In November 2006 3 shorts sediment cores from 3 fjord ecosystems located along Labrador's East coast, have been sampled from CCGS Amundsen. In August 2008 4 lakes in Saglek fjord area have been sampled. Data about the properties of the water column and short sediment cores have been taken. In November 2009, a ~8m long piston-core and a ~80cm long gravity-core have been taken in the Nachvak fjord from the CCGS Amundsen. In addition, surface sediment samples were taken through box-cores in the Nachvak, Saglek, Okak and Anaktalak fjords.The cores have been analyzed for various physical and chemical properties, such as sediment density, magnetic susceptibility and contaminant levels. The biostratigraphic analyses involved sediment sub-sampling at 1-2 cm intervals to determine changes in the composition and concentration of fossil diatoms and dinocysts throughout the marine cores, only diatoms for the lacustrine cores. The chronology of each core has been established based on AMS-14C dates on marine shells preserved within the sediments and on the radioactive decay of the 210Pb in the sediments. The surface sediment sampled in the fjord will be used to document the modern dinocyst assemblages in the area to allow more precise past climatic reconstructions.

Sampling took place on legs 6, 7, 8b, and 9 of the CFL project on the CCGS Amundsen (2008). Zooplankton were sampled with a 1x1m2 (200 µm mesh) net through the moon-pool and with a 1m diameter (200 µm mesh) ring net on the ice at ice covered stations. In open water, samples were collected with 2x1 sq.m (500 µm mesh), 4x1 sq.m (500 and 200 µm mesh), and rectangular mid-water trawl (1600 µm mesh). Samples were live sorted to species and frozen at -25C. Algae were collected from the bottom ice via ice cores and the dive program, from the ice interface/surface water with a Hg clean Niskin and a hose and pump on a 1m arm, and from the chlorophyll a maximum depth via the rosette. Samples in ice were frozen in the dark, while samples in water were filtered via dual filtration following Morrison and Watras (1999) and filters were frozen at -25C. Zooplankton species Calanus glacialis and Calanus hyperboreus were analyzed for total mercury using CVAAS; C. hyperboreus was also analyzed for methyl mercury via Gas Chromatography Atomic Fluorescence Spectrophotometry (GC AFS). The algae samples were analyzed for THg using cold vapour atomic absorption spectrometry (CVAAS) and MeHg using cold vapour atomic fluorescence spectroscopy (CVAFS).

The datasets present new data from microscopic counts and selected nutrient and physical data assembled from the following missions. Aboard the CCGS Louis St-Laurent: IPY Canada's Three Oceans 2007. Aboard the CCGS Amundsen: International Polar Year (IPY) Circumpolar Flaw Lead Study 2008; ArcticNet 2008. Temporal coverage is July-September. Cell density of the three sub-clades MAST-1A, MAST-1B and MAST-1C was measured by cell-counts using fluorescent in situ hybridization with taxa-specific probe. Biomass of phototrophic organisms, of different size classes, was obtained by counts of DAPI-stained cells under epifluorescence microscopy. Samples for total chlorophyll a (chl a) were filtered onto GF/F filters, extracted in either ethanol or acetone and analysed by spectrofluorometry. Chl a was also measured for the < 3 µm size fraction, and chl a in the < 3 µm size fraction was calculate by simple substraction. CCGS Amundsen data: Temperature, salinity, transmissivity, oxygen, and photosynthetically active radiation were provided by Dr. Y. Gratton (Institut National de la Recherche Scientifique, Québec). Nitrate and Phosphate concentrations were provided by Dr. J.-É. Tremblay (Université Laval, Québec). CCGS Louis St-Laurent data were supplied by Drs. E.C. Carmack and J. Nelson (Institute of Ocean Sciences, Sidney, B.C.). Distance to ice edge was obtained from the Canadian Ice Services (http://ice-glaces.ec.gc.ca).

An incubation experiment was conducted on board of the Canadian research icebreaker CCGS Amundsen between 6 and 15 August 2015. The water was collected near the nitracline at 38 m depth in Baffin Bay using 12-L Niskin-type bottles deployed on a CTD rosette system. A natural Arctic plankton community in a pre-bloom stage (initial high nutrient-low Chl a concentrations) was exposed over 9 days to reduced pH conditions under two contrasting light regimes. The two light regimes were designed to simulate the mean irradiance in an ice-free 5-m thick surface mixed layer (HL, marginal ice bloom conditions) and the mean irradiance at 5 m depth under a melting ponded ice pack (LL, under-ice bloom/ subsurface chlorophyll maximum conditions). The pH gradient comprised 6 levels covering the range of pH expected between the present and the year 2300. During the incubation, a phytoplankton bloom developed in every incubation bag and diatoms dominated the biomass (Chaetoceros spp.). Temporal variations of pH, dissolved inorganic carbon, total alkalinity, chlorophyll a, macronutrients, DMS(P), flow cytometry (nano- and pico-phytoplankton, bacteria, virus), taxonomy, salinity and incubator's temperature are available.

The datasets present new data from microscopic counts and selected nutrient and physical data assembled from the following cruises. Aboard the CCGS Amundsen: ArcticNet Expeditions 2006, 2008, 2009, 2010; International Polar Year (IPY) Circumpolar Flaw Lead Study 2008 and MALINA Project 2009 (French IPY project headed by Dr. M. Babin). Aboard the CCGS Louis St-Laurent: IPY Canada's Three Oceans 2007. Temporal coverage is Feb.-Nov., but varies by year, with the greatest sampling effort in July-Oct. Cryothecomonas abundance was measured by cell-counts using fluorescent in situ hybridization with a taxon-specific probe. Biomass of phototrophic and heterotrophic organisms, of different size classes, was obtained by counts of DAPI-stained cells under epifluorescence microscopy. Samples for total chlorophyll a (chl a) were filtered onto GF/F filters, extracted in either ethanol or acetone and analysed by spectrofluorometry. Chl a was also measured for the < 3 µm size fraction. CCGS Amundsen data: Temperature, salinity, oxygen, and photosynthetically active radiation were provided by Dr. Y. Gratton (Institut National de la Recherche Scientifique, Québec). Nitrate and Phosphate concentrations were provided by Dr. J.-É. Tremblay (Université Laval, Québec). CCGS Louis St-Laurent data were supplied by Drs. EC Carmack and John Nelson (Institute of Ocean Sciences, Sidney, B.C.). Distance to ice edge was obtained from the Canadian Ice Services (http://ice-glaces.ec.gc.ca).