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Energy flow and elemental concentrations in the Steina River ecosystem (Black Forest, Germany) |
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| Authors: | Giulio P Genoni Elisabeth I Meyer Andrea Ulrich |
| Institution: | Departments of Limnology and Biogeochemistry, Swiss Federal Institute for Environmental Science and Technology (EAWAG), CH-8600 Duebendorf, Switzerland, CH Department of Limnology, Institute for Animal Evolution and Ecology, University of Muenster, D-48149 Muenster, Germany; e-mail: meyere@uni-muenster.de, DE Swiss Federal Laboratories for Materials Testing and Research (EMPA), CH-8600 Duebendorf, Switzerland; e-mail: andrea.ulrich@empa.ch, CH |
| Abstract: | Considering food web energetics and elemental cycling together allows the testing of hypotheses about the coevolution of biological systems and their physical environment. We investigated the energy flow and the distribution of 25 elements in the Steina River.¶We constructed an annual energy flow network and estimated the emergy ("embodied energy" that includes all the energy involved in a process) contributions of resources sustaining the system. Furthermore, we measured the concentration of various macronutrients, essential elements, and heavy metals in the physical environment and trophic compartments. Finally, we examined the hypothesis of a positive relationship between the "rarity" of an element and its tendency to bioaccumulate. To do so, we used transformity, the relative energy input required to sustain a compartment's net production or the concentration differential of an element between the living community and the physical environment.¶The resulting energy flow network is one of the most complete available for streams. In the Steina, over 99% of the energy input is transported through the system without being processed. Dissolved inorganic matter and sunlight are the largest inputs, but uptake efficiency is much higher for dissolved and particulate organic matter. Transformities of trophic compartments and elements span 6 to 7 orders of magnitude.¶The tendency to bioaccumulate was as predicted for most elements, with macronutrients showing no accumulation and heavy elements accumulating in high-transformity compartments. However, Na and K were found at highest concentrations in consumers, and Pb, Ga, and Cd in algae. Improved estimates may become possible as more knowledge is available on ecosystem flows. We suggest further ways of testing hypotheses about strategies of element processing. |
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