Peipoch, M. , F.R. Hauer, and H.M. Valett University of Montana Division of Biological Sciences

1. BIOGEOCHEMICAL VARIATION AMONG AQUATIC HABITATS OF RIVERINE FLOODPLAINS • Peipoch, M.,F.R. Hauer, and H.M. Valett • University of Montana • Division of Biological Sciences • Montana Institute on Ecosystems

2. Habitat Heterogeneity vs. Niche Diversity Physical Heterogeneity Increases Biofilm Resource Use and Its Molecular Diversity in Stream Mesocosms Singer et al. 2012 Ecology’s most general, yet protean pattern: the species-area relationship Lomolino 2000 NICHE DIVERSITY BIODIVERSITY ECOSYSTEM FUNCTION HABITAT HETEROGENEITY • Species Richness • C uptake Biodiversity improves water quality through niche partitioning Cardinale 2011 • Habitat area • Flow heterogeneity • NO3 uptake • Species richness BIOCOMPLEXITY “Michener et al. 2001, Thompson et al. 2001”

3. Floodplain Complexity Floodplain complexity: ‘a measure of the variation in geomorphic, hydrologic, and biological forms and processes that exist among ecologically distinct habitats of floodplain landscapes’ • Stanford et al. 2005

4. Multi-scale Assessment of Riverscape Complexity (MARC) Project • 10 river floodplains across Montana • Milk • Swan • Missouri • Clark Fork • Boulder • Bitterroot • Big horn • Madison • Tongue • Big hole Variation in nutrient concentrations among floodplain aquatic habitats Variation in biomass abundance among floodplain aquatic habitats Quantification of ecosystem metabolism for four critical habitats in riverine floodplains

5. Floodplain aquatic habitats • Main channel habitats (n=5 per floodplain, n=3 per habitat) • Off-channel habitats (n=5 per floodplain, n=3 per habitat) • Parafluvial springbrooks • Ponds • Shore line • Pools • Runs • Backwaters • Confluence zones • Riffles • Runs • Orthofluvial springbrooks • Flow channels

6. Biogeochemical variation among floodplain habitats

7. Biogeochemical variation: Ammonium • SURFACE WATERS • HYPORHEIC WATERS • NH4concentration vs. O2concentration; r = -0.6 , p-value < 0.01

8. Biogeochemical variation: Nitrate • SURFACE WATER • HYPORHEIC WATER • Low NO3- concentration in surface waters despite of high NO3- concentration in the hyporheic zone

9. Biogeochemical variation: Soluble reactive phosphorus (SRP) • SURFACE WATER • HYPORHEIC WATER

10. N:P ratios vs. Chlorophyll

11. Biogeochemical variation in floodplain habitats • Biomass abundance • Chl-a abundance Off-channel habitats play a critical role on the niche diversity of river floodplains by generating larger biogeochemical variation • Ammonium • Dissolved Oxygen • Nitrate

12. Ecosystem metabolism among floodplain habitats

13. Gross Primary Production & Ecosystem Respiration • MC • n=4 • MC • n=4 • PS • n=2 • PS • n=2 • OS • n=3 • OS • n=3 • PN • n=4 • PN • n=4

14. GPP:ER ratios • All river floodplains • MC • n=4 • PS • n=2 • OS • n=3 • PN • n=4

15. General Conclusions • Off-channel habitats are responsible for the majority of biogeochemical variation observedin river floodplains. • Variation in N:P ratios (i.e., Nitrate) determines Chl-a standing stocks among aquatic habitats of river floodplains. • Main-channel habitats are mostly autotrophic environments while off-channel habitats, especially orthofluvial ponds, are principally heterotrophic ecosystems (i.e., ER > GPP). • GPP:ER ratios in main-channel and off-channel zones seem to be driven by SRP and NO3 concentrations, respectively.