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1.
Toxic cyanobacteria(TCB) are well-known worldwide for their adverse impacts on humans. Species compositions and seasonal variations of TCB in reservoirs depend on interactions between physical and chemical factors. This study was conducted to evaluate the water quality in the Aha Reservoir, Southwest China, focusing on cyanobacteria and cyanotoxins. Water samples were collected weekly or biweekly from May to September of 2015 and used to delineate temporal variations in density and distribution of toxic cyanobacteria and cyanotoxins in the reservoir. Toxic cyanobacteria identified consisted of Aphanizomenon flos-aquae, Pseudanabaena limnetica, Cylindrospermopsis sp., and Microcystis sp., with Aphanizomenon flos-aquae and Pseudanabaena limnetica being the most common and significant toxic genera. The total biomass of cyanobacteria was 17.0 mg/L. Identification and quantification of microcystin variants were conducted by high performance liquid chromatography(HPLC) using a system equipped with a photodiode array detector. Microcystin levels were between 0–3.0 μg/L, MC-RR was around 0–3.0 μg/L and MC-LR was approximately 0–0.9 μg/L. Overall, the results of this study indicate that the investigated reservoirs should be monitored regularly to minimize potential health risks to the human population.  相似文献   

2.
To evaluate how the decay of bloom-forming algae affect the coastal dissolved oxygen,a laboratory simulation was conducted in terms of three typical harmful algae,Alexandrium catenella,Prorocentrum donghaiense,and Skeletonema costatum.Algae of same biomass(55 μg/mL) were conducted in lightproof columns,and the cell density,dissolved oxygen(DO),and ammonia nitrogen of different layers were monitored at certain time series.Results show that the decomposition of algae significantly decreased the DO,and increased the ammonia nitrogen in all layers;and significant deference between different species was observed.The A.catenella treatment showed the lowest DO(average concentration of 3.4 mg/L) and the highest ammonia nitrogen(average concentration of 0.98 mg/L) at the end of test,followed by P.donghaiense; and the S.costatum showed relatively high DO and low ammonia nitrogen due to slow decay rate.Results indicate that decomposition of harmful bloom algae,especially dinoflagellate,would cause significantly DO depletion and toxic ammonia nitrogen increase,which will detrimentally affect both pelagic and benthic ecosystem.  相似文献   

3.
Effect of temperature and irradiance on growth and reproduction of Enteromorpha prolifera that bloomed offshore along the Qingdao coast in summer 2008, was studied. It was showed that E. prolifera propagated mainly asexually with specific growth rate (SGR) of 10.47 at 25℃/40 μmol m^-2s^-1. Under this condition, gametes with two flagellate formed and released in 5 days. At the beginning of the development, the unicell gamete divided into two cells with heteropolarity, and then the apical cell developed into thalli primordial cells, whereas the basal cell developed into rhizoid primordial cells. In 8-day culture, the monoplast gamete developed into juvenile germling of 240 μm in length. Unreleased gametes can develop directly within the alga body. E. prolifera could either reproduce through lateral branching or fragmenting except apomixis revealed by Microscopic observation. On aged tissue of E. prolifera, although the degraded pigments partially remained in faded algal filaments, numerous vegetative cells could still divide actively in the algal tissues.  相似文献   

4.
Throughout the world, the coastal zones of many countries are used increasingly for aquaculture in addition to other activities such as waste disposal. These activities can cause environmental problems and health problems where they overlap. The interaction between aquaculture and waste disposal, and their relationship with eutrophication are the subjects of this paper. Sewage discharge without adequate dispersion can lead to nutrient elevation and hence eutrophication which has clearly negative effects on aquaculture with the potential for toxic blooms. Blooms may be either toxic or anoxia-causing through the decay process or simply clog the gills of filter-feeding animals in some cases. With the development of aquaculture, especially intensive aquaculture, many environmental problems appeared, and have resulted in eutrophication in some areas. Eutrophication may destroy the health of whole ecosystem which is important for sustainable aquaculture. Sewage discharge may also cause serious public health problems. Filter-feeding shellfish growing in sewage-polluted waters accumulate micro-organisms, including human pathogenic bacteria and viruses, and heavy metal ion, presenting a signiticant health risk. Some farmed animals may also accumulate heavy metals from sewage. Bivalves growing in areas affected by toxic algae blooms may accumulate toxins (such as PSP, DSP) which can be harmful to human beings.  相似文献   

5.
Zhang  Chunhui  Liu  Jianguo  Zhang  Litao 《中国海洋湖沼学报》2017,35(5):1205-1211
Most studies on Haematococcus pluvialis have been focused on cell growth and astaxanthin accumulation;far less attention has been paid to cell cycles and proliferation patterns.The purpose of this study was to clarify cell cycles and proliferation patterns in H.pluvialis microscopically using a camera and video recorder system.The complicated life history of H.pluvial i s can be divided into two stages:the motile stage and the non-motile stage.All the cells can be classifi ed into forms as follows:motile cell,nonmotile cell,zoospore and aplanospore.The main cell proliferation,both in the motile phase and non-motile phase in H.pluvialis,is by asexual reproduction.Under normal growth conditions,a motile cell usually produces two,sometimes four,and exceptionally eight zoospores.Under unfavorable conditions,the motile cell loses its fl agella and transforms into a non-motile cell,and the non-motile cell usually produces 2,4 or 8 aplanospores,and occasionally 20–32 aplanospores,which further develop into non-motile cells.Under suitable conditions,the non-motile cell is also able to release zoospores.The larger non-motile cells produce more than 16 zoospores,and the smaller ones produce 4 or 8 zoospores.Vegetative reproduction is by direct cell division in the motile phase and by occasional cell budding in the non-motile phase.There is,as yet,no convincing direct evidence for sexual reproduction.  相似文献   

6.
Abalone Haliotis diversicolor supertexta is an important economic mollusk. The settlement and metamorphosis are two critical stages during its development period, which has direct influence on abalone survival and production. The influence of reactive oxygen species (hydrogen peroxide) on abalone embryo and juvenile development were examined in this study. Larvae of Haliotis diversicolor supertexta were induced to settlement and metamorphose by exposure to seawater supplemented with hydrogen peroxide. They had the best performance at 800 μmol/L. The concentration of 1 000 μmol/L or higher was toxic to the larvae, as the larvae could settle down only at benthic diatom plates without complete metamorphosis. In addition, H2O2 adding time was critical to the larval performance. 24h after two-day post-fertilization was proved to be the optimal adding time. In this paper, two action mechanisms of hydrogen peroxide are discussed: (1) hydrogen peroxide has direct toxicity to ciliated cells, thus cause apoptosis; (2) hydrogen peroxide, as a product from catecholamines' autoxidation process in vivo, can reverse this process to produce neuro-transmitters to induce abalone metamorphosis.  相似文献   

7.
Abalone Haliotis diversicolor supertexta is an important economic mollusk.The settlement and metamorphosis are two critical stages during its development period,which has direct influence on abalone survival and production.The influence of reactive oxygen species(hydrogen peroxide) on abalone embryo and juvenile development were examined in this study.Larvae of Haliotis diversicolor supertexta were induced to settlement and metamorphose by exposure to seawater supplemented with hydrogen peroxide.They had the best performance at 800 μmol/L.The concentration of 1 000 μmol/L or higher was toxic to the larvae,as the larvae could settle down only at benthic diatom plates without complete metamorphosis.In addition,H2O2 adding time was critical to the larval performance.24h after two-day post-fertilization was proved to be the optimal adding time.In this paper,two action mechanisms of hydrogen peroxide are discussed:(1) hydrogen peroxide has direct toxicity to ciliated cells,thus cause apoptosis;(2) hydrogen peroxide,as a product from catecholamines' autoxidation process in vivo,can reverse this process to produce neuro-transmitters to induce abalone metamorphosis.  相似文献   

