Variations in retention efficiency of bivalves to different concentrations and organic content of suspended particles

Retention efficiencies (RE) of scallop (Chlamys farreri),oyster (Crassostrea gigas) and mussel (Mytilus edulis) in a flow-through system were measured to understand the short-term response to various particle and organic matter concentrations.By comparing the RE of C.farreri with that of C.gigas and M.edulis,we gained further knowledge on the feeding physiological characteristics of C.farreri and ascertained the possible cause of high summer mortalities of this species.The experimental feeding conditions in...     

Variations of the suspended matter and the particulate organic carbon in the entry of the Gironde Estuary,France

The effects of using different types of glass fiber filters (GF/F, GF/C) and of sample treatments were evaluated. Studies on the variation of suspended matter (SM) and particulate organic carbon (POC) showed that: 1) the transversal and day to night variations are important and must be taken into account in order to get a correct river flux; 2) no regular seasonal variations of SM and POC were observed, as they are controlled essentially by the climatological, hydrologic, physiochemical, biological, and geological conditions of the drainage area. Contribution No 2246 from the Institute of Oceanology, Chinese Academy of Sciences.     

Variations of antioxidant enzyme activity and malondialdehyde content in nemertean Cephalothrix hongkongiensis after exposure to heavy metals

The antioxidant enzyme activity and malondialdehyde (MDA) content of Cephalothrix hongkongiensis were studied to assess variations in the biochemical/physiological parameters of nemerteans under heavy metal stress. Worms were exposed to copper, zinc and cadmium solutions at different concentrations, and the activity of three antioxidant enzymes, catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPX), and MDA content were measured. The results show that the activity of each enzyme changed immediately after exposure to heavy metals. CAT was invariably inhibited throughout the experimental period, while the SOD activity was significantly elevated by exposure to Cu²⁺ for 48 h, but then decreased. SOD was inhibited by Zn²⁺during the first 12 h of exposure, but activated when exposed for longer periods. Under Cd²⁺ stress, SOD activity decreased within 72 h. GPX activity varied greatly, being significantly increased by both Cu²⁺ and Zn²⁺, but significantly inhibited by Cd²⁺ in the first 12–24 h after exposure. MDA content increased on Cu²⁺ exposure, but normally decreased on Zn²⁺ exposure. MDA content followed an increase-decrease-increase pattern under Cd²⁺ stress. In conclusion, the antioxidant system of this nemertean is sensitive to heavy metals, and its CAT activity may be a potential biomarker for monitoring heavy metal levels in the environment.     

Impact of suspended particles and enhancement techniques on ultraviolet disinfection of a secondary effluent

The concentration of suspended solids in the secondary effluent often varies widely, leading to frequent adjustment of the UV dosage to meet the disinfection criterion. In addition, a desired disinfection rate is difficult to achieve sometimes. The authors studied the particle size distribution, contribution of particle-associated Fecal Coliform （F. C. ）, and their influences on UV disinfection. A combined disinfection process （chlorination with a subsequent UV disinfection） was tested to improve the disinfection effect. The results indicated that the content of suspended solids, especially that of large particles, has a strong impact on UV disinfection efficiency; D〉 10 μm particles associated F.C. are difficult to be disinfected and are the main part of the tailings of F.C. inactivation curves. Pre-chlorination could decrease the number of particles in the secondary effluent and transform the large particles into small ones, reducing the influence of particles on UV disinfection and enhancing the resistance ability of the combined process to particle loading.     

Variations of suction and suction stress of unsaturated loess due to changes in lignin content and sample preparation method

Unsaturated loess in natural sites loses stability as the overburden load continuously increases. Traditional soil modifiers such as cement and fly ash affect the surrounding environment. A new type of material, i.e., lignin, is environmentally friendly and able to increase the strength of loess. However, the engineering characteristics of the improved loess under unsaturated conditions are not yet clear. In this study, the soil-water characteristic curves(SWCCs) of lignin-improved loess samples were determined from 0 k Pa to 700 k Pa using a pressure plate instrument, and then, they were fitted using the van Genuchten(VG) model and the Fredlund and Xing(FX) model. In addition, the effects of the lignin content and sample preparation methods on the SWCCs were investigated to determine the optimal lignin content and a suitable sample preparation method for loess foundations. As the lignin content increases, the matric suction and residual water content of the improved loess increase. The suction stress increases with the increasing lignin contents of 1%-2%. At lignin contents of 3%-4%, the suction stress begins to decrease and the samples prepared using the slurry method has a lower suction stress than that prepared using the wet mixing method. The air entry value(AEV) increases with increasing lignin content. In addition, scanning electron microscopy(SEM) was used to investigate the microstructural variations. It was found that after the addition of lignin, the entrapment of the loess particles by the lignin fibers created some larger particles and smaller pore diameters, which in turn led to poor connectivity of the loess pores. These changes cause the matric suction of the modified loess to increase.     

