Become a diatom taxonomist, certified by the Society for Freshwater Science.

The Level 1 Diatom Taxonomic Certification indicates an up-to-date working knowledge of the diagnostic characteristics of North American inland diatom genera based on The Level 2 certification indicates a working knowledge of species identification.

The Society of Freshwater Science Taxonomic Certification Program was implemented to certify that trained and skilled people are providing aquatic identifications in North America. The Stroud Water Research Center currently administers the Taxonomic Certification Program for SFS. The successful completion of the taxonomic certification process results in a certificate of proficiency in performing taxonomic identifications of inland diatoms that stands for 5 years.

The program also helps promote undergraduate and graduate training of new taxonomic experts, training of taxonomic technicians through workshops, development of new manuals for identifying aquatic invertebrates and algae, and taxonomic excellence in other disciplines and other parts of the world.

BACKGROUND: The Diatom Taxonomic Certification Committee (Diatom TCC) led by Sylvia Lee, has worked to develop the first exam as one of a series of exams of diatom certification. The committee (Sylvia Lee, Melissa Vaccarino, David Burge, Julianne Heinlein, Mark Edlund, Jan Stevenson and Sarah Spaulding) have been meeting regularly over the past years to develop details of certification.


The Level 1 exam is based on composite light and electron micrograph images of diatom genera. Participants can learn about the genera included in the exam and the exam format. A practice test is available to learn the style of the exam and the software that operates it. The taxonomic treatment of the exam will be based on this website, Be sure to visit the links on this page for study material.


Level 2 Diatom Taxonomic Certification indicates knowledge of 1) variation in diatom morphology within a species, 2) morphological operational taxonomic units (mOTUs), and 3) basic concepts of diatom nomenclature. A Level 2 Certification is intended to indicate a practical base for using a voucher flora to identify inland diatoms. The primary goal of the Level 2 exam is to acknowledge a practitioner’s proficiency in the skills used to distinguish mOTUs, identify specimens that should not be included in an mOTU without further investigation, assign formal scientific names to mOTUs using, and an understanding of basic rules of botanical nomenclature.

There are three sections in this exam. In section one, 3-5 images of diatoms within a morphological size series are placed on the left. You will be asked if the specimen on the right belongs to the size series. Respond to the question based on the morphological range shown by the images grouped together. Do not consider species or morphological concepts beyond those illustrated. For example, do not use taxonomic keys, voucher floras, publications, or your personal collections which may show different size ranges and morphological variation.

Section two shows a series of diatom images that the Diatom TCC considers to belong to a single taxon. You will respond by entering the formal scientific name of the taxon. Each taxon is represented on at Include the genus name, specific epithet, and if applicable, the interspecific name (e.g., variety, subspecies, form). It is strongly recommended to copy and paste the taxon name from The exam administrator will resolve issues related to spelling. In most cases, incorrect spelling of taxonomic names will not be accepted.

The questions in section three are structured as multiple choice. You will be asked to a) select the one complete and correct scientific name from four options, or b) determine the one correct basionym from four options. Go to to find the information needed to answer these questions.

All questions in the first two sections of the exam will contain an image and a link. The displayed test image is a lower resolution quality, but can be tapped to enlarge.

ADDITIONAL DETAILS: The Level 1 exam includes 60 questions and participants will have 120 minutes to complete the questions. The Level 2 exam is proposed to include 100 questions and for participants to have 180 minutes (3 hours) to complete the questions (subject to change depending on community feedback). We hope to gain feedback from a wide range of participants so that the Level 2 exam is a fair measure of expertise in diatom species identification. Both exams are offered online, at the Society for Freshwater Science annual meeting, and at biannual North American Diatom Symposium meetings. Both exams require a score of 95% for certification or a score of 90% to retake the exam at no additional fee.

COST: The Level 1 exam fee is set at $100 ($75 for Society for Freshwater Science members). The Level 2 exam fee is to be determined. Additional information about examination fees can be found on the Stroud website.

FOR MORE INFORMATION: Contact [email protected]