8.
In late May 2016, a cyanobacterial harmful algal bloom(cHAB) was detected in the Maumee River, the largest tributary to Lake Erie, the southernmost lake of the Laurentian Great Lakes system. Testing on 31 May identified Planktothrix agardhii as the dominant cyanobacterium with cell abundance exceeding 1.7×10~9 cells/L and total microcystins(MC) reaching 19 μg/L MC-LR equivalents, a level over 10-fold higher than the 2015 revised U.S. Environmental Protection Agency(EPA) national health advisory levels for drinking water exposure to adults. Low river discharge coincident with negligible precipitation through the latter half of May coincided with an 80% decline in river turbidity that likely favored bloom formation by a low-light adapted P. agardhii population. Also contributing to the c HAB were high initial nutrient loads and an increase of the river temperature from 13℃ to 26℃ over this same period. The bloom persisted through 5 June with microcystins exceeding 22 μg/L MC-LR equivalents at the bloom peak. By 6 June, the river had returned to its muddy character following a rain event and sampling on 7 June detected only low levels of toxin(0.6 μg/L) at public water systems located near the bloom origin. The elevated toxin production associated with this early onset bloom was without precedent for the Maumee River and an unique attribute of the c HAB was the high proportion of potentially-toxic genotypes. Whereas Planktothrix spp. is common in lotic environments, and has been previously detected in the Maumee, blooms are not commonly reported. This early onset, microcystin-producing c HAB provided a rare opportunity to glean insights into environmental factors that promote bloom development and dominance by Planktothrix in lotic environments.  相似文献   

9.
The morphology and toxicity of Pseudo-nitzschia strain PP0201-01, isolated near the estuary of Changjiang (Yangtze) River in Year 2002 and tentatively identified as Pseudo-nitzschia pungens, were studied. The strain was identified morphologically as P. pungens using scanning electronic microscope (SEM). The analytical results of LC-PDA (liquid chromatography with photodiode array detector), LC-MS (liquid chromatography with mass detector), and the toxicity data from mouse bioassay, showed that no domoic acid was produced by the strain. However, the mechanism of domoic acid production by Pseudo-nitzschia species is complicated. More works are needed to assess the toxic species and to evaluate the potential risk of amnesic shellfish poisoning (ASP) in China.  相似文献   

10.
Chai  Zhaoyang  Hu  Zhangxi  Liu  Yuyang  Tang  Yingzhong 《中国海洋湖沼学报》2020,38(1):114-123
Resting cysts play crucial roles in the ecology of dino?agellates, especially in wintering or surviving unfavorable conditions, seeding harmful algal blooms(HABs), and facilitating the geographic expansion. Encystment of dino?agellates is tightly coupled with sexual reproduction in most cases, which can occur either through homothallism(self-fertilization) or heterothallism(intercrossing of +/-strains). The types of sexual reproduction have important ecological implications. The toxic and HAB-forming dino?agellate, Pheopolykrikoides hartmannii has been previously reported to be heterothallic. Here, we provide visual con?rmation of homothally of P. hartmannii and the ?rst detailed visual recording of cyst germination based on the observations of a clonal isolate from Jiaozhou Bay, China. To document the homothallism, we ?rst observed cell pairs in sexual mating, planozygotes with two longitudinal ?agella, and cysts with typical morphology as described previously from the clonal culture. We then germinated a single cyst, established a new clonal culture from one of the two daughter cells after the ?rst cell division of the germling(i.e. from the diploid germling to two haploid cells), and produced cysts again from the newly established clonal culture. For the observation of the germination time-series, we took micrographs and videos to show all germination processes, particularly with an interesting observation of the short amoeboid stage of the germling releasing from the archeopyle(~15 s), which was a landmark of the germination process and has not been reported elsewhere. This de?nitive evidence of homothallic sexuality and cyst production in P. hartmannii provides a new insight into the biology and ecology of the species, particularly a mechanism that may partly account for the population dynamics and ubiquitous distribution of the species.  相似文献   

11.
There are many reports that cells (protoplasts) separated from the thallus of Porphyra by enzyme can develop to normal leafy thalli in the same way as monopores. But there are few investigations on the subcellular structure of the isolated vegetative cell for ccmparison with the subcellular structure of monospores. To clarify whether the separated and cultured cells undergo the same or similar ultrastructure changes during culture and germination as monospores undergo in their formation and germination, we observed their ultrastructure, ccxnpared them with those of the monospore and found that the ultrastructure of separated and cultured cells did not have the characteristic feature as that of monospore formarion, such as production of small and large fibrous vesicles, but was acccxnpanied by vacuolation andstarch mobilization like that in monospore germination. The paper also discusses the relations between monospores and separated and cultured cells.  相似文献   

