The Isotopic Composition Of Carbon And Nitrogen In Suspended Particulate Organic Matter In The Daya Bay And The Jiaozhou Bay

The isotopic compositions of carbon and nitrogen in suspended particulate organic(POM)matter in the Daya Bay and the Jiaozhou Bay were studied during the National Program on Key Research Project(973 Program).Spatial and temporal variations of POC,PN,?13CPOC and ?15NPN were discussed.Based on the characteristics of ?13CPOC and ?15NPN,the mixing model with three end members was used to calculate the contribution of different sources for the suspended particulate organic matter.The factors influencing the sources of suspended particles in the Daya Bay and the Jiaozhou Bay were also discussed.The main conclusions we obtained were as follows.The spatio-temporal variations of isotopic compositions of carbon and nitrogen isotopes in the Daya Bay and the Jiaozhou Bay showed different characteristics of in different sub zones.Three sources for POM,namely marine organic matter,terrestrial organic matter and estuarine organic matter,were identified based on the the characteristics of ?13CPOC and ?15NPN.The results from mixing model with three end members suggested,that marine organic matter is the main source of POM in the Daya Bay,which accounts for 59 ± 16%,71 ± 20%,70 ± 18%and 48 ± 13%of POM in the spring,summer,autumn and winter respectively.Meanwhile,the proportions of the marine organic matter were 52 ± 11%,47 ± 8%,66 ± 6%,and 24 ± 17%in the Jiaozhou Bay during the four seasons,respectively.Marine organic matter was the main source of POM in spring and autumn in the Jiaozhou Bay.The annual averages of POC,PN,?13CPOC,?15NPN and POCm in the Daya Bay are significantly higher than those in the Jiaozhou Bay,being corresponded to the higher phytoplankton biomass in the Daya Bay.The terrestrial organic matter was mainly come from the runoffs in the Daya Bay and the Jiaozhou Bay,which was significantly affected by wastewaters.The characteristics of high ?13CPOC and low ?15NPN were observed in some regions in both bays,indicating the influence of estuarine organic matter.The slopes of the linear relationship between POCm and Chl-a varied in different seasons in the Daya Bay,which was regulated by the relative abundance of diatoms in phytoplankton.A positive correlation between POCm/Chl-a ratio and R ?+?(the ratio of skeletonema costatum and cyanobacteria to total phytoplankton abundance)was observed,further suggesting the role of small size algae in regulating the correlation between POCm and Chl-a in the Daya Bay.The ratio of POCm/Chl-a ratio was higher when the small size algae were abundant.