五种培养液对萱藻丝状体生长发育的影响

提要 本文以实验室保存的萱藻丝状体为材料,采用实验生态学方法,探讨了L1、PES、F1、f/2以及ESNW等五种培养液对萱藻丝状体生长发育的影响,并以去除氮或磷成分的L1培养液为基础,研究了不同外加浓度氮和磷对萱藻丝状体生长发育的影响。结果显示:(1)五种培养液中,L1培养液最有利于萱藻丝状体的生长发育,培养28天后,丝状体生物量增重倍比可达560.48%,孢子囊枝比例高达46.88%,孢子囊直径为18.95μm;(2)萱藻丝状体生长发育最适添加NO3--N浓度为6.00mg/L,在此NO3--N浓度条件下,萱藻丝状体生长速度最快,培养20天后,孢子囊枝比例高达46.78%,孢子囊直径可达18.78μm。在添加NO3--N浓度为0.00mg/L和高氮(96.00mg/L、192.00mg/L)条件下,萱藻丝状体生长速度均相对较慢,培养20天后,孢子囊枝比例分别仅为0.00%、9.06%和7.65%,孢子囊直径仅9.00~10.00μm;(3)萱藻丝状体生长发育的最适外加PO43--P浓度为1.32mg/L,在此PO43--P浓度条件下,萱藻丝状体生长速度最快,培养20天后,孢子囊枝比例高达47.12%,孢子囊直径可达18.89μm。外加PO43--P为0.00mg/L时,培养20天后,孢子囊枝比例仅为10.12%,孢子囊直径仅有9.78μm。外加PO43--P高于15.84mg/L时,均没有孢子囊枝的形成。研究证明,在萱藻丝状体的生长发育过程中,选择一种合适的培养液以及适时地控制硝酸盐与磷酸盐的浓度,使其维持在一定范围内,从而促进萱藻丝状体的快速生长,提高其孢子囊枝比例、增大孢子囊直径。     

威海湾营养盐季节变化特征及与环境因子的相关性分析

根据2006-2007年威海湾4个航次营养盐的调查资料,分析该海域海水中无机氮(DIN)、磷酸盐(PO43--P)和硅酸盐(SiO32--Si)的季节变化规律及其与环境因子的典型相关性。结果表明,NO3--N是DIN的主要存在形式,比例达50%以上。营养盐季节性变化明显,秋冬季DIN和PO43--P浓度较高,春夏季较低,SiO32--Si的变化则相反。四季DIN和PO43--P浓度均大于浮游植物生长阈值,仅冬季SiO23--Si浓度低于浮游植物生长阈值。冬季浮游植物生长的限制因子是Si,其他季节具有P限制的潜在性。营养盐和环境因子具有较大的典型相关性,其中,盐度、pH和NO3--N、PO43--P、SiO23--Si相关性最大,典型相关系数达到0.979。     

不同氮、磷浓度下亚心形扁藻的生长及水体中氮、磷变化

自然条件下,采用湛水107-13营养液为基础配方,在经消毒处理的天然海水中添加不同氮、磷质量浓度的营养盐进行亚心形扁藻的培养。结果表明,当氮、磷质量比为17时,最适合亚心形扁藻的生长。不同磷质量浓度梯度对亚心形扁藻的生长和生长率K具有显著性的影响(P<0.05)。当磷质量浓度为8 mg/L时,其相对生长常数和生长率K值均高于其他质量浓度处理。不同氮质量浓度梯度对亚心形扁藻生长具有显著性影响(P<0.05),但对亚心形扁藻生长率K的影响不显著(P>0.05)。高质量浓度氮对亚心形扁藻的生长影响作用最大(P<0.05)。在培养过程中,高质量浓度氮、磷培养液中NO3--N和PO43--P的下降速率高于低质量浓度中NO3--N和PO43--P浓度的变化,并呈现出显著性的差异(P<0.05)。表明在高质量浓度营养盐条件下培养亚心形扁藻,会导致营养盐相对利用率的下降。     