12.
Pure fraction (92% - 95%) of phagocytes (FP) and a mixture of amoebocytes (62%) and morula cells (38 % )-FPMC- of the holothurian Eupentacta fraudatrix ( Holothuroidea,Dendrochirota ) were obtained by using ficoll-verographine step gradient. Basal production of reactive oxygen species (ROS) in FP quantified by using reduction of nitroblue tetrazolium (NBT) was more than twice that in FPMC. Thermostable toxin of Yersinia pseudotuberculosis (TST) at differentconcentrations ( 0.2; 0.5; 2.5 μg/ml, but not 0.1 μg/ml) stimulated NBT reduction in FPMC after 24 h incubation. In FP, TST at concentrations of 0.1 and 0.2 μg/ml inhibited and at concentrations of 0.5 and 2.5 μg/ml stimulated NBT reduction after 24 h incubation. Maximal effect was observed in FP and FPMC at TST concentrations of 0.5 and 0.2 μg/ml, respectively. Addition of catalase (0.7 μg/ml) to the cells treated with TST (2.5 μg/ml) was followed by a decrease in NBT reduction compared to that under toxin treatment alone. TST stimulated superoxide dismutase activity in ccncentration-dependent manner (maximum at 0.5 μg/ml concentration in FP) after 24 htreatment, and this stimulation was prevented by a commercial catalase. Plant lectin concanavalin A stimulated NBT reduction more than 5-fold in FPMC compared to the control. With addition of TST, lectin stimulated ROS to lesser extent than that with lectin alone. When catalase, TST, and lectin were added into the FPMC simultaneously, ROS increase was similar to that under lectin treatment alone. On the whole, data obtained indicated that ROS generation in holothurian coelomocytes especially occurs in both stimulated and not stimulated phagocytes, and that changes in ROS production by these cells may be one of the mechanisms of antibacterial protection of holothurians.  相似文献   

13.
Microcystis often dominates phytoplankton in eutrophic lakes and must survive a long period of cold or dark conditions.However,the survival strategies of Microcystis to withstand cold or dark stress are less well known.In this study,we conducted experiments on the responses of two toxic Microcystis aeruginosa strains(FACHB-905 and FACHB-915) and their microcystin release in conditions of low temperature(15℃ or 4℃,with illumination) or darkness,and subsequent recovery in standard conditions(25℃ with illumination).On exposure to 15℃,a small decrease in cell viability was observed,but the cell number increased gradually,suggesting that M.aeruginosa FACHB-905 and FACHB-915 cells seem in general tolerant in 15℃.Interestingly,our results show that a higher carotenoid content and microcystin release potentially enhance the fitness of surviving cells at 15℃.M.aeruginosa cells exposed to lower temperature light stress(4℃) did not completely lose viability and retained the ability to reinitiate growth.In darkness,the maximum quantum yield(F_v/F_m) and the maximum electron transport rate(ETR_(max)) values and cell viability of M.aeruginosa cells gradually decreased with time.During the recovery period,the photosynthetic efficiency of M.aeruginosa reverted to the normal level.Additionally,M.aeruginosa FACHB-905 and FACHB-915 exposed to low temperature had increased caspase-3-like activity and DNA fragmentation,which suggests the occurrence of a type of cell death in M.aeruginosa cells under cold stress similar to programmed cell death.Overall,our findings could confer certain advantages on the Microcystis for surviving cold or dark conditions encountered in the annual cycle,and help explain its repeated occurrence in water blooms in large and shallow lakes.  相似文献   

