ENV330H5 Lecture Notes - Lecture 2: Indicator Species, Spatial Gradient
Document Summary
Levels of exposure to mine effluent should differ between exposure and reference areas but should be similar among the stations within each area. Habitats should be as similar as possible in terms of substrate, depth, current velocity, water properties, environmental gradients, land use, etc. Works for simple, homogeneous rivers and streams without confounding upstream or near- site discharges from other sources. Two of the major problems associated with the use of a single reference area: 1. it can be easily confounded by other factors. 2. there is a lack of independence among the stations in a single reference area (pseudo replication) Multiple control-impact (mc-i) designs help overcome these problems. Additional reference areas should be in adjacent watersheds or bays. Should have habitat types spanning the range of habitats found within the exposure area(s) Get a better sense of the natural variability in the system. Might be too variable harder to detect a signal in the impact area.
