【作者】 王超；

【导师】 周名江； 于仁成；

【作者基本信息】 中国科学院研究生院（海洋研究所） ， 环境科学， 2010， 博士

【摘要】 2008年,青岛近海出现大规模浒苔绿藻,大量浒苔堆积在青岛沿海一线,对青岛近海的旅游景观和海水养殖业造成了巨大破坏。浒苔绿潮的出现正值青岛奥帆赛准备期间,绿潮的成因及其潜在的危害效应得到了国内外的普遍关注。但是,对于绿潮这一异常生态现象,国内此前缺乏相关的研究,特别是对于浒苔绿潮的生态环境效应认识不足,亟待开展深入的研究工作。本文选择了几种海洋微藻、黑褐新糠虾(Neomysis awatschensis)、以及栉孔扇贝(Chlamys farreri)、太平洋牡蛎(Crassostrea gigas)、皱纹盘鲍(Haliotis discus hannai)和刺参(Apostichopus japonicus)等海洋生物,研究了浒苔绿潮对不同类群海洋生物的毒性效应及致毒机制,为深入探讨浒苔绿潮对海洋生态系统的潜在影响提供科技支撑。通过鲜活浒苔对微藻生长的影响研究发现,浒苔培养液对塔玛亚历山大藻(Alexandrium tamarense)、东海原甲藻(Prorocentrum donghaiense)、赤潮异弯藻(Heterosigma akashiwo)、中肋骨条藻(Skeletonema costatum)和小球藻(Chlorella vulgaris)等五种微藻有不同程度的化感抑制作用,对赤潮异弯藻的抑制作用最强,小球藻次之。新鲜浒苔与微藻共培养能够显著抑制微藻的生长。研究结果表明,鲜活的浒苔能够通过化感作用和营养竞争抑制微藻的生长,抑制效应影响因藻种而异。因此,绿潮发生时有可能改变浮游植物的组成和生物量,从而影响生态系统的结构和功能。通过腐烂浒苔溢出液对微藻生长的影响实验发现,浒苔在腐烂过程中能够释放铵盐和磷酸盐,进而影响微藻的生长。低浓度的腐烂浒苔溢出液(1 g/L)对赤潮异弯藻、亚历山大藻和东海原甲藻的生长具有刺激作用,而高浓度的溢出液(10 g/L)仅对赤潮异弯藻的生长具有刺激作用,对其它微藻的生长表现出抑制作用,其机制在于溢出液中高浓度的铵氮具有一定的毒性效应,而赤潮异弯藻对铵氮的耐受性较强,因此更有利于其形成赤潮。通过本实验可以看出,浒苔绿潮消退后,大量绿潮的腐烂极有可能刺激部分赤潮藻类的生长,引发区域性赤潮,这一效应值得密切关注。通过浒苔对黑褐新康虾的毒性实验发现,腐烂浒苔的溢出液对黑褐新糠虾有急性致死作用。长期暴露于高浓度鲜活浒苔培养液中的糠虾,其存活和生殖能力也表现出下降的趋势。因此,长期持续的浒苔绿潮有可能对浮游动物类群构成威胁。通过浒苔对扇贝和牡蛎受精卵孵化的影响实验发现,鲜活浒苔培养液和腐烂浒苔溢出液都能显著抑制栉孔扇贝受精卵的发育。应用不同极性的有机溶剂提取鲜活浒苔后用于测试其对牡蛎受精卵孵化的影响,发现浒苔的甲醇和丙酮粗提物对太平洋牡蛎受精卵孵化有显著的抑制效应。对甲醇提取物用乙酸乙酯和石油醚进一步液-液萃取后,发现乙酸乙酯和石油醚提取相都有很强的抑制活性。这表明鲜活浒苔中存在能够抑制贝类受精卵孵化的物质,这类物质应具有较高的极性。通过浒苔对皱纹盘鲍和刺参等养殖动物的毒性实验发现,浒苔的培养液和腐烂溢出液对皱纹盘鲍都有急性致死作用,腐烂溢出液对刺参也有急性致死作用。大型藻浒苔腐败过程中会释放出大量铵盐,并造成水体缺氧和硫化物的产生,使养殖环境恶化,在封闭的系统中导致皱纹盘鲍和刺参死亡。综合本实验的结果可以看出:(1)浒苔绿潮发生过程中,大量绿藻有可能通过化感作用和营养盐竞争抑制浮游植物的生长,同时,长期持续的浒苔绿潮也会对浮游动物的生长和繁殖构成威胁,并抑制双壳贝类受精卵的孵化;(2)浒苔绿潮衰退后,积累的浒苔在腐烂分解过程中,会消耗大量的溶解氧,并产生硫化物、铵氮等有毒化学物质,对海洋生物的毒性效应更为显著,同时,释放的铵氮和磷酸盐等营养物质还有可能被赤潮藻类所利用,诱导有害赤潮的形成。(3)近岸养殖的生物,受到养殖区水交换能力的限制,更容易受到浒苔绿潮的危害。综上所述,绿潮的发生对近海生态系统的结构和功能及沿岸地区社会经济发展构成了潜在的威胁,但是,要阐明浒苔绿潮的危害效应,还需要针对浒苔影响海域生态系统的结构和功能开展长期调查和研究。更多还原

【Abstract】 During the bloom of green alga Ulva prolifera (the so-called“green tide”) in 2008, huge amounts of floating green algae accumulated along the coast of Qingdao. The occurrence of green tide was just at the stage of preparation for the 2008 Olympic Sailing Game in Qingdao, which caused wide attention from domestic and abroad. However, there was little knowledge about the mechanism and potential impacts of green tides in China, and it is urgent to carry out relative studies. In this paper, the effects of green alga U. prolifera on different marine organisms were studied, using 5 species of microalgae, the misid shrimp Neomysis awatschensis, scallop Chlamys farreri, oyster Crassostrea gigas, abalone Haliotis discus hannai and sea cucumber Apostichopus japonicus, and potential impacts of green tide on marine ecosystems were also discussed.It was found that algal culture medium of U. prolifera showed varying allelopathic effects on 5 species of microalgae, Alexandrium tamarense, Prorocentrum donghaiense, Heterosigma akashiwo, Skeletonema costatum and Chlorella vulgaris. The growth of H. akashiwo was significantly inhibited, followed by C. vulgaris. Co-culture of U. prolifera and microalgae could significantly inhibit the growth of the microalgae. The combined effects of allelopathy and allelospoly would inhibit the growth of microalgae. It is therefore suggested that the phytoplankton community, as well as the the primary productivity, could be affected during the period of a green tide.The decomposing green alga U. prolifera could release ammonium and phosphate into seawater, which influenced the growth of microalgae. Low concentration of decomposing algal effluent ( 1 g/L) stimulated the growth of H. akashiwo, A. tamarense, P. donghaiense. High concentration of decomposing algal effluent (10 g/L) showed stimulatory effect only to the growth of H. akashiwo, and had inhibiting effects on the growth of other 3 species of microalgae. The inhibitory effect was mainly duo to the high concentration of ammonium presented in decomposing algal effluent, and H. akashiwo had higher resistant capability to ammonium than the other species. It was proposed that the decomposation of accumulated algae could lead to the occurrence of harmful blooms formed by microalgae like H. akashiwo.The experiment on the toxicity of U. prolifera to the misid shrimp Neomysis awatschensis revealed that decomposing algal effluent had acute toxic effects on N. awatschensis. In the 62-d experiment, the misid shrimps exposed to the culture medium of live U. prolifera also showed decreased survival and reproduction. It was suggested that the survival and reproduction of zooplankton community could be affected by the green tide of U. prolifera.The culture medium and decomposing effluent of U. prolifera both significantly inhibited the egg development of the scallop Chlamys farreri. The crude extracts of U. prolifera with three different organic solvents were applied to test their inhibitory effect on the oyster eggs. It was found that the methanol and acetone extracts had strong inhibitory effects. The methanol extract of U. prolifera was further purified by liquid-liquid extraction with ethyl acetate and petroleum ether, and both extracts could significantly inhibit the hatching of oyster eggs. It was suggested that the live U. prolifera could produce polar chemicals which inhibited the fertilization of mollusca eggs.It was found that both the culture medium and decomposing effluent of U. prolifera showed acute toxic effects to abalones and sea cucumbers. The decomposing algal effluent showed a much higher acute toxicity than the algal culture medium. The ammonium and sulfide produced during the decomposation of green algae account for a major proportion of the acute toxicity of decomposing algal effluent. In the semi-enclosed culture ponds of abalones and sea cucumbers, the hypoxia condition caused by the respiration or decomposition of green algae, could further deteriorate water quality, and led to mass mortality of cultured animals.In summary, it can be concluded that: (1) during the period of green tide, the rapid proliferation of of green algae may inhibit the growth of phytoplankton through the effects of both allelopathy and allelopoly. Meanwhile, a green tide last for a long time may threat the survival and reproduction of zooplankton. (2) after the collapse of the green tide, decomposition of the accumulated green algae will consume dissolved oxygen in seawater and release sulfide and ammonium into seawater, which will lead to the toxic effects to marine organisms. In addition, the released ammonium and phosphate may be assimilated by microalgae and lead to red tides. (3) animals cultured along the coast are more vulnerable to the occurrence of green tides, Due to the low exchange rate of sea water in the culture ponds. It can be seen that the occurrence of green tides in the Yellwo Sea may have potential impacts on the structure and function of coastal and marine ecosystems. However, more intensive field investigations and researches are still needed in future to elucidate the impacts of green tide on marine ecosystems, as well as socioeconomic development.更多还原