Biology ETDs

Publication Date

5-1-2009

Abstract

The Middle Rio Grande is the second largest watershed in the southwestern United States and is a vitally important component for the biodiversity in the region. Similar to many other rivers, the MRG is a temporally dynamic system that unfortunately, has been subjected to river regulation. As a result, the river has become channelised in many reaches disconnecting it from the surrounding floodplain. The effects of river regulation on the MRG and its surrounding riparian zone were largely unknown. I tested three main hypothesis with regards to the macroinvertebrates in the MRG: 1) Does flow variability structure the aquatic macroinvertebrate community; 2) Does flow variability affect lateral subsidies and food web dynamics of terrestrial and aquatic macroinvertebrates; and 3) Does channelisation affect the linkages between the aquatic and terrestrial systems with a focus on lateral subsidies and arthropod predators? Five years of survey data and stable isotope analyses of the common macroinvertebrates and arthropod predators was used to address these hypotheses. During the course of this study period there was a large amount of variability in discharge having a significant impact on the macroinvertebrate community. Higher densities of macroinvertebrates were associated with lower discharge. Drought and flooding reduced the density of macroinvertebrates. Lateral inputs between the aquatic and terrestrial systems were also highest during times of low discharge and were reduced during higher discharge. The transition zone harbored higher rates of predators. Stable isotope analyses indicated that predators near the waters edge were heavily subsidized by lateral inputs from algae production. In channelised reaches, aquatic and terrestrial macroinvertebrate densities and richness were lower. The riparian zone and the wetted channel are intricately linked together and processes that occur in the river affect the surrounding riparian zone. Consequently, channelisation may be a threat to diversity by negatively impacting transition zone communities and adversely affecting predaceous arthropods.

Project Sponsors

Freshwater Sciences Integrative Doctoral Program funded by the Integrated Graduate Education and Research Training grant from the National Science Foundation The Cliff Crawford Scholarship from the University of New Mexico

Language

English

Keywords

aquatic invertebrates, lateral subsidies, river regulation, allochthonous inputs, flooding, drought, disturbance

Document Type

Dissertation

Degree Name

Biology

Level of Degree

Doctoral

Department Name

UNM Biology Department

First Committee Member (Chair)

Collins, Scott

Second Committee Member

Jacobi, Gerald

Third Committee Member

Gutzler, David

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