extracted pigments was determined spectroscopically. The results show that： （1） among the six organic solvents, acetone was the most effective one for the extraction; （2） the optimum extraction conditions were as follows： the ratio of S/M （solvent volume/ material weight） was 30 ml/g; fresh seaweed was extracted 2 times in 2 h; （3） the average total content of pigments was 1.85 mg/g （calculated with dry L. japonica）.     

Impact of Phenanthrene on Denitrification Activity and Transcription of Related Functional Genes in Estuarine and Marine Sediments

The effects of phenanthrene(Phe)on the denitrification activity and denitrifying genes(narG,nirS and nosZ)were evaluated by dose-response experiments in sediments of Dagu River Estuary(DRE)and Jiaozhou Bay(JZB).The results showed that potential denitrification activity(PDA),N2O,NO3−and NO2−reduction rates of both areas were inhibited with an increase of Phe concentrations.The PDA,N2O,NO3−and NO2−reduction rates of both areas was highest and lowest in the control(DRE:0.453,0.427,7.439 and 3.222mgNkg−1 h−1,JZB:0.592,0.555,8.470 and 3.793mgNkg−1 h−1)and highest Phe amended treatments(DRE:0.069,0.001,4.486,and 1.563 mgNkg−1 h−1;JZB:0.114,0.024,5.527 and 2.200 mgNkg−1 h−1).The inhibition rate of PDA was highest,follow by NO2−reduction and then NO3−reduction.Moreover,with the increasing of Phe concentrations,total bacteria count and the abundance of denitrifying genes were decreased.And N2O accumulation was promoted with the addition of Phe for both areas.Based on the comparison of EC50 values,denitrifiers harboring three genes were more sensitive to Phe than PDA,and denitrifiers harboring nirS gene were more sensitive,followed by nosZ gene,and then narG gene.Furthermore,according to correlation analysis,the relative abundance of denitrifying genes was much more positively correlated with PDA,NO3−and NO2−reduction than total bacteria count.In addition,the denitrification activity and total bacteria count in JZB were more inhibited than that of DRE.This study is useful for understanding the impact of Phe pollution on denitrification in estuary and marine sediments,with profound implications for the management of aquatic ecosystems regarding eutrophication(N-removal)and greenhouse effect.     

Applicability of Perinereis aibuhitensis Grube for Fish Waste Removal from Fish Cages in Sanggou Bay,P.R.China

The present study investigated the applicability of integrated polychaete-fish culture for fish waste removal to offset negative impact induced by organic benthic enrichment.A field study demonstrated that deposition rate was significantly higher underneath the fish farm than that in control area.The material settling under the farm was characterized by a high amount of fish feces(45%) and uneaten feed(27%).Both feeding rate(FR) and apparent digestibility rate(ADR) increased with decreasing body weight,as was indicated by significantly a higher rate observed for the groups containing smaller individuals in a lab study.The nutrient in fresh deposited material(De) was higher than that in sediments collected under the farm(Se),resulting in lower feces production but higher apparent digestibility rate for the De group as feeding rate was similar.Consequently,higher nutrient removal efficiency was observed in the De group.A mass balance approach indicated that approximately 400–500 individuals m~(-2) is required for removing all waste materials deposited underneath the fish farm,whereas abundance can be lower(about 300–350 individuals m~(-2)) when only the fish waste needs to be removed.The results showed that a significant amount of waste had been accumulated in the fish cages in Sanggou Bay.The integration of fish with P.aibuhitensis seems promising for preventing organic pollution in the sediment and therefore is an effective strategy for mitigating negative effect of fish farms.Thus such integration can become a new IMTA(integrated multi-trophic aquaculture) model in Sanggou Bay.     

