HR: 15:30h
AN: NB24C-01    [Abstracts]
TI: Function and Food Webs of Springs Near Treeline in the Swiss National Park
AU: * Robinson, C T
EM: robinson@eawag.ch
AF: EAWAG/ETHZ, Department of Limnology, Ueberlandstrasse 133, Duebendorf, 8600 Switzerland
AU: Schmid, D
EM: dschmid@student.ethz.ch
AF: EAWAG/ETHZ, Department of Limnology, Ueberlandstrasse 133, Duebendorf, 8600 Switzerland
AU: Svoboda, M
EM: msvoboda@student.ethz.ch
AF: EAWAG/ETHZ, Department of Limnology, Ueberlandstrasse 133, Duebendorf, 8600 Switzerland
AB: We investigated ecosystem function and food web structure of high elevation springs in the Swiss National Park. Functional characteristics were derived from measures of ecosystem metabolism, sediment respiration, and nutrient uptake experiments in 4 springs. Food webs were assessed using stable isotope analysis (C, N) of different ecosystem compartments from 20 springs encompassing 6 different spring types. Gross primary production (GPP) ranged from 2.4 to 4.3 g O₂ m^-2 d^-1 and ecosystem respiration (ER) from 3.6 to 6.7 g O₂ m^-2 d^-1, suggesting springs were net-heterotrophic (P/R<0.75). One iron-oxide rich spring had GPP = 65 and ER = 96 g O₂ m^-2 d^-1. Bacterial abundances (DAPI) ranged from 2-3×10⁸ cells/ml, and benthic sediments were mostly anaerobic. Uptake lengths of both N and P were <50 m, with uptake rates of P at 0.3-3.1 mg m^-2 h^-1 and N at 57-178 mg m^-2 h^-1, suggesting springs were important nutrient sinks. Food webs were simple (<8 taxa) and primarily detritus based. The dominate stonefly predator relied on instream production of invertebrates. Terrestrial predators (lycosid spiders) near springs fed on a terrestrial diet. These data suggest these springs derive most of their energy from allochthonous sources and are net-heterotrophic ecosystems.
DE: 1845 Limnology
DE: 1878 Water/energy interactions
DE: 1899 General or miscellaneous
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly