沙湖叶绿素a的时空分布特征及其与环境因子的关系

为探究沙湖水体叶绿素a的时空分布特征及其与水环境因子关系,2015-2017年冬季(1月)、春季(4月)、夏季(7月)、秋季(10月)对沙湖水体叶绿素a含量和常规水环境因子进行采样与检测,分析沙湖叶绿素a含量与环境因子之间的相关性,通过逐步回归法和通径分析探讨了时空性变化对叶绿素a含量的影响。结果表明,沙湖叶绿素a季节变化明显,夏季最高,冬春两季相对较低,最大值出现在2017年7月(夏季),最小值出现在2015年4月(春季),2017年叶绿素a含量最高,年均值为18.94μg/L,空间分布也存在明显差异。相关分析表明,总磷(TP)、化学需氧量(COD_(Cr))、五日生化需氧量(BOD_5)和透明度(SD)是影响沙湖叶绿素a含量的主要环境因子;逐步回归分析表明,不同季节、不同采样点影响沙湖叶绿素a含量的环境因子存在差异,有机污染物与氮磷营养盐是主要的影响因子;通径分析表明,化学需氧量和总磷的总决定系数(d_(ij))分别为0.379和0.373,是影响沙湖叶绿素a含量最主要的两个环境因子;其中总磷对沙湖叶绿素a含量的直接作用较大,是对叶绿素a起决定性作用的限定性营养盐。     

沙湖叶绿素a的时空分布特征及其与环境因子关系

为探究沙湖水体叶绿素a的时空分布特征及其与水环境因子关系,2015-2017年冬季（1月）、春季（4月）、夏季（7月）、秋季（10月）对沙湖水体叶绿素a含量和常规水环境因子进行采样与检测,分析沙湖叶绿素a含量与环境因子之间的相关性,通过逐步回归法和通径分析探讨了时空性变化和季节性变化对叶绿素a含量的影响。结果表明,沙湖叶绿素a季节变化明显,夏季最高,冬春两季相对较低,最大值出现在2017年7月（夏季）,最小值出现在2015年4月（春季）,2017年叶绿素含量最高,年均值为18.94 μg/L,空间分布也存在明显差异。相关分析表明,总磷(TP)、化学需氧量(CODCr)、五日生化需氧量(BOD5)和透明度(SD)是影响沙湖叶绿素a含量的主要环境因子;逐步回归分析表明,不同季节、不同采样点影响沙湖叶绿素a含量的环境因子存在差异,有机污染物与氮磷营养盐是主要的影响因素;通径分析表明,化学需氧量和总磷的总决定系数(dij)分别为0.379和0.373,是影响沙湖叶绿素a含量最主要的两个环境因子;其中总磷对沙湖叶绿素a含量的直接作用较大,是对叶绿素a起决定性作用的限定性营养盐。     

2008年闽江口海域叶绿素a时空分布及其与环境因子的相关性分析

2008年3月-12月对闽江口海域进行了每月1次共10航次的调查,分析了该海域叶绿素a的时空分布特征,以及与环境因子的相关性.结果表明:闽江口海域叶绿素a浓度范围为0.25 ～45.38μg/L,平均值为3.93 μg/L.叶绿素a浓度的平面分布在春季和夏季总体呈琅岐岛附近海域＞川石岛以东海域＞定海湾的趋势,秋季和冬季平面分布较均匀.叶绿素a浓度的季节变化总体呈现为夏季＞秋季＞春季＞冬季的特征.相关性分析显示,叶绿素a与水温呈极显著正相关,与盐度、活性磷酸盐呈显著负相关.     

