Discostella lacuskarluki (Manguin ex Kociolek & Reviers) comb. nov.: a common nanoplanktonic diatom of Arctic and boreal lakes

Abstract

Cyclotella lacuskarluki Manguin ex Kociolek & Reviers is a small diatom known only from the original drawing that provides little information on the morphology of this taxon. As Manguin’s original materials are lost, recently collected samples from Lake Karluk, Alaska, the type locality of the species, were studied with light and scanning electron microscopy to determine its identity. As a result of this investigation, C. lacuskarluki is transferred here to the genus Discostella. Discostella lacuskarluki is 2.5–7 µm in diameter, has a shallow mantle, a stellar pattern of alveoli in the valve centre that may be reduced or completely absent, bifurcating costae and 4–5 marginal fultoportulae opening externally by short thickened tubes with round openings. We observed this species in numerous lakes across Alaska, in Lake Tahoe, Nevada, in several lakes across Canada, and in tundra and tree-line lakes of Northeastern Siberia. Although direct comparison with other Discostella species is difficult because the small size of these diatoms requires high-resolution imagery to reveal ultrastructural details, it appears that D. lacuskarluki is conspecific with D. tatrica Procházková et al. recently described from lakes of Central Europe and also reported from the European part of Russia. It is also conspecific with D. nipponica (Skvotzov) Tuji & D. M. Williams known from Japan. The apparent wide distributional range of this species indicates that it has been overlooked and commonly reported as D. pseudostelligera or D. stelligera in arctic, boreal and alpine lakes.

Keywords:

• Discostella
• lakes
• Lake Karluk
• new combination
• Alaska
• Europe
• Siberia

Acknowledgements

The field trip to Lake Karluk in 2019 was organized and partially sponsored by the ANSP volunteer Gregory Aaron, who together with Cate Aaron participated in sample collection. Kodiak National Wildlife Refuge and Deputy Refuge Manager Tevis Underwood provided valuable assistance with the on-site transportation, accommodations, and safety in the field. Logistics for the 2012 Kolyma Lowland, Siberia field trip were provided by Eugene Potapov, Sergei, Galina, Nikita and Anastasia Zimov. Several samples used in this study were collected within the framework of NEON Program supported by the National Science Foundation. The US National Lakes Assessment and National Rivers and Streams Assessment samples were collected with support from the US EPA and Alaska Department of Environmental Conservation. Kathryn Longwill processed the NEON and EPA samples and prepared permanent diatom slides at ANSP. The authors gratefully acknowledge the use of the Centralized Research Facilities, Drexel University for the SEM.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplemental data

Supplemental data for this article can be accessed https://doi.org/10.1080/0269249X.2020.1727569