Biosorption of Cr (VI), Cr (III), Pb (II) and Cd (II) from aqueous solutions by Sargassum wightii and Caulerpa racemosa algal biomass

Heavy metal pollution is one of the most important environmental problems today.Biosorption is an innovative tech-nology that employs biological materials to accumulate heavy metals from waste water through metabolic process or physicochemi-cal pathways of uptake.Even though several physical and chemical methods are available for removal of heavy metals,currently many biological materials such as bacteria,algae,yeasts and fungi have been widely used due to their good performance,low cost and large quantity of availability.The aim of the present study is to explore the biosorption of toxic heavy metals,Cr(VI),Cr(III),Pb(II) and Cd(II) by algal biomass obtained from algae Sargassum wightii(brown) and Caulerpa racemosa(green).Biosorption of algal biomass was found to be biomass concentration-and pH-dependent,while the maximal biosorption was found at pH 5.0 and with the metal concentration of 100 mg L-1.S.wightii showed the maximal metal biosorption at the biomass concentration of 25 g L-1,followed by C.racemosa with the maximal biosorption at 30 g L-1.S.wightii showed 78% biosorption of Cr(VI),Cr(III),Pb(II) and Cd(II) ions.C.racemosa exhibited 85% biosorption of Cd(II) and Cr(VI),and 50% biosorption of Cr(III) and Pb(II).The results of our study suggest that seaweed biomass can be used efficiently for     

Application of CFD Modeling to Hydrodynamics of CycloBioFluidized Sand Bed in Recirculating Aquaculture Systems

To improve the efficiency of a CycloBio fluidized sand bed （CB FSB） in removal of dissolved wastes in recirculatingaquaculture systems, the hydrodynamics of solid-liquid flow was investigated using computational fluid dynamics （CFD） modelingtools. The dynamic characteristics of silica sand within the CB FSB were determined using three-dimensional, unsteady-state simula-tions with the granular Eulerian multiphase approach and the RNG k-e turbulence model, and the simulation results were validatedusing available lab-scale measurements. The bed expansion of CB FSB increased with the increase in water inflow rate in numericalsimulations. Upon validation, the simulation involving 0.55 mm particles, the Gidaspow correlation for drag coefficient model andthe Syamlal-O＇Brien correlation for kinetic granular viscosity showed the closest match to the experimental results. The volume frac-tion of numerical simulations peaked as the wall was approached. The hydrodynamics of a pilot-scale CB FSB was simulated in or-der to predict the range of water flow to avoid the silica sand overflowing. The numerical simulations were in agreement with theexperimental results qualitatively and quantitatively, and thus can be used to study the hydrodynamics of solid-liquid multiphase flowin CB FSB, which is of importance to the design, optimization, and amplification of CB FSBs.     

Effects of temperature, algae biomass and ambient nutrient on the absorption of dissolved nitrogen and phosphate by Rhodophyte Gracilaria asiatica

Gracilaria asiatica,being highly efficient in nutrient absorption,is cultivated in sea cucumber ponds to remove nutrients such as nitrogen and phosphate.It was cultured in a laboratory simulating field conditions,and its nutrient absorption was measured to evaluate effects of environmental conditions.Ammonia nitrogen(AN),nitrate nitrogen(NN),total inorganic nitrogen(TIN),and soluble reactive phosphorus(SRP) uptake rate and removal efficiency were determined in a 4×2 factorial design experiment in water temperatures(T) at 15℃ and 25℃,algae biomass(AB) at 0.5 g/L and 1.0 g/L,total inorganic nitrogen(TIN) at 30 μmol/L and 60 μmol/L,and soluble reactive phosphorus(SRP) at 3 and 6 μmol/L.AB and ambient TIN or SRP levels significantly affected uptake rate and removal efficiency of AN,NN,TIN,and SRP(P<0.001).G.asiatica in AB of 0.5 g/L showed higher uptake rate and lower removal efficiency relative to that with AB of 1.0 g/L.Nitrogen and phosphorus uptake rate rose with increasing ambient nutrient concentrations;nutrient removal efficiency decreased at higher environmental nutrient concentrations.The algae preferred to absorb AN to NN.Uptake rates of AN,NN,and SRP were significantly affected by temperature(P<0.001);uptake rate was higher for the 25℃ group than for the 15℃ group at the initial experiment stage.Only the removal efficiency of AN and SRP showed a significant difference between the two temperature groups(P<0.01).The four factors had significant interactive effects on absorption of N and P,implying that G.asiatica has great bioremedial potential in sea cucumber culture ponds.     

