HR: 16:45h
AN: NB14B-06    [Abstracts]
TI: Hyporheic Respiration and Metazoan Dynamics Using an In-situ Flow-through Mesocosm.
AU: * Reid, B
EM: brian.reid@umontana.edu
AF: Flathead Lake Biological Station, Division of Biological Sciences, University of Montana, 300 Bio Station Lane, Polson, MT 59860
AU: Hauer, R
EM: ric.hauer@umontana.edu
AF: Flathead Lake Biological Station, Division of Biological Sciences, University of Montana, 300 Bio Station Lane, Polson, MT 59860
AB: We developed an in situ flow-through mesocosm to study the limits to metazoan production and sources of carbon in alluvial groundwater on the Middle Fork, Flathead River (MT). Eight 440-liter mesocosms were situated in pairs, representing lateral hyporheic positions (HP): infiltration, midgradient and exfiltration zones. We used local sediments simulating a bimodal gravel formation, typical of alluvial aquifers except that particulate carbon was removed. Whole mesocosm respiration was approximately 6.8 ug O2 per liter sediment per hr, 50 per cent lower than previous lab-based estimates, with highest rates at the infiltration site near the river. Metazoans, dominated by copepods and other meiofauna, reached mean densities of 5, 4 and 3 per liter, and richness of 6, 5 and 4 taxa for respective HPs, similar to results from well pumping. DOC based microbial production, estimated at 0.464 ugC/lhr, was sufficient to explain estimated metazoan production (0.041ugC/lhr). Evidence from well sampling indicates that high levels of invertebrate production may be associated with buried wood jams. We are currently monitoring the response to an experimental amendment of debris jam sediment and organic matter, and we expect an increase in community respiration and metazoan biomass downgradient of the amendment.
DE: 0400 Biogeosciences
DE: 1845 Limnology
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly