1 The Green Edge cruise : Understanding the onset , life and fate of the Arctic phytoplankton spring bloom

The Green Edge project was designed to investigate the onset, life and fate of a phytoplankton spring bloom (PSB) in the Arctic Ocean. The lengthening of the ice-free period and the warming of seawater, amongst other factors, have induced major changes in arctic ocean biology over the last decades. Because the PSB is at the base of the Arctic Ocean food chain, it 70 is crucial to understand how changes in the arctic environment will affect it. Green Edge was a large multidisciplinary collaborative project bringing researchers and technicians from 28 different institutions in seven countries, together aiming at understanding these changes and their impacts into the future. The fieldwork for the Green Edge project took place over two years (2015 and 2016) and was carried out from both an ice-camp and a research vessel in the Baffin Bay, canadian arctic. This paper describes the sampling strategy and the data set obtained from the research cruise, which took place aboard the 75 Canadian Coast Guard Ship (CCGS) Amundsen in spring 2016. The dataset is available at https://doi.org/10.17882/59892 (Massicotte et al., 2019a).


Introduction
The Arctic Ocean is currently experiencing unprecedented environmental changes. The increase of the summer ice-retreat lengthens the phytoplankton growing season but also increases the area of the marginal ice zone (MIZ). If trends are 80 maintained, the MIZ may cover the entire Arctic Ocean as early as twenty years from now (Meredith et al., 2019). Ice edge blooms represent much of the annual phytoplankton primary production in the Arctic Ocean (Perrette et al., 2011;Ardyna et al., 2013), and their current phenology is relatively well known (Wassmann and Reigstad, 2011;Leu et al., 2015). However, we currently do not know how precisely primary production will respond to climate changes. The overarching goal of Green Edge was to understand the processes that control an arctic PSB as it expands northward, and to determine its fate through the 85 investigation of related carbon fluxes. This study was also motivated by the discovery that PSBs can and do occur underneath the ice (Arrigo et al., 2014) despite the limited amounts of underice available light (Mundy et al., 2009;Arrigo et al., 2014;Lowry et al., 2014;Assmy et al., 2017. Field studies for the Green Edge project were carried out in 2015 and 2016 at an ice-camp located on landfast sea ice close to Qikiqtarjuaq (NU, Canada). Additionally, during spring 2016, a cruise aboard CCGS Amundsen was conducted in Baffin Bay. As explained in Randelhoff et al. (2019), Baffin Bay is 90 both relatively easy to access and represents an ideal framework for this study, because environmental conditions are representative of what is observed at the pan-arctic scale. Particularly, the warm Greenland current flowing north on the Greenland side, and colder waters on the Canadian side flowing south (Baffin Island current) induce an evenly retreating ice edge, allowing a straightforward sampling strategy. Here, we present an overview of the dataset gathered during this cruise.

