Control of zooplankton dependence on allochthonous organic carbon

• Main Authors: Jan Karlsson, Anders Jonsson, Markus Meili
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2003
• Subjects: Tranvik; Northern Sweden
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.419.7387; http://www.aslo.org/lo/toc/vol_48/issue_1/0269.pdf

We compared the stable carbon isotopic composition ( � 13 C) of crustacean zooplankton with that of potential carbon sources in 15 lakes in northern Sweden with different dissolved organic carbon (DOC) concentrations (2–9 mg L �1) to test the hypothesis that zooplankton depended more on allochthonous carbon in humic lakes than in clear-water lakes. Based on � 13 C signature, we found that the pool of organic matter in the lakes was dominated by carbon of allochthonous origin over the whole DOC gradient. Zooplankton were generally depleted in 13 C compared to organic matter in the catchment, particulate organic matter in the lake water, and shallow surface sediment. However, the isotopic composition of zooplankton could not be explained without a significant contribution from both allochthonous and autochthonous carbon sources in all lakes. The relative importance of these two carbon sources did not relate to the concentration of, or proportion between, allochthonous and autochthonous organic carbon in the water. Instead, the proportion between allochthonous and autochthonous carbon in the crustacean zooplankton was consistent with a rather conservative use of the energy mobilized by bacterioplankton and phytoplankton in the lakes. Both allochthonous and autochthonous carbon sources can support secondary production in lakes (Hessen and Tranvik