Seasonality of stable carbon and nitrogen isotopes within the pelagic food web of Taihu Lake

• Published in: Annales de limnologie Vol. 44; no. 1; pp. 1 - 6
• Main Authors: ZENG, Q. F, KONG, F. X, ZHANG, E. L, TAN, X, WU, X. D
• Format: Journal Article
• Language: English
• Published: Toulouse Université Paul Sabatier 01.01.2008
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Cladocera; Fresh water ecosystems; Freshwater; Fundamental and applied biological sciences. Psychology; Marine; Synecology; China, People's Rep., Tai Hu L; China, People's Rep., Jiangsu Prov., Taihu L; pelagic food web; Trophic relation; stable isotope; Nitrogen; Spatial variation; seasonal cycle; Cycle; Pelagic zone; Freshwater environment; Aquatic environment; Trophic chain; Food web; Seasonal variation; Lakes; Isotopes; Taihu Lake
• ISSN: 0003-4088; 2100-000X
• DOI: 10.1051/limn:2008019

Particulate organic matter (POM), dissolved organic matter (DOM), bacteria and cladoceran were sampled seasonally at Zhihugang Estuary and Lake Center in Taihu Lake. The d super(13)C of the four organic matter fractions showed consistent temporal variation, with heaviest values in summer and lower at other times of the year. The cladoceran d super(13)C showed a significant correlation with that of POM, reflecting a heavy dietary dependence on POM during the study period. The bacteria became enriched in super(13)C compared with that of DOM throughout the sampling dates, although no significant relationship was found between the two fractions. d super(13)C values of POM, cladoceran and bacteria were all negative significantly correlated with oxidation and reduction potential (ORP), and specific conductivity (SpCond). As for d super(15)N, the seasonal pattern of food web components was variable. The POM d super(15)N signature exhibited the most enriched isotope ratios during the summer months when dissolved inorganic nitrogen (DIN) nutrients were at their lowest concentrations. The consumption of DIN in summer can explain in part the progressive accumulation of heavy nitrogen isotopes during this period. Spatially, d super(13)C and d super(15)N of the food web components were all slightly depleted at Estuary than that at Lake Center during the study period, possibly due to large allochthonous inputs at Zhihugang Estuary. Relatively wide ranges of stable isotopic values from both sites suggest that seasonality should be considered when attempting to establish food web structures in a eutrophic lake.