Dynamics of algae growth and nutrients in experimental enclosures culturing bighead carp and common carp:Phosphorus dynamics

This is the third paper of the series about “Dynamics of algae growth and nutrients in experimental enclosures culturing bighead carp and common carp”. In this paper, phosphorus dynamics were inves-tigated under the condition of culturing bighead carp and common carp with added fish food (nitrogen dynamics is discussed in the second paper because their behaviors are so different from each other). Nearly fifty days’ observation results indicated that the reservoir water was typical of “phosphorus limited” water, and soluble reactive phosphorus (SRP) was the main constituent of measured total phosphorus (TP). The presence of fish food resulted in significantly higher SRP, dissolved total phos-phorus (DTP) and TP concentrations in contrast with the reservoir water. Moreover, continuous supply of fish food led to the decline of total nitrogen to total phosphorus (TN:TP) from more than 100 to less than 5. Variations in the ratio of TN to TP favored the growth of blue-green algae. Fish species affected phosphorus concentrations, and culturing bait-eating common carp contributed more to reducing the SRP, DTP and TP concentrations than culturing planktivorous bighead carp. 0.5%, 4.1%and 3.1%TP can be removed in enclosures with culturing bighead carp, common carp and mixed bighead carp and common carp, respectively. Abundant phosphorus in the fish culturing activities may be present as the uneaten food, algae cells, and within the water column and sediment, which should be taken into serious con-sideration for the target of future water eutrophication prevention and safety of the drinking water supply.     

老爷海潟湖内底层缺氧规模对南海季风气候节律的响应

在海南岛形成春旱时,老爷海潟湖内常常发生网箱养殖鱼类因缺氧(DO2mg/L或者30%)而迅速(1—2天内)大规模死亡的事件;然而,其中的缺氧成因至今仍未见相关研究报道。本文在2008—2011年对老爷海执行了7个航次的生物地球化学调查。在形成充沛春雨的2009年春季季风转换期所执行航次(气象条件表现为风速高和多雨)中,很难观察到底层缺氧现象;与此相对应,潟湖水体的垂直稳定度差,浮游植物群落以微微型(2μm)和微型(2—10μm)藻类占优势。在形成显著春旱的2010年春季季风转换期所执行航次(气象条件表现为微风和少雨)中有大规模底层缺氧形成,缺氧水体从内湾深坑水柱(水深约6m)底层一直蔓延到外湾浅水养殖区;与此相对应,内湾深坑水柱明显层化并形成高盐度生境,浮游植物群落以海洋角管藻(硅藻)占优势,而病毒丰度则达到所有7个航次调查中的最高值。在2008、2009和2011年西南季风盛行期所执行航次(气象条件表现为高温、微风和多雨)中都有小规模底层缺氧形成,且仅局限在内湾深坑底层水中;与此相对应,深坑水柱强烈层化并形成低盐度生境,浮游植物群落以微微型和微型藻类占优势。以上调查结果说明,老爷海潟湖内的底层缺氧规模对上界面的南海季风气候节律有着明显响应;其中,春旱气象条件在潟湖内湾所营造的水柱层化(阻碍复氧)和高盐度生境(有利于硅藻成为浮游植物群落优势种)相耦合,则可促成从潟湖内湾深坑底层一直蔓延到外湾网箱养殖区的大规模底层缺氧现象。     

Effects of overgrazing and rainfall variability on the dynamics of semiarid banded vegetation patterns: A simulation study with cellular automata

The effects of factors acting at small scale (grass/grass and grass/shrub biological interactions) and landscape scale (overgrazing and rainfall changes) on the development and permanence of banded vegetation patterns (VB) are assessed with a spatially explicit cellular automaton model. In particular, the influence of two environmental factors that are changing in many VB arid lands (rainfall and grazing pressures) is studied. Three rainfall regimes (representing 0.5, 1.0, and 2.0 times the long-term rainfall average), five grazing intensities, two types (reversible and irreversible) of grazing disturbance, two grazing periodicities (chronic and pulse), two levels of grass colonization ability, positive and negative interactions between shrubs and grasses, and the efficiency of endozoochorous seed dispersal are simulated.The results show that the permanence of undisturbed VB depends on the interaction of two factors, rainfall regime and grass colonization ability. Type and intensity of grazing also modify VB cover and permanence; furthermore, long-term overgrazing may convert mixed grass/shrub plant communities to pure scrublands dominated by endozoochorous-dispersed shrubs due to competitive interactions between shrubs and grasses.Besides providing an adequate representation of the system’s dynamics, the model is a useful tool that may be used to explore the consequences of climate change on management scenarios.     

STUDIES ON IMMUNODIAGNOSIS OFHEPATOPANCREATIC PARVO- LIKEVIRUS DISEASE OF THE CHINESEPENAEID, PENAEUS CHINENSISI. PURIFICATION OF THE VIRUS

The viral disease of penaeids is indistinct but highly dangerous because their symptoms are often masked by some secondary ones.In order to gain knowledge on how to prevent the occurrence and spread of this viral disease, diagnostic studies on the early phase of the hepatopancreatic parvo-like viral (HPV)disease of cultured Penaeus chinensis was conducted using immuno-serological techniques. The purification of HPV was successfully done by density gradient ultracentrifugation of cane sugar.     

Genetic mapping and QTL analysis for body weight in Jian carp (Cyprinus carpio var. Jian) compared with mirror carp (Cyprinus carpio L.)

