海洋酸化对水生动物骨骼和耳石钙化、生长发育的影响与机理

正自18世纪以来,大气中的pCO2增加了大约36%,大气中1/3以上的CO2为海水吸收,形成了大量的碳酸氢根(HCO-3)离子,使海洋表面的pH下降,形成不断加剧的海洋酸化现象[1],若不能有效控制CO2排放,到21世纪末,海洋表面的pH将下降0.3~0.4个单位,使表层海水pH达到80万年以来的最低值[2],影响海洋的生态环境和海洋生     

海洋生物对海洋环境限制因子变化的响应

海洋是地球生态系统的重要组成,是海洋生物赖以生存的繁殖地和栖息地,温度、pH以及盐度是海洋生态系统的重要环境限制因子。工业革命以来,由于二氧化碳(CO2)过量排放引起的全球性气温升高,直接导致了海水温度和表层CO2分压(pCO2)的急剧升高,改变了海水pH以及盐度的动态平衡,不同程度地影响了全球海洋生态系统原有的稳定性和生物多样性,对近岸海洋渔业发展以及海洋生态资源的可持续利用也产生诸多不利影响。本文从全球变暖引起的海水温度、海水pH以及海水盐度变化三个方面,综述了海洋生物在生长、发育、繁殖以及种群迁徙等方面对海洋环境限制因子变化的响应。     

中国海洋酸化及生态效应的研究进展

正[海洋吸收大气CO2会导致海洋酸化1-5],影响海洋生物的生长、繁殖和代谢等过程,最终影响海洋生态系统平衡及其对人类的服务功能[6]。此外,由上升流或富营养化导致的近海酸化进程要远快于大洋,对生物会造成更大的环境胁迫[7]。因此,海洋酸化已成为继全球变化和环境污染后严重影响和威胁人类社会发展的第三大环境问题[8]。由于缺乏海洋酸化及其生态效应的观测研究,目前尚     

海洋酸化对水生动物免疫系统的影响及机理

正自工业革命以来,人类活动和工农业发展使大气中的CO_2水平以前所未有的速度上升~[1-2],海洋吸收CO_2量不断增加,海水pH值下降,这种由大气CO_2体积分数升高导致海水酸度增加的过程称为海洋酸化[3]。与工业革命前相比,目前海洋的pH值已经下降了0.1,预测到本世纪末将再下降0.3至0.4~[4-6]。与此同时,大气中CO_2含量上升导致全球气候变暖,水温升高。因此,由于CO_2升高     

渔业科技前沿

全球海洋酸化正在加剧西班牙国家研究委员会(CSIC)、加泰罗尼亚高等研究院(ICREA)及巴塞罗那自治大学的研究人员警告说,人类排放的二氧化碳已经严重改变了海水的化学结构,海洋正以前所未有的速度酸化。其相关研究成果发表在《科学》杂志上。研究表明,海洋酸化正影响着海洋生物和生态系统。在过去的300万年中,海洋化学环境发生了较大变化,但目前海洋水质的酸化速度要比过去的任何一个时间点都要快,这或将为整个海洋生态系统带来毁灭性的灾难。人类活动排放的二氧化碳有30%进入了海洋,这直接导致了海洋的酸化。海洋酸化威胁到了一些海洋生物种类的生存。比如,海洋酸化降低了珊瑚、软体动物等生     

海水酸化对青蛤耗氧率和排氨率的影响

在水温(29.5±0.5)℃、盐度25条件下,用3个独立循环水槽系统同时充入空气和纯CO2气体,利用气体质量流量计控制CO2的流量使海水pH为7.7±0.05和7.4±0.05,以pH 8.3的天然海水为对照,研究海水酸化对青蛤耗氧率、排氨率及O∶N的影响。试验结果表明,随着海水酸化的加强,青蛤累计死亡数上升,呈正相关性,死亡率依次为pH 7.4pH 7.7pH 8.3;耗氧率随pH的升高而降低,而较低的pH对青蛤排氨率有促进作用;O∶N值随pH的降低而降低,一定范围内的海水酸化会对青蛤的存活及代谢有影响,但这些影响对青蛤的生存和代谢并不致命,青蛤会随着海水酸化时间来调节自身代谢以适应海洋酸化,本结果为青蛤对海洋酸化适应提供了基础理论。     