华阳河湖群叶绿素a浓度的季节动态和空间分布

为了探究华阳河湖群叶绿素a浓度的季节动态与空间分布规律,2016年4月(春季)、7月(夏季)、10月(秋季)和2017年1月(冬季),对华阳河湖群叶绿素a的季节动态及环境因子进行调查,在龙感湖、黄大湖和泊湖分别设置9个(S_1～S_9)、8个(S_(10)～S_(17))和7个(S_(18)～S_(24))采样点,共计24个采样点;通过分层聚类法分析叶绿素a的时空分布特征,并运用主成分分析法探讨了华阳河湖群叶绿素a与环境因子的关系。结果显示,华阳河湖群水体叶绿素a浓度呈现明显的时空分布特征,叶绿素a年均值为7.18μg/L,变化范围0.27～66.61μg/L,最大值出现在2016年10月(秋季),最小值出现在2017年1月(冬季);叶绿素a浓度的季节变化呈现夏、秋季较高,春、冬季较低的动态特征。在空间变化上,叶绿素a浓度在龙感湖最高,其次是泊湖,黄大湖最低。运用分层聚类分析法将华阳河湖群的叶绿素a的时空特征分为三类;主成分分析表明,水体中营养盐是影响叶绿素a季节动态和空间分布的主要环境因子,总氮在3个湖泊中与叶绿素a显著正相关,总磷与叶绿素a在泊湖和黄大湖呈负相关,而在龙感湖呈正相关。研究表明,越冬水鸟的排泄物对叶绿素a的时空分布有重要影响。     

汕头南澳-东山海域初级生产力的时空特征

根据2014年9月(秋季)、12月(冬季)、2015年4月(春季)、2016年7月(夏季)在南澳岛与东山岛之间的近海海域进行的生态环境调查,分析了该海域叶绿素a浓度和初级生产力的时空变化特征。结果表明,叶绿素a浓度变化范围为0.37～14.9μg/L,平均值分别为:夏季(8.2μg/L)>秋季(4.9μg/L)>冬季(1.52μg/L)>春季(1.47μg/L)。表层初级生产力的波动范围为0.6～45 mg(C)/(m^3·h),平均值分别为:秋季20.3 mg(C)/(m^3·h)>夏季18.2 mg(C)/(m^3·h)>春季14.4 mg(C)/(m^3·h)>冬季5.6 mg(C)/(m^3·h)。水柱初级生产力变动范围为14.1～3066.6 mg(C)/(m^2·d),平均值分别为:秋季1034.2 mg(C)/(m^2·d)>夏季715.5 mg(C)/(m^2·d)>春季453.4 mg(C)/(m^2·d)>冬季133.8 mg(C)/(m^2·d)。除夏季外,整个调查海域的叶绿素a浓度空间变化规律基本为由西北向东南方向递减;夏季调查海域表层叶绿素a的浓度都较高,在南澳岛的南面出现一个叶绿素a的低值区。该海域初级生产力的空间分布规律性较差。叶绿素a和初级生产力与营养盐浓度在春季均呈显著正相关,但在其他季节相关性不强。氮营养盐在春季和秋季可能是南澳-东山海域浮游植物生长的潜在限制因子。为获得较好的渔业增养殖效益,应该根据初级生产力现状对该海域的养殖品种和规模进行合理规划。     

夏季和冬季辽东湾海域水体中叶绿素a含量分布特征

为研究辽东湾海域水体中叶绿素a含量的分布特征,于2013年8月(夏季)和12月(冬季)在辽东湾设置38个站位,分别采集了表、中、底层的海水样品,检测夏季和冬季两个航次水体中叶绿素a的含量,分析该海域叶绿素a的季节分布与空间变化特征。同时利用相关性统计分析的方法,将各水质因子对叶绿素a含量影响的差异显著性进行了分析。结果显示,调查海域夏季的叶绿素a平均质量浓度为6.90μg/L,冬季为1.26μg/L,时间分布上夏季质量浓度明显高于冬季;空间水平分布上,夏季辽东湾湾口的平均叶绿素a质量浓度明显高于湾内的平均质量浓度,而冬季则越靠近湾口处叶绿素a的平均质量浓度越低,与夏季规律正好相反;空间垂直分布上,夏季表层叶绿素a的质量浓度最高,10m层次之,底层的质量浓度最低;而冬季的叶绿素a质量浓度则呈现10m层最高,底层次之,表层质量浓度最低的趋势。说明辽东湾叶绿素a含量存在明显的时间和空间分布特征;结合同期的温度、盐度、溶解氧等环境因子的调查结果,统计分析结果表明调查海域中环境因子温度、盐度、溶解氧和营养盐的季节性变化是导致叶绿素a含量趋势变化的最可能原因之一。     

泼河水库的水质变化特征及富营养化评价

为了明确泼河水库氮磷的分布特征及其富营养化水平现状,笔者根据2012年9月至2013年9月对泼河水库的监测数据,分析了泼河水库氮磷分布特征,并应用综合营养状态指数法对研究水域富营养化现状进行了评价与分析。结果表明：（1）泼河水库氮磷分布呈夏季高、春季次之、冬季最低的特征;（2）泼河水库营养状态为中营养。     

洱海水体光学特性的季节变化及其影响因素分析

为了探究人类活动对洱海水体富营养化进程的影响,2014年4月、7月、11月和2015年1月在洱海全湖设置36个采样点进行采样监测,研究洱海光学衰减系数(K)、透明度(SD)、浊度(Turb)和叶绿素a(Chl-a)的季节变化规律及其相关性,并分析沉水植物分布对光学特性的影响,以期为洱海富营养化治理和控制提供基本数据支持。结果表明,光学衰减系数的季节变化规律为春季(0.59 m-1)冬季(0.68 m-1)秋季(0.95 m-1)夏季(1.05 m-1);叶绿素a含量与光学衰减系数的季节变化规律相同,为春季(5.24μg/L)冬季(5.49μg/L)秋季(12.33μg/L)夏季(14.22μg/L);透明度季节变化规律为夏季(1.86 m)秋季(2.28 m)春季(3.00 m)冬季(3.07 m);浊度季节变化规律是春季(32.50 mg/L)冬季(32.52 mg/L)秋季(32.64 mg/L)夏季(32.70 mg/L)。光学衰减系数与透明度、浊度和叶绿素a均呈显著正相关(P0.01),相关系数分别为0.648、0.523和0.467;透明度与叶绿素a和浊度均呈显著负相关(P0.01),相关系数分别为0.497和0.564;浊度与叶绿素a显著正相关(P0.01),相关系数为0.241。叶绿素a在一定程度上会影响光学衰减系数,但不是其主要影响因素。在秋季和冬季,沉水植物区的水体光学衰减系数显著低于无沉水植物区(P0.05),但这种差异在春季和夏季不显著(P0.05)。在一年中的各季节,沉水植物区与无沉水植物区的水体透明度和叶绿素a含量均无显著差异(P0.05);沉水植物区的水体浊度显著低于无沉水植物区(P0.01)。     

老鸦河水库水质的时空变化趋势与富营养化评价

为了明确老鸦河水库水质的时空变化趋势及其富营养化状态,测定了老鸦河水库的总氮、总磷、叶绿素、高锰酸盐指数、透明度等水质指标,分析了老鸦河水库水质的时空变化趋势,并应用综合营养状态指数法评价了水库富营养化现状。结果表明:(1)老鸦河水库氮磷分布呈夏季高,秋季次之,春季较低,冬季最低的季节变化趋势;空间分布变化规律不明显。(2)老鸦河水库全年营养状态为中度富营养。     

香溪河库湾不同季节叶绿素a浓度影响因子分析

研究叶绿素a浓度与环境因子之间的相关关系,为香溪河水质预警、水华防治等水环境保护工作提供科学依据。监测点为香溪河库湾XX06站点,2015年每日1次定点采样,监测指标为氮磷营养盐、叶绿素a浓度、水温、溶解氧、pH、浊度、混合层深度、真光层深度、表底温差、水位及流量等。使用SPSS20.0对环境因子指标和叶绿素a进行person相关性分析。叶绿素a浓度季节性变化显著,夏季最高、春秋季次之、冬季最低,全年平均值为14.38μg/L,变化范围为0.36~108.00μg/L。总氮、总磷和叶绿素a的浓度水平均指示香溪河水体处于富营养化状态。叶绿素a浓度春季与水温、pH、混合层深度正相关,与浊度、总氮、真光层深度负相关;夏季与水温、pH、滞留时间、混合层深度正相关,与总氮负相关;秋季与水温、混合层深度正相关,与浊度、真光层深度负相关;冬季与各环境因子具有一定的相关性,但相关性不显著。     

Rare serotype occurrence and PFGE genotypic diversity of Streptococcus agalactiae isolated from tilapia in China

Previously, we reported 10 PEGE types of 85 tilapia Streptococcus agalactiae(GBS), which shifted from Streptococcus iniae in China, by using PEGE method. Presently, larger and more representative tilapia GBS were isolated, for the ?rst time in China, to characterize their serotypes and genetic diversities more precisely than had done before. 168 GBS strains were distributed in ?ve provinces of China, in which Guangdong, Guangxi and Hainan were the major ones, holding36.9%(62/168), 37.5%(63/168) and 19.6%(33/168), respectively. Serotypes, Ia, Ib and III, were observed in these strains and the most predominant one was Ia(95.2%), which mainly distributed in Guangdong, Guangxi and Hainan. Ia initially occurred in 2009, it shoot up to 32.1% in 2010,but decreased to 16.1% in 2011 before went up to 45.2% in 2012. Ib sporadically occurred during2007–2011, III onlyoccurred in 2012. 14 different PFGE types, including 4 new types(N, O,P and Q), were observed, in which B, D, F and G were the predominant types, holding 83.9%(141/168) of the total GBS strains. Ia corresponded to 11 PFGE types(A–H, N–P), in which type D predominated(51%). Ib represented 3 genotypes(I, J and Q) and III harbored only 2genotypes(N and F). Type N and Fsynchronously presented in Ia and III. In summary, the genetic diversity of tilapia GBS varied by serotypes and changed with geographical locations and years.Although Iastillpredominated, new rareserotypeIII alreadyoccurred in China.     

Purification and partial characterization of GtHs (cfLH and cfFSH) from Indian walking catfish (Clarias batrachus) (L.) and development of a homologous ELISA for cfLH

Two gonadotropins (GtH; Qa and Qb) were purified by gel filtration and ion exchange chromatography from the pituitaries of Indian walking catfish (Clarias batrachus). The presence of GtH during purification was assessed by in vitro oocyte maturation and in vivo steroidogenic activity, and their identities were determined by elution profiles, molecular weight, biological activities and yield. The molecular weights of Qa and Qb were 37 and 42 kDa, respectively, and composed of distinct subunits (Qa: 20 and 14 kDa and Qb: 26 and 18 kDa). Polyclonal antibodies raised against Qa immunostained Qa, Qb and pituitary GtH cells. A competitive Qa‐ELISA was developed whose sensitivity was 6.25 ng mL^?1 (1.25 ng well^?1) with intra‐ (3.5%) and inter‐ (12.4%) assay coefficients of variation. Displacement curves parallel to the standard were obtained with plasma and pituitary extracts of catfish, Qb and carp GtHII. The assay was validated by measuring the plasma Qa levels after LHRH treatment and in relation to ovarian growth in the female catfish during different reproductive phases. Based on the results, Qa and Qb corresponded to fish LH and FSH respectively. The findings will increase the knowledge of the mechanisms controlling fish reproduction and identification of sensitive phases in fish in captivity for hormonal manipulation.     

