基于稳定同位素方法的珊瑚礁鱼类营养层次研究

以珊瑚礁生态系统中的鱼类作为研究对象,对2006年9月至2007年8月期间在徐闻珊瑚礁海区采集到的鱼类样本分类鉴定后,运用稳定碳氮同位素方法进行鱼类营养层次的分析。结果表明,δ13C值和δ15N值的跨度都很大,δ13C值的范围为–20.98‰～–9.05‰,相差11.93‰;δ15N值的范围为11.66‰～18.15‰,差值达6.49‰。与其他海区相比,δ13C值和δ15N值显得更为富集。由δ15N值计算出来的营养层次表明,徐闻珊瑚礁鱼类分布在两端(杂食性鱼类与高级肉食性鱼类)的只占少数,绝大多数居于中间的层次(低级肉食性鱼类与中级肉食性鱼类)。在134种鱼类中,种类数最多的是以条尾鲱鲤、少鳞代表的低级肉食性鱼类,有70种,占鱼类总数的52%;其次是以细鳞鯻、龙头鱼为代表的中级肉食性鱼类,有47种,占鱼类总数的35%;鰶以斑、前鳞骨鲻为代表的杂食性鱼类和以宽尾斜齿鲨、杂食豆齿鳗为代表的高级肉食性鱼类各有11种、6种,分别占鱼类总种类数的8%和5%。在此基础上选取54种鱼类进行稳定同位素方法与胃含物法分析结果对比,发现约85%的鱼种采用两种方法测定的结果在0.5个营养级的误差范围内一致,只有少数鱼种的差值大于0.5个营养级。由此可见稳定同位素分析法与传统的胃含物分析法所得的结果有很好的一致性,稳定同位素分析法是一种研究海洋食物网营养层次的有效方法。

Measurement of the trophic level of fish in a coral reef ecosystem using stable isotopes

We evaluated the trophic ecology of fish on the Xuwen Coral reef.We collected samples of representa-tive species and quantified levels of δ13C and δ15N.There was significant variation in the δ13C and δ15N values.δ13C ranged from –20.98‰ to –9.05‰ and δ15N ranged from 11.66‰ to18.15‰.The levels of δ13C and δ15N were generally higher than in fish from other regions.We estimated the trophic level based on the δ15N values.The ma-jority of fish species in the Xuwen Coral Reef were lower and mid-level carnivores.The remainder were omni-vores and higher carnivores.Among all fish species,more than half were lower carnivores(70 species,52% of the total species).The mid-level carnivores(47 species) accounted for 35% of the total species.The omnivores(11 species) and higher carnivores(8 species) accounted for 8 and 5%,respectively,of the total species count.We compared these results to those of gut-contents analysis for 54 species.For the majority of species(85%),the tro-phic level estimated by the two methods differed by less than 0.5 units.Thus,stable isotope analysis provides a rapid,reliable method for documenting ocean food webs.