Retrieval of chlorophyll a and suspended solid concentrations by hyperspectral remote sensing in Taihu Lake, China

Chlorophyll α（ch1-α） and suspended solid concentrations are two frequently used water quality parameters for monitoring a lake. Traditional measurement of ch1-α and suspended solids, requiring laborious laboratory work, which is often expensive and time consuming. Hyperspectral remote-sensing measurement provides a fast and easy tool for estimating water trophic status. In situ hyperspectral data on March 7-8, July 6-7, September 20 and December 7-8, 2004 and the corresponding water chemical data were used to regress the algorithm of water quality parameters. Results showed that the peak of water leaving radiance around 700 nm （R700） varied proportionally with ch1-α concentration, and moved to infrared when algal bloom occurred. The reflectance ratio of R702/R685 was well correlated with ch1-α when water surface in no algal bloom case and the correlation coefficient was better if absorption of phycocyanin was considered. The reflectance ratio R620/R531 was highly correlated to the concentration of suspended solids. The relationship between suspended solids and other band groups were also compared. Secchi disk depth could be calculated by non-linear correlation with suspended solids concentration.     

Properties of coarse particles in suspended particulate matter of the North Yellow Sea during summer

Fine particles in seawater commonly form large porous aggregates. Aggregate density and settling velocity determine the behavior of this suspended particulate matter(SPM) within the water column.However, few studies of aggregate particles over a continental shelf have been undertaken. In our case study, properties of aggregate particles, including size and composition, over the continental shelf of the North Yellow Sea were investigated. During a scienti?c cruise in July 2016, in situ ef fective particle size distributions of SPM at 10 stations were measured, while temperature and turbidity measurements and samples of water were obtained from surface, middle, and bottom layers. Dispersed and inorganic particle size distributions were determined in the laboratory. The in situ SPM was divided into(1) small particles(32 μm),(2) medium particles(32–256 μm) and(3) large particles(256 μm). Large particles and medium particles dominated the total volume concentrations(VCs) of in situ SPM. After dispersion, the VCs of medium particles decreased to low values(0.1 μL/L). The VCs of large particles in the surface and middle layers also decreased markedly, although they had higher peak values(0.1–1 μL/L). This suggests that almost all in situ medium particles and some large particles were aggregated, while other large particles were single particles. Correlation analysis showed that primary particles 32 μm in?uenced the formation of these aggregates. Microscopic examination revealed that these aggregates consisted of both organic and inorganic ?ne particles, while large particles were mucus-bound organic aggregates or individual plankton.The vertical distribution of coarser particles was clearly related to water strati?cation. Generally, medium aggregate particles were dominant in SPM of the bottom layer. A thermocline blocked resuspension of?ne material into upper layers, yielding low VCs of medium-sized aggregate particles in the surface layer.Abundant large biogenic particles were present in both surface and middle layers.     

Study on Optical Properties of Unpigmented Suspended Particles,Yellow Substance and Phytoplankton Algae in Taihu Lake

The optical properties of a waterbody are subjects of research on limnological hydrooptics. The optical properties of, and parameterization methods for, three impurities in Taihu Lake, namely unpigmented suspensions, yellow substance and phytoplankton algae, are analyzed in detail in this paper dealing with the optical types of Taihu Lake waters both in winter and in summer. The results showed that : 1 ) The optical parameters of suspended particles can be calculated by the application of Mie Theory; 2) The absorption of yellow substance decreases exponentially with increasing wavelength, with the mean value of decreasing rate being about 0.014 nm^-1 ; 3) Taihu Lake waters appeared to be of type PY in winter, with suspended particles and yellow substance being the dominant light absorbers, and type CPY in summer, with suspended particles, yellow substance and phytoplankton algae being the dominant light absorbers; 4) In winter or summer, unpigmented suspension has the main effect on the scattering property of Taihu Lake waters.     