Study area, sampling strategy and ship-based operations 95
For logistical reasons, the cruise was divided into two legs. Leg 1A started on June 3rd in Québec City, ended on June 23rd in in Iqaluit (NU) on July 14th. During the five-week period spent in the Baffin Bay, the ship crossed the MIZ, from open waters (in the east) to sea ice-covered areas (in the west) and back again following latitudinal transects. A total of seven transects were covered between 68.0° N and 70.5° N (Fig. 1A). Three transects were covered during Leg1A (68.5° N to 69.0° N) and 100 four during leg 1B (68.0° N and 69.5° N to 70.5° N). For each transect, stations were separated by six nautical miles (approximately 11 km) to obtain a relatively high spatial resolution. Fifteen to twenty-five stations were sampled within each transect, for a total of 144 stations visited during the campaign.
The activities conducted at each type of station are detailed in Table 1. Briefly, at so-called CTD (Current Temperature Depth) stations, rosette casts did not include seawater collection. The rosette, a Sea-Bird model 32 carousel equipped with twenty-two 105 12-L Niskin bottles, was geared with multiple sensors (see Table 2 for details). At NUT stations, seawater samples were additionally collected at several depths between 2 and 2000 m for nutrient analyses. At BASIC stations, the apparent optical properties of seawater were measured using underwater profiling optical instruments. The variables measured at BASIC stations included the concentration of chlorophyll, phytoplankton pigment, particulate carbon and nitrogen, and particulate absorption spectra. Finally, at FULL stations, a suite of measurements was made on seawater samples, and several underwater 110 instruments were deployed as well. Vertical plankton nets geared with a plankton imager, horizontal net trawls, benthic trawls and Ursnel box corers were also deployed at each FULL station. Note that the number of variables measured on seawater samples was significantly larger at FULL stations, where three rosette casts were necessary to cover the demand in water volume, compared with one rosette at BASIC stations (see Table 3). At least one FULL station was sampled in each of the three major domains covered by each transect, namely open waters, the MIZ and the ice-covered area. A schematic synopsis 115 of all operations carried out during the campaign can be found in Fig. 2. During Leg 1B a larger emphasis was placed on collecting ice-cores for analyses and measurements of light propagation through the ice and snow. FULL stations sampled in the ice-covered domain did not include trawling operations.
Our sampling strategy allowed successive crossings of different PSB stages: the early-bloom stage at the western end of transects covered in sea-ice, late-to post-bloom stages at the eastern end of transects in open waters, and full-bloom stage in 120 the middle of transects around the ice edge (see Randelhoff et al., 2019). Between the stations, the ship-track water monitoring system (TSG SBE45 from Sea-Bird, WETStar fluorometer from WetLabs, LiCOR non-dispersive infra-red spectrometer (model Li-7000), Campbell Scientific CR1000 data logger) recorded temperature, salinity, chlorophyll a fluorescence and pCO2 at 7 m depth continuously when navigating outside the ice pack. A moving vessel profiler (MVP300-1700, AML Oceanographic, Victoria, BC Canada), equipped with a micro CTD (AML), a WetLabs C-Star transmissometer and a WetLabs 125 Eco-FLRTD fluorometer, was deployed in open waters.
To significantly extend the monitoring of the PSB beyond the duration and space covered by the cruise, we deployed four and communication system as the BGC-Argo floats, rendering the possibility of inter-calibration (Fig. 3). Gliders were primarily used in the MIZ where a 90-m icebreaker would disturb the fragile hydrological structure of shallow under-ice water masses. Gliders were deliberately directed through the same area as the BGC-Argo floats to compare CTD and optical data from both platforms. Results in Fig. 3 show a good agreement for the data. Gliders travel following a programmed sawtooth pattern, joining pre-defined waypoints. Data and instructions were transmitted both ways via iridium when the glider surfaced. 145 Figure 4 shows an example of the level of detail provided by the gliders when travelling through complex water structures.
Representing chlorophyll fluorescence measured over a three-week journey covering almost 500 km, the data show that the glider(s) did travel through both surface blooms and a subsurface chlorophyll maximum between 20-50 m. The data presented in Fig. 4 represents 693,000 chlorophyll fluorescence measurements. These constitute robust results towards the validation of the use of multiple measurement platforms to investigate complex systems. 150

Data quality control and processing
More than 150 variables were measured during the Green Edge cruise (Table 3). One of the challenging tasks, when assembling data from a large group of researchers, is to adopt a common frame for spatial and temporal tagging of samples. In particular, geographic positions require a lot of attention and conversion of latitude and longitude into one format (we used decimal degrees east) to ensure data could be easily merged. The concomitant use of local time and coordinated universal time (UTC) 155 during the cruise also represented a challenge. For the Green Edge cruise, an operation logbook was created to keep track of all operations conducted on the ship in sequential order during each day (local time). Each operation was associated with a unique operation ID to which all other data could be referenced. The use of ordinal date (number of days since January first) was used to avoid confusion between European and American date writing conventions. Each cast within a given operation type (CTD/RO for Rosette, AOP for Apparent Optical Properties, etc.) was numbered sequentially, starting from 001, 160 throughout the entire cruise. As a result, any given operation received a unique code which thereafter could be used to merge all the data acquired during that operation.
Different control procedures were adopted to ensure the quality of the data. First, the raw data were screened to eliminate errors originating from the measurement devices, including sensor (systematic or random) errors inherent to measurement procedures and methods. Instrumental pre-and post-calibration corrections were applied when necessary. Statistical 165 summaries such as average, standard deviation and range were computed to detect and remove anomalous values in the data.
Then, data were checked for duplicates and remaining outliers. Once raw measurements were cleaned, data were structured and gathered into single comma-separated values (CSV) files. Each of these files was constructed to gather variables of the same nature (ex.: nutrients). In each file, a minimum number of variables (columns) was always included in order to make dataset merging easier and accurate (Table 4).  Fig. 5). A major change in wind patterns happened between Leg 1A (June, light 1-2 m s-1 southward winds) and 1B 180 (July, 4-5 m s-1 northward winds), which impacts sea ice movements and potential changes in MIZ location. Figure 6 shows sea-ice cover over four periods covering the total sampling time of the cruise (https://nsidc.org/data/g02186). The north-south general orientation of the ice edge is visible, along with, over time, the westward progression of the MIZ.

