Abstract
A commonly used method to evaluate the water quality is to calculate the property and amount of water intoxicant, or to use bio-indicators. However, few studies combine water quality analysis with bio-indicator. Recently the IFIM (Instream Flow Incremental Methodology) has been applied to evaluate habitats in Taiwan. As most of Taiwan’s rivers are heavily polluted, water quality has become the single determining factor while estimating the WUA (Weighted Usable Area) of fishes, exerting far more influence than other factors. Previous studies have focused on the influences of microhabitats (cover, velocity, substrate and depth etc). No HSC (Habitat Suitability Criteria) studies on macrohabitats have been implemented so far. The principle of AOD (Aquatic Organism Environment Diagnostics) is based on freeze-concentrating water samples to different concentrations, applying indicator organisms to the concentrated water samples, and then implementing a 48-hour bioassay. Sequentially, the fifty-percent lethal concentration (LC50) is computed and the water quality is determined. A high AOD value means low toxicity of water to aquatic organisms. In this study, AOD provides a completely quantitative measurement of various water quality parameters. The quantification allows AOD values to be analyzed against, and found statistical relationships with, water quality parameters and other water quality indicators such as diversity, richness, exotic species percentage and discharge. Therefore, AOD is more precise and better reflect bio-community changes which is due to water quality. After comparing various water quality parameters, we found that the test shrimp species (Neocaridina denticulara) is more sensitive to Ag, Cr, Cu, Ni and Sn than test fish species (Tanichthys albonubes). According AOD-HSC, we found that the exotic species (such as Tilapia and Leopard pleco) have highest tolerability for pollution (AOD=135%). Meanwhile, the establishment of AOD-HSC can provide the determining factor of macrohabitats in IFIM’s applications.