循环养殖系统中牙鲆生长及营养盐状况研究

研究了一个包括鱼池、沉淀池、硝化滤器和大型海藻滤器的循环养殖系统长期运行的水质状况及养殖牙鲆的生长状况。报道了该系统中的牙鲆在一定时间内的生长情况,建立了牙鲆体重(抽样平均湿重)与生长时间的回归方程:W=4.654 e0.0181 t。同时监测系统中的NH4 -N、NO2--N、NO3--N、PO43--P浓度,其NH4 -N在实验时间内一直保持在0.4 mg/L以下,NO2--N低于0.2 mg/L以下,NO3--N、PO43--P在开始时有一定积累,后来有下降趋势。实验表明,该循环养殖系统可以满足牙鲆工厂化循环养殖的要求。     

大口黑鲈投喂两种不同饲料对水质指标的影响

为了研究投喂两种不同饲料(冰鲜下杂鱼与配合饲料)对大口黑鲈养殖水质指标的影响,在室内水泥池进行了28d的饲养试验.对水体中的COD、PO4--P、TP、TN、NH3-N、NO3--N、NO2-N等指标进行了测定.结果表明,投喂两种饲料各指标均有不同程度的增加,但养殖一个月后冰鲜组比饲料组要高许多:杂鱼组COD、PO4--P、TP、TN、NH3-N、NO3--N、NO2--N分别为25.3mg/L、2.4mg/L、2.28mg/L、3.44mg/L、2.91mg/L、0.52mg/L、0.075mg/L,而配合饲料组分别为10.2mg/L、0.58mg/L、0.855mg/L、2.17mg/L、0.29mg/L、0.048mg/L、0.03mg/L.特别是PO4--P、TP,冰鲜组分别为饲料组的4.2倍和2.7倍.这说明投喂人工饲料可以减轻有机污染程度,特别是在控制PO4--P、TP的增加方面效果显著.试验结果对于控制水体的富营养化具有重要的指导意义.     

几种环境因子对循环水养殖系统中生物膜净化效率的研究

为研究环境因子对生物膜水质净化效果,对爆炸棉为滤料的生物滤器进行了试验。采用优势菌种挂膜后,在不同水温、溶氧(DO)、盐度、p H条件下,研究生物滤器对人工加富的海水养殖废水水质的净化效果。结果显示,水温28℃时,化学需氧量(CODMn)、氨氮(NH4+-N)、亚硝酸盐氮(NO2--N)、磷酸盐(PO43--P)去除率分别为69.3%、93.7%、93.7%、19.4%;DO 6.00 mg/L时,CODMn、NH4+-N、NO2--N、PO43--P去除率分别为72.8%、91.7%、97%、15.6%;盐度25时,CODMn、NH4+-N、NO2--N、硝酸盐氮(NO3--N)、PO43--P去除率分别为57.1%、98.4%、99.9%、100%、42%;p H 7.5时,CODMn、NH4+-N去除率分别为72.8%、93.3%。研究表明,水温28℃、DO 6.00mg/L、盐度25和p H 7.5为该生物滤器最适水质净化条件,此时生物膜净化效率较高,出水水质较好。     

小球藻与芽孢杆菌对对虾养殖水质调控作用的研究

通过在凡纳滨对虾养殖水体中添加小球藻和芽孢杆菌,研究其对养殖水质的调控作用。结果表明,小球藻和芽孢杆菌联合处理组对水质的调控效果优于只添加芽孢杆菌组或小球藻组。菌-藻联合处理组能很好地降低水体中氮、磷的含量,对氨氮的作用尤为明显;实验进行的第5天内,NH4 -N含量显著低于对照组(P<0·05),降低率为32·94%,NO2--N降低率为10·29%,PO34--P降低率为36·02%。小球藻 芽孢杆菌组NH4 -N含量平均为0·277mg/L,日均积累速率0·0135mg/L·d,而对照组为0·0472mg/L·d;NO2--N平均含量为0·334mg/L,日均积累速率为0·0617mg/L·d。小球藻在调控水质的同时也向水体释放有机物,从而引起水体COD的上升。     

水葫芦对水质改良效果的研究

研究了水葫芦在改良水质中的作用.经过水质测定表明,当平均照度1379Lx、平均水温15℃时,测得每公斤水葫芦可以从水体中吸收PO43--P5.0mg/d,吸收NO2--N和NH4 -N 47.9mg/d;并且在15d内消除水体中的NO2--N.水葫芦不仅是一种优良的水生植物性饲料、绿肥,而且能有效地改良水质,降低水体污染.     