Application of CFD modeling to hydrodynamics of CycloBio fluidized sand bed in recirculating aquaculture systems

To improve the efficiency of a CycloBio fluidized sand bed(CB FSB) in removal of dissolved wastes in recirculating aquaculture systems, the hydrodynamics of solid-liquid flow was investigated using computational fluid dynamics(CFD) modeling tools. The dynamic characteristics of silica sand within the CB FSB were determined using three-dimensional, unsteady-state simulations with the granular Eulerian multiphase approach and the RNG k-ε turbulence model, and the simulation results were validated using available lab-scale measurements. The bed expansion of CB FSB increased with the increase in water inflow rate in numerical simulations. Upon validation, the simulation involving 0.55 mm particles, the Gidaspow correlation for drag coefficient model and the Syamlal-O'Brien correlation for kinetic granular viscosity showed the closest match to the experimental results. The volume fraction of numerical simulations peaked as the wall was approached. The hydrodynamics of a pilot-scale CB FSB was simulated in order to predict the range of water flow to avoid the silica sand overflowing. The numerical simulations were in agreement with the experimental results qualitatively and quantitatively, and thus can be used to study the hydrodynamics of solid-liquid multiphase flow in CB FSB, which is of importance to the design, optimization, and amplification of CB FSBs.     

Analysis of effects of operating parameters on rate of penetration in drilling process with air down-the-hole hammer

Air down-the-hole(DTH)hammer drilling has long been recognized to have the potential of drilling faster than conventional rotary drill,especially in some hard rocks such as granite,sandstone,limestone,dolomite,etc.with the same weight on bit(WOB)and rotations per minute(RPM).So,it has been widely used in many drilling fields including mineral resource exploration drilling,oil and gas drilling and geothermal drilling.In order to reduce drilling cost by selecting optimal drilling parameters,rate of penetration(ROP)should be estimated accurately and the effects of different factors on ROP should be analyzed.In this research,ANN model with several multi-layer perception back propagation(BP)networks for predicting ROP of air DTH hammer drilling was developed using controllable parameters such as impact energy,impact frequency,WOB,RPM and bit operating time for the formations with a certain drillability index of rock.Several BP neural networks with the different neurons in hidden layers were developed and compared for selecting optimal architecture of ANN.The effects of the drilling parameters such as impact energy,impacting frequency,WOB,RPM and bit operating time on the ROP of air DTH hammer drilling were investigated by trained ANN.From the analyses,the optimum range of drilling parameters for providing high ROP were determined and analyzed for a formation with a certain drillability index of rock.The methodology proposed in this study can be used in many mathematical problems for optimization of drilling process with air DTH hammer.     

Construction of a growth model in the green alga Tetraselmis subcordiformis using a response surface approach

The green alga Tetraselmis subcordiformis has been widely used as a quality live food for aquaculture species, and also has been studied as a model organism for the photo-biological production of hydrogen. We attempted to quantify the relationship between T. subcordiformis specific growth rate(SGR) and three important environmental factors(temperature, salinity, and p H) using the central composite design and response surface method under laboratory conditions. The results showed that the linear effects of temperature and salinity were significant( P 0.05), and they were equally important in impacting T. subcordiformis specific growth; the linear effect of p H was not significant( P 0.05); the interactive effect of temperature and p H was significant( P 0.05), whereas the temperature ′ salinity and salinity ′ p H interactions were not significant( P 0.05); all of the quadratic effects of the three factors were significant( P 0.05). A model equation for specific growth rate with the three factors was established, with the unadjusted and predictive R~2 as high as 0.990 and 0.921, respectively, suggesting that the model was a very good fit and that it could be used to predict SGR. Through optimizing the reliable model, an optimal 3-factor combination of 25 ° C/35 of salinity/p H 7.9 was obtained, at which the maximum specific growth rate(0.65) was recorded, with a desirability value of 93.8%. These experimental results could serve as guidelines for increasing T. subcordiformis production efficiency.     

