Presentation on theme: "Effects of the Rio Salado Confluence on Benthic Substrate in the Rio Grande Harmony Lu REU Project Summer 2010."— Presentation transcript:
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 -biological communities also change to match the local conditions -discontinuities in these gradients occur, instead view the river as a network
Background Flood events in an intermittent stream
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?
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
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
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
Research Site Sevilleta National Wildlife Refuge
Procedure 1– mapping 11 transects from the west bank to the east bank 4 samples along each transect at each site, 3 measurements: 1.% cobble 2.depth 3.sediment sample taken for texture analysis
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
Procedure – invert collection Invertebrate sampling: - sediment core sampling 4 cores of the top 1 cm of benthic substrate samples preserved in 70% ethanol
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 Day Site ChironomidaeSimuliidaeTricorythidaeBaetidaeLeptoceridaeHempiteraOdonataCladocera 11512000000 1237001000 131114030000 1417653000000
Results and Discussion Confluence map Invertebrate community Environmental influence on invertebrate community Lasting effects of the confluence
Invertebrate Community Data (Global R): 0.536 p: 0.001 Similarity of communities – positioning around confluence 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
Invertebrate Community Data (Global R): 0.536 p: 0.001 Temporal Changes – succession of species over the summer
Correlation between environment and biological communities CorrelationVariables 0.330gravel, vv fine sand + silt 0.330gravel, vv fine sand + silt, v fine sand 0.321gravel, vv fine sand + silt - 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
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
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)
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, Elida Iniguez) Brenda Nieto National Science Foundation Sevilleta National Wildlife Refuge & LTER
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