吉富罗非鱼温棚池塘上覆水−沉积物间隙水营养盐垂直分布特征及其界面交换通量

利用Peeper(pore water equilibriums)技术采集上覆水-沉积物间隙水整个垂直剖面的原位水样,然后使用微量分光光度法测定样品中主要营养盐NH4+-N、NO3--N、NO2--N、PO43--P和SO42--S的浓度,从而分析吉富罗非鱼(GIFT,Oreochromis niloticus)温棚养殖池塘各营养盐的垂直分布特征,并估算其在上覆水-沉积物界面处的交换通量。结果表明:(1)两罗非鱼温棚养殖池塘,4个Peeper实验组在上覆水-沉积物间隙水中各营养盐组间重复性都较好,且各营养盐都有较强的垂直分布规律。NH4+-N主要存在于沉积物间隙水中,从其表面深度0至6 cm间隙水中NH4+-N浓度迅速增高,8 cm后趋于相对稳定;NO3--N主要存在于上覆水中,沉积物0至4 cm间隙水中3NO--N浓度迅速降低;NO2--N浓度在沉积物表层2 cm处出现峰值;PO43--P浓度在沉积物0至4 cm间隙水中浓度迅速增加至最大值,深度超过4 cm浓度有降低趋势;SO42--S主要存在于上覆水中,沉积物0至8 cm间隙水中SO42--S浓度迅速降低。(2)不同深度的水样根据营养盐浓度,各实验组都可聚类为3组差异显著的类群:上覆水组、表层沉积物组(上覆水-沉积物交界面组)和深层沉积物组。(3)通过Fick第一定律估算营养盐在上覆水-沉积物界面的扩散通量得出:NH4+-N和PO43--P为从沉积物间隙水扩散至上覆水中;NO3--N和SO42--S为从上覆水扩散至沉积物中。4个Peeper实验组NH4+-N的扩散通量分别为22.44 mg/(m2·d)、22.93 mg/(m2·d)、50.84 mg/(m2·d)和16.74 mg/(m2·d),为两罗非鱼温棚养殖池塘主要的沉积物内源释放营养盐。与类似研究比较,本研究通量相对较高,表明养殖池塘沉积物有机质含量相对较高。SO42--S的扩散通量分别为–87.05 mg/(m2·d)、–164.87 mg/(m2·d)、–77.37 mg/(m2·d)和–91.30 mg/(m2·d),为两养殖池塘沉积物最大的吸收营养盐,表明SO42--S还原可能为罗非鱼养殖池塘沉积物中有机质降解的主要途径之一。     

基于^15N稳定同位素技术的斜生栅藻对硝氮和氨氮吸收研究

硝氮（NO3--N）和氨氮（NH4＋-N）是水体中无机氮的主要形态。利用15N稳定同位素技术研究了斜生栅藻（Scendesmus obliquus）对NO3--N和NH4＋-N的吸收特征。结果显示,在相同浓度条件下,斜生栅藻对NH4＋-N的吸收速率显著高于对NO3--N的吸收率,在180min的试验中,对15NH4＋-N的吸收速率为0.62～1.15μmol/（g·min）;对15NO3--N的吸收速率为0.08～0.15μmol/（g·min）。在NO3--N和NH4＋-N2种形态氮源同时存在的混合组中     

