沙蚕(Nereis diversicolor)暴露于镉、铜和石油烃单一与复合污染的生态毒理化学研究

沙蚕（Nereis diversicolor）是一种栖息于水陆交错带沉积物中、具有重要生态学意义的底栖无脊椎动物。本项研究以水陆交错带典型重金属污染物（Cd、Cu）和石油烃为代表，就其单一与复合污染对沙蚕的生态毒理效应进行研究，从污染生态化学的角度对其毒性机理进行探讨，并找出可用于对潮间带地区重金属和石油烃污染进行生态毒理评价的敏感生物标记物（biomarker），为水生生态系统的水质监测、污染诊断以及环境管理工作提供理论支持。 研究表明，在急性毒性污染暴露过程中，各污染物均可对沙蚕种群产生毒性效应，其毒性大小依次为： Cu＞Cd＞石油烃；复合污染对沙蚕的联合毒性效应机制十分复杂，可用联合效应广义理论加以解释。 随着时间的延长，Cd、石油烃单一污染暴露导致SOD活性先上升后下降，POD活性未表现出一致的变化趋势，而可溶性蛋白含量下降；Cu单一污染使SOD活性与可溶性蛋白含量先被诱导后抑制，POD活性先是显著下降，而后缓慢上升；Cd、Cu与石油烃的复合污染效应对沙蚕体内SOD、POD活性以及可溶性蛋白含量的影响与其不同浓度组合以及染毒时间有关；初步认为SOD活性可作为敏感的生物标记物来反映水陆交错带地区重金属和石油烃污染状况。 在实验浓度范围内，低浓度石油烃（100μl L-1）与高浓度Cu复合污染会在一定程度上促进Cu在沙蚕体内的蓄积量，而Cd与石油烃复合污染并未诱导Cd在沙蚕体内积累量的增加。研究还发现，沙蚕体型大小对Cu和石油烃在沙蚕体内的积累量没有影响，重要的是沙蚕体内Cd、Cu与石油烃的含量基本能够反映出其生境中重金属与石油烃的污染状况，但在实践应用中需要考虑采样时间、海水温度以及盐度等因素的影响。

沙蚕(Nereis diversicolor )耐铜、镉和石油烃污染的分子生态毒理学研究

沙蚕作为海陆交错带的关键性物种，常被作为环境污染的指示生物。沙蚕生态毒理学已成为生态毒理学研究中又一大有发展前途的研究方向，而有关其耐受高污染胁迫机理的研究则会促进其在生物修复等应用技术领域的发展。针对目前国内外对耐受性机理研究较少的这一现状，并根据我国近岸海域污染的客观事实，本研究确立了以重金属Cu/Cd和有机物石油烃为主要污染物的沙蚕耐污染毒理效应研究，从分子生态毒理学角度对其耐受机制进行探讨。 本研究所采用的三种单一污染物对沙蚕均具有潜在的生理毒性，根据半致死剂量的高低确定毒性强弱顺序依次为：石油烃>Cu>Cd。乙酰胆碱酯酶对石油烃毒性效应的灵敏性明显强于重金属，可溶性蛋白对三种污染物毒害响应的敏感性则较差。两种不同类型的重金属均可以诱导MT的合成，污染物与解毒系统之间存在时间－效应和剂量－效应关系，但当达到一定浓度时MT基本达到饱和，并维持某一稳定水平。沙蚕对重金属和石油烃均表现出显著的生物富集现象。 重金属Cu/Cd和石油烃的联合作用对沙蚕的毒性效应与污染物浓度组合有关，在高浓度石油烃组合中，两种污染物表现出拮抗作用，重金属对于石油烃所引起的神经毒性有钝化作用，而以可溶性蛋白含量作为单一指示则表现出一定的局限性。石油烃不能显著诱导沙蚕MT的合成，但与重金属Cu/Cd联合作用时能够显著影响MT含量。沙蚕对不同污染物的生物富集受两者浓度组合关系的影响。 根据以上结果推测沙蚕耐受重金属的机制可能与MT的解毒功能有关，因此通过分子生物学手段获得了沙蚕金属硫蛋白基因的部分cDNA序列，该序列长度为287bp，编码65个氨基酸，富含Cys达24.2%。但有关其全序列基因的研究还有待进一步深入。

The polychaete worm Nereis diversicolor increases mercury lability and methylation in intertidal mudflats

The polychaete worm Nereis diversicolor engineers its environment by creating oxygenated burrows in anoxic intertidal sediments. The authors carried out a laboratory microcosm experiment to test the impact of polychaete burrowing and feeding activity on the lability and methylation of mercury in sediments from the Bay of Fundy, Canada. The concentration of labile inorganic mercury and methylmercury in burrow walls was elevated compared to worm-free sediments. Mucus secretions and organic detritus in worm burrows increased labile mercury concentrations. Worms decreased sulfide concentrations, which increased Hg bioavailability to sulfate-reducing bacteria and increased methylmercury concentrations in burrow linings. Because the walls of polychaete burrows have a greater interaction with organisms, and the overlying water, the concentrations of mercury and methylmercury they contain is more toxicologically relevant to the base of a coastal food web than bulk samples. The authors recommend that researchers examining Hg in marine environments account for sediment dwelling invertebrate activity to more fully assess mercury bioavailability.

The use of biological indicators of heavy metal contamination in estuaries. Occasional Publication of the Marine Biological Association 1

The use of the deposit-feeding molluscs Scrobicularia plana and Macoma balthica and the burrowing polychaete Nereis diversicolor as indicators of the biological availability of heavy metals in sediments has been evaluated. Concentrations of Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Sn and Zn have been measured in organisms and sediments from more than 30 estuaries in south west England and South Wales and indicate that the biological availability of most metals varies by order of magnitude between uncontaminated and contaminated sites. The results have been compared with those obtained with the use of other species of indicator organisms in estuaries.

Polychaete burrows harbour distinct microbial communities in oil-contaminated coastal sediments

Previous studies have shown that the bioturbating polychaete Hediste (Nereis) diversicolor can affect the composition of bacterial communities in oil-contaminated sediments, but have not considered diversity specifically within bioturbator burrows or the impact on microbial eukaryotes. We tested the hypothesis that H. diversicolor burrows harbour different eukaryotic and bacterial communities compared with un-bioturbated sediment, and that bioturbation stimulates oil degradation. Oil-contaminated sediment was incubated with or without H. diversicolor for 30 days, after which sediment un-affected by H. diversicolor and burrow DNA/RNA samples were analysed using quantitative reverse transcription PCR (Q-RT-PCR) and high-throughput sequencing. Fungi dominated both burrow and un-bioturbated sediment sequence libraries; however, there was significant enrichment of bacterivorous protists and nematodes in the burrows. There were also significant differences between the bacterial communities in burrows compared with un-bioturbated sediment. Increased activity and relative abundance of aerobic hydrocarbon-degrading bacteria in the burrows coincided with the significant reduction in hydrocarbon concentration in the bioturbated sediment. This study represents the first detailed assessment of the effect of bioturbation on total microbial communities in oil-contaminated sediments. In addition, it further shows that bioturbation is a significant factor in determining microbial diversity within polluted sediments and plays an important role in stimulating bioremediation.