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Diatoms of the United States is now known as Diatoms of North America.
This site has been redesigned and updated, and will be closing soon.


Identification Guide and Ecological Resource for Diatoms of the United States

The primary purpose of this publicly accessible resource is to provide analysts with accurate information on taxonomy, nomenclature, and ecology of diatoms to help federal and state agencies in the United States comply with the Clean Water Act. However, a basic problem arises when trying to provide this information.

The Problem

Diatom species composition and abundance are well known indicators of the biotic condition of freshwater streams and lakes and are used to monitor environmental stresses including human impacts on watersheds. Diatoms commonly grow on submerged surfaces, a growth habit known as the periphyton (see our glossary). The U.S. Environmental Protection Agency (USEPA) recognizes the value of monitoring the periphyton and now advises state and federal agencies to include it together with aquatic invertebrates and fish in biological assessments used to comply with the Clean Water Act. Many states now include the periphyton in their assessments.

Until recently accurate information on diatoms of North America has not been available. The lack of recent taxonomic and ecologic research on North American diatoms has encouraged these diatom analysts to routinely use European taxonomic resources to identify North American diatoms, which may or may not exist in North America. This has led to a situation where species are sometimes misidentified and where analyses across federal and state programs sometimes lack consistency.

Our Solution

This web-based resource attempts to improve the diatom information for North America for use by analysts and the public.

Genesis, Community Support and Collaboration

This project was initiated with a grant from the USEPA Office of Research and Development through the regional Environmental Monitoring and Assessment Program (EMAP) in 2007. We set out to produce an innovative website backed by a robust database to accommodate a large number of taxonomic records. In the process of developing and planning the site our vision expanded to incorporate a unique visual key, a means for non-specialists to gain access to understanding of critical diatom species. We began by thinking about a regional database centered on the western United States with the goal of presenting a taxonomic and ecological resource on diatoms. As our vision expanded, we had inevitable delays during development but we also gained substantial interest and support from the scientific community of diatomists.

With the added support of the National Water Quality Assessment Program of the U.S. Geological Survey (NAWQA), the Academy of Natural Sciences of Drexel University, and other academic institutions, we were able to expand the scope of the project even before the first version of the site was launched. Beginning in 2014, the USEPA Biological Criteria Program partnered with the NAWQA program to 1) build analyst capacity through a series of workshops and 2) support taxonomic research resulting in the "content" for species pages. With this support, the Diatoms of the US web flora is able to serve as the national resource, and standard, for diatom taxonomic identification. With their continuing support, the database and website have also been expanded.

We have also established an Editorial Review Board with a formal process for reviewing the species taxon pages. The content that you see on species pages has been prepared by an expert diatomist and reviewed by at least one member of the review board.

Site FAQ

Our list of Frequently Asked Questions (FAQ) serves as further guide to using the site, specific questions on content, and information on the database and code.