人工湿地基质氧化还原酶与净水效果的相关性

为研究氧化还原酶活性对人工湿地中污染物去除率的影响,探讨将基质酶活性作为评判人工湿地整体去除效能的指标,本研究以生物陶粒和鹅卵石为基质并搭配种植再力花(Thalia dealbata)、美人蕉(Canna indica)和梭鱼草(Pontederia cordata)的复合垂直流人工湿地为研究对象,2016年6月至11月每月采样1次,对基质中4种氧化还原酶(脱氢酶、多酚氧化酶、过氧化物酶和硝酸还原酶)的酶活性进行测定,并从酶学的角度探讨这4种氧化还原酶的活性与养殖尾水中总氮(TN)、硝态氮(NO_3~–-N)、总磷(TP)、正磷酸盐(PO_4~(3–)-P)、COD_(Mn)去除率之间的关系。结果表明,氧化还原酶活性在整个实验过程中发生了显著变化,脱氢酶和过氧化物酶活性先上升后下降,酶活性分别在植物生长高峰期的8月和9月达到最高;多酚氧化酶和硝酸还原酶活性夏季(6—8月)变化不大,植物生长末期达到最高。空间分布上,脱氢酶、多酚氧化酶和过氧化物酶活性沿垂直方向分布表现出相同趋势,即表层最高,中层次之,底层最低。硝酸还原酶活性则表现出相反的趋势。脱氢酶活性与COD_(Mn)的去除率显著正相关(R~2=0.6783,P0.05);硝酸还原酶活性与NO3–-N的去除率显著正相关(R~2=0.6768,P0.05);多酚氧化酶和过氧化物酶活性与TN、NO_3~–-N、TP、PO_4~(3–)-P以及COD_(Mn)的去除率无显著相关性(P0.05)。结论认为,脱氢酶可作为人工湿地中去除COD_(Mn)的效能指标,硝酸还原酶可作为人工湿地中去除NO_3~–-N的效能指标。     

藻-菌单一及共生系统对海水养殖尾水的净化作用

为探索高效可行的海水养殖尾水处理技术,在净化尾水污染物的同时达到微藻生物量积累,本文对比了普通小球藻(Chlorellavulgaris)和芽孢杆菌(Bacillusspp.)在游离和固定形态下,单一和共生系统的细胞生长及其对尾水中氨氮(NH_4~+-N),正磷酸盐(PO_4~(3–)-P),总磷(TP),化学需氧量(COD_(Mn))的去除效果。实验结果表明:游离状态下,藻–菌共生系统促进小球藻细胞生长及尾水中PO_4~(3–)-P和COD_(Mn)的去除。固定态藻–菌共生系统对NH4~+-N, PO43–-P和TP的处理效果优于单一固定态小球藻和单一固定态芽孢杆菌。对比实验设计的所有处理(游离或固定态下的单一藻、单一菌、藻–菌共生),藻–菌共固定系统的处理效果相对最优,对NH_4~+-N, PO_4~(3–)-P, TP和COD_(Mn)的去除率分别达到96.57%, 98.62%, 89.89%和39.09%,出水NH_4~+-N, PO_4~(3–)-P分别达到中国《渔业水质标准》和《海水养殖水排放要求》二级标准, COD_(Mn)达到《污水综合排放标准》二级标准。     

絮团浓度对革胡子鲇零换水养殖效果的影响

为研究絮团浓度对革胡子鲇零换水养殖效果的影响,在不额外添加有机碳源（只利用饲料中的碳）的革胡子鲇（）养殖系统中,设置了平均絮团质量浓度为561.18 mg/L和780.41 mg/L两个处理组,比较了两实验组的水质、菌群结构、鱼生长及氮利用效率。结果表明,两种浓度絮团条件下,总氨氮（total ammonia nitrogen,TAN）和亚硝酸氮（NO₂^--N）能分别维持1.84 mg/L和1.79 mg/L以下。两处理组间pH、溶解氧（dissolved oxygen,DO）、TAN、NO₂^--N、氮素利用效率及主要生长指标无显著差异（-N）浓度（822.0 mg/L）明显高于低浓度絮团组（623.33 mg/L）。高通量测序分析菌群结构结果表明,两组间门水平的菌群组成种类及优势度无显著性差异（<0.05）。两处理组中的革胡子鲇存活率分别达到（91.11±1.53）%和（94.44±2.08）%,饲料系数为（1.41±0.18）和（1.27±0.26）,特殊生长率为（2.13±0.04）%/d和（2.19±0.08）%/d,均无显著差异（>0.05）。两实验组饲料氮的利用率分别达到了72.17%和71.34%。综合以上结果认为,仅利用饲料中的碳既能维持革胡子鲇的零换水养殖且能取得较高的氮素利用效率,两种絮团浓度对革胡子鲇的生长无显著影响,高浓度絮团组中的硝化作用更明显。     

