Pathways of organic carbon utilization in small lakes: Results from a whole‐lake 13C addition and coupled model

By J. Cole, Stephen R. Carpenter, J. Kitchell, Michael M. Pace. 2002

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In many small aquatic ecosystems, watershed loading of organic C exceeds autochthonous primary production. Although this allochthonous organic C has long been thought of as refractory, multiple lines of evidence indicate that substantial portions are respired in the receiving aquatic ecosystem. To what extent does this terrestrial C support secondary production of invertebrates and fish? Do current models adequately trace the pathways of allochthonous and autochthonous C through the food web? We evaluated the roles of allochthonous and autochthonous organic C by manipulating 13C content of dissolved inorganic C in a small, softwater, humic lake, thereby labeling autochthonous primary production for about 20 d. To ensure rapid and sufficient uptake of inorganic 13C, we enriched the lake with modest amounts of N and P. We constructed a carbon flow model based on the ambient and manipulated levels of 13C in C compartments in the lake, along with information on key rate processes. Despite the short nature of this experiment, several results emerged. (1) Fractionation of photosynthetically assimilated 13C‐CO2 by phytoplankton (ɛ) is lower (~6‰) than physiologic models would estimate (~20‰). (2) Bacteria respire, but do not assimilate, a large amount of terrestrially derived dissolved organic C (DOC) and pass little of this C to higher trophic levels. (3) The oxidation of terrestrial DOC is the major source of dissolved inorganic C in the lake. (4) Zooplankton production, a major food of young‐of‐year fishes, is predominantly derived from current autochthonous carbon sources under the conditions of this experiment.

Subfields: Environmental Chemistry, Oceanography

View Paper: https://www.semanticscholar.org/paper/b6a8838f7901478ca2e894513b94882bbd7c1fc1

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Citations in the corpus

Changes in bacterial activity and community structure in response to dissolved organic matter in the Hudson River, New York (2004, background): “Lakes and rivers may be ideal systems to explore relationships between community structure and DOM properties, since the amount and composition of DOM can vary greatly in these aquatic systems (Cotner et al. 2000, Mulholland et al. 2001, Cole et al. 2002).”
Carbon‐nitrogen coupling and algal‐bacterial interactions during an experimental bloom: Modeling a 13C tracer experiment (2004, methodology): “CO2 exchange with the atmosphere was therefore considered, as similarly described in Cole et al. (2002) (eq.”
Carbon flows through a benthic food web: Integrating biomass, isotope and tracer data (2006, background): “Recent studies of food webs in estuaries (Thompson and Schaffner, 2001; Sobczak et al., 2002; Chanton and Lewis, 2002), streams (Tank et al., 2000) and lakes (Cole et al., 2002) report a similar dominant contribution of autochthonous production in diets of metazoan grazers.”
High intraspecific variability in carbon and nitrogen stable isotope ratios of lake chironomid larvae (2004, background): “In systems with high respiration, d13C values for dissolved inorganic carbon can approach 220‰ and via fractionation during photosynthesis could in principle result in phytoplankton of 245‰ (Peterson and Fry 1987), although this may be rare in practice (Jones et al. 2001; Cole et al. 2002).”
The Temperature Dependence of the Carbon Cycle in Aquatic Ecosystems (2010, background): “…DEPENDENCE OF THE AQUATIC CARBON CYCLE allochthonous carbon subsidies, as is frequently prevalent in freshwater, estuarine and coastal ecosystems (Cole et al. , 2000, 2002; del Giorgio and Peters, 1994; del Giorgio et al. , 1997; Pace et al. , 2004; Ram et al. , 2007), the temperature…”