三峡水库小江回水区叶绿素a与环境因子时空变化

于2013年1-12月在小江水华暴发的敏感区域高阳断面开展了水文、营养盐、叶绿素a等指标长期、定点监测,分析库湾水体叶绿素a及环境因子的时空变化特征及其相互关系。结果表明高阳断面水体在1月、10-12月处于混合状态,3-8月则处于弱分层到稳定分层状态。水体在混合状态时各理化因子、营养盐及叶绿素a分层变化不显著；而处于分层状态时,各层水体氮磷营养盐呈现较显著差异,时间分布上冬季略高于夏季,干流倒灌对高阳断面营养盐的季节分布影响显著。叶绿素a浓度呈现明显的夏季高、冬季低的趋势,水体分层对叶绿素a垂向分布影响显著,当水体处于分层状态时,表层叶绿素浓度明显高于中、底层。高阳断面各层水体叶绿素a浓度与硝氮和可溶性磷酸盐呈显著负相关,表明营养盐是小江高阳叶绿素变化的限制因素。表层水体叶绿素a与硝氮、磷酸盐、溶解氧、透明度、水温、表底温差等呈显著相关(P<0.01),表明表层叶绿素a与环境因子相关性较强；中层叶绿素a与硝氮、总氮、总磷、磷酸盐、水温、透明度、水深、水体稳定系数等呈显著相关(P<0.01),表明水体的扰动是影响中层水体叶绿素a增长的关键因素之一；底层水体叶绿素a与硝氮(P<0.01)、磷酸盐(P<0.05)、水深(P<0.05)呈显著相关。     

三峡库区神农溪不同时期溶解氧与叶绿素a垂向分布特征

为探究三峡库区支流垂向水环境的分布特征及其影响因素,采用2018年2月（高水位期）和7月（汛期）对三峡水库典型一级支流——神农溪回水区水质监测数据,分析和对比了神农溪不同季节的溶解氧和叶绿素a等指标垂向分布特征,讨论了影响其垂向分布的环境因子。结果表明,神农溪高水位期与汛期的溶解氧含量在0~12 m和0~6 m水体分层现象明显,其表层水体的溶解氧饱和度(SDO)分别为104.04%和171.96%,已经达到过度饱和状态（SDO>100%）;中层水体溶解氧浓度存在分层现象,底层水体溶解氧浓度较稳定,无分层现象。高水位期与汛期的叶绿素a含量在0~10 m水体分层现象明显,表层水体的叶绿素a浓度整体上表现为中度富营养化（5 μg/L相似文献   

汛末蓄水期神农溪库湾倒灌异重流特性及其对水华的影响

为研究三峡水库神农溪库湾倒灌异重流特性、光混比特性及其对水华的影响,根据神农溪库湾的地理特性及库湾区域性水华特性,从神农溪河口至回水末端,沿渡河镇河道中泓线设置7个监测点位(SN01~SN06),于2014年汛末蓄水期对神农溪库湾的水温等指标进行跟踪监测分析。结果表明,三峡水库蓄水过程通过倒灌异重流作用,最大单日水位变幅为1.04 m,干流水体分别从表层、中上层和底层倒灌潜入库湾;倒灌异重流增强了干支流间水体交换,缩小了干支流间水温差,打破支流水温分层,使支流混合层深度逐步增大。库湾叶绿素a浓度呈现时空差异性,整个蓄水周期内,SN02受干流水体影响明显,叶绿素a浓度始终维持在低水平,均小于20 mg/m~3,蓄水过程中,SN05和SN06断面混合层深度由6.0 m上升至22.5 m,叶绿素a浓度由高于30 mg/m~3降低至10.30 mg/m~3,导致神农溪库湾叶绿素a浓度降低的主要原因是蓄水过程加强了干支流水体交换程度,减小光混比至0.2,库湾叶绿素a浓度均值降低为11.00 mg/m~3,水华情势最终得到有效控制。     

