Path modeling analysis for the understanding of stream water quality and fish diversity in the Great Lake surrounding areas

Abstract

Fish richness and diversity serve as important indicators of a healthy stream ecosystem, which are influenced by a complex web of ecological factors, including regional climate, watershed characteristics, riparian zone quality, and water quality. Investigating how these factors interconnect and impact fish community is crucial for developing effective management strategies to safeguard freshwater ecosystems. In this study, we used partial least squares regression to develop a causal understanding of how watershed development and climate factors affect fish richness and diversity by altering water temperature, pH, conductivity, total nitrogen, and total phosphorous (TP) in 277 watersheds in the Great Lakesurrounding areas. After identifying TP as a potential threat to fish biodiversity, we examined how watershed land use, slope, and soil interacted to drive changes in TP concentration with multiple linear regression. Results suggested that moderate watershed development (average 5% developed percentage in the study site) can enhance fish diversity by increasing pH, temperature, and conductivity. However, watershed development and riparian degradation diminished fish diversity by increasing nutrient concentrations. We also found that landcover-slope interaction was an important factor affecting TP concentration, while landcover-soil interaction was not significant. Future ecosystem management in the study area should therefore emphasize a dual focus on watershed management approaches and riparian zone preservation to improve fish diversity and stream ecosystem health.