Protist enumerations from lakes and fiords along the northern coastline of Ellesmere Island (Ward Hunt Island observatory)

Protist samples were taken using a 6.2 L Kemmerer sampler, transferred to acid-washed, opaque 20 L plastic containers and stored in the dark at 4°C until processing. They were preserved with paraformaldehyde (0.1% final concentration) and glutaraldehyde (1% final concentration) in duplicate 50 mL polypropylene centrifuge tubes and stored at 4°C for up to 6 months in the dark until analysis; cellular features were well preserved and showed no evidence of degradation during storage. Protists were counted and identified using a combined system of fluorescence, Nomarski interference and Utermöhl sedimentation (FNU). 60 mL samples (16 mL for Lake A at 5 m on 24 August 2008, Lake B at 2 m on 24 August 2008 and Milne Fiord at 5 m on 13 July 2007) were concentrated in Utermöhl sedimentation chambers for 24 hours and stained with DAPI (0.1 mg/mL). Counts and identifications were made with a Zeiss Axiovert 100 inverted epifluorescence microscope under 400 and 1000X magnification (cells > 2 um in diameter). Cells were identified to genus wherever possible and were classified as heterotrophic when no chloroplast was observed. The microscopy detection limit was 2.67 x 10^3 cells/L. A minimum of 400 cells and 15 fields were counted wherever possible.