摘要
浮游生物是湖泊食物网的重要组成,其碳、氮稳定同位素能够反映元素地球化学循环和食物来源的波动,是了解水域生态系统结构变化的重要手段之一.本文选取云南4个不同类型湖泊,开展浮游生物碳、氮稳定同位素组成(δ^(13)C、δ^(15)N)的季节变化与湖泊对比研究.大型深水湖泊(抚仙湖和阳宗海)中,浮游植物δ^(13)C值在夏、秋季(-20.34‰±1.98‰)显著高于冬、春季(-28.00‰±2.51‰),反映夏秋季藻类生长速率较高、HCO3-无机碳源利用增多等的影响.而小型浅水湖泊(长桥海和大屯海)中浮游植物δ^(13)C值在夏季最高(-21.24‰±0.88‰),可能与雨季流域输入增强、陆源有机质占比增加有关.4个湖泊浮游生物δ^(15)N值具有一致的变化特征,春季显著高于其他季节.分析表明,云南地区雨季以面源污染为主向旱季以点源污染为主的转变,导致氮素营养盐季节性来源差异,并通过生物吸收作用影响了浮游生物δ^(15)N值的季节变化.在浮游动物与浮游植物的稳定同位素差值(即富集度)方面,营养水平高的小型浅水湖泊中δ^(13)C富集度为1.61‰±0.90‰、δ^(15)N富集度为2.71‰±1.22‰,显著小于营养水平低的大型深水湖泊(分别为2.60‰±0.98‰和4.19‰±1.25‰),表明随着湖泊营养水平的增加,浮游动物更多地以浮游植物为食,导致有机碳在不同营养级之间的传输过程中具有更强的耦合作用,且相邻营养级之间具有更低的δ^(15)N富集度特征.
Plankton is an important component of lake food webs.Their carbon and nitrogen stable isotope values can reflect the fluctuation of biogeochemical cycling and food sources and can be applied to track the changes of aquatic ecosystem structure.In this paper,four lakes with distinct typology from Yunnan Province were selected to uncover the seasonal changes in carbon and nitrogen stable isotopic compositions of plankton.The carbon stable isotope values of phytoplankton in large deep lakes(Lake Fuxian and Lake Yangzong)are enriched in summer and autumn(mean±SD:-20.34‰±1.98‰),but relatively depleted in winter and spring(-28.00‰±2.51‰),which may reflect a higher growth rate of plankton and greater assimilation of bicarbonate(HCO3-)during the growing season.In small shallow lakes(Lake Changqiao and Lake Datun),carbon stable isotopic values of phytoplankton are mostly enriched in summer(-21.24‰±0.88‰)among the four sampling seasons.This may be related to the increased input of terrigenous organic matter during the rainy season,and a decreased lower water level due to overuse of agricultural irrigation in summer.In contrast to the carbon stable isotope values,the nitrogen stable isotope composition of plankton displayed a similar trend of seasonal variations across lakes where a significantly more positive value was found in spring than in other seasons.Further analyses revealed that that seasonal variation in the nitrogen stable isotope of plankton is related to the seasonal difference of nitrogen sources and their distinct isotopic compositions.Specifically,non-point source pollution,mainly related to agricultural fertilizers with depleted nitrogen stable isotopic value,is often dominant in the rainy season,while point source pollution predominantly derived from sewage input with enriched nitrogen stable isotopic composition is commonly observed in the dry season.In terms of stable isotope fractionation between zooplankton and phytoplankton(i.e.trophic enrichment),small shallow lakes were characterized by smaller carbon(1.61‰±0.90‰)and nitrogen(2.71‰±1.22‰)stable isotopic enrichment than those in large deep lakes(2.60‰±0.98‰and 4.19‰±1.25‰,respectively)in this study.Zooplankton often displays a higher degree of dependence on autochthonous organic carbon(such as phytoplankton)with increasing nutrient status,reflecting a stronger coupling of organic carbon transfer between trophic levels.Similarly,a smaller degree of nitrogen stable isotope enrichment is evidenced in more eutrophic lakes in this study.
作者
陈子栋
黄林培
陈丽
梁红
刘园园
陈小林
张涛
陈光杰
Chen Zidong;Huang Linpei;Chen Li;Liang Hong;Liu Yuanyuan;Chen Xiaolin;Zhang Tao;Chen Guangjie(Yunnan Key Laboratory of Plateau Geographical Processes and Environmental Change,Faculty of Geography,Yunnan Normal University,Kunming 650500,P.R.China)
出处
《湖泊科学》
EI
CAS
CSCD
北大核心
2021年第3期761-773,共13页
Journal of Lake Sciences
基金
国家重点研发计划项目(2017YFA0605202)
国家自然科学基金项目(41771239,U1133601,42067064)联合资助。
关键词
碳、氮稳定同位素
浮游植物
浮游动物
季节波动
云南湖泊
抚仙湖
阳宗海
Carbon and nitrogen stable isotopes
phytoplankton
zooplankton
seasonal fluctuation
Yunnan lakes
Lake Fuxian
Lake Yangzong
