New Directions in Aquatic Plant Assessment: Standard Methodology for Describing Species Abundance Patterns and Community Dominance

Both the abundance and composition of macrophyte communities affects habitat, recreation, angling, aesthetics, and water quality.  Due to historic challenges of quantitatively assessing macrophyte abundance, practitioners have used a variety of qualitative methods generating little more than species lists and relative abundance for a few sampled areas in lakes.  Due to advances in GPS, GIS, and hydroacoustic technology, practitioners are employing more comprehensive quantitative methods of assessing aquatic plants.  We describe new standardized methodology for simultaneously assessing both macrophyte abundance and species composition.   Using data from 22 lakes across the US, we describe a dominance index that incorporates both species composition and vegetation biovolume in order to evaluate the degree that an invasive species dominates a local assemblage. We found that the extent of aquatic plant growth and invasive dominance was related to lake productivity with highest biovolume and dominance occurring in meso- to eutrophic study lakes.  We also found no significant differences between dominance calculated from a simple metric that gives equal weight to all species at a survey site and a metric that incorporated rake fullness.   Given the standard, repeatable methodology and automated data processing, “big data” models can be built with widespread adoption.