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Desertification, salinization, and biotic homogenization in a dryland river ecosystem
Seiji Miyazono1, Reynaldo Patiño2, Christopher M Taylor3
1Texas Cooperative Fish and Wildlife Research Unit, Texas Tech University, Lubbock, TX 79409-2120, USA.
The Science of the Total Environment
|January 9, 2015
Summary
Decreasing flow and increasing salinity in the Rio Grande, driven by reduced Rio Conchos discharge, caused significant biotic homogenization of fish assemblages in this dryland river ecosystem.
Area of Science:
- Ecology
- Environmental Science
- Hydrology
Background:
- Dryland river ecosystems face unique challenges from fluctuating water availability and quality.
- Biotic homogenization, the process by which species become more evenly distributed, is a growing concern in aquatic ecosystems.
- The Rio Grande/Rio Bravo del Norte is a critical transboundary river system experiencing significant environmental changes.
Purpose of the Study:
- To determine long-term changes in fish assemblages, river discharge, and salinity in the Rio Grande.
- To examine the hydrological drivers of biotic homogenization in this dryland river.
- To compare historical and current fish community data to assess ecological shifts.
Main Methods:
- Analysis of historical (1977-1989) and current (2010-2011) fish assemblages using rarefaction, NMDS, MRPP, and t-tests.
- Examination of hydrological trends (1970s-2010s) using Kendall tau and quantile regression.
- Generalized linear models to associate streamflow with specific conductance (salinity).
Main Results:
- Fish species richness and assemblage variability decreased in the Rio Grande below the Rio Conchos confluence.
- Homogenization occurred due to increased abundance of low-flow/high-salinity tolerant species, primarily native.
- Decreased Rio Conchos discharge led to reduced Rio Grande flow and increased salinity below the confluence.
Conclusions:
- Reduced discharge from the Rio Conchos has significantly altered Rio Grande hydrology, increasing salinity.
- These hydrological changes are the primary drivers of biotic homogenization in the fish assemblages.
- The study highlights the impact of altered tributary flow on downstream ecological integrity in arid regions.
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