草鱼复合养殖系统间隙水与上覆水中营养盐分布特征

采用陆基围隔实验法,于2009年6～10月调查并分析了草鱼复合养殖系统上覆水和沉积物间隙水营养盐(NH4-N,NO3-N,NO2-N,PO4-P)的时空分布及沉积物总氮(TN)、总磷(TP)和总碳(TC)含量的变化.结果显示,(1)草鱼复合养殖系统上覆水中NH4-N,NO3-N,NOz-N和PO4-P的 含量波动范围分别为0.056～1.499、0.022～0.228、0.049～3.903、0.003～1.882 mg/L,间隙水中营养盐的平面分布中,NH4-N在总无机氮(DIN)中所占比例随着养殖时间的增加而增加,不同复合养殖系统的营养盐垂直分布特征不同,规律也不明显.(2)实验结束与实验开始时相比,沉积物中TN和TP含量无明显变化,但TC含量显著降低,以混养模式(GSC)的减少幅度最大.结果表明,在本实验条件下,草鱼、鲢鱼与鲤鱼复合养殖系统可有效降低养殖过程中有机物的积累,降低底层中潜在释放的NH4-N含量,是一种较为合理的草鱼复合养殖模式.     

Enhancement of <Emphasis Type="Italic">Penaeus monodon</Emphasis> shrimp postlarvae growth and survival without water exchange using marine <Emphasis Type="Italic">Bacillus pumilus</Emphasis> and periphytic microalgae

We have investigated the possibility of using a consortium of marine bacterium and periphytic microalgae to improve the water quality and increase the growth and survival of the shrimp Penaeus monodon in a hatchery system. Three treatments were evaluated for their effect on P. monodon postlarvae (PL) when the culture water was not changed: Bacillus pumilus alone (B); periphytic microalgae alone (M); B. pumilus + periphytic microalgae (BM). P. monodon PL raised in a tank of unchanged water without bacterium and periphytic microalgae served as the control. The water in tanks of the M and BM treatments had significantly low levels of total ammonia-nitrogen (TAN) (0.03 and 0.01 mg l⁻¹, respectively) and nitrite-nitrogen (NO₂-N) (0.03, 0.01 mg l⁻¹, respectively) than that in the B (TAN 0.80, NO₂-N 0.68 mg l⁻¹) and control (TAN 1.11, NO₂-N 1.12 mg l⁻¹) tanks. Moreover, PL cultured in tanks M and BM had significantly higher survival and specific growth rates and a significantly higher resistance to the reverse salinity stress test than those in the B and control tanks. Compared to the control PL, the PL cultured in the BM tanks had significantly higher levels of protein, lipid, polyunsaturated fatty acids, ecosapentaenoic acid, and docosahexaenoic acid. The culture water in tanks BM also contained significantly less Vibrio than the control water. Our results illustrate the beneficial effects of a B. pumilus and periphytic microalgae consortium on improving the water quality and the growth and survival of shrimp PL grown in a hatchery system.     