The Effect of Temperature on Growth and Energy Budget of the Polychaete,Neanthes japonica Izuka

Growth and energy budget of the polychaete, Neanthesjaponica, at various temperatures (17, 20, 23, 26 and 29 ℃) were investigated in this study. The growth, as indicated by final dry weight and specific growth rate (SGR), increased with increasing temperature, with the maximum level at 26℃, and then decreased significantly at 29℃. A similar trend was observed in feeding rate, food conversion efficiency (FCE) and apparent digestive rate (ADR). However, no significant differences were detected in ADR among all the temperature treatments. In the pattern of energy allocation, faeces energy was only a small component of energy budget and had little influence on the proportion of food energy allocated to growth. The metabolic energy accounted for a large portion of energy intake for each temperature treatment. The nitrogen excretion was appreciable with changing temperature. The two expendi-ture terms (respiration energy and excretion energy) in energy budget were the major factors influencing the proportion of food en-ergy allocated to growth. These results revealed that temperature affected the growth of N. japonica mainly by influencing feeding rate and FCE. In addition, regression equations describing the relationship between feeding rate, faecal production, SGR, FCE and temperature were obtained. The optimum temperatures for feeding rate, FCE and SGR were estimated at 25.01 ℃, 24.24℃ and 24.73 ℃, respectively, from the regression equations.     

Measurement and Scaling of Mercury on Soil and Air in a Historical Artisanal Gold Mining Area in Northeastern China

The Jiapigou gold mine area, located in the upper reaches of the Songhua River, was the first and largest artisanal gold mine once in China, and it used to be prominent in two marking years(1870 and 1974). Jiapigou area had a gold mining history of more than 190 years, which was first opened in 1820. Gold extraction with algamation was applied as the dominant method of excavation from 1940 to 2008, and a total of more than 100 t of gold were extracted from the mine using this method and it was estimated that 100–200 t Hg were released, thus causing severe mercury environmental pollution in the mining area. In the experimental campaigns of this study, in situ air and soil Hg concentrations and air-soil Hg fluxes were measured from April 2009 to December 2011. The results showed that in the study area the total gaseous mercury(TGM) concentration exhibited remarkable spatial and temporal distribution patterns, i.e. the TGM gradually decreased following the increase in distance to gold mining sites in space, and the values in spring, summer and autumn were elevated by 1–2 orders of magnitude in comparison with those in winter. Furthermore, at other sampling sites the total soil mercury(TSM) concentration in spring was higher than that in autumn, except for the contrary laws demonstrated at the Erdaogou mining site. However, in spring and winter the Hg flux between air and soil was under the control of different environmental factors, and the characteristics were clear and distinct. In spring the Hg flux between air and soil was directly under the control of solar irradiation, and the releasing process was predominant with a remarkable positive correlation to solar irradiation. Nevertheless, in winter the Hg fluxes were indirectly under the control of solar irradiation, which caused thermal inversion due to the thick snow cover. The depositing process was predominant and the correlations between Hg flux and air temperature was remarkably negative, and there was a positive correlation between Hg flux and solar irradiation.     

An assessment of variations in mercury deposition to Antarctica over the past 34,000 years

We performed a comparison analysis of the variations .in Mercury ( Hg) concentrations and the precipitation proxies ( e. g. , 18 O values and 10 Be concentrations) in the Dome C ice core. The results showed that there were significant correlations between Hg and δ 10O values, 10Be concentrations, indicating that the accumulation rate in Dome C is one of the key factors controlling the variations of Hg concentrations in the past 34 ,000 years, and implying that Hg concentrations in ice core can be used as another reliable proxy of precipitation rate in Antarctica. Based upon the high-resolution δ 18O values, we estimated the variations in mercury deposition flux to Antarctica over the past 34,000 years. The highest mercury deposition flux is about 3. 80 pg cm-2 yr-1 during the Last Glacial Maxium (LGM) as high as 3. 5 times of the mercury deposition flux ( about 1. 08 pg cm -2 yr -1) in Holocene due to the fluctuations in natural mercury emissions such as the oceanic biological emissions.     

An innovative process to improve turbidity and Organics Removal by BAC filters

The turbidity criterion for the product water of a WTP according to the State Project ‘863＇ on the safeguard technology of drinking water in the southern areas of China is 0.1 NTU. The turbidity removal in the activated carbon filter was analyzed in a pilot-scale test and an innovative technology to improve the turbidity removal in a biologically activated carbon （BAC） filter was put forward in order to meet the criterion. Experimental results showed that the enhanced filtration by adding polymerized aluminium chloride （PAC） into the BAC filter was quite effective in turbidity control. The effluent turbidity was kept at a stable level （mean） of 0.033 NTU with a high removal of about 80% for influent turbidity of 0.110- 0240 NTU with an addition of PAC at 0.05 mg L^-1, meeting the requirement for filtrate turbidity equal to or less than 0.1NTUC totally. In addition, the larger the PAC dosage was, the lower the effluent turbidity was. However, further improvement of turbidity removal was not obvious for PAC dosages beyond 0.10 mg L^- 1, and an optimal PAC dosage in the range of 0.05 - 0.10 mg L^- 1 was proposed.     

