Theses and Dissertations


Title: LONG-TERM PATTERNS IN FISH AND MACROINVERTEBRATE ASSEMBLAGES IN THE CONECUH-ESCAMBIA RIVER (ESCAMBIA COUNTY, ALABAMA)

Name: Popp, Karen Jean

Degree: MS

Chair: David R. Bayne

Resides: FAA Library

University: Auburn University

Location: Auburn, Alabama

Date: 2005

Pages: 88

Keywords: water quality, Conecuh-Escambia river, macroinvertebrate, point-source pollution

Abstract:

I examined long-term trends in water quality and lotic communities in the Conecuh-Escambia River (Escambia County, AL). My goal was to determine if municipal and industrial point-source pollution influenced downstream lotic assemblages, and to determine the role of natural and anthropogenic disturbance in the structure of lotic communities. Water quality, fishes, and macroinvertebrates were sampled at two stations, one upstream and one downstream, of municipal and industrial point-source inputs once per year over 22 years during low-flow periods. Differences between sites in assemblage persistence and stability, water quality, and assemblage structure and function were compared. Relationships between water quality, discharge, and fish and macroinvertebrate assemblages were examined using multiple regression analyses. Results indicated that fish and macroinvertebrate assemblages were persistent, but only the macroinvertebrate assemblage at the downstream site was stable. Water quality variables such as biochemical oxygen demand (BOD), soluble reactive phosphorus (SRP), nitrite-nitrogen, ammonia-nitrogen, and chlorophyll a, were significantly higher at the downstream site. Total macroinvertebrate density (specifically, collector-filterers, collector-gatherers, and shredders) was significantly higher at the downstream site. The downstream site also had higher total biomass of fishes,including gar(Lepisosteidae) and predator abundance, and sunfish, gar, insectivore, and predator biomass. Regression analyses indicated that both water quality and discharge variables were important to lotic assemblage structure, but water quality variables were more important than discharge variables. Overall trends in regression analyses illustrated several independent variables important to many fish assemblage variables, including the number of dry-season high-flow events (positive relationship) and BOD and SRP (negative relationships).

Point and nonpoint source nutrient loading from urban runoff, municipal wastewater treatment, and a paper manufacturer were occurring at the downstream site. Alterations in lotic community structure were attributed to nutrient enrichment. The effects of sustained nutrient enrichment were transferred up the food chain to the top predators. Although water flow and water quality both influenced the lotic community, water quality variables were more influential in determining assemblage structure. Urban influence likely contributed to a negative relationship among BOD and fish abundance
and biomass, and nutrient loading also may be responsible for nitrogen-limitation downstream. Although, the lotic community of was affected by nutrient loading over the study period, both macroinvertebrate and fish assemblages were persistent and resilient.

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