Pigments phytoplanctoniques de lacs et de fjords du nord de l'île d'Ellesmere, Nunavut, Canada

Phytoplankton communities in Arctic lakes and fiords are diverse despite oligotrophic conditions. Phytoplankton pigment analyses allow the estimation of the potential primary production of aquatic ecosystems with chlorophyll a concentration (biomass). This method is also used to describe the composition of the phytoplankton community as signature pigments are known to be present only in specific phytoplankton groups. Finally, phytoplankton pigment concentrations reflect the physiological status of phytoplnakton as some carotenoids are photoprotectors, while others are photosynthetics. As an exemple, a high zeaxanthin to chlorophyll a ratio may indicate a photoprotection strategy induced by increased irradiance. It is essential to study phytoplankton dynamics as changes in primary production or species composition can indicate changes in the environment (e.g. climate warming or nutrient enrichment). This Nordicana D issue consists of phytoplanktonic pigment concentrations of lakes and fiords located on the northern coastline of Ellesmere Island. These aquatic ecosystems have been sampled at different depths since 2005. These data are used to evaluate changes in biomass and in the community composition vertically, between years and between lakes. We also aim to understand the phototrophic characteristics of these water columns. Water samples (0.35-1.05 L) for high-performance liquid chromatography (HPLC) were taken in lakes and fiords with a 6.2 L Kemmerer sampler or a 7 L Limnos sampler at different depths. Samples were transferred to plastic containers and transported back to a field laboratory. Samples were always keep in the dark. Samples were filtered onto 25-mm-diameter GF/F glass fibre filters that were frozen immediately in the field in a Dry Shipper (-80 °C) and subsequently stored in a -80 °C freezer until analysis. Pigments were extracted from the frozen phytoplankton filters by sonication, cleared by centrifugation, and filtered with PTFE syringe filters (pore size 0.2 µm) into HPLC vials. Shortly following extraction, 100 µL of phytoplankton pigment extracts were injected into an HPLC system.