Benthic index of biological integrity (B-IBI) for the South Fork Trinity River watershed

Graduation Date

2006

Document Type

Thesis

Program

Other

Program

Thesis (M.A.)--Humboldt State University, Biological Sciences, 2006

Committee Chair Name

Michael A. Camann

Committee Chair Affiliation

HSU Faculty or Staff

Keywords

B-IBI, IBI, Multimetric index, Biological monitoring, Biological integrity, South Fork Trinity River, River health, Macroinvertebrates, Benthic, Humboldt State University -- Theses -- Biology

Abstract

The South Fork Trinity River is an undammed river in Northern California that drains a watershed with a long history of varied anthropogenic uses including mining, logging, cattle grazing, and associated road construction. These activities modify riparian and aquatic habitats by contributing sediment to rivers and altering basic environmental processes on a watershed scale. Aquatic biota respond to and integrate the effects of anthropogenic habitat alterations, many of which are generally not detected by chemical toxicity tests. The United States Environmental Protection Agency (US EPA) is charged with fulfilling the mandates of the Clean Water Act of 1972, which are to maintain and restore the chemical, physical, and biological integrity of surface waters. Indexes that use biotic indicators of stream health, such as the Benthic Index of Biological Integrity (B-IBI), meet these goals of the US EPA. This study evaluated metrics (biological characteristics) in small streams of the South Fork Trinity River for use in a B-IBI, and constructed the B-IBI using benthic macroinvertebrate data collected during the summer of 2000. The least- and most-impacted streams in the watershed were selected a posteriori using data from the preponderance of accepted metrics. Sixteen metrics were retained for the B-IBI, 14 of which were strong performers. B-IBI scores ranged from 22--74, out of a possible range of 16--80. Nonmetric multidimensional scaling (NMDS) ordination of the benthic invertebrate taxa abundance data provided an alternative assessment of the relationships of streams relative to each other, and generated hypotheses about land management activities most strongly impacting biological integrity in streams surrounded by late seral forests. The two lowest-scoring late-seral reaches had high watershed temperatures and greater amounts of coarse woody debris (CWD). The other low-scoring late-seral reaches had relatively high watershed road densities. The most efficient way to increase biological integrity in these streams would be to address those activities most strongly correlated with the streams' extreme positions on the NMDS axes. High-scoring late-seral streams were not correlated with extremes of the ordination axes, indicating the absence of high road densities, hotter watershed temperatures, and high amounts of CWD.

https://scholarworks.calstate.edu/concern/theses/kh04ds25v

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