铁离子对固定化和游离态硝化细菌活性的影响

采用聚乙二醇—海藻酸钠—氯化钙方法包埋淡水型和海水型硝化细菌,比较分析铁离子对固定化和游离态硝化细菌中氨氧化菌和亚硝酸盐氧化菌活性的影响。结果表明,Fe~(3+)对游离态硝化细菌的影响大于固定化硝化细菌,当Fe~(3+)浓度为1mg·L~(-1)时固定化淡水硝化细菌氨氧化活性最高,游离态淡水型氨氧化活性受Fe~(3+)影响较大,120h后明显降低,但对亚硝酸盐氧化活性影响均较小。在不同Fe~(3+)浓度条件下,固定化海水硝化细菌氨氧化活性和亚硝酸盐氧化活性与不加Fe~(3+)组基本相同,而游离态海水型氨氧化和亚硝酸盐氧化活性均随Fe~(3+)浓度增大而略有降低。     

1株亚硝酸盐降解菌的筛选、鉴定、降解条件及效果

从养殖水体中筛选出1株对哑硝酸盐具有高效降解能力、增殖速度快、稳定和安全的优良菌株,经细菌学常规榆测和16S rRNA序列分析确定为巨大芽孢杆菌(Bacillus megaterium,),并命名为SZ-3.对SZ-3菌株降解条件的单因素实验发现,其最佳降解条件是:pH 7.0,温度33℃,降解所需的最低葡萄糖含量为0.01 mg/L,在24 h内对亚硝酸盐的降解率达69.58%.在哑硝酸盐质量浓度为5 mg/L的100 L污染水体养殖实验中,添加1 000 mL,含量为1×108 CFU/mL的SZ-3培养菌液离心后的纯菌体,在28℃的水温条件下经96 h,SZ-3菌株对亚硝酸盐的降解率可达91.78%.表明该菌株对污染水体中的亚硝酸盐具有较强的降解效果.本研究旨在为研发高效实用的降解亚硝酸盐微生态活性菌奠定基础.     

一株亚硝酸盐降解菌的分离鉴定及其降解特性

为获得高效降解亚硝酸盐菌，从鄱阳湖水域筛选出1株新型反硝化细菌，命名为X10。本实验对菌株进行16S rDNA基因序列分析，构建系统发育树并结合生化指标对该菌株进行鉴定；研究了亚硝酸盐浓度、pH值、温度、接种量对其生长及脱氮能力的影响，以及菌株对养殖水体中亚硝酸盐氮的降解能力。结果显示，X10鉴定为木糖氧化无色杆菌；温度30 ℃、pH 7.0、接种量3%，经48 h培养后菌株对筛选培养基中亚硝酸盐(浓度300 mg/L)的降解率最高，达99.8%；将该菌液(2×10⁸ CFU/mL)按1%的接种量加入人工养殖池塘水中(亚硝酸盐质量浓度为0.45 mg/L，pH为6.7)，28 ℃水温下经96 h后亚硝酸盐降解率达82.6%；安全性评价实验显示，X10菌落周围无溶血现象，并且高浓度菌液(5×10⁸ CFU/mL)对斑马鱼无致死作用。研究表明X10在水产养殖中具有较好的应用前景。     

固定化光合细菌净化养殖水质研究

采用海藻酸钠进行光合细菌固定化试验,比较了固定化菌和悬浮态菌的生长和生理特性,观察了其在载体中的分布,并对其净化养殖水的能力进行了初步研究.结果表明,固定化大大提高了光合细菌的生长速率;粒径为3.5mm,菌初始密度为0.12mg/L为最佳固定化条件.在生长初期,细菌在载体内的分布不均匀,后期趋于一致.固定化光合细菌对养殖水的净化能力大大优于悬浮态菌.     

不同载体固定化海洋微生物酯酶ETM-b的性能比较

分别采用海藻酸钠包埋法、明胶包埋交联法、壳聚糖吸附交联法制备固定化海洋芽孢杆菌酯酶ETM-b,并对其固定化条件进行了研究。结果发现,壳聚糖制备的固定化酶效果最好,壳聚糖2%、戊二醛浓度1%、小球与酶液4∶3(g/ml)时制备的固定化酶的活性回收最高,达到66%。壳聚糖制备的固定化酶使用10次,相对活性保留70%,具有良好的操作稳定性。固定化酶在非水介质中具有转化α-乙酸萘酯(α-Naphthyl acetate)的能力,在异辛烷、正辛烷、正己烷中活性表现最高。     

复合硝化菌制剂对水质改良的应用效果

室内静态水体中0.25mg/L复合硝化菌制剂使用后,7d内氨氮平均降解率为34.84%,亚硝酸盐氮的平均降解率为19.05%。0.5mg/L组氨氮平均降解率为45.05%,亚硝酸盐的平均降解率为41.79%。1.0mg/L组的氨氮平均降解率为55.26%,亚硝酸盐氮平均降解率为51.20%。氨氮和亚硝酸盐氮的最大的降解峰值出现6d之间。而养殖池塘中,0.5mg/L复合硝化菌制剂后,5d内氨氮的降解率为13.61%～28.03%,7d内亚硝酸盐氮的降解率为9.30%～25.58%。0.2mg/L复合硝化菌制剂使用后,6d内氨氮的降解为23.40%～34.75%,7d内亚硝酸盐氮的降解率为16.33%～36.13%。试验结果表明,复合硝化菌制剂在养殖池塘中使用后,有降解速度快、降解能力强、维持时间长等特点,适宜于作为净化和调控养殖水质的渔用微生物制剂使用。     

光合细菌的固定化及对养殖水体的净化作用

为了解固定化光合细菌对养殖水体的净化作用,分别采用海藻酸钠、PVA/海藻酸钠和NaCS微胶囊3种不同材料对光合细菌进行包埋,并比较了包埋后的光合细菌对养殖水体的净化效果。结果表明:以3种不同材料包埋的光合细菌,对养殖水体中氨氮、亚硝酸盐和COD的去除效果比对照组显著。以海藻酸钠—CaCl2法包埋的光合细菌小球,对养殖水体中氨氮、亚硝酸盐和COD的去除效果较好,但抗冲击力和机械性能较差;而以PVA/海藻酸钠—饱和硼酸法制备的光合细菌小球,传质性稍差;NaCS-PDMDAAC微胶囊,因其膜较薄,故抗冲击力较差,但其中空的纯液态环境为细胞的生长提供了更大的空间,尤其是在水处理10 d后,被包埋的细胞对氨氮、亚硝酸盐和COD的去除效果明显。     

亚硝酸盐氮对金鱼鱼种的急性毒性效应

采用常规生物急性毒性试验方法,研究了亚硝酸盐氮对体长(6.50±0.50) cm、体质量(9.12±0.45) g金鱼的急性毒性效应.试验结果表明:金鱼对亚硝酸盐氮的耐受性随接触时间的增加而明显降低;亚硝酸盐氮对金鱼24、48、72、96 h半致死质量浓度分别为1328.726、784.352、731.890、341.470 mg/L,95%可信区间依次为(1070.889～1648.393)、(578.031～1064.193)、(580.943～922.001)、(283.320～411.504) mg/L,安全质量浓度为34.15 mg/L.     