14.
The phytoplankton reproduction capacity (PRC), as a new concept regarding chlorophyll-a and primary production (PP) is described. PRC is different from PP, carbon assimilation number (CAN) or photosynthetic rate ( P^B ) . PRC quantifies phytoplankton growth with a special consideration of the effect of seawater temperature. Observation data in Jiaozhou Bay, Qingdao, China, collected from May 1991 to February 1994 were used to analyze the horizontal distribution and seasonal variation of the PRC in Jiaozhou Bay in order to determine the characteristics, dynamic cycles and trends of phytoplankton growth in Jiaozhou Bay; and to develop a corresponding dynamic model of seawater temperature vs. PRC. Simulation curves showed that seawater temperature has a dual function of limiting and enhancing PRC. PRC‘s periodicity and fluctuation are similar to those of the seawater temperature. Nutrient silicon in Jiaozhou Bay satisfies phytoplankton growth from June 7 to November 3. When nutrients N, P and Si satisfy the phytoplankton growth and solar irradiation is sufficient, the PRC would reflect the influence of seawater temperature on phytoplankton growth. Moreover, the result quantitatively explains the scenario of one-peak or two-peak phytoplankton reproduction in Jiaozhou Bay, and also quantitatively elucidates the internal mechanism of the one- or two-peak phytoplankton reproduction in the global marine areas.  相似文献   

15.
To investigate the effects of flow rate on phytoplankton dynamics and related environment variables,a set of enclosure experiments with different fl ow rates were conducted in an artificial lake. We monitored nutrients,temperature,dissolved oxygen,p H,conductivity,turbidity,chlorophyll-a and phytoplankton levels. The lower biomass in all flowing enclosures showed that flow rate significantly inhibited the growth of phytoplankton. A critical flow rate occurred near 0.06 m/s,which was the lowest relative inhibitory rate. Changes in flow conditions affected algal competition for light,resulting in a dramatic shift in phytoplankton composition,from blue-green algae in still waters to green algae in flowing conditions. These findings indicate that critical flow rate can be useful in developing methods to reduce algal bloom occurrence. However,flow rate significantly enhanced the inter-relationships among environmental variables,in particular by inducing higher water turbidity and vegetative reproduction of periphyton( Spirogyra). These changes were accompanied by a decrease in underwater light intensity,which consequently inhibited the photosynthetic intensity of phytoplankton. These results warn that a universal critical flow rate might not exist,because the effect of flow rate on phytoplankton is interlinked with many other environmental variables.  相似文献   

16.
Guppies( Poecilia reticulata) are considered a candidate model species for the identification and testing of endocrine-disrupting chemicals. Male guppies may be used to address the challenge of making potential linkages between alterations of biomarkers, both at the cellular and organ level, and adverse outcomes. In the present study, a predictive relationship between sex characteristics and reproductive output was observed in male guppies that underwent a long-term toxicity test with 0.5 μg/L 17 β-estradiol administered during the juvenile period. Radioimmunoassay and western blot analyses demonstrated that 17 β-estradiol exposure caused a significant increase in testicular 17 β-estradiol levels as well as the induction of exposure biomarkers, namely hepatic vitellogenin. Exposure to 17 β-estradiol also caused a significant decrease in testosterone levels, which consequently reduced the gonadosomatic index, sperm counts, and the coloration index. These changes of male sexual characteristics further translated into adverse influences on reproduction, as measured by a decrease in offspring production and survival rate. Our results suggest that the above-mentioned sexual characteristics of male guppies may be considered potential in vivo biomarkers of estrogen effects on reproduction.  相似文献   

17.
It had been demonstrated that individual or protoplasts isolated from Porphyra thallus by enzyme could develop into normal leafy thalli in the same way as monosproes,and that isolated cells develop in different way in liquid and on semi-solid media,The authors observed the ultrastructure of isolated vegetative cells cultured on semi-solid media and compared them with those of monospores and isolated cells cultured in liquid media,The results showed that subcellular struce-tures were quite different among cells in different conditions.In their development,isolated cells on semi-solid media did not show the characteristic subcellular eature of monospore formation ,such as production of fibrous vesicles,Callus-like cells formed on semi-solid media underwent a distinctive modification in cellular organization.They developed characteristic cell inclusions and a special 2-layer cell covering,Golgi bodies,ER ,starch grains,mitochondria,Vaculoes were not commonly found in them.  相似文献   