Annual time-series analyses of total gaseous mercury measurement and its impact factors on the Gongga Mountains in the southeastern fringe of the Qinghai-Tibetan Plateau

Long-term monitoring programs for measurement of atmospheric mercury concentrations are presently recognized as powerful tools for local,regional and global studies of atmospheric long-range transport processes,and they could also provide valuable information about the impact of emission controls on the global budget of atmospheric mercury,their observance and an insight into the global mercury cycle. China is believed to be an increasing atmospheric mercury emission source. However,only a few measurements of mercury,to our knowledge,have been done in ambient air over China. The highly-time resolved atmospheric mercury concen-trations have been measured at Moxi Base Station （102°72′E 29°92′N,1640 m asl） of the Gongga Alpine Ecosystem Observation and Experiment Station of Chinese Academy of Sciences （CAS） from May 2005 to June 2006 by using a set of Automatic Atmospheric Mercury Speciation Analyzers （Tekran 2537A）. Measurements were carried out with a time resolution of every 15 minutes. The overall average total gaseous mercury （TGM） covering the measurement periods was 4±1.38 ng·m^-3 （N=57310）,which is higher than the global background level of approximately 1.5～2.0 ng·m^-3. The measurements in all seasons showed a similar diurnal change pattern with a high concentration during daytime relative to nighttime and maximum concentration near solar noon and minimum concentration immediately before sunrise. The presence of diurnal TGM peaks during spring and summer was found earlier than that during autumn and winter. When divided seasonally,it was found that the concentrations of TGM were highest in winter with 6.13 ± 1.78 ng·m^-3 and lowest in summer with 3.17 ± 0.67 ng·m^-3. There were no significant differences in TGM among wind sectors during each season. Whereas Hg generally exhibited significant correlations with the parameters,such as temperature,saturated vapor pressure,precipitation,ultraviolet radiation （UV） and atmospheric pressure at the whole measurement stage,and t     

Screening and isolation of the algicidal compounds from marine green alga Ulva intestinalis

Twenty species of seaweed were collected from the coast of Zhejiang, China, extracted with ethanol, and screened for algicidal activity against red tide microalgae H eterosigma akashiwo and Prorocentrum micans. Inhibitory eff ects of fresh and dried tissues of green alga U lva intestinalis were assessed and the main algicidal compounds were isolated, purifi ed, and identifi ed. Five seaweed species, U. intestinalis, U. fasciata, Grateloupia romosissima, Chondria crassicaulis, and Gracilariopsis lemaneiformis, were investigated for their algicidal activities. Fresh tissues of 8.0 and 16.0 mg/m L of U. intestinalis dissolved in media signifi cantly inhibited growth of H. akashiwo and P. micans, respectively. Dried tissue and ethyl acetate(Et OAc) extracts of U. intestinalis at greater than 1.2 and 0.04 mg/m L, respectively, were fatal to H. akashiwo, while its water and Et OAc extracts in excess of 0.96 and 0.32 mg/m L, respectively, were lethal to P. micans. Three algicidal compounds in the Et OAc extracts were identifi ed as 15-ethoxy-(6z,9z,12z)-hexadecatrienoic acid(I),(6E,9E,12E)-(2-acetoxy- β- D-glucose)-octadecatrienoic acid ester(II) and hexadecanoic acid(III). Of these, compound II displayed the most potent algicidal activity with IC_(50) values of 4.9 and 14.1 μg/m L for H. akashiwo and P. micans, respectively. Compound I showed moderate algicidal activity with IC_(50) values of 13.4 and 24.7 μg/m L for H. akashiwo and P. micans, respectively. These fi ndings suggested that certain macroalgae or products therefrom could be used as ef fective biological control agents against red tide algae.