Premium
Respiration of allochthonous organic carbon in unproductive forest lakes determined by the Keeling plot method
Author(s) -
Karlsson Jan,
Jansson Mats,
Jonsson Anders
Publication year - 2007
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.2007.52.2.0603
Subject(s) - hypolimnion , dissolved organic carbon , respiration , environmental chemistry , environmental science , total organic carbon , carbon fibers , carbon cycle , ecosystem respiration , ecosystem , primary production , total inorganic carbon , ecology , carbon dioxide , chemistry , biology , botany , nutrient , eutrophication , materials science , composite number , composite material
We carried out short‐term (2 d) experiments in nine unproductive lakes in northern Sweden in order to investigate organic carbon sources supporting lake water respiration. Surface water was incubated in gas‐tight bottles in the dark, and the concentration and isotopic composition (δ 13 C) of dissolved inorganic carbon (DIC) were measured at the start and end of the incubations. Keeling plot analyses revealed that the δ 13 C of the respired carbon was between ‐28.4% and ‐30.6% in the lakes and that the respired carbon was mainly of allochthonous organic carbon (AlloOC) origin. The respiration of AlloOC corresponded well with metabolic imbalances indicated by negative net ecosystem production (NEP) values in the lake waters. Keeling plot analysis of DIC accumulating in the hypolimnion of two lakes during summer stratification showed δ 13 C values of around ‐26.6% for excess DIC, implying that the accumulation of DIC was mainly derived from respiration of AlloOC. Our data provide direct evidence that net heterotrophy of these lakes is caused by input and respiration of AlloOC. We conclude that the Keeling plot method is a powerful technique that enables characterization and quantification of the organic carbon sources contributing to respiration in aquatic systems.