We report the genetic linkage map of Jian carp(C yprinus carpio var. Jian). An F1 population comprising 94 Jian carp individuals was mapped using 254 microsatellite markers. The genetic map spanned 1 381.592 c M and comprised 44 linkage groups,with an average marker distance of 6.58 c M. We identified eight quantitative trait loci(QTLs) for body weight(BW) in seven linkage groups,explaining 12.6% to 17.3% of the phenotypic variance. Comparative mapping was performed between Jian carp and mirror carp( Cyprinus carpio L.),which both have 50 chromosomes. One hundred and ninety-eight Jian carp marker loci were found in common with the mirror carp map,with 186(93.94%) showing synteny. All 44 Jian carp linkage groups could be one-to-one aligned to the 44 mirror carp linkage groups,mostly sharing two or more common loci. Three QTLs for BW in Jian carp were conserved in mirror carp. QTL comparison suggested that the QTL confidence interval in mirror carp was more precise than the homologous interval in Jian carp,which was contained within the QTL interval in Jian carp. The syntenic relationship and consensus QTLs between the two varieties provide a foundation for genomic research and genetic breeding in common carp.     

Do physicochemical variables regulate the distribution of zooplankton communities in reservoirs dominated by filter-feeding carp?

The temporal and spatial distributions of zooplankton communities in the upper, middle, and lower reaches of the Xin＇anjiang Reservoir, Zhejiang, China, were investigated monthly, between 2009 and 2010. Silver carp （Hypophthalmichthys moBtrix） and bighead carp （Aristichthys nobilis） dominated the pelagic fish community of this large, deep reservoir. Cladocerans were distributed evenly throughout the reservoir. Rotifers were mainly found in the upper reaches, while copepods tended to assemble in the lower reaches. The Pearson correlation analysis and stepwise multiple regression were used to identify the major physicochemical gradients influencing community variations. Zooplankton community distributions were influenced by water temperature, dissolved oxygen, phosphorus, nitrogen, and silicon. Excess nutrients, in particular silicon, stimulated rotifer growth. Based on these findings, it is possible to use rotifer density as a bioindicator of eutrophic status in deep reservoir ecosystems.     

Inhibition of fish nodavirus by gymnemagenol extracted from Gymnema sylvestre

Viral nervous necrosis(VNN)has emerged to become a major problem in the culture of larval and juvenile marine fish worldwide.Bioactive phytochemicals isolated from commonly available medicinal plants are often screened for their efficacy in controlling fish viral diseases.Occurrence of newer viral strains and resistance to existing antiviral drugs are problems currently as-sociated with treatment of VNN,which necessitates looking for alternate sources for effective antiviral drugs.The aim of the present study was to screen antiviral potential of gymnemagenol(C30H50O4)previously extracted from leaves of Gymnema sylvestre.The fish nodavirus,grouper nervous necrosis virus(GNNV)in infected Sahul Indian Grouper Eye(SIGE)cell lines were used to study the antiviral activity of gymnemagenol under in vitro conditions.The susceptibility of the virus to gymnemagenol was confirmed by measuring the viral titre(TCID50 mL?1)in virus-infected SIGE cells every 24 h.Gymnemagenol at 20 μg mL?1 inhibited the prolifera-tion of GNNV to 53% at the end of the 6th d by inhibiting the proliferation of GNNV-infected SIGE cells.The viable SIGE cells were reduced to 47% as determined by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide(MTT)assay.The viral titre(TCID50 mL?1)was also reduced to log 2.8 at the end of the 7th d in gymnemagenol-treated SIGE cells after inoculated with GNNV when compared to untreated control SIGE cell viral titre(log 4.1).Based on our results it can be concluded that gymnemagenol could be used as an antiviral agent against GNNV infection.     

一种带节点移动的手机蓝牙病毒传播模型

研究了手机节点的空间特性和移动特性,提出了一种新的手机蓝牙病毒传播模型。结合人类运动的行为模式,给出了移动环境下手机节点平均度的计算方法。结合渗流理论分析了蓝牙病毒大规模爆发的可能性,讨论了节点分布密度、蓝牙连接概率等参数对手机蓝牙病毒传播的影响。仿真结果表明,该模型较好地模拟了手机蓝牙病毒的传播过程,符合手机蓝牙病毒的传播规律。     

Existence of Microsatellites in Expressed Sequence Tags of Common Carp （Cyprinus carpio L. ） Available in GenBank dbEST Database

Common carp expressed sequence tags （ESTs） were analyzed for the existence of microsatellites, or simple sequence repeats （SSRs）. In the NCBI dbEST database, a total of 10612 sequences were registered before December 31, 2004. A complete search of 2-6 nucleotide microsatellites resulted in the identification of 513 SSR-containing ESTs, accounting for 4.8% of the total. Cluster analysis indicated that 73 sequences of SSR-containing ESTs fell into 27 groups and the remaining 440 ESTs were independent. A total of 467 unique SSR-containing ESTs were identified. These EST-SSRs contained a vari- ety of simple sequence types, and di- and tri-nucleotide repeats were the most abundant, accounting for 42.1% and 27.9% of the whole, respectively. Of the dinucleotide repeats, CA/TG was the most abundant, followed by GA/TC. BLASTx search showed that 38.1% of the SSR loci could be associated with genes or proteins of known or unknown function. BLASTx searches of SSR-containing ESTs also showed high frequencies （98/179） of hits on zebrafish sequences.