18.
Since the industrial revolution, human activities have both expanded and intensified across the globe resulting in accelerated land use change. Land use change driven by China's development has put pressure on the limited arable land resources, which has affected grain production. Competing land use interests are a potential threat to food security in China. Therefore, studying arable land use changes is critical for ensuring future food security and maintaining the sustainable development of arable land. Based on data from several major sources, we analyzed the spatio-temporal differences of arable land among different agricultural regions in China from 2000 to 2010 and identified the drivers of arable land expansion and loss. The results revealed that arable land decreased by 5.92 million ha or 3.31%. Arable land increased in the north and decreased in the south of China. Urbanization and ecological restoration programs were the main drivers of arable land loss, while the reclamation of other land cover types(e.g., forest, grassland, and wetland) was the primary source of the increased arable land. The majority of arable land expansion occurred in the Northwest, but the centroid for grain production moved to northeast, which indicated that new arable land was of poor quality and did not significantly contribute to the grain production capacity. When combined with the current ‘Red Line of Arable Land Policy'(RAL) and ‘Ecological Redline Policy'(EPR), this study can provide effective information for arable land policymaking and help guide the sustainable development of arable land.  相似文献   

19.
We measured the concentrations of dimethylsulfide (DMS), acrylic acid (AA), and dimethylsulfoniopropionate (DMSP) during growth of three microalgae: Prorocentrum micans, Gephyrocapsa oceanica, and Platymonas subcordiformis. The DMSP, AA, and DMS concentrations in culture media varied significantly among algal growth stages, with the highest concentrations in the late stationary growth stage or the senescent stage. In the stationary growth stage, the average DMSP concentration per cell in P. micans (0.066 5 pmol/cell) was 1.3 times that in G. oceanica (0.049 5 pmol/ cell) and 20.2 times that in P. subcordiformis (0.003 29 pmol/cell). The average concentrations of AA were 0.044 6, 0.026 9, and 0.003 05 pmol/cell in P. micans, G. oceanica, and P. subcordiformis, respectively, higher than the concentrations of DMS (0.272, 0.497, and 0.086 2 fmol/cell, respectively). There were significant positive correlations between cell density and AA, DMSP, and DMS concentrations. The ratios of DMS/AA and AA/(DMSP+AA) in the three algae differed significantly over the growth cycle. In all three microalgae, the DMS/AA ratios were less than 25% during the growth period, suggesting that the enzymatic cleavage pathway, which generates DMS, was not the main DMSP degradation pathway. The changes in the DMS/AA ratio indicated that there was a higher rate of enzymatic breakdown of DMSP in the early growth period and a lower rate during senescence. In all three microalgae, the AA/(DMSP+AA) ratio (degradation ratio of DMSP) decreased during the exponential growth phase, and then increased. The variations in these ratios can approximately indicate the cleavage mechanism of DMSP at different stages of algal growth.  相似文献   

20.
Statistical analysis on data collected in the Jiaozhou Bay (Shandong, China) from May 1991 to February 1994 and those collected in Hawaii from March 1958 to December 2007 shows dynamic and cyclic changes in atmospheric carbon in the Northern Pacific Ocean (NPO), as well as the variation in space-time distribution of phytoplankton primary production and atmospheric carbon in the study regions. The study indicates that the human beings have imposed an important impact on the changing trends of the atmospheric carbon. Primary production in the Jiaozhou Bay presents a good example in this regard. In this paper, dynamic models of the atmospheric carbon in the NPO, the cyclic variations in the atmospheric carbon, and primary production in the Jiaozhou Bay are studied with simulation curves presented. A set of equations were established that able to calculate the rate and acceleration of increasing carbon discharged anthropologically into the atmosphere and the conversion rate of phytoplankton to atmospheric carbon. Our calculation shows that the amount of atmospheric carbon absorbed by one unit of primary production in the Jiaozhou Bay is (3.21–9.74)×10-9/(mgC·m-2d-1), and the amount of primary production consumed by a unit of atmospheric carbon is 102.66–311.52 (mgC·m-2d-1/10-6). Therefore, we consider that the variation of atmospheric carbon is a dynamic process controlled by the increase of carbon compound and its cyclic variation, and those from anthropologic discharge, and phytoplankton growth.  相似文献   

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