Indiana lakes as a model for the use of aquatic macrophyte community information in the development of indexes for the assessment of lake quality

Mitchell Steven Alix, Purdue University

Abstract

Indiana lakes were used as a model to study the use of aquatic macrophytes in the determination of floristic and habitat quality of lacustrine systems, which resulted in the modification of the floristic quality assessment (FQA) methodology to adequately evaluate quality conditions in a lake ecosystem context and the development of the index of aquatic macrophyte community quality (IAMCQ). Problems with the application of standard FQA methodology to lakes were identified as low taxa richness, the exclusion of charophytes and non-native taxa, and the absence of the calibration of threshold values. By addressing these issues, the diagnostic resolution of FQA should substantially improve. In the present study, the adequacy of FQA methodology was enhanced by (1) defining coefficients of conservatism (C values) for 137 aquatic macrophyte taxa, including 17 species of charophytes, (2) calibrating threshold values of the floristic quality index (I) by applying FQA with the aforementioned C values to 42 natural lakes, and (3) developing a novel approach to assess the impact of non-native aquatic macrophyte taxa by using quantitative measures of their relative frequencies. The development of the IAMCQ resulted from an evaluation of the plant index of biotic integrity (PIBI) and the aquatic macrophyte community index (AMCI). Twelve metrics out of a possible 30 were established and defined across two groups of attributes. The richness and diversity attribute was composed of three negative metrics and three positive metrics. The littoral zone composition and abundance attribute was composed of one fixed metric, three negative metrics, and two positive metrics. None of the 12 metrics were highly correlated with another, so all of them were retained in the index. Floristic surveys of 20 lakes used in the development of the IAMCQ resulted in the documentation of 85 taxa, including 16 state-listed taxa, 11 charophytes, four non-native species, and one hybrid pondweed. Results were presented in terms of taxonomic enumerations and frequency of occurrence and discussed in terms of transformations of associated metric values to scores and conversions of scores to index values. Considerations and limitations associated with the development and use of the IAMCQ were presented.

Degree

Ph.D.

Advisors

Lembi, Purdue University.

Subject Area

Botany|Limnology

COinS