2020年冬季大亚湾西南海域主要渔业生物碳氮稳定同位素研究

Study on stable isotopes of carbon and nitrogen of main fishery organisms in the southwestern waters of Daya Bay,South China Sea in winter 2020

为了解大亚湾西南海域食物网的营养结构特征,本研究于2020年1月份使用底拖网采集了该海域的渔业生物,并分析了35种主要渔业生物的碳氮稳定同位素值。根据δ^(13)C和δ^(15)N值,计算出该海域食物网6种营养结构的生态指标和主要渔业生物的营养级,并绘制了连续营养谱。本次调查渔业生物主要为鱼类和虾蟹类,鱼类的δ^(13)C和δ^(15)N值范围分别为–17.63‰~–14.85‰和12.92‰~15.46‰,平均值分别为–16.47‰和13.80‰;虾蟹类的δ^(13)C和δ^(15)N值范围分别为–17.67‰~–15.51‰和11.05‰~12.62‰,平均值分别为–16.30‰和11.85‰。根据δ^(15)N值,用相加模型(trophic position by the additive model,TPA)和缩比模型(trophic position by the scaled model,TPS)分别计算了主要渔业生物的营养级,结果显示两个模型计算的结果无显著性差异(P>0.1),呈现鱼类平均营养级>虾蟹类的趋势。本研究发现大亚湾西南海域食物网初始食物来源较为单一,存在食物链营养层级较少和长度不足,食物网营养级多样性较低和营养结构冗余程度高的现象。与30多年前相比,大亚湾近年高营养级生物量减少,食物网结构由复杂趋向简单化,生态系统稳定性较差。本研究结果不仅为了解大亚湾食物网结构组成提供了基础资料,也为保护大亚湾渔业资源,维持生态系统结构的稳定性提供参考依据。

To understand the trophic structure of food webs in the southwestern waters of Daya Bay,35 fishery organisms were collected by bottom trawl in January 2020,and the stable isotopes of carbon and nitrogen(δ^(13)C andδ^(15)N)of the fishery organisms were analyzed.Based on the stable isotopes of carbon and nitrogen,six quantitative ecological indicators for nutritional structure of the food web and the trophic levels of the main fishery organisms were calculated;and a continuous nutrition spectrum was made.Most of the fishery organisms captured were fish,crabs and shrimp.Theδ^(13)C andδ^(15)N values were-17.63‰to-14.85‰and 12.92‰to 15.46‰for fishes,respectively,with average values being-16.47‰and 13.80‰.They were-17.67‰to-15.51‰and 11.05‰to 12.62‰for shrimp and crabs,with average values of-16.30‰and 11.85‰,respectively.According to the value ofδ^(15)N,the trophic levels of the main fishery organisms were calculated using the additive model(trophic position by the additive model,TPA)and the scaled model(trophic position by the scaled model,TPS).The result showed that there was no significant differences between the results calculated by the two models(P>0.1),and the average trophic level of fish was higher than that of shrimp and crabs.This study indicates the food web in the southwestern waters of Daya Bay is characterized by a relatively simple initial food source,few trophic levels,short food chain,low trophic level diversity,and high degree of redundancy in trophic structure.The abundance of organisms with high trophic levels decreased,and the structure of the food web shifted from complex to simplistic,and the ecosystem became less stable in the past 30 years.The study adds new basic information about the food web structure in the study area.It also provides a reference for protecting the fishery resources of Daya Bay and maintaining the stability of the ecosystem structure there.