悬浮液中硫酸根对改性粘土去除藻华生物效率的影响

本文研究了改性粘土悬浮液中硫酸根对其去除藻华生物效率的影响,通过Zeta电位、沉降速率和粒径分布等分析了改性粘土对藻华生物的去除效率,探讨了硫酸根与改性粘土的作用机制。结果显示:改性粘土对抑食金球藻(Aureococcus anophagefferens)的去除效率随悬浮液中硫酸根浓度的增加呈现先降低后升高的趋势,改性湖北土和改性江苏土对抑食金球藻去除率较低时(40%)的硫酸根浓度分别为6.46×10–3—2.42×10–1mol/L和6.46×10–3—2.42×10–2mol/L;改性粘土颗粒的Zeta电位随着硫酸根浓度的增加而降低,然后保持相对稳定;悬浮液中改性粘土颗粒的沉降速率和中值粒径D50呈现先增加后降低的趋势,对于改性江苏土,在硫酸根浓度为2.42×10–2mol/L时颗粒的沉降速率最大。综上所述,悬浮液中硫酸根主要通过降低粘土颗粒表面电荷密度、桥联改性粘土组分和影响粘土颗粒分散性等作用影响改性粘土对藻华生物的去除效率。     

Algal epibiosis on Megabalanus tintinnabulum and its role in segregation of the Balanus amphitrite population

Ulva sp. and Gracilaria sp. were found colonizing shell surfaces of an acorn barnacle, Megabalanus tintinnabulum. However, this association was not noticed in the case of Balanus amphitrite, which was a co‐inhabitant. Such a difference in intergeneric interactions with the algae was examined in laboratory experiments. For this, the influence that extracts of algae, extracts of algae‐associated bacteria and natural leachants from M. tintinnabulum exerted on cyprid metamorphosis of B. amphitrite was examined. Extracts of algae and associated bacteria showed no effect on the metamorphosis of B. amphitrite. This may be attributed to absence of cue‐specific sugars in the exopolysaccharides and culture supernatants of bacteria. On the other hand, natural leachants of M. tintinnabulum, which showed the presence of N‐acetyl‐d ‐glucosamine, a known algal spore attractant, also inhibited metamorphosis of B. amphitrite. Thus, hosting specific epibionts could have important roles in the segregation of barnacle population.     

Distribution patterns of the invasive herbivore Siganus luridus (Rüppell, 1829) and its relation to native benthic communities in the central Aegean Sea,Northeastern Mediterranean

The present study explores the distribution of the invasive herbivore fish Siganus luridus (Rüppell 1829) and its relationship to native herbivores and macroalgal assemblages in the shallow sublittoral of the Cyclades Archipelago, Aegean Sea, Greece. In situ underwater surveys of herbivore abundance (fishes and sea urchins) and algal coverage were carried out at 180 sampling sites in 18 islands. Siganus luridus accounted for 17% of the total herbivore abundance, with a decrease in relative abundance from the southeastern to the northwestern islands. In Santorini Island (in the southeast of the study area) S. luridus abundance accounted for 90% of the total herbivore fish abundance, while in Kea Island (at the northwestern limit of the study area), S. luridus was absent. The spatial variation of minimum sea surface temperature is possibly the reason for its distributional pattern. Siganus luridus abundance was found to be positively correlated to the native herbivore Sparisoma cretense (Linnaeus 1758). A significant negative relationship was found between the abundance of the invasive species and the sum of erect and canopy algae cover (Dictyotales and Cystoseira spp.), which are the main components of its diet in the region. On the other hand, its occurrence was particularly high in barren sites. The results arising from this study reinforce evidence from studies in the Eastern Mediterranean Basin that the expansion of the invasive species S. luridus may have profound impacts on native communities in the Mediterranean infralittoral zone.     

Autotrophic response to lake age,conductivity and temperature in two West Greenland lakes

Predicted changes in future climate necessitate a better understanding of climate impacts on lake biota, and the role of within-lake processes in modifying biotic response. Therefore we examined two climate-related variables (lake-water conductivity and GRIP temperatures) and lake ontogeny (lake age), to determine their influence on lake autotrophic communities in two neighbouring closed-basin lakes from West Greenland spanning the past 8,000 years. Using sedimentary pigments as proxies for lake autotrophic communities, we used synchrony and variance partitioning analyses (VPA) to test three specific hypotheses (a) that lake primary production would increase with lake age, (b) that climate would be the dominant process controlling autotrophic communities in these pristine lakes and (c) that the response of autotrophs to conductivity and temperature would vary depending upon the age of the lake. The results supported our first hypothesis, showing that lakes changed significantly with age, exhibiting an increase and decline in production in the first millennium of their existence, followed by a steady increase in production and increasingly frequent abrupt switches between mixed and meromictic states. The highly synchronous detrended response (r = 0.769) of lake autotrophs in the two study lakes, supported our hypothesis that climate was the dominant factor controlling lake autotrophs. However, VPA revealed that our climate-related variables (temperature and conductivity) explained only small amounts of variance alone (<12.9%) because covariance among them hindered efficient partitioning. In support of our third hypothesis, autotrophs responded significantly to temperature and conductivity in interaction with lake age (>50% variance explained) and with each other (>28% variance explained), such that autotrophic response changed as lakes aged. In spite of this, lakes sometimes responded independently, as a result of differences in the relative proportion of benthic to pelagic production and because of differences in lake morphometry. Together these results show that long-term control of lake autotrophs by climate and lake age is modified on shorter timescales by non-linear responses related to within-lake processes, and by the interaction of different climate variables with each other and with lake age.     

