Traditional approaches for managing aquatic resources have often failed to account for effects of anthropogenic
disturbances on biota that are not directly reflected by chemical and physical proxies of
environmental condition. The index of biotic integrity (IBI) is a potentially effective assessment method
to integrate ecological, functional, and structural aspects of aquatic systems. A macrophyte-based IBI was
developed for Minnesota lakes to assess the ability of aquatic plant communities to indicate environmental
condition. The index was developed using quantitative point intercept vegetation surveys for 97 lakes
that represent a range of limnological and watershed characteristics. We followed an approach similar
to that used in Wisconsin to develop the aquatic macrophyte community index (AMCI). Regional adaptation
of the AMCI required the identification of species representative of macrophyte communities in
Minnesota. Metrics and scaling methods were also substantially modified to produce a more empirically
robust index. Regression analyses indicated that IBI scores reflected statewide differences in lake trophic
state (R2 = 0.57, F = 130.3, df = 1, 95, p < 0.005), agricultural (R2 = 0.51, F = 83.0, df = 1, 79, p < 0.005), urban
(R2 = 0.22, F = 23.0, df = 1, 79, p < 0.005), and forested land uses (R2 = 0.51, F = 84.7, df = 1, 79, p < 0.005), and
county population density (R2 = 0.14, F = 16.6, df = 1, 95, p < 0.005). Variance partitioning analyses using
multiple regression models indicated a unique response of the IBI to human-induced stress separate from
a response to natural lake characteristics. The IBI was minimally affected by differences in sample point
density as indicated by Monte Carlo analyses of reduced sampling effort. Our analysis indicates that a
macrophyte IBI calibrated for Minnesota lakes could be useful for identifying differences in environmental
condition attributed to human-induced stress gradients.
Beck, Marcus, W.; Hatch, Lorin, K.; Vondracek, Bruce; Valley, Ray, D..
Development of a macrophyte-based index of biotic integrity for Minnesota Lakes.
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