Growth hormone (GH) and reproduction: a review

Interaction between growth and reproduction occurs in many vertebrates and is particularly obvious at certain stages of the life cycle in fish. Endocrine interactions between the gonadotropic axis and the somatotropic axis are described, the potential role of GH being emphasised. A comparative analysis of these phenomena in mammals, amphibians and fish, suggests a specific role of GH in the physiology of puberty, gametogenesis and fertility. It also shows the original contribution made by studies on the fish model in this field of investigations.     

Controlled infection of Poecilia reticulata Peters (guppy) with Tetrahymena by immersion and intraperitoneal injection

Tetrahymena is a protozoan parasite, which infects guppy, Poecilia reticulata Peters, and causes substantial economical losses in commercial farms worldwide. Studies of guppy infected by Tetrahymena require standardized infection protocols. The LD50 for Tetrahymena infection of guppies by intraperitoneal (IP) injection was calibrated, and the level obtained was 946 parasites per fish. Guppy infection with Tetrahymena by immersion, imitating the natural route of infection via the integument, was studied under normal or stress conditions. Exposure to cold and netting (CNI) and to cold only (CI) followed by immersion exposure to 10 000 Tetrahymena per mL resulted in 22.5% and 19.2% mortality, respectively, as compared to 14.2% and 10% in groups that were netted only (NI) or non‐stressed (I). Histopathology revealed that immersion infection resulted in a systemic infection. Lysozyme levels, measured 3 weeks after infection, were significantly higher in the CNI group (288 μg per mg protein) compared with CI‐, NI‐ and I‐treated groups (94.5, 64 and 62.3 μg mg^?1, respectively). There was no evident parasite immobilization activity in body homogenates, suggesting no development of acquired immunity. Re‐infection by IP injection revealed no increase in protection in any of the treatment groups, mortality range of 56.3–75%, higher than in the non‐exposed control (40.6% mortality).     

Imported ornamental fish are colonized with antibiotic‐resistant bacteria

There has been growing concern about the overuse of antibiotics in the ornamental fish industry and its possible effect on the increasing drug resistance in both commensal and pathogenic organisms in these fish. The aim of this study was to carry out an assessment of the diversity of bacteria, including pathogens, in ornamental fish species imported into North America and to assess their antibiotic resistance. Kidney samples were collected from 32 freshwater ornamental fish of various species, which arrived to an importing facility in Portland, Oregon from Colombia, Singapore and Florida. Sixty‐four unique bacterial colonies were isolated and identified by PCR using bacterial 16S primers and DNA sequencing. Multiple isolates were identified as bacteria with potential to cause disease in both fish and humans. The antibiotic resistance profile of each isolate was performed for nine different antibiotics. Among them, cefotaxime (16% resistance among isolates) was the antibiotic associated with more activity, while the least active was tetracycline (77% resistant). Knowing information about the diversity of bacteria in imported ornamental fish, as well as the resistance profiles for the bacteria will be useful in more effectively treating clinical infected fish, and also potential zoonoses in the future.     

Effect of iodophor disinfection of non‐hardened Salmo trutta eggs on their bacterial and fungus load

This study investigated the efficiency of iodophor disinfection (135 ppm active iodine for 15–30 min) of non‐hardened Salmo trutta eggs against different groups of bacteria and against fungus. Egg samples were taken from non‐disinfected and from disinfected eggs, microorganisms were cultured on specific nutrient media and their mass was measured by turbidimetric methods. Bacteria and fungus mass of non‐hardened eggs could be reduced but not eliminated by iodophor disinfection with 135 ppm active iodine for 15 min. The extent of reduction was 47–65% (Experiment 1). The efficiency of disinfection increased with disinfection time as the reduction in bacteria and fungus mass was 40–55% after 15 min and 58–74% after 30 min (Experiment 2). Disinfection efficiency of iodophor solution diluted in water (reduction 49–57%) and of iodophor solution diluted in sodium chloride solution iso‐osmolar to the oocytes (reduction 52–61%) was similar (Experiment 3). The reduction in bacteria and fungus mass was persistent as it was 39–72% lower in embryos deriving from disinfected eggs than in embryos deriving from non‐disinfected ones (Experiment 4). In conclusion, the tested disinfection method is inadequate to eliminate pathogens completely but it could positively influence immune defence of eggs and embryos.     

