A voucher flora of diatoms from fens in the Tanana River floodplain, Alaska.
Climate change and human activities may alter the structure and function of boreal peatlands by warming waters and changing their hydrology. Diatoms can be used to assess or track these changes. However, effective biomonitoring requires consistent, reliable identification. To address this need, this study developed a diatom voucher flora of species found across a boreal fen gradient (e.g., pH and vegetation) in interior Alaskan peatlands. Composite diatom samples were collected weekly from three peatland complexes (rich, moderate, poor) over the 2017 summer. The morphological range of each taxon was imaged. The fens contained 184 taxa across 35 genera. Eunotia (45), Gomphonema (24), and Pinnularia (23) commonly occurred in each peatland. Tabellaria was common in the rich and moderate fens but sparse in the poor fen. Eunotia showed the opposite trend. Twenty-five percent of the species matched those at risk or declining status on the diatom Red List (developed in Germany), highlighting the conservation value of boreal wetlands. This voucher flora expands knowledge of regional diatom biodiversity and provides updated, verifiable taxonomic information for inland Alaskan diatoms, building on Foged’s 1981 treatment. This flora strengthens the potential to effectively track changes in boreal waterways sensitive to climate change and anthropogenic stressors.