Temporal variation in community–environment relationships and stream classifications in benthic diatoms: Implications for bioassessment

Diatom based biomonitoring tools are proven to be a practical way to indicate stream conditions, but only little is known how stable diatom inferred stream classifications are in time. We studied annual variation in diatom community–environment relationships, community structure and diatom indices (Index of Pollution Sensitivity, IPS and Trophic Diatom Index, TDI) during three consecutive years (2010–2012) in four drainage basins distributed in Finland. We also used a cluster analysis to examine if stream classifications resulted in distinct and temporally stable community types. We found only subtle temporal variation in community–environment relationships, nutrient concentrations (N, P) and conductivity consistently being the main factors structuring communities. According to Mantel tests, diatom communities resembled each other significantly at different years, and the values of IPS and TDI indices remained relatively stable in the basins through time. The stream classification based on diatoms also resulted in temporally stable and statistically distinct community types. We thus suggest that sampling of diatoms, e.g., in every three years seems to be a reliable procedure to assess biological water quality. Generally, to choose the correct metrics to assess water quality is essential, and both biological and physicochemical factors should be considered.     

Modern analogues and the early history of microbial life

Revealing the geological history of microbial life is very challenging. Microbes rarely are preserved with morphological fidelity, and even when they are, morphology is a poor guide to phylogeny and metabolism. Biological studies of environments considered analogous to those of paleobiological interest on the ancient Earth can inform interpretations and suggest new approaches. This paper reviews recent advances in our understanding of the biological diversity of two environments relevant to Archean paleobiology: those of extreme acidity and temperature (the Mt. Hood and White Island volcanoes), and high salinity (living stromatolites in Shark Bay). The combination of traditional microbial isolation with the use of modern molecular techniques has revealed that the microbial communities in these environments are much more diverse than originally thought. Through the extraction of whole microbial community DNA, enzymatic amplification of evolutionarily conserved genes, and cloning and sequencing of these genes, more specific and informed inferences concerning functional complexity in these extreme environments have now been made. Studies of the modern stromatolites have demonstrated that they have a very diverse range of micoorganisms, and contrary to previous interpretations, cyanobacteria are not the most abundant microbes present. In addition, many of the microorganisms are unique with no known close relatives, and these microorganisms may also possess novel physiologies vital to the integrity and persistence of stromatolites through space and time. Microbes in the volcanoes studied are present ubiquitously and include geochemically significant sulfur- and iron-cycling taxa. The findings from the studies reviewed here suggest that the Archean biota may have been functionally diverse and much more complex than has yet been revealed. The importance of studying modern analogues is stressed in that the biogeochemical processes occurring in these communities leave morphological, mineralogical, lipid and isotopic signals that could be sought in the rock record.     

Water Quality Characteristics and Variations of Lake Dian

In order to understand the seasonal change tendencies of the water quality of the Lake Dian (Dianchi), the monitoring data from April to September 2015 at four sites distributed in the central part from North to south were analyzed, these data includes the profiles of the water temperature (Temperature or Temp.), Dissolved Oxygen content (DO), pH values, Chlorophyll-a (Chl-a), Phycocyanin (PC) and Conductivity (CD). At the same time, the Cyanophyte Relative Quantity Index (CRQI) was calculated based on the contents of Phycocyanin and Chlorophyll-a. The results demonstrate that along with the air temperature increase, the water temperature also increased step by step from April and May, and reach the maximum in June, from July to September, the water temperature kept relatively stable and decrease steadily. It also shows that the water temperature is not only various with different water depth, but also show that the temperature increase at different speed, even generally show that the surface temperature increase more rapidly than the deep water. The water temperature and its changes may adjust the air temperature of Kunming strongly and therefore, it is important for the forming of the Four Springs City of Kunming. We found that the amount of eukaryotes represented by Chlorophyll-a increased quickly and reach the highest level in the April, but the blue-green algae, which represented by the Phycocyanin is blooming in the September. This might imply that when the blue-green algae dominated the algae, the algae blooming occur. This is of great importance to understand the algae blooming processes in Lake Dian. We hope the further monitoring will provide us more detailed and useful information. Mean while, the changes of DO, pH and CD all have shown their unique that inspire us to continue the lake water monitoring. This monitoring work also proves that the single site measurements cannot provide any reliable and useful information about the lake water quality. More detailed and sustained monitoring works need to be done before we have a fully understanding on the changes of the lake water quality.     

Biosorption Kinetics and Isotherm Studies of Cd(II) by Dried Enteromorpha compressa Macroalgae Cells from Aqueous Solutions

For the first time ever, Enteromorpha compressa macroalgae (ECM), which is commonly found in Turkey, has been used as biosorbent by us. This study aims to investigate the biosorption of Cd²⁺ from aqueous solutions in a batch system by using an alga of ECM in different concentrations, pH levels, agitation rates (90–150 rpm), and contact periods. The maximum biosorption capacity of the ECM was found to be 9.50 mg/g at pH 6, Cd²⁺ initial concentration of 10 mg/L and agitation rate 150 rpm. Cadmium removal efficiency was about 95%. The experimental isotherm data were analyzed using the Langmuir and Freundlich equations. Isotherm parameters for both equations were determined and discussed. The stated biosorption mechanism is explained by the Freundlich isotherm (r² = 0.998) theory. Two simplified kinetic models including a pseudo‐first‐ and second‐order equation were selected to follow the biosorption process. Kinetic parameters; rate constants, equilibrium adsorption capacities and related correlation coefficients, for each kinetic model were calculated and discussed. It was shown that the biosorption of cadmium onto ECM could be described by the pseudo‐second‐order equation (r² > 0.99).