Behavior of different phosphorus species in suspended particulate matter in the Changjiang estuary

Suspended particulate matter (SPM) collected in the Changjiang (Yangtze River) estuary in June 2006 was separated into five fractions via water elutriation: clay-very fine silt (<8 μm), fine silt (8–16 μm), medium silt (16–32 μm), coarse silt (32-63 μm) and sand (>63 μm). The SPM and fractionated particles were sequentially analyzed by a modified SEDEX sequential extraction method to obtain six species of phosphorus: exchangeable or loosely-sorbed P, organic P, Fe-bound P, authigenic P, detrital P and refractory P. The results indicated that all particulate phosphorus species except for detrital P were negatively correlated to particle size; a high detrital P content was found in coarse silt and very coarse silt. From the inside of the river mouth to the gate of the river mouth, organic P, Fe-bound P and refractory P in the suspended particles decreased and a higher amount of exchangeable P appeared around the gate of the river mouth. From the gate of the river mouth to the sea, exchangeable P and organic P in suspended particles increased distinctly. The total particulate P flux into the estuary from the Changjiang River was about 45.45×10⁸ μmol/s during sampling. Of this, about 8.27×10⁸ μmol/s was associated with the “truly suspended” fraction. The bio-available particulate P flux was about 13.58×10⁸ μmol/s. Of this, about 4.24×10⁸ μmol/s was transported by “truly suspended” particles.     

Study on the isotherms of the interaction between suspended particles and Cu (II) in the Huanghe River

The isotherms of the interaction between the suspended particles and Cu²⁺, and the effects of lysine and asparaginic acid on the isotherms in the Huanghe (Yellow) River were studied by applying the theory and method of interfacial stepwise ion/coordination particle exchange. We obtained a new stepped river isotherm, formed by two curves joined together with a “plateau” in the middle. The adsorption equilibrium constantsK ₁ andK ₂ were calculated by using the isothermal equation of surface stepwise ion exchange. Amino acid in small amount promotes exchange adsorption of the suspended particles with Cu²⁺. The degree of promotive action relates to the isoelectric point of amino acid. The promotive effect of lysine is bigger than that of asparaginic acid. Project 29361001 supported by NSFC.     

Oxidative stress responses of submerged macrophyte Vallisneria asiatica to different concentrations of cyanobacteria

In a 10-day aquarium experiment,this investigation examines macrophyte restoration in eutrophic Lake Taihu,the physiological effects of different plant biomass levels and of increasing natural cyanobacterial concentrations on a submerged macrophyte,Vallisneria asiatica. Cyanobacterial stress suppressed the superoxide dismutase(SOD) activity of the plant's leaves and induced the catalase(CAT) and peroxidase(POD) activities of its roots. The soluble protein content in V. asiatica decreased with an increase in natural cyanobacterial concentrations,whereas the malonaldehyde(MDA) increased significantly at chlorophylla(Chl a) concentrations of 222 and 262 μg/L in water. V. asiatica adapted to the stress caused by cyanobacterial concentrations by adjusting its antioxidant defense system to remove the excessive reactive oxygen species when the algal Chl a concentration was 109 μg/L. Additionally,high biomass of V. asiatica(2 222 g FW/m 2) can inhibit the reproduction of cyanobacteria more significantly than low biomass(1 111 g FW/m2). High biomass of V. asiatica increased the oxidative stress in an individual plant when the initial Chl a concentration in the water reached 222 and 262 μg/L,as expressed by the increased MDA in leaves,compared with low biomass of V. asiatica. This provides a basis for controlling cyanobacterial concentrations and V. asiatica biomass for the recovery of V. asiatica in eutrophic Lake Taihu.     

