Diatoms make up a significant portion of the phytoplankton biovolume in the Laurentian Great Lakes and are powerful indicators of many stressors such as nutrient pollution and climate change. Despite their ecological significance, our understanding of their taxonomy and diversity is still evolving. Recently, we named five new species of very common diatoms from the genera Fragilaria and Pantocsekiella, and we are now (re)considering species from the genus Stephanodiscus. Stephanodiscus spp. are common in the pelagic region of all five great lakes and are dominant in the spring assemblages of the more productive lakes Erie and Ontario. Several cosmopolitan species are excellent ecological indicators; for example, S. parvus and S. binderanus are often considered indicators of eutrophication. We use high-resolution microscopy to investigate the most commonly encountered species of Stephanodiscus. The results from morphometric analyses and ecological assessments of these taxa will aid in the identification and documentation of these species. By bettering our understanding of their taxonomy and morphology, we can improve our detection of these critical species and the ecological shifts that determine their presence. These early warnings are especially important in the Laurentian Great Lakes, which are facing threats from nutrient loading, anthropogenic warming, and harmful algal blooms.

Primary Presenter: Elizabeth Alexson, Natural Resources Research Institute, University of Minnesota Duluth (alexs005@d.umn.edu)

Authors:

Elizabeth Alexson, Natural Resources Research Institute, University of Minnesota Duluth  (alexs005@d.umn.edu)

Euan Reavie, Natural Resources Research Institute, University of Minnesota Duluth  (ereavie@d.umn.edu)

David Burge, Natural Resources Research Institute, University of Minnesota Duluth  (burge236@d.umn.edu)