Influence of the antibacterial herbs, Solanum trilobatum, Andrographis paniculata and Psoralea corylifolia on the survival, growth and bacterial load of Penaeus monodon post larvae

The indiscriminate use of antibiotics and chemicals in shrimp hatcheries has led to biomagnification and that in turn could lead to rejection of a whole consignment. The application of the bioencapsulation technique as a tool for curative treatment in shrimp larvae was investigated. Herbs having antibacterial properties such as Solanum trilobatum, Andrographis paniculata and Psoralea corylifolia (methanolic extracts) were bioencapsulated in Artemia and fed to Penaeus monodon post larvae PL 1–25. The post larvae were reared in a medium inoculated with pathogenic bacteria such as Pseudomonas aeruginosa, Staphylococcus aureus, Salmonella typhi and Vibrio sp. Post larvae reared in the non-inoculated water and fed with non-enriched Artemia exhibited 90% survival, highest specific growth rate (12.43%) and reduced bacterial load. P. monodon reared in the bacterial inoculated water and fed with the non-enriched Artemia exhibited the lowest survival (10–30%), specific growth rate (8.42–9.1%) and increased bacterial load (2.86 × 10³ to 3.76 × 10⁵ cfu/g). The methanolic extracts of the herbs helped to increase survival and specific growth rate and reduced bacterial load in the P. monodon culture system. Among the three herbal extracts, P. corylifolia enriched Artemia fed post larvae showed the tendency to higher survival (>50%), growth rate (11.5 averaged) and low bacterial load (1.12 × 10⁵ cfu/g). This revised version was published online in August 2006 with corrections to the Cover Date.     

Nitrogenous waste excretion and accumulation of urea and ammonia inChalcalburnus tarichi (Cyprinidae), endemic to the extremely alkaline Lake Van (Eastern Turkey)

The endemic, anadromous cyprinidChalcalburnus tarichi is the only fish species known to occur in alkaline Lake Van (Eastern Anatolia, Turkey). EightC. tarichi were maintained individually in Lake Van water (17 – 19°C; pH 9.8; 153 mEq·I^–1 total alkalinity; 22 total salinity) and tank water samples analyzed for 24 h in 2 to 4 h intervals. At zero time, < 1µM ammonia was present and urea was undetectable in the tank water; at 24 h, total ammonia and urea made up 114±32 and 35±25µM, respectively. Over the experimental period, ammonia-N and urea-N excretion averaged 1041±494 and 607±169moles·kg^–1 fish·h^–1, respectively. The extent of urea excretion was highly variable between specimens. Uric acid excretion was not detectable.Urea was present at high concentrations in all tissues and plasma (25 – 35moles·g^–1·ml^–1) of freshly caughtC. tarichi; total ammonia content of the tissues was by a factor of 1.9 (liver) to 3.0 (brain) lower. High arginase activity (2.4±0.2 U·min^–1·g^–1) was detected in the liver ofC. tarichi but ornithine carbamoylphosphate transferase, a key enzyme of the ornithine-urea-cycle, was absent. Ureagenesis is likely through degradation of arginine and/or uricolysis. High glutamine synthetase activity (11±0.6 U·min^–1·g^–1) and low ammonia content in brain suggest that, like other teleosts,C. tarichi has an efficient ammonia detoxification in the brain, but in no other tissue.Nitrogenous waste excretion at alkaline pH is discussed. The ability ofC. tarichi to excrete high levels of ammonia at extremely alkaline pH is unique among teleosts studied so far. The mechanism of ammonia excretion under Lake Van conditions remains to be elucidated.