基于碳氮稳定同位素技术探究太湖北部湖区鲢、鳙食性差异

为探究太湖北部湖区4个不同水域鲢Hypophthalmichthys molitrix、鳙Aristichthys nobilis食性的差异,运用碳氮稳定同位素技术对太湖竺山湖、月亮湾、三国城和乌龟山水域的鲢、鳙、悬浮颗粒有机物(SPM)和水华蓝藻的δ13C和δ15N值进行了分析研究。结果表明:各个湖区SPM与水华蓝藻的δ13C差值为0.1‰~1.5‰,δ15N差值为0.3‰~1.6‰,单因素方差分析表明,SPM与水华蓝藻的δ13C和δ15N值均无显著性差异(P0.05),说明SPM主要组分是水华蓝藻;水华蓝藻的δ15N值为12.8‰~15.8‰,均高于污染较小水域浮游植物的δ15N值(2‰~8‰),说明这4个水域氮源污染仍比较严重;鲢、鳙的食性在4个水域内有一定的差异,除乌龟山水域鲢、鳙营养级有显著性差异(P0.05)外,其他水域鲢、鳙的营养级均无显著性差异(P0.05)。研究表明,竺山湖、月亮湾、三国城3个水域鲢、鳙在水华蓝藻爆发高峰期食物组成相似,摄食以水华蓝藻为主;月亮湾水域鲢、鳙的营养级均高于其他3个水域,可能是由于该水域的鲢、鳙在摄食蓝藻的同时,也摄食了少量的浮游动物,但对于其具体食物组成仍需要进一步研究。本研究结果能帮助揭示太湖北部不同水域鲢、鳙的主要食物来源为悬浮颗粒有机物,并分析悬浮颗粒有机物的主要来源为水华蓝藻,进而能够为利用鲢、鳙控藻和水资源的可持续利用提供一定的理论依据。

Feeding differences of silver carp and bighead carp in the northern part of Taihu Lake: based on stable carbon and nitrogen isotope analysis

The dynamics ofδ13 C andδ15 N were determined in water, suspended particulate organic matter ( SPM) , Cyanobacteria bloom and dorsal muscles of silver carp Hypophthalmichthys molitrix and bighead carp Aristichthys no-bilis sampled from Zhushan Lake, Yueliang Bay, Sanguo City and Wugui Mountain in the northern part of Taihu Lake via stable carbon and nitrogen isotope analysis technique in order to investigate feeding differences of silver carp and bighead carp in the northern part of Taihu Lake. The one-way ANOVA revealed that there were no signifi-cant difference inδ13C and δ15N values of SPM and Cyanobacteria(P>0. 05), with range from 0. 1‰ to 1. 5‰ inδ13 C and range from 0. 3‰ to 1. 6‰ inδ15 N in SPM and Cyanobacteria,indicating that SPM was the main compo-nent in Cyanobacteria bloom. The high δ15 N values ( ranged from 12. 8‰ to 15. 8‰) of Cyanobacteria, higher than that of phytoplankton in less polluted waters ( about 2‰-8‰) , showed that nitrogen pollution was serious in all sampling sites. There was to some extent differences in feeding habit between silver carp and bighead carp in the four sampling sites in Taihu Lake, with significant difference in trophic levels between silver carp and bighead carp in Wugui Mountain (P<0. 05) and without significant differences in other three sampling sites(P>0. 05), indica-ting that the similar food composition ( primarily of Cyanobacteria) in silver carp and bighead carp during the Cya-nobacteria bloom. The silver carp and bighead carp had higher trophic levels in Yueliang Bay than those in other three waters did, which probably reveals that the two species ingest small amount of zooplankton besides Cyanobac-teria, as well in Yueliang Bay. But further research is required to explain the food composition specifically. The findings showed that SPM was the main food sources of silver carp and bighead carp in the northern part of Taihu Lake. However, Cyanobacteria was the main component of SPM, and provide a new basis for algal control and sus-tainable utilization of algae in waters by silver carp and bighead carp.