Water Quality, Ecology, and Evaluation of a Rapid Algae Monitoring Technique in Human-Controlled Water Bodies

Abstract

Increasing urbanization worldwide has led to increased water body alterations, including the discharge of effluent into aquatic ecosystems. As the world’s population continues to grow, the development of new wastewater treatment plants will be crucial and the discharge of effluent into water bodies will increase. Despite this growing trend, the impacts of effluent on receiving water bodies are still relatively poorly understood. This dissertation (1) reviews the effects of effluent input into streams across the globe, (2) examines how water quality in effluent-dependent streams varies spatially and temporally in Arizona, and (3) tests a potential new rapid water quality monitoring technique for better management of these systems. Across the globe, effluent inputs generally impaired water quality in streams near effluent discharge points. The majority of ecological studies reviewed found that basal resources, aquatic invertebrates, and fish were negatively affected in a variety of ways (e.g. biodiversity losses, replacement of sensitive with tolerant species). However, several studies showed the importance of effluent in providing environmental flows to streams that had been dewatered by anthropogenic water withdrawals, especially in semi-arid and arid regions. Our study of effluent-dependent streams in Arizona indicates that conditions may be stressful for the most sensitive taxa at sites closest to effluent outfalls (e.g. elevated temperature and nutrient level), especially in summer. However, overall, these streams have the capacity to serve as refuges for native biota in Arizona. Furthermore, they may become the only aquatic habitat available in many urbanizing arid regions. The combination of elevated temperatures and nutrient levels we observed closest to effluent outfalls could lead to increased frequent algal blooms. Our evaluation study of a hand-held fluorometer to measure chlorophyll-a as an indicator for potential harmful algal bloom demonstrated that the probe is not sensitive to ambient light, performed well at low chlorophyll-a concentrations (< 25 µg/L) across a range of turbidity levels (50 to 70 NTU), and with some adjustments would be useful for monitoring in effluent-fed streams or other water bodies. Although effluent-fed streams were historically of lower quality than natural streams, newer treatment techniques can result in high quality water and support numerous native species and diverse ecosystems despite our increasingly dry climate.