Stauroneis terryi D.B. Ward ex T.C. Palmer: a forgotten diatom from northeastern North America

Stauroneis terryi D.B. Ward ex T.C. Palmer is a diatom so far reported from only five locations in the states of Connecticut, Massachusetts and Maine, USA, where it was collected in 1890—1911. There were no records of this large and rather conspicuous species in any collections made after 1911 despite the considerable number of diatom surveys and paleolimnological studies conducted in the northeastern USA. We studied material from the type locality of this species to document its morphology with SEM, and screened diatom slides representing recent and subfossil samples collected from 169 lakes in northeastern North America from 1979 to 2017 for the presence of this species. Using both whole-slide scanning and traditional microscopy, we detected S. terryi in 15 lakes in the northeastern USA north of 41° N latitude and in five lakes of Labrador and adjacent Quebec, Canada. In the USA, S. terryi populations have declined since pre-industrial times, although the species is still present in a few lakes with relatively undisturbed watersheds. Our observations demonstrate the value of museum collections for generating data on diatom ecology and biogeography and the need for the development of high-throughput methods of extracting information from diatom slides and images.