海洋酸化呈现多米诺效应

澳大利亚海洋科学研究所（AIMS）的工作人员目前正在研究浅海火山排放的二氧化碳溶入巴布亚新几内亚米尔恩海湾东部水域所造成的影响，探讨海洋酸化（OA）如何影响海洋环境。 该研究所科学家Katharina Fabricius博士表示，这些实验和实地考察对研究越来越多的二氧化碳与海水混合时自然界的最初表现是必不可少的。大气中的二氧化碳溶入水中造成海洋酸化，海水中pH值偏低，形成碳酸氢盐。这将反过来使大面积的海洋动物更难形成外壳和身体骨骼。     

论海洋环境保护的国际合作

联合国教科文组织曾经发出过警告，全球海水正在变酸。美国《科学》杂志发表文章指出，过去200年问排放到大气中的二氧化碳，有近一半已经溶解到海水中，致使海洋生态系统遭到破坏，影响了海洋生物的生长。从近10年科学家对海水监测研究结果看，海水中二氧化碳的含量上升较快，如果照此速度继续增加50年，酸化的海水会使许多海洋生物无法生存，进而破坏海洋食物链，从而以人们现在尚无法预测的方法改变海洋。     

海洋酸化将促使生态系统毁灭

美国加州大学戴维斯分校公布的一项研究结果显示，海洋酸化将对海洋生态系统造成毁灭性的影响。该研究成果发表在最新一期的《美国国家科学院院刊》上。     

两种海水酸化模式对中间球海胆早期发育及存活的影响

采用二氧化碳法和强酸法模拟海水酸化效应,研究两种海水酸化模式对中间球海胆早期发育及存活的影响。试验结果显示,两种海水酸化模式均能降低中间球海胆胚胎的上浮率和四腕浮游幼体的存活率;显微观察得知,两种海水酸化模式下,中间球海胆四腕浮游幼体均出现对称性缺失和骨针外露现象,且对称性缺失程度随海水pH的降低而升高;扫描电镜观察发现,两种海水酸化模式下,中间球海胆四腕浮游幼体骨针的表面及横截面均有溶蚀痕迹,且溶蚀程度随海水pH的降低而加剧。结果提示,海水酸化可通过降低胚胎上浮率、浮游幼体存活率以及破坏幼体对称性和骨针结构影响中间球海胆的早期发育及存活。     

Association between the interannual variation in the oceanic environment and catch rates of bigeye tuna (Thunnus obesus) in the Atlantic Ocean

The environmental processes associated with variability in the catch rates of bigeye tuna in the Atlantic Ocean are largely unexplored. This study used generalized additive models (GAMs) fitted to Taiwanese longline fishery data from 1990 to 2009 and investigated the association between environmental variables and catch rates to identify the processes influencing bigeye tuna distribution in the Atlantic Ocean. The present findings reveal that the year (temporal factor), latitude and longitude (spatial factors), and major regular longline target species of albacore catches are significant for the standardization of bigeye tuna catch rates in the Atlantic Ocean. The standardized catch rates and distribution of bigeye tuna were found to be related to environmental and climatic variation. The model selection processes showed that the selected GAMs explained 70% of the cumulative deviance in the entire Atlantic Ocean. Regarding environmental factors, the depth of the 20 degree isotherm (D20) substantially contributed to the explained deviance; other important factors were sea surface temperature (SST) and sea surface height deviation (SSHD). The potential fishing grounds were observed with SSTs of 22–28°C, a D20 shallower than 150 m and negative SSHDs in the Atlantic Ocean. The higher predicted catch rates were increased in the positive northern tropical Atlantic and negative North Atlantic Oscillation events with a higher SST and shallow D20, suggesting that climatic oscillations affect the population abundance and distribution of bigeye tuna.     

