Diversity of benthic macroinvertebrate communitues at tributary confluences of the Pecos River

Authors: Kelbi D. Delaune, Scott Longing, Allison A. Pease

Year: 2016 (xlviii)

Abstract

Tributary streams offer basal resources for aquatic food webs and unique habitats to taxa that differ from the mainstem of the river. Because of this, many tributary confluences are known to be biological ‘hot spots’ for species diversity, making them important for river conservation strategies. This is especially true for rivers in arid regions where resources are limited and anthrop ogenic influences are often great, as stream tributaries may serve as refuge locations for biota. The Pecos River flows from New Mexico through Texas, and offers an ideal study system to investigate diversity in stream tributary junctions across both natural and impacted conditions. In this study, we explored the effects of tributary confluences on the diversity of benthic macroinvertebrate assemblages across four sites that encompass a range of habitat conditions. Our study sites were at the confluences of Taiban Creek, Rio Hondo, Black River, and Independence Creek. Across sites, we found an increase in macroinvertebrate diversity both at and below the tributary confluence. This difference was most pronounced for the Independence Creek and Black River sites, whe re coarse substrates and riffle habitats supported relatively high diversity. Total phosphorous levels decreased below tributary confluences except Independence Creek, where levels were too low to be detected. The Taiban Creek confluence had the highest levels of phosphorous, followed by the Black River and Rio Hondo confluences. These findings support other studies showing that tributaries influence in-stream habitat characteristics and macroinvertebrate diversity in rivers.