effects of the rio salado confluence on benthic substrate in the rio grande

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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 - PowerPoint PPT Presentation


  • Effects of the Rio Salado Confluence on Benthic Substrate in the Rio GrandeHarmony LuREU ProjectSummer 2010

  • BackgroundRiver Continuum Conceptto Network Hypothesisgradient of change from headwaters to mouth of hydrological propertiesbiological communities also change to match the local conditionsdiscontinuities in these gradients occur, instead view the river as a network

  • BackgroundFlood events in an intermittent stream

  • Research QuestionsAre 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?

  • Possible lasting effects of an intermittent tributary

    focus on substrate variation in the main channelwater energy determines particle carriage/depositiontributary carries sediment into main channelbenthic substrate important habitat characteristic

  • BackgroundRio Grandemajor water source for agriculture, domestic use, natural habitats (riparian areas)also is a habitat itself for many speciessandy-bottomed with wide floodplain

  • BackgroundInvertebrate communities are useful biological indicators in freshwatercommonly studiedmany are sedentary and provide assessment of localized effectsare important parts of river communities

  • Research SiteSevilleta National Wildlife Refuge

  • Research Site

  • Procedure 1 mapping11 transects from the west bank to the east bank4 samples along each transectat each site, 3 measurements:% cobbledepthsediment sample taken for texture analysis

  • Procedure 2 invertebrate sampling2 sets of samples taken (Day 1: June 4+6, Day 2: June 23)7 sites along the west bankData from each site (3 types):sediment texturewater characteristicsinvertebrate community

  • Invertebrate Sampling Sites

  • Procedure invert collectionInvertebrate sampling:- sediment core sampling4 cores of the top 1 cm of benthic substratesamples preserved in 70% ethanol

  • Procedure sample analysisSedimenthydrometer soil texture analysis used to assess % compositionInvertebrateinvertebrates separated from debris/sedimentidentified to Order or Family using dissecting microscope

    DaySiteChironomidaeSimuliidae TricorythidaeBaetidaeLeptoceridaeHempiteraOdonataCladocera1151200000012370010001311140300001417653000000

  • Results and DiscussionConfluence mapInvertebrate communityEnvironmental influence on invertebrate communityLasting effects of the confluence

  • Confluence Depth MapRio Salado

  • Confluence Cobble Cover MapRio Saladobubble size indicates % cobble cover

  • Invertebrate Data

  • Invertebrate Community Data (Global R): 0.536p: 0.001Similarity of communities positioning around confluenceMultidimensional Scaling (MDS)

    multivariate can look at community as a whole each sites 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 keycloseness implies similarity

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

  • 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

    CorrelationVariables0.330gravel, vv fine sand + silt 0.330gravel, vv fine sand + silt,v fine sand 0.321gravel, vv fine sand + silt

  • MDSsize indicates relative % gravelsize indicates relative % vv fine sand + silt

  • Confluence Sand MapRio Saladobubble size indicates % sand (by mass)

  • Confluence Gravel MapRio Saladobubble size indicates % gravel (by mass)

  • Rio SaladoConfluence vv fine sand and silt Mapbubble size indicates % (by mass)gravelsiltvv fine sand

  • Matching up to observationsRio Salado

  • ConclusionsInvertebrate communities changed through timeVariation in invertebrate communities could be correlated with substrate qualitiesThe main channel around the confluence shows high variation in substrate qualityPatterns of substrate quality match observations of tributary inputsImplications that tributary has lasting influence on habitat quality of main channel

  • Further ResearchIntermittent streams as sources of disturbance that change throughout the yearInterannual variation of precipitation and flow rates of intermittent tributariesVariability in the benthic substrate of the Rio Grande overall (temporal and spatial)

  • AcknowledgementsAyesha Burdett, Jennifer JohnsonSevilleta 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, Elida Iniguez)Brenda NietoNational Science FoundationSevilleta National Wildlife Refuge & LTER

  • ReferencesBenda, 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: 325338.Gensler, G. R. Oad, K. Kinzli. (2009). Irrigation System Modernization: Case Study of the MiddleRio 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: 25182530.Palmer, M.A., H.L. Menniger, E. Bernhardt. (2010). River restoration, habitat heterogeneity and biodiversity: a failure of theory or practice? Freshwater Biology. 55: 205222.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: 27932803.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: 25532566.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: 284296.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.

  • Questions?

    Background conceptual ideas.Define river continuum conceptBUT [click] life is more complicatedRiver continuum concept probably too simple to really capture things, for ex: Confluence place where two rivers meetMay have water at different gradient, energy and therefore cause a sudden change in the gradient. Thus, a sudden local change creating a different habitat and increasing the overall heterogeneity of the riverInstead, look at it from the perspective of a complicated, complex drainage networkAdditionally, less is known about rivers in arid and semi-arid environments.

    River continuum concept diagram: http://science.kennesaw.edu/~jdirnber/limno/LecStream/RCC.jpgRio diagram: http://nm.water.usgs.gov/nawqa/riog/images/basinmap.jpg*Hydrology of water in arid and semi arid environments is unique.precip will often occur rarely but with more at once (monsoon season) leading to the high probs that it will be enough to exceed flood thresh holds and have overland flow.Thus, in arid environment, streams that only flow occasionally intermittent are commonAn intermittent stream is one that doesnt always have flowing water in it. With enough rainfall, the river will flood and have running waterEMPHASIZE THAT ONLY SOME OF THE YEAR THERE IS WATERFlooded arroyo picture: http://farm4.static.flickr.com/3409/3571502166_53863fc588.jpg?v=0*Interested in this arid land confluence stuff: PARTICULARLY IN THE FACT THAT EPHEMERAL CONFLUENCES AND WHETHER THEY HAVE LASTING EFFECTS DESPITE THE FACT THAT THEY ARE NOT FLOWING YEAR ROUND, LIKE A REGULAR CONFLUENCE

    But Im a biologist at heart, so Im really interested in how this hydrology may be affecting the organisms present*What are the effects that an int trib confluence might have?Fluid dynamics tells us that how fast the river flows and this will change at a confluence. Sediment carriage and deposition will also be very important for a seasonal, int stream that will flow at varying rates throughout the year strong in the monsoon (such as now) and then down to none for the rest of the yearSubstrate is one of the most important characteristics that determines the stream habitatTherefore my focus will be on the benthic substrate of the rio grande main channel around this confluenceSand: http://www.tomi.com.my/products/SievedRiverSand2.jpgGravel: http://www.tomi.com.my/products/LandscapingDrainage.jpg*A bit about the Rio Grande Its important to understand! I want to look at it as a habitat (which is of course an important consideration for other aspects)Much river work focuses on gravel or c

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