非离子氨氮和亚硝酸盐氮对暗纹东方鲀稚鱼的急性毒性试验

在水温21~23℃,pH 8.2~8.5,溶解氧6.00~7.50mg/L的条件下,采用半静水法研究了非离子氨氮和亚硝酸盐氮对全长(1.6±0.2)cm、体质量为(0.11±0.05)g的暗纹东方鲀稚鱼的急性毒性效应。试验结果表明,暗纹东方鲀稚鱼受到非离子氨氮和亚硝酸盐氮胁迫后,先后出现鱼体体色变白、扭曲、侧游、失去平衡、昏迷等中毒症状。随着非离子氨氮和亚硝酸盐氮质量浓度的提高和胁迫时间的延长,暗纹东方鲀稚鱼死亡率逐渐升高,存在明显的剂量效应和时间效应关系。非离子氨氮和亚硝酸盐氮对暗纹东方鲀稚鱼96h半致死质量浓度分别为0.46mg/L(95%置信限0.34~0.64mg/L)和290.12mg/L(95%置信限255.16~329.87mg/L),安全质量浓度分别为0.046 mg/L和29.01mg/L。非离子氨氮和亚硝酸盐氮对暗纹东方鲀稚鱼具有一定毒性,且非离子氨氮毒性大于亚硝酸盐氮毒性。     

金属离子对嗜油不动杆菌YT03降解亚硝酸盐的影响

由0.05g·L~(-1 )Na NO_2、0.54g·L~(-1)丁二酸钠、0.33g·L~(-1)K_2HPO_4·3H_2O和0.13g·L~(-1)Na Cl,以及一定量的金属离子溶液配成亚硝酸盐好氧反硝化培养液。将-20℃甘油保存的嗜油不动杆菌Acinetobacter oleivorans YT03菌液(菌液与40%甘油体积比为1∶1),以1%接种量分别接种至含不同质量浓度的Mg~(2+)、Ca~(2+)、Mn~(2+)、Fe~(2+)、Mo~(6+)、Zn~(2+)、Cu~(2+)和Co~(2+)的好氧反硝化培养液中,在30℃、摇床转速150r·min~(-1)条件下培养6h,取样测定培养液中亚硝酸盐氮质量浓度和亚硝酸盐氮的去除率,研究不同金属离子对嗜油不动杆菌YT03好氧反硝化降解养殖水体中亚硝酸盐的影响。结果表明,在优选的金属离子添加浓度下,0.50mg·L~(-1)Fe~(2+)使YT03菌对亚硝酸盐的去除率显著提高至不添加Fe~(2+)时的4.93倍,而18.48 mg·L~(-1)或0.65mg·L~(-1)的Mg~(2+)或Mn~(2+)则使YT03菌的亚硝酸盐去除率分别提高至不添加相应金属离子时的1.25或1.16倍。Ca~(2+)和Mo~(6+)对YT03菌降解亚硝酸盐的影响不明显。而在培养液中分别添加0.51 mg·L~(-1)、0.06 mg·L~(-1)或0.05mg·L~(-1)以上的Zn~(2+)、Cu~(2+)或Co~(2+)时,YT03菌对亚硝酸盐的去除率显著下降,呈显著抑制作用。     

Protein and amino acid composition from the mantle of juvenile O ctopus vulgaris exposed to prolonged starvation

Protein and amino acid composition of the mantle of juvenile O ctopus vulgaris (Cuvier, 1797) during fasting for 27 days were determined. Average protein content of octopus mantle was of 711.19 ± 46.80 g kg^?1 DW, and it decreased with increasing fasting days. The non‐essential amino acids content was higher (486.18 ± 11.08 g kg^?1 protein) than essential amino acids (425.82 ± 9.15 g kg^?1 protein) at the start of the experiment (unstarved animals). The results suggest that the amino acid profile of the mantle where the most abundant amino acids are Arg, His, Lys, Gly, Leu and Pro could indicate a prolonged fasting condition (>20 days) or poor nutrition of O . vulgaris. This study supports the idea of using mantle for metabolic needs of starved O . vulgaris suggesting that the degradation pathway of amino acids to pyruvate and tricarboxylic acid cycle intermediates was favoured contrary to the degradation pathway of ketogenic amino acids. Special considerations should be taken concerning Thr, Ile, Ser, Ala, Asx (Asp, Asn), Glx (Glu, Gln) (because of their fast intake) and Lys and His (due to their stable contents) during a prolonged period of fasting.     

