Diatoms of North AmericaIndiana Department of Environmental Management (IDEM) recently collected data on benthic diatoms to assess diatom communities and to recognize the natural variation in assemblage characteristics across the different types of streams in Indiana (e.g., ecoregions, temperature, stream size, and geology). The diatom data used for the index development analysis included a total of 497 samples from 409 sites. The 497 samples included 709 unique diatom taxa identified by IDEM that were reconciled with standardized taxa names in the U.S. Geological Survey BioData database. Diatom taxa were associated with traits based on two sources. One source was provided by diatoms.org. The second source was a database of trait values compiled by Tetra Tech and based on literature and regional studies (van Dam et al. 1994, Kelly and Whitton 1995, among others).
With these data, IDEM and collaborators developed a diatom Index of Biotic Integrity (IBI) that would provide a diatom-based assessment of biological conditions in Indiana. A diatom IBI will enhance the state of Indiana’s monitoring and assessment strategy by adding a numeric indicator of diatom community structure that could be used to assess aquatic life use. Refer to the StoryMap link to learn about the details of defining the disturbance gradient, site classification, metric selection, index testing and performance, and condition threshold development.
To try calculating your own IBI scores, go to the IDEMtools Shiny app developed by Tetra Tech, Inc. The app allows IDEM and their partners to calculate IBI scores for diatom samples. The diatom IBIs improve IDEM’s diagnostic ability to identify degradation in biological integrity and water quality. The app is streamlined and easy to operate, and only requires an input dataset to function. Shiny apps are interactive web applications that serve as graphical user interfaces. They are linked to R, which is an open source programming language and software environment for statistical computing.