三峡水库小江回水区叶绿素a与环境因子的时空变化

2013年1-12月在小江水华暴发的敏感区域高阳断面开展了水文、营养盐、叶绿素a等指标长期、定点监测,分析库湾水体叶绿素a及环境因子的时空变化特征及其相互关系。结果表明,高阳断面水体在1月、10-12月处于混合状态,3-8月则处于弱分层到稳定分层状态。水体处于混合状态时,各层营养盐浓度变化不显著,处于分层状态时,则呈现较显著差异;时间分布上,冬季氮磷营养盐浓度(TN:1.52~1.74 mg/L,TP:0.092~0.095 mg/L)略高于夏季(TN:1.16~1.56 mg/L,TP:0.037~0.085 mg/L),干流水体倒灌作用对其影响显著。叶绿素a浓度呈现夏季高、冬季低的趋势,水体分层对叶绿素a垂向分布影响显著;当水体处于分层状态时,表层叶绿素a浓度(18.56~92.23 mg/m~3)明显高于中、底层(2.54~21.56 mg/m~3)。营养盐为小江高阳叶绿素a变化的限制因素,各层水体叶绿素a浓度与硝氮和可溶性磷酸盐呈显著负相关。表层水体叶绿素a与环境因子相关性较强,叶绿素a与营养盐、溶解氧、透明度、水温、表底温差等呈极显著相关(P0.01);中层叶绿素a与营养盐、水温、透明度、水深、水体稳定系数等呈极显著相关(P0.01),表明水体扰动是影响中层水体叶绿素a增长的关键因素之一;底层水体叶绿素a与硝氮(P0.01)、磷酸盐(P0.05)、水深(P0.05)呈极显著或显著相关。     

桑沟湾春季营养盐分布特征及赤潮暴发诱因

根据2006年4月和2011年4月两个航次的调查数据,对比分析了桑沟湾水域春季水温、盐度及溶解无机氮(DIN)、活性磷酸盐(PO₄^3-)、活性硅酸盐(Si₃² -Si)含量的时空分布特征,探讨了目前大面积赤潮暴发的可能原因。结果显示,2011年的氮、磷、硅浓度都高于2006年同期调查结果,分别是2006年的5.6倍,1.3倍和3.2倍。氮磷比高达(66.33?47.16),硅磷比为(35.12?21.44),硅氮比为(0.82?0.77),严重偏离Redfield比值。块状分布明显,氮、磷、硅的空间分布情况相似,都是在湾口的东南部(褚岛外海)有高值区,向湾内递减;在湾底的西北部赤潮的始发区,有次高值区,与盐度的低值区几乎重叠。从营养盐、水文、大型藻类营养盐竞争与克生作用及水温4个方面,分析了赤潮暴发的可能原因。     

三峡水库香溪河库湾水温结构及其对春季水华的影响

2007年9月至2008年8月对香溪河库湾进行每月1次的水温现场监测，分析研究了香溪河库湾水温结构特征，并初步探讨了水温对春季水华的影响。结果表明，整体上香溪河库湾水体下游水温高于上游，中、上游存在明显的底层温差异重流现象；垂向水温全年以正温层为主，春、夏季出现了水温分层现象；水温年变化明显，夏季高，春秋季次之，冬季最低；分析发现，水温的迅速上升是香溪河库湾2008年春季水华暴发的重要诱导因素之一，在春季水华暴发严重的区域，表征水温结构特征的水体稳定度与表层叶绿素a浓度具有较好的正相关关系，水体稳定度对春季水华暴发的强弱程度具有较大的影响。     

洞庭湖氮磷时空分布及形态组成特征

为探究洞庭湖水体营养盐形态结构与时空分布特征,分别于2014年8月(丰水期)和2015年1月(枯水期)在入湖河流、湖体、出湖口设置16个代表性断面采集水样,分析了氮、磷营养盐的特征指标。结果表明:1洞庭湖水体中,总氮(TN)含量为1.60~3.65 mg/L,平均值2.25 mg/L,总磷(TP)含量为0.060~0.359 mg/L,平均值0.138 mg/L;颗粒态总氮(TPN)含量为0.07~1.39 mg/L,平均值0.25 mg/L,颗粒态总磷(TPP)含量为0.003~0.172 mg/L,平均值0.05 mg/L;2时空分布上,水体中氮、磷含量整体表现为丰水期高于枯水期,出湖口最高,东洞庭湖高于西、南洞庭湖,入湖河流差异大的特征,颗粒态氮磷呈现自西向东呈逐渐增加趋势,与悬浮物(SS)的空间分布一致;3形态组成上,洞庭湖水体中氮磷以溶解态为主(TDN/TN为88.0%、TDP/TP为66.7%),三峡工程2003年蓄水前后,洞庭湖磷营养盐形态组成发生了大的变化,由以颗粒态磷为主(TDP/TP 20.0%~35.6%)转变为以溶解态为主,而氮营养盐形态组成基本未变;4营养结构上,洞庭湖大多数断面TN/TP在10~22,且氮、磷浓度远高于水体富营养的限制阈值,比较适宜藻类生长。相关分析显示,洞庭湖TN、TP、TDN、TDP均与Chl-a相关性不显著,因此认为洞庭湖氮、磷营养盐对藻类生长的限制作用不明显。     

