摘要
浮游动物在食物链能量流动与物质循环中发挥着重要作用,能将摄入的浮游植物转化为不同形态的碳,在海洋碳循环中发挥重要作用。应用14C标记示踪方法,定量分析海洋浮游动物褶皱臂尾轮虫Brachionus plicatilis摄入碳的碳同化与碳排放。喂食不同密度小球藻Chlorella sp.(1×10~5个/m L、5×10~5个/m L、1×10~6个/m L)后,褶皱臂尾轮虫对小球藻碳的同化率(AE)为34%—51%,呈现随饵料密度增加而减小的趋势;未被轮虫同化的碳,主要以溶解有机碳(DOC)的形态排放到水体中,DOC占碳排放的比例为37%—51%,随着饵料密度增加而增加;二氧化碳(CO2)的比例为15%—40%,随着饵料密度增加而减小;颗粒有机碳(POC)占碳排放的比例较少,为23%—34%,随着饵料密度的增加而增加。此外,分析褶皱臂尾轮虫排放DOC的粒径组成,发现低分子量有机碳(LMW,<3 k Da)的量大于胶体有机碳(COC,3 k Da—0.22μm)的量,COC占DOC比例为33%—43%;LMW占DOC比例为57%—67%。本研究结果表明,浮游动物可把相当部分食物中的碳转化为DOC,排放到水体中为细菌所利用,在海洋碳循环中发挥重要作用。
Zooplankton plays important roles in the energy and nutrient flows in the aquatic food webs. They also influence the ocean carbon cycle by producing sinking fecal pellets and dissolved organic carbon （DOC） and regulate the structure of phytoplankton assemblages. Phytoplankton carbon ingested by zooplankton will be assimilated as biological carbon or released into the environment as carbon dioxide （CO2）, DOC, and fecal pellets. So far, it is not clear how the unassimilated carbon is allocated to the three forms. We here employed rotifer Brachionus plicatilis, a common marine species that is widespread in estuarine and coastal areas and widely used as a model species for ecotoxiological and ecological studies, to examine the carbon assimilation and release in marine zooplankton. This study quantified the carbon budgets and assimilation efficiencies （AEs） of the rotifer using 14C tracing techniques. The rotifers were fed Chlorella sp. at three different food densities （1×105, 5×105, and 1×106 cells/mL）. The rotifer was first fed 14C-labeled Chlorella for a short duration and then fed non-labeled algae at the same food density several times during a 12-h depuration period. 14CO2, DO14C, and 14C-labeled fecal pellets were collected before each feeding interval during the depuration period. The 14C retained in the rotifer after the 12-h depuration period was calculated as the assimilated carbon. The results showed that AE was 34%-51% and decreased as the amount of food ingested by the rotifer increased. The released carbon was predominant as DOC, accounting for 37%-51%, followed by CO2 （15%-40%） and POC （23%-34%）. The results also showed that DOC and POC proportions increased whereas CO2 proportionally decreased as food density increased. DOC excreted by the rotifers was further size-fractionated into colloidal organic carbon （COC, with size range of 3 kDa to 0.2 μm） and low molecular weight organic carbon （LMW, 〈 3 kDa in size）. The results showed that COC and LMW accounted for 33%-43% and 57%-67% of the total DOC, respectively. The COC proportion increased as food density increased. This study shows that the rotifer can transform a substantial fraction （18%-34%） of their ingested food carbon into DOC, which provides carbon sources for bacterial growth and fuels the microbial loop. The high proportions of organic carbon released by rotifer also support the idea that zooplankton diel vertical migration could be an important source of organic carbon for the mesopelagic ocean.
作者
刘庆霞
周林滨
毋赟
杨玉敏
张黎
LIU Qingxia;ZHOU Linbin;WU Yun;YANG Yumin;ZHANG Li(Key Laboratory of Tropical Marine Bio-resources and Ecology,South China Sea Institute of Oceanology,Chinese Academy of Sciences,Guangzhou 510301,China;University of Chinese Academy of Sciences,Beijing 100049,China;School of Environment Science and Engineering,Nanjing University of Information Science ＆ Technology,Nanjing 210044,China;Environmental Monitoring and Forecast Center of Guangdong Marine Fisheries Department,Guangzhou 511400,China)
出处
《生态学报》
CAS
CSCD
北大核心
2018年第18期6768-6777,共10页
Acta Ecologica Sinica
基金
国家重点研发计划(2016YFC0502805)
国家重点基础研究发展计划项目(2015CB452904)
广东省自然科学基金(2015A030310169)
关键词
褶皱臂尾轮虫
碳同化率
碳排放
胶体有机碳
^14C
Brachionus plicatilis
assimilation efficiency
carbon release
colloidal organic carbon
^14C
