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Effects of the Rio Salado Confluence on Benthic Substrate in the Rio Grande

Effects of the Rio Salado Confluence on Benthic Substrate in the Rio Grande. Harmony Lu REU Project Summer 2010. Background. River Continuum Concept to Network Hypothesis gradient of change from headwaters to mouth of hydrological properties

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Effects of the Rio Salado Confluence on Benthic Substrate in the Rio Grande

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  1. Effects of the Rio Salado Confluence on Benthic Substrate in the Rio Grande Harmony Lu REU Project Summer 2010

  2. Background River Continuum Concept to Network Hypothesis • gradient of change from headwaters to mouth of hydrological properties • biological communities also change to match the local conditions • discontinuities in these gradients occur, instead view the river as a network

  3. Background Flood events in an intermittent stream

  4. Research Questions • Are there observable effects from the confluence of an intermittent stream, the Rio Salado, on the main channel, the Rio Grande? • Do these effects alter the local habitat?

  5. Possible lasting effects of an intermittent tributary • focus on substrate variation in the main channel • water energy determines particle carriage/deposition • tributary carries sediment into main channel • benthic substrate important habitat characteristic

  6. Background Rio Grande • major water source for agriculture, domestic use, natural habitats (riparian areas) • also is a habitat itself for many species • sandy-bottomed with wide floodplain

  7. Background Invertebrate communities are useful biological indicators in freshwater • commonly studied • many are sedentary and provide assessment of localized effects • are important parts of river communities

  8. Research Site Sevilleta National Wildlife Refuge

  9. Research Site

  10. Procedure 1– mapping • 11 transects from the west bank to the east bank • 4 samples along each transect • at each site, 3 measurements: • % cobble • depth • sediment sample taken for texture analysis

  11. Procedure 2– invertebrate sampling • 2 sets of samples taken (Day 1: June 4+6, Day 2: June 23) • 7 sites along the west bank • Data from each site (3 types): • sediment texture • water characteristics • invertebrate community

  12. Invertebrate Sampling Sites

  13. Procedure – invert collection • Invertebrate sampling: - sediment core sampling • 4 cores of the top 1 cm of benthic substrate • samples preserved in 70% ethanol

  14. Procedure – sample analysis • Sediment • hydrometer soil texture analysis used to assess % composition • Invertebrate • invertebrates separated from debris/sediment • identified to Order or Family using dissecting microscope

  15. Results and Discussion • Confluence map • Invertebrate community • Environmental influence on invertebrate community • Lasting effects of the confluence

  16. Confluence Depth Map Rio Salado

  17. Confluence Cobble Cover Map Rio Salado bubble size indicates % cobble cover

  18. Invertebrate Data

  19. Invertebrate Community Data • Multidimensional Scaling (MDS) • multivariate – can look at community as a whole • each site’s community data viewed as a matrix • calculated a similarity between all of the matrices • plot similarity in multidimensional space • compress to 2D plot with meaningless axis • Bottom line: • relative distance is key • closeness implies similarity (Global R): 0.536 p: 0.001 Similarity of communities – positioning around confluence

  20. Invertebrate Community Data (Global R): 0.536 p: 0.001 Temporal Changes – succession of species over the summer

  21. Correlation between environment and biological communities • water characteristics: showed very small variation between sites • sediment texture: much higher variation between sites • BEST analysis: compares environmental information (soil texture) to biological information (community) - % gravel and % vv fine sand + silt explain most of the variation in biological communities

  22. MDS size indicates relative % gravel size indicates relative %vv fine sand + silt

  23. Confluence Sand Map Rio Salado bubble size indicates % sand (by mass)

  24. Confluence Gravel Map Rio Salado bubble size indicates % gravel (by mass)

  25. Confluence vv fine sand and silt Map Rio Salado silt vv fine sand gravel bubble size indicates % (by mass)

  26. Matching up to observations Rio Salado

  27. Conclusions • Invertebrate communities changed through time • Variation in invertebrate communities could be correlated with substrate qualities • The main channel around the confluence shows high variation in substrate quality • Patterns of substrate quality match observations of tributary inputs • Implications that tributary has lasting influence on habitat quality of main channel

  28. Further Research • Intermittent streams as sources of disturbance that change throughout the year • Interannual variation of precipitation and flow rates of intermittent tributaries • Variability in the benthic substrate of the Rio Grande overall (temporal and spatial)

  29. Acknowledgements Ayesha Burdett, Jennifer Johnson Sevilleta LTER REU 2010 students (Christopher Shepard, Shayla Burnett, Amanda Labrado, Ricardo Duran, Cynthia Malone, Ileana Betancourt, Melissa Shaginoff, Mitch Nakai, Natasha Ribeiro, Amanda Liebrecht, Antonio Nevarez, ElidaIniguez) Brenda Nieto National Science Foundation Sevilleta National Wildlife Refuge & LTER

  30. References Benda, L., N.L. Poff, D. Miller, T. Dunne, G. Reeves, G. Pess, M. Pollock. (2004). The Network Dynamics Hypothesis: How Channel Networks Structure Riverine Habitats. BioScience. 54: 413-427. Best, J.L. (1988). Sediment transport and bed morphology at river channel confluences. Sedimentology. 35: 481-498. Burdett, A, R. Bixby. (2008). Effects of nutrient availability on periphyton growth and diversity in the Middle Rio Grande: top-down and bottom-up factors. Middle Rio Grande Endangered Species Collaborative Program Annual Report. 1-53. Duan, X., Z. Wang, M. Xu, K. Zhang. (2009). Effect of streambed sediment on benthic ecology. International Journal of Sediment Research. 24: 325–338. Gensler, G. R. Oad, K. Kinzli. (2009). Irrigation System Modernization: Case Study of the Middle Rio Grande Valley. Journal of Irrigation and Drainage Engineering. 169-176. Kiffney, P.M., C.M. Greene, J.E. Hall, and J.R. Davies. (2006). Tributary streams create spatial discontinuities in habitat, biological productivity, and diversity in mainstem rivers. Can. J. Fish. Aquat. Sci. 63: 2518–2530. Palmer, M.A., H.L. Menniger, E. Bernhardt. (2010). River restoration, habitat heterogeneity and biodiversity: a failure of theory or practice? Freshwater Biology. 55: 205–222. Rice, S.P., M.T. Greenwood, C.B. Joyce. (2001). Macroinvertebrate community changes at coarse sediment recruitment points along two gravel bed rivers. Water Resources Research. 37: 2793–2803. Rice, S.P., R.I. Ferguson, T.B. Hoey. (2006). Tributary control of physical heterogeneity and biological diversity at river confluences. Can. J. Fish. Aquat. Sci. 63: 2553–2566. Svendsen, K.M., C. E. Renshaw, F.J. Magilligan, K.H. Nislow, J.M. Kaste. (2009). Flow and sediment regimes at tributary junctions on a regulated river: impact on sediment residence time and benthic macroinvertebrate communities. Hydrol. Process. 23: 284–296. Vannote, R.L., G.W. Minshall, K.W. Cummins, J.R. Sedell, C.E. Cushing. (1980). The River Continuum Concept. Can. J. Fish. Aquat. Sci. 37: 130-137.

  31. Questions?

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