不同组织碳、氮元素含量和同位素分馏特征研究—以抚仙湖草鱼、鱇浪白鱼为例

结合抚仙湖浮游植物、水生植物等样品,对野生植食性草鱼(Ctenopharyngodon idellus)31个组织和野生肉食性鱇浪白鱼(Anabarilius grahami)17个组织样品碳、氮元素含量和稳定同位素比值(δ13C、δ15N)进行了对比分析.结果显示,鱼类不同组织的碳稳定同位素分馏效应显著,草鱼不同组织...

Carbon and nitrogen contents and isotopic fractionation in different tissues of Ctenopharyngodon idellus and Anabarilius grahami in Fuxian Lake

Stable isotope signal and element composition of carbon and nitrogen in lake organisms have been widely applied to identify food sources and trophic structure of lake food webs. This study was conducted to evaluate ecological processes of elemental assimilation and stable isotope fractionation among different tissues by determining carbon and nitrogen contents and stable isotopes of 31 tissues of Ctenopharyngodon idellus and 17 tissues of Anabarilius grahami collected from Fuxian Lake. The results show that there are significant carbon isotopic fractionations among tissues, ranging from -20.66‰ to -11.62‰ for Ctenopharyngodon idellus and from -27.55‰ to -19.71‰ for Anabarilius grahami. Meanwhile, the nitrogen isotope fractionations are relatively moderate for both kinds of fish, with a maximum range of 1.88‰ and 4.60‰, respectively. The δ¹³C values show a significantly negative correlation with carbon contents of tissues. A 10% increase in carbon content results in a depletion of δ¹³C value by -1.83‰ for Ctenopharyngodon idellus and -1.35‰ for Anabarilius grahami, indicating that the absorption and synthesis of carbon in tissues are accompanied by significant isotopic fractionation. However, the δ¹⁵N values of different tissues may be affected by essential amino acids but not associated with nitrogen content; because a high content of essential amino acids in tissues often leads to a depletion of ¹⁵N. The isotopic fractionation coefficients between the dorsal muscle of Ctenopharyngodon idellus and intestinal content (Vallisneria natans) are 0.40‰ for carbon isotope and 2.66‰ for nitrogen isotope, suggesting carbon and nitrogen isotopic compositions of dorsal muscle are a reliable indicator of food source and trophic level. For fish without obvious dietary change over life time, the δ¹³C value of mucus and the δ¹⁵N value of scales (after correction) can be used as alternative indices for dorsal muscles. Obviously, the carbon and nitrogen contents and isotope fractionations of fish tissues can be used to identify the trophic structure and the pathway of trophic flow in lakes of southwest China. The alternative sampling of non-lethal tissues such as mucus and scales can be of great potential for effectively conservation of endangered fish.