太湖贡湖湾食物网特征研究

THE STUDIES ON THE STRUCTURES OF THE FOOD WEB AND THE TROPHIC RELATIONSHIPS IN THE GONGHU BAY OF THE TAIHU LAKE

应用稳定性同位素技术(δ^(13)C和δ^(15)N)研究了太湖贡湖湾食物网特征,结果显示由于食物来源变化多样性影响,导致贡湖的食物网结构和营养级关系变化较为复杂,贡湖主要生物类群δ^(13)C、δ^(15)N值表现出较大的种间差异。消费者δ^(13)C值从摇蚊幼虫的–32.3‰到锯齿米虾的–22.1‰,其值大小与营养级的关系没有规律性。消费者平均δ^(15)N值从褶纹冠蚌的10.3‰到位于顶端间下鳙的19.0‰,随营养级位置而升高。群落中所有种类的δ^(15)N、δ^(13)C值之间没有相关性(r=0.1835,P>0.05),表明该食物网是非线性食物网。研究结果验证了杂食性生物有机体普遍存在于富营养化的贡湖水域生态系统中,且δ^(13)C结果表明,浮游植物、固着藻类以及沉水植物为贡湖食物网中大多数生物有机体的主要碳源。贡湖食物链长度为4.44营养级。

In this study, we investigated the food web and the trophic relationships in the Gonghu Bay of the Taihu Lake by using the stable carbon and nitrogen isotopes. The present study showed that the structure of the food web and the trophic interaction were complex in the shallow lakes due to changes in the material sources, the bio-food sources and other factors. We found that omnivores were common species in the aquatic ecosystems. The complexity in the carbon sources and the bio-interactions was a limiting factor in the evaluation of the network in the aquatic ecosystems. Nevertheless, we still discovered that the major sources for the food web of the Gonghu Bay were phytoplankton, benthic algae, and macrophytes, and that the terrestrial sources of carbon only made a small contributed to the food web. We also observed some differences in the ratios of δ^15N and δ^13C among the major organisms in the Gonghu Bay. The δ^13C values of the consumers ranged from-32.3‰ （Chironomus sp.） to -22.1‰ （Neocaridina denticulata sinensis）, and the consumers at higher trophic levels had lager δ^15N values. The lowest δ^15N value was 10.3‰ （Cristaria plcata）, and the highest was 19.0‰ （Hyporhamphus intermedius）. There was no correlation between the ratios of δ^13C and the trophic relationships, neither between the ratios of δ^13C and δ^15N （r = 0.1835, P 〉 0.05）, which suggested that the food web had a nonlinear structure. The length of the food chain in the Gonghu Bay was 4.44 trophic level.