美人鱼发光杆菌对凡纳滨对虾非特异性 免疫功能及抗病力的影响

在基础饲料中分别添加0.1%和1%美人鱼发光杆菌灭活菌、0.1%美人鱼发光杆菌活菌配制成3种免疫实验饲料,以基础饲料为空白对照组饲料,每组设3个平行样。对个体质量为(4.83±0.36)g的凡纳滨对虾进行为期20 d的饲养实验,分别在0、5、10、15和20d进行取样,以血清中的酚氧化酶(PO)、酸性磷酸酶(ACP)、碱性磷酸酶(AKP)、超氧化物歧化酶(SOD)和溶菌酶(UL)活性为免疫指标,探讨了美人鱼发光杆菌作为免疫制剂对凡纳滨对虾非特异性免疫效应的影响;在投喂免疫饲料后的第22天,按0.004 2 kg/kg体重的剂量,直接投喂对虾白斑综合征病毒(WSSV)病料,并记录累积死亡率。结果表明,美人鱼发光杆菌免疫实验组对凡纳滨对虾血清中PO、ACP、AKP、UL和SOD活性影响明显高于对照组,并且在饲料中添加美人鱼发光杆菌后,明显提高了对虾抵御WSSV感染的能力。其中0.1%美人鱼发光杆菌活菌实验组的抗病毒感染能力最强,WSSV感染14d内累计死亡率为63.3%±5.8%;而对照组为96.7%±3.3%。研究表明,美人鱼发光杆菌添加在对虾饲料中能提高凡纳滨对虾非特异性免疫水平,增强抵抗疾病的能力,将其作为对虾免疫增强剂具有良好的应用前景。     

Effects of Spirulina platensis as a feed additive on growth and coloration of blue dolphin cichlids (Cyrtocara moorii Boulunger, 1902)

This study was carried out to investigate the effects of replacing fish meal with dietary Spirulina as a feed supplement on the growth performance and coloration of blue dolphin cichlids (Cyrtocara moorii). Five isonitrogenous (47% crude protein) and isocaloric (17.36 kJ/g digestible energy) diets were for formulated to replace FM with 0, 5, 10, 15 and 20% Spirulina (designated as Control, SP5, SP10, SP15 and SP20 respectively) and fed to the fish (initial body weight, 3.15 ± 0.01 g). Fish were randomly distributed into fifteen 120 L aquariums (26.5 ± 1.00°C), 15 fish per aquarium. The diets were tested in triplicate for 12 weeks. Experimental groups were fed twice daily (09:00 and 17:00) by hand to satiation. At the end of the feeding trial, significantly (p < 0.05) higher weight gain (WG), specific growth rate (SGR), protein efficiency ratio (PER) and lower feed conversion ratio (FCR) were observed in fish fed the SP10 diet when compared to the SP20 diet. There was no significant difference in these parameters between the other groups. The skin coloration of blue dolphin cichlid fed a diet containing Spirulina meal was enhanced. The best coloration was observed in the SP15 group. These impressions were objectively validated by chemical determinations of carotenoids extracted from fish skins and passed statistical tests of significance. The study findings show that Spirulina meal does not diminish growth rates except at very high levels.     

Sea bream culture in Egypt; status, constraints and potential

Marine fish farming in Egypt began in 1976 with the culture of gilthead sea bream, (Sparus aurata) as this fish was notably adaptable to brackish and marine pond conditions. Today, marine fish and shrimp farms amount to about 19,000 ha, out of which 42% is already in production while the rest, i.e., 58% is still under construction. In 1997, cultured gilthead sea bream production of 2,250 tons made up 3% of the 75,000 tons total aquaculture catch. In polyculture, usually with the grey mullet and sea bass, gilthead sea bream contributed 440 kg ha^–1 to the total yield of 1,700 kg ha^–1 (26%) over a period of 16 months. For the same period, the yield of monoculture ponds averaged 100 kg ha^–1, while in marine cages, yields ranged from 4–10 kg m³. In 1996–1997, fry of 0.25–1 g and fingerlings 1–10 g with a total of 3 million, were collected from the wild and 1 million fry were produced in the three marine hatcheries out of the four existing ones. The development of sea bream culture in Egypt is now severely inhibited by the shortage of seeds and adequate feeds. Exports of both sea bream and sea bass, during 1994–1996 averaged 1,300 tons per year.     

Dietary thiamin and pyridoxine requirements of fingerling Indian major carp,Cirrhinus mrigala (Hamilton)

Two experiments were conducted to quantify the dietary thiamin (experiment I) and pyridoxine (experiment II) requirements of fingerling Cirrhinus mrigala for 16 weeks. In experiment I, dietary thiamin requirement was determined by feeding seven casein–gelatin‐based diets (400 g kg^?1 CP; 18.69 kJ g^?1 GE) with graded levels of thiamin (0, 0.5, 1, 2, 4, 8 and 16 mg kg^?1 diet) to triplicate groups of fish (6.15 ± 0.37 cm; 1.89 ± 0.12 g). Fish fed diet with 2 mg kg^?1 thiamin had highest specific growth rate (SGR), protein retention (PR), RNA/DNA ratio, haemoglobin (Hb), haematocrit (Hct), RBCs and best feed conversion ratio (FCR). However, highest liver thiamin concentration was recorded in fish fed 4 mg thiamin kg^?1 diet. Broken‐line analysis of SGR, PR and liver thiamin concentrations exhibited the thiamin requirement in the range of 1.79–3.34 mg kg^?1 diet (0.096–0.179 μg thiamin kJ^?1 gross energy). In experiment II, six casein–gelatin‐based diets (400 g kg^?1 CP; 18.69 kJ g^?1 GE) containing graded levels of pyridoxine (0, 2, 4, 6, 8 and 10 mg kg^?1 diet) were fed to triplicate groups of fish (6.35 ± 0.37 cm; 1.97 ± 0.12 g). Fish fed diet containing 6 mg kg^?1 pyridoxine showed best SGR, FCR, PR, RNA/DNA ratio, Hb, Hct and RBCs, whereas maximum liver pyridoxine concentration was recorded in fish fed 8 mg kg^?1 dietary pyridoxine. Broken‐line analysis of SGR, PR and liver pyridoxine concentrations reflected the pyridoxine requirement from 5.63 to 8.61 mg kg^?1 diet. Data generated during this study would be useful in formulating thiamin‐ and pyridoxine‐balanced feeds for the intensive culture of this fish.     

A Minchinia mercenariae‐like parasite infects cockles Cerastoderma edule in Galicia (NW Spain)

The cockle Cerastoderma edule fishery has traditionally been the most important shellfish species in terms of biomass in Galicia (NW Spain). In the course of a survey of the histopathological conditions affecting this species in the Ria of Arousa, a haplosporidan parasite that had not been observed in Galicia was detected in one of the most productive cockle beds of Galicia. Uni‐ and binucleate cells and multinucleate plasmodia were observed in the connective tissue mainly in the digestive area, gills and gonad. The parasite showed low prevalence, and it was not associated with abnormal cockle mortality. Molecular identification showed that this parasite was closely related to the haplosporidan Minchinia mercenariae that had been reported infecting hard clams Mercenaria mercenaria from the Atlantic coast of the United States. The molecular characterization of its SSU rDNA region allowed obtaining a fragment of 1,796 bp showing 98% homology with M. mercenariae parasite. Phylogenetic analysis supported this identification as this parasite was clustered in the same clade as M. mercenariae from the United States and other M. mercenariae‐like sequences from the UK, with bootstrap value of 99%. The occurrence of M. mercenariae‐like parasites infecting molluscs outside the United States is confirmed.     