凡纳滨对虾养殖塘叶绿素a与水质因子的多元回归分析

2009年4-9月期间,对上海市奉贤区某凡纳滨对虾养殖场22个养殖池塘水体叶绿素a、水温、pH、溶解氧、透明度、悬浮物(SS)、总有机碳(TOC)、五日生化需氧量(BOD₅)、高锰酸盐指数(COD_Mn)等15项水质因子进行测定。取164组测定数据,进行描述性统计,分析叶绿素a与各项因子的相关性系数。分析结果显示,与叶绿素a呈极显著线性正相关的水质因子为SS、TOC、BOD₅、COD_Mn、TN、TP;呈显著正相关的为DO;而叶绿素a与透明度呈极显著线性负相关,与PO^3-₄-P呈显著线性负相关;与水温、pH、NO^-₂-N、 NO^-₃-N、NH₃-N则未呈现显著相关性。根据多元线性回归选择自变量的原则,选择了TOC、TN、PO^3-₄-P和TP₄项水质因子,建立了叶绿素a与4项水质因子的逐步回归模型:Chl.a =-0.054 5+0.0034 9 TOC+0.015 3 TN-0.418 PO^3-₄-P+0.276 TP(r=0.715 5)。利用偏回归系数检验各水质因子对叶绿素a的影响,结果表明,对叶绿素a影响从大到小依次是TP、TOC、PO^3-₄-P和TN。研究结果对进一步探讨养殖池塘生态系统的变化规律及水环境质量保护提供了依据。     

Some Aspects of the Growth of Gracilaria birdiae (Gracilariales, Rhodophyta) in an Estuary in Northeast Brazil

The agarophyte Gracilaria birdiae Plastino & Oliveira was cultivated under field conditions in an estuary over a 6-month period. Biomass production varied significantly (p<0.01) and ranged from 900.0 to 3537.0 g m⁻² with a mean of 2124.4±1004.36 g m⁻² over the cultivation period. The epiphyte-biomass varied from 64.7 to 313 g m⁻², with maximum values observed in July. Relative growth rate (RGR) of G. birdiae varying from −0.59 to 4.67% day⁻¹, with a maximum mean observed in July. Correlation analysis showed that RGR was positively correlated with epiphyte-biomass (R-Pearson=0.69; p< 0.01) and negatively correlated with salinity (R-Pearson=−0.41; p<0.05). These correlations were used in a mathematical regression model to estimate the growth of Gracilaria in an estuary. The regression model explained 61% of RGR variability demonstrating that growth rates of Gracilaria were directly related to the variables salinity and epiphytes. The model was developed to help to predict production at a cultivation site in order to evaluate its suitability for Gracilaria cultivation.     

鲢鳙混养对三角帆蚌生长和养殖水质影响的围隔实验

2008年4月23日—9月21日通过围隔实验,研究了不同鲢鳙混养比例对三角帆蚌生长及水化学指标的影响。实验中鲢鳙混养比例设置了6个水平,分别为0/0(对照组),100/0,70/30,50/50,30/70和0/100。实验开始和结束时测量三角帆蚌湿重,壳长和壳宽。每个月上下旬测量围隔水化学指标包括NO3N、NO2N、NH3N、TN、TP、PO4P和COD。实验结果表明,鲢鳙混养比例100/0的围隔蚌壳长相对生长率显著低于混养比例0/0,50/50和0/100的围隔(P<0.05),而不同混养比例下蚌的成活率、蚌壳宽及蚌重增长均无显著差异(P>0.05)。从水质来看,混养比例30/70围隔TP显著低于100/0(P<0.05),COD显著低于100/0及70/30(P<0.05),NH3N显著低于100/0(P<0.05)以及PO4P显著低于70/30(P<0.05)。因此,综合蚌生长及水质指标,混养比例30/70围隔对三角帆蚌养殖最有利。     

Activated sludge denitrification in marine recirculating aquaculture system effluent using external and internal carbon sources