Temporal variation in biodeposit organic content and sinking velocity in long-line shellfish culture

We measured the organic content and sinking velocities of biodeposits from two scallop species (Chlamys farreri, Patinopecten yessoensis) and abalone (Haliotis discus hannai) that were cultured on suspended long-lines. Measurements were conducted every two months from April 2010 to February 2011. The shellfish were divided into three size groups (small, middle, and big sizes). At each sample point, we assessed biodeposit organic content, average sinking velocity, the frequency distribution of sinking velocities, and the correlation between organic content and sinking velocity. The organic content of biodeposits varied significantly among months (P<0.05) and the pattern of change varied among species. Sinking velocities varied significantly, ranging from <0.5 cm/s to >1.9 cm/s. The sinking velocities of biodeposits from C. farreri and P. yessoensis were 0.5–1.5 cm/s and from H. discus hannai were <0.7 cm/s. The organic content was significantly negatively correlated to the sinking velocity of biodeposits in C. farreri (P<0.001) and P. yessoensis (P<0.05).     

Adsorption of Th and Pa onto particles and the effect of organic compounds in natural seawater

Journal of Oceanology and Limnology - 231Pa and 230Th are two crucial isotopes in the ongoing GEOTRACES Project. However, the controversy on 231Pa/230Th proxy pertaining to archiving ocean...     

Labile organic matter content and distribution as affected by six-year soil amendments to eroded Chinese mollisols

Labile organic carbon （LOC） is a fraction of soil organic carbon （SOC） with rapid turnover time and is affected by soil fertilization. This investigation characterized the SOC content, LOC content and LOC distribution in the treatment plots of surface soil erosion at five levels （0-, 5-, 10-, 20- and 30-cm erosion）. The soil had received contrasting fertilizer treatments （i.e., chemical fertilizer or chemical fertilizer ＋ manure） for 6 years. This study demonstrated that both SOC and various LOC fractions contents were higher in the plots with fertilizer ＋ manure than in those with fertilizer alone under the same erosion conditions. The SOC and LOC contents de- creased as the erosion depth increased. Light fraction organic carbon, particulate organic carbon, easily oxidizable organic carbon （KMnO4-oxydizable organic carbon）, and microbial biomass carbon were 27% 57%, 37%-7%, 20%-25%, and 29%-33% higher respectively in the fertilizer ＋ manure plots, than in the fertilizer alone plots. Positive correlations （p 〈 0.05） between SOC content and different fractions contents were observed in all plots except the correlation between total SOC content and water-soluble organic carbon content in the different fertilization treatments. Obviously, fertilizer ＋ manure treatments would be conducive to the accumulation of LOC and SOC in the Black soil of Northeast China.     

Assessment of total suspended sediment concentrations in Poyang Lake using HJ-1A/1B CCD imagery

We explored the potential of the environment and disaster monitoring and forecasting small satellite constellations (HJ-1A/1B satellites) charge-coupled device (CCD) imagery (spatial resolution of 30 m, revisit time of 2 days) in the monitoring of total suspended sediment (TSS) concentrations in dynamic water bodies using Poyang Lake, the largest freshwater lake in China, as an example. Field surveys conducted during October 17-26, 2009 showed a wide range of TSS concentration (3-524 mg/L). Atmospheric correction was implemented using the Fast Line-of-sight Atmospheric Analysis of Spectral Hypercubes (FLAASH) module in ENVI with the aid of aerosol information retrieved from concurrent Terra/Moderate Resolution Imaging Spectroradiometer (MODIS) surveys, which worked well at the CCD bands with relatively high reflectance. A practical exponential retrieval algorithm was created between satellite remote sensing reflectance and in-situ measured TSS concentration. The retrieved results for the whole water area matched the in-situ data well at most stations. The retrieval errors may be related to the problem of scale matching and mixed pixel. In three selected subregions of Poyang Lake, the distribution trend of retrieved TSS was consistent with that of the field investigation. It was shown that HJ-1A/1B CCD imagery can be used to estimate TSS concentrations in Poyang Lake over synoptic scales after applying an appropriate atmospheric correction method and retrieval algorithm.     

The changes of three components in coelomic fluid of Urechis unicinctus exposed to different concentrations of sulfide

The changes in heme （associated with hemoglobin）, hemoglobin and hematin in the coelomic fluid of marine worm, Urechis unicinctus, exposed to different concentrations of sulfide, were investigated using biochemical techniques. When exposed to different sulfide concentrations for up to 96 h, the relative amounts of the three components changed in a regular pattern suggesting that the coelomocytes play an important role in the worm＇s tolerance to sulfide. The possible roles of heme compounds in sulfide tolerance of this species are discussed on the basis of our experimental data.     