A novel approach to denitrification processes in a zero-discharge recirculating system for small-scale urban aquaculture

This paper presents an innovative process to solve the nitrate build-up problem in recirculating aquaculture systems (RAS). The novel aspects of the process lie in a denitrification bioreactor system that uses solid cotton wool as the primary carbon source and a unique degassing chamber. In the latter, the water is physically stripped of dissolved gaseous O₂ (by means of a Venturi vacuum tube), and the subsequent denitrification becomes more efficient due to elimination of the problems of oxygen inhibition of denitrification and aerobic consumption of cotton wool. The cotton wool medium also serves as a physical barrier that traps organic particles, which, in turn, act as an additional carbon source for denitrification. Operation in the proposed system gives an extremely low C/N ratio of 0.82 g of cotton wool/g of nitrate N, which contributes to a significant reduction of biofilter volume. The additional advantage of using solid cotton wool as the carbon source is that it does not release organic residuals into the liquid to be recycled. Operation of the system over a long period consistently produced effluents with low nitrate levels (below 10 mg N/l), and there was only a very small need to replace system water. The overall treatment scheme, also incorporating an aerobic nitrification biofilter and a granular filtration device, produced water of excellent quality, i.e., with near-zero levels of nitrite and ammonia, a sufficiently high pH for aquaculture, and low turbidity. The proposed system thus provides a solution for sustainable small-scale, urban aquaculture operation with a very high recovery of water (over 99%) and minimal waste disposal.     

Fertilization by refrigerator stored sperm of the Indian major carp, Labeo calbasu (Hamilton, 1822)

This study reports on the spermatological properties, and on the development of a protocol for refrigerator storage (4°C) of Labeo calbasu (Hamilton, 1822) sperm for artificial breeding. Volume, motility, concentration and pH of the freshly collected sperm were 2.21 ± 0.53 (μL g^?1 of fish weight) (mean ± SD), 95 ± 1 (%), 1.93 ± 0.44 × 10⁹ (cells mL^?1) and 7.56 ± 0.17 respectively. Sperm activation was evaluated at different osmolalities of NaCl solution, and motility ceased completely when osmolality of the extender was ≥287 mOsmol kg^?1. Sperm retained motility for 24, 72 and 108 h, after refrigerator storage when sperm were undiluted, suspended in Alsever's solution and suspended in Alsever's solution containing 5% methanol respectively. Fertilization rate of fresh eggs with sperm stored at 4°C in Alsever's solution and Alsever's solution containing 5% methanol was 77% and 60% with a hatching rate of 60% and 43% respectively. The fertilization and hatching success of the stored sperm suggests potential to use refrigeration for transporting genetic material to hatcheries for artificial breeding of L. calbasu in Bangladesh.     

Effects of metomidate anaesthesia or transfer to pur sea water on plasma parameters in ammonia-exposed Atlantic salmon (Salmo salar L) in sea water

Atlantic salmon (Salmo salar L) postsmolts weighing 150 ± 53 g were exposed to 14–15 mg l^–1 TA-N (total ammonia-N) in sea water in 1 m³ tanks for 24h. Blood samples were then taken A) immediately after the fish were netted from the exposure tanks and stunned by a blow to the head; B) 2–20 min after the fish were transferred to 15 l of an anaesthetic solution of metomidate in ammonia-free sea water; or C) 2–20 min after the fish were transferred to 15 l of ammonia-free sea water. Plasma TA-N level was 18% lower in the anaesthetised fish compared to in the fish sampled directly from the exposure tanks (p 0.05), and accordingly 16% lower in the fish transferred to pure sea water although this difference was not significant (p = 0.07). Plasma glucose level was higher in the fish transferred to pure sea water than in the fish receiving the two other treatments (p 0.05), but plasma urea, osmolality, Na^{+, Cl–, Ca2+ or Mg2+} levels did not vary significantly between the different treatments. Plasma TA-N level increased with time in the fish in the metomidate solution (p 0.02).