獐子岛养殖海域氮、磷的分布特征

根据2005年4个季节的调查资料，研究了獐子岛养殖海区的氮、磷营养盐的季节变化及平面分布特性，重点分析了7月营养盐、叶绿素及环境因子的相关性，探讨了与底播养殖的可能内在联系。结果表明，溶解性无机氮、活性磷酸盐的平面分布和垂直分布较均匀，仅在7月，表底层的氨氮浓度及磷酸盐浓度存在显著性差异。根据氮磷摩尔比和浮游植物生长的阈值分析，在该海区氮、磷营养盐限制呈季节性交替变化，7月磷限制的潜在性较大，3月和5月氮限制的潜在性较大。尽管目前的养殖生产活动并未对该海区的营养盐浓度产生较大的影响或压力，但是，3、5和7月底层水的无机氮以氨氮为主以及贝类养殖密度较大的区域叶绿素浓度较低的现象，可能与养殖活动有关，应引起关注．     

菲律宾蛤仔养殖池塘初级生产力的变化及其影响因子研究

为初步了解菲律宾蛤仔(Ruditapes philippinarum)养殖水体浮游植物初级生产力(PP)的变化规律及其与环境因子的相关性。于2013年8月—2014年1月,采用黑白瓶法对莆田后海垦区2个菲律宾蛤仔养殖池的初级生产力进行逐月采样调查。结果显示,PP平均值分别为(1.17±0.31)g O2/(m2·d)、(0.76±0.21)g O2/(m2·d),夏秋季节显著高于冬季(P0.05);PP与叶绿素a(Chl-a)的变化并不同步,呈先下降后上升趋势;PP与温度、总氮呈极显著正相关(P0.01),与透明度呈极显著负相关(P0.01),与溶氧、氨氮呈显著负相关(P0.05);Chl-a与水温呈显著负相关(P0.05)、与总氮呈极显著负相关(P0.01),与溶氧呈极显著正相关(P0.01),与氨氮、亚硝酸盐呈显著正相关(P0.05)。建立了多个水质因子与Chl-a、PP的相关线性方程,并结合典型相关分析结果。研究表明,透明度、溶氧、营养盐是浮游植物PP的主要影响因子。     

南太湖入湖口叶绿素ａ时空变化及其与环境因子的关系

根据2010年1-12月专项监测数据,分析南太湖入湖口水域叶绿素a含量的时空变化特征以及与水温和营养盐等主要环境因子的相关性.研究表明,叶绿素a含量随时间变化明显,夏季最高,秋冬季次之,春季最低;在空间分布上,太湖西南入湖口水域的叶绿素a含量明显高于太湖南部入湖口水域.叶绿素a含量全年平均值为(15.71 ±11.24) μg/L,变化范围在1.50～74.3μg/L.叶绿素a含量与水温、pH、高锰酸盐指数(CODMn)、总磷(TP)、氨氮(NH4+-N)呈极显著正相关,与溶解氧(DO)、总氮(TN)、TN/TP呈极显著负相关.叶绿素a含量变化受多个因子共同影响,水温是叶绿素a含量变化的关键因子.氮磷比平均值为17.8,在藻类生长氮磷比的最佳范围内,易发生蓝藻水华.叶绿素a含量的对数与TP的对数呈极显著正相关,与TN和TN/TP的对数呈极显著负相关.磷是南太湖入湖口水域浮游植物生长的限制因子.     

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).