Base cation concentrations in forest litter and topsoil have different responses to climate and tree species along elevational gradients

The forest litter is an essential reservoir of nutrients in forests, supplying a large part of absorbable base cations(BC) to topsoil, and facilitating plant growth within litter-soil system. To characterize elevational patterns of base cation concentrations in the forest litter and topsoil, and explore the effects of climate and tree species, we measured microclimate and collected the forest litter and topsoil(0-10 cm) samples across an elevational range of more than 2000 m(1243 ～ 3316 m a.s.l.),and analyzed the concentrations of BC in laboratory. Results showed that: 1) litter Ca concentration displayed a hump-shaped pattern along the elevational gradients, but litter K and Mg showed saddle-shaped patterns. Soil Ca concentration increased with elevation, while soil K and Mg had no significant changes. 2) Ca concentration in the forest litter under aspen(Populus davidiana) was significantly higher than that in all other species, but in topsoil, Ca concentration was higher under coniferous larch and fir(Larix chinensis and Abies fargesii). Litter K and Mg concentrations was higher under coniferous larch and fir, whereas there were nosignificant differences among tree species in the concentrations of K and Mg in topsoil. 3) Climatic factors including mean annual temperature(MAT), growing season precipitation(GSP) and non-growing season precipitation(NGSP) determined BC concentrations in the forest litter and topsoil. Soil C/N and C/P also influenced BC cycling between litter and soil. Observation along elevations within different tree species implies that above-ground tree species can redistribute below-ground cations, and this process is profoundly impacted by climate. Litter and soil Ca, K and Mg with different responses to environmental variables depend on their soluble capacity and mobile ability.     

Key variables explaining soil organic carbon content variations in croplands and non-croplands in Chinese provinces

Soil organic carbon (SOC) plays an important role in global carbon cycles.Large spatial variations in SOC contents result in uncertain estimates of the SOC pool and its changes.In the present study,the key variables explaining the SOC contents of croplands (CPs) and non-croplands (NCPs) in Chinese provinces were investigated.Data on SOC and other soil properties (obtained from the Second National Soil Survey conducted in the late 1970s to the early 1990s),climate parameters,as well as the proportion of the CP to the total land area (Pcp) were used.SOC content variations within a province were larger than those among provinces.Soil clay and total phosphorus content,ratio of annual precipitation to mean temperature,as well as Pcp were able to explain 75% of the SOC content variations in whole soil samples.Soil pH,mean temperature during the growing season from May to October,and mean annual wind velocity were able to explain 63% of the SOC content variations in NCP soils.Compared with NCP soils,CP soils had lower SOC contents,with smaller variations within and among provinces and lower C/N ratios.Stepwise regression showed that the soil clay content was a unique factor significantly correlated with the SOC content of CP soils.However,this factor only explained 24% of the variations.This result suggested that variables related to human activities had greater effects on SOC content variations in CP soils than soil properties and climate parameters.Based on SOC contents directly averaged from soil samples and estimated by regression equations,the total SOC pool in the topsoil (0-20 cm) of China was estimated at 60.02 Pg and 57.6 Pg.Thousands of years of intensive cultivation in China resulted in CP topsoil SOC loss of 4.34-4.98 Pg.     

Responses in growth, lipid accumulation, and fatty acid composition of four oleaginous microalgae to different nitrogen sources and concentrations

Nitrogen deficiency is an effective strategy for enhancing lipid production in microalgae. Close relationships exist among lipid production, microalgal species, and nitrogen sources. We report growth, lipid accumulation, and fatty acid composition in four microalgae （Chloroeoccum ellipsoideum UTEX972, Chlorococcum nivale LB2225, Chlorococcum tatrense UTEX2227, and Scenedesmus deserticola JNU19） under nitrate- and urea-nitrogen deficiencies. We found three patterns of response to nitrogen deficiency： Type-A （decrease in biomass and increase in lipid content）, Type-B （reduction in both biomass and lipid content）, and Type-C （enhancement of both biomass and lipid content）. Type-C microalgae are potential candidates for large-scale oil production. Chlorococcum ellipsoideum, for example, exhibited a neutral lipid production of up to 239.6 mg/（L＇d） under urea-nitrogen deficiency. In addition, nitrogen deficiency showed only a slight influence on lipid fractions and fatty acid composition. Our study provides useful information for further screening hyper-lipid microalgal strains for biofuel production.