Stringent environmental legislation in Europe, especially in the Baltic Sea area, limits the discharge of nutrients to natural water bodies, limiting the aquaculture production in the region. Therefore, cost-efficient end-of-pipe treatment technologies to reduce nitrogen (N) discharge are required for the sustainable growth of marine land-based RAS. The following study examined the potential of fed batch reactors (FBR) in treating saline RAS effluents, aiming to define optimal operational conditions and evaluate the activated sludge denitrification capacity using external (acetate, propionate and ethanol) and internal carbon sources (RAS fish organic waste (FOW) and RAS fermented fish organic waste (FFOW)). The results show that between the evaluated operation cycle times (2, 4, and 6 h), the highest nitrate/nitrite removal rate was achieved at an operation cycle time of 2 h (corresponding to a hydraulic retention time of 2.5 h) when acetate was used as a carbon source. The specific denitrification rates were 98.7 ± 3.4 mg NO₃⁻-N/(h g biomass) and 93.2 ± 13.6 mg NO_x⁻-N/(h g biomass), with a resulting volumetric denitrification capacity of 1.20 kg NO₃⁻-N/(m³ reactor d). The usage of external and internal carbon sources at an operation cycle time of 4 h demonstrated that acetate had the highest nitrate removal rate (57.6 ± 6.6 mg N/(h g biomass)), followed by propionate (37.5 ± 6.3 mg NO₃⁻-N/(h g biomass)), ethanol (25.5 ± 6.0 mg NO₃⁻-N/(h g biomass)) and internal carbon sources (7.7 ± 1.6–14.1 ± 2.2 mg NO₃⁻-N/(h g biomass)). No TAN (Total Ammonia Nitrogen) or PO₄^3- accumulation was observed in the effluent when using the external carbon sources, while 0.9 ± 0.5 mg TAN/L and 3.9 ± 1.5 mg PO₄^3--P/L was found in the effluent when using the FOW, and 8.1±0.7 mg TAN/L and 7.3 ± 0.9 mg PO₄^3--P/L when using FFOW. Average sulfide concentrations varied between 0.002 and 0.008 mg S^2-/L when using the acetate, propionate and FOW, while using ethanol resulted in the accumulation of sulfide (0.26 ± 0.17 mg S^2-/L). Altogether, it was demonstrated that FBR has a great potential for end-of-pipe denitrification in marine land-based RAS, with a reliable operation and a reduced reactor volume as compared to the other available technologies. Using acetate, the required reactor volume is less than half of what is needed for other evaluated carbon sources, due to the higher denitrification rate achieved. Additionally, combined use of both internal and external carbon sources would further reduce the operational carbon cost.     

Production, release and olfactory detection of sex steroids by the tench (Tinca tinca L.)

The present study is concerned with pheromone communication in tench (Tinca tinca L.), establishing firstly whether males have a high olfactory sensitivity to some typical teleost sex steroids and prostaglandins; and secondly whether males and females might be able to synthesise and release some of these steroids into the water. The C₂₁ steroid, 17,20β-dihydroxy-4-pregnen-3-one (17,20β-P) was found to give large electro-olfactogram responses with an estimated threshold of detection of 10⁻¹² M. The male tench were equally sensitive to glucuronidated 17,20β-P (10^−11.6 M) but 100 times less sensitive to sulphated 17,20β-P (11^−9.7 M). Preliminary data from cross-adaptation studies suggest that both the free and conjugated forms are detected by the same olfactory receptor(s). Male tench also had high olfactory sensitivity to prostaglandin F_2α (PGF_2α) and 15-keto PGF_2α (11^−11.5 and 10^−11.4 M). They were relatively insensitive, however, to testosterone (T), androstenedione (AD), 11-ketotestosterone (11-KT), 17β-oestradiol (E₂), 17,20β,21-trihydroxy-4-pregnen-3-one (17,20β,21-P) and 17,20α-dihydroxy-4-pregnen-3-one (17,20α-P). Radioimmunoassays were used to measure the steroids in plasma and water and all samples were processed for the measurement of free, sulphated and glucuronidated fractions. In females, free 17,20β-P, 17,20α-P, free and glucuronidated T, and AD in plasma showed the largest increases in response to injection with mammalian gonadotropin-releasing hormone analogue (GnRHa) or Ovaprim (a mixture of GnRHa and a dopamine inhibitor). Free 17,20β-P was released into the water at the greatest rate. Plasma concentrations of the two conjugated forms of 17,20β-P were also elevated 18 h after the administration of GnRHa, but not by as much as the free steroid. In males, AD and 11-KT showed the greatest increase in response to GnRHa and were moreover released into the water at a higher rate in the treated group than in the control. The data support a possible pheromonal role for free and glucuronidated 17,20β-P. This revised version was published online in July 2006 with corrections to the Cover Date.