Image Analysis Techniques to Evaluate Effects of Nearshore Lake Development on Aquatic Macrophytes

Recent development of multimetric biological indices for lakes has improved the ability to detect impacts of multiple stressors on aquatic organisms.  However, integrating these indices within water quality programs is challenging because a biological response does not explicitly indicate causes of impairment.  A paucity of quantitative techniques to understand mechanisms of biological response and inadequate stressor data are challenges that need to be addressed before causes of biological impairment can be identified.  Moreover, the increasing rate of nearshore lake development in Minnesota is expected to negatively impact aquatic organisms and is a concern for managers responsible for maintaining biological integrity.  The effects of nearshore development on aquatic plants have particular importance because macrophytes provide habitat for fish and other aquatic biota.  Advanced image analysis techniques that focus on objects at spatial scales relevant to aquatic plants, such as docks or beaches, could be used to more accurately quantify stressors.  As such, we developed an approach for image analysis of nearshore areas to quantify stressors from aerial photos at 1m resolution.  These stressors will be used to model the behavior of a macrophyte-based index of biotic integrity developed for lakes in Minnesota.  Results indicate that these techniques can efficiently and accurately extract nearshore land use data at ecologically relevant spatial scales.  These techniques will ultimately provide managers with adequate data on nearshore stressors to facilitate implementation of biological remediation in water quality programs.