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.     

Growth performance,digestive enzyme activity and immune response of Japanese sea bass,Lateolabrax japonicus fed with fructooligosaccharide

In this experiment, a feeding trial was performed to determine the effects of fructooligosaccharide (FOS) on growth performance, digestive enzyme activity and immune response of Japanese sea bass, Lateolabrax japonicus juveniles (initial weight 38.3 ± 0.5 g), and the fish were examined following feeding with six levels of FOS (0, 0.5, 1, 2, 4 and 6 g/kg) for 28 days. Significant enhancement of weight gain (WG) and specific growth rate (SGR) was found in fish fed 1 g/kg FOS incorporated diets (p < .05), while the feed conversion ratio (FCR) in the 1, 2 g/kg FOS groups reduced significantly compared with the control (p < .05). Besides, the crude lipid in the 4, 6 g/kg FOS groups increased significantly compared with the control (p < .05). On the other hand, the erepsin and lipase activities significantly elevated in intestine of fish fed 2 g/kg FOS (p < .05) and the lysozyme activity in serum of fish fed 2 g/kg FOS were significantly higher than that in the control (p < .05). Moreover, the alkaline phosphatase activities in serum of fish fed 0.5, 1, 2 g/kg FOS were significantly higher than in control (p < .05). Regression analysis showed that the relationships between dietary FOS levels and either SGR, FCR, erepsin or lysozyme activities were best expressed by regression equations, and the optimal inclusion levels are 1.37, 1.80, 3.06, 3.11, 1.93 and 1.80 g/kg for SGR, FCR, erepsin, lipase, lysozyme and total superoxide dismutase activities, respectively. Overall, this study revealed that FOS incorporated diets could beneficial for L. japonicus culture in terms of increasing the growth, digestion and immune activities. Under the present experimental condition, the optimal supplementary level of FOS in the diet of L. japonicus is 1–3 g/kg.     

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.     

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.     

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.     

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.     

Involvement of gonadal steroids in final oocyte maturation of white perch (Morone americana) and white bass (M. chrysops): in vivo and in vitro studies

Plasma estradiol-17 (E₂), testosterone (T), 17,20-dihydroxy-4-pregnen-3-one (DHP) and 17,20,21-tri-hydroxy-4-pregnen-3-one (20-S) levels were measured by radioimmunoassay (RIA) in white perch (Morone americana) and white bass (M. chrysops) that were induced to undergo final oocyte maturation (FOM) with human chorionic gonadotropin (hCG). Plasma DHP levels increased in females of both species in association with oocyte germinal vesicle migration (GVM) and germinal vesicle breakdown (GVBD) and decreased thereafter. Plasma 20-S levels also increased with oocyte GVM in white bass, but were several-fold lower than DHP levels. Circulating E₂ and T levels were greatest during GVM and GVBD in both species and decreased to low levels during oocyte hydration and ovulation. Follicles from white perch and white bass which received a priming injection of hCG in vivo, produced both DHP and 20-S in vitro after exposure to hCG and their oocytes underwent GVBD. Ovarian incubates from unprimed fish of either species produced only E₂ and T and their oocytes did not complete GVBD. Oocytes from unprimed bass, but not perch, matured when follicles were exposed to hCG in vitro. Both trilostane and cycloheximide blocked in vitro production of DHP and 20-S and oocyte GVBD by white perch follices. DHP and 20-S were equipotent inducers of FOM in the GVBD bioassay. None of several other structurally-related steroids tested were effective within a physiological range of concentrations. These results indicate a role for DHP and 20-S in the control of FOM in white perch and white bass.