July in
Ice cover history was compiled and expressed as Open Water Days (OWD) before sampling day (Fig. 7), calculated from the difference (in day number) between the date of sampling and the date at which the sea-ice concentration reached 10 (panel A), 185 50 (panel B) and 80 % (panel C) in the geographical location under study. Ice concentration data was obtained from the advanced microwave scanning radiometer (AMSR) -2 sea-ice concentration data on the 3.125 km grid (Spreen et al., 2008), downloaded from http://www.iup.uni-bremen.de:8084/amsr2data/asi_daygrid_swath/n3125/ (see Randelhoff et al.,

Sea ice
During sea-ice sampling operations, snow depth, ice thickness and freeboard were measured at each ice coring site. Over the cruise, ice thickness varied between 32 and 108 cm, while freeboard varied between 10 and -8 cm. Several cores were retrieved at each site using a 9 cm diameter Mark II ice-corer (Kovacs Enterprises Inc., Roseburg, OR USA). Each ice core was sliced 200 into 10 cm segments after temperature was measured. Salinity was assessed after thawing and filtration using a salinometer

Water masses
Hydrological conditions during the cruise were determined using several tools. A moving vessel profiler (MVP) was deployed, 205 oscillating between 0 and 300 m depth while towed at an average speed of 12 knots, rendering a very high spatial resolution ( Fig. 8 bottom row, one profile every 2 km). Data obtained with the MVP matched the patterns observed from the rosette data acquired on sampling stations ( Fig. 8 middle row). Profiles of conductivity, temperature and pressure were collected using a Sea-Bird SBE-911Plus CTD system rigged on the rosette. The data were post-processed according to the standard procedures recommended by the manufacturer and averaged over 0.2 m vertical bins (Guillot, 2016). While there was a sharp transition 210 in SIC at the ice edge along transect 300, the change in SIC was less steep in the more extensive MIZ of transect 500 (top row in Fig. 8). Nonetheless, both transects show similar patterns, with 100 % SIC, colder (below -1 °C) and fresher (salinity below 33.5 g kg-1) waters close to the surface on the western side, and 0% SIC, saltier (above 33.6 g kg-1) and warmer (above 0 °C) waters within the first 50 m on the eastern side. These observations were consistent with the northward inflow of Atlanticorigin waters along the Greenland shelf break, and the southward outflow of Arctic/Pacific-origin waters along the Baffin 215 Island shelf break.
Currents in the water column were measured using a hull-mounted 150 kHz Acoustic doppler current profiler (ADCP, Teledyne RD Instruments Ocean Surveyor, California, USA), as well as two L-ADCP installed on the rosette structure (RDI,

Chemistry
Partial pressure of CO2 (pCO2) was measured continuously (every two minutes) using a Li-7000 CO2 analyzer (LICOR, Lincoln NE, USA) coupled to a General Oceanics Underway System model 8050 (General Oceanics, Miami FL, USA) 225 connected to the ship-track water monitoring system. At each FULL, BASIC and NUT station, discrete samples were collected using the Niskin bottles at 10 or more depths for seawater analysis (see Table 3 for the complete list). To complement the pCO2 data from the underway system and provide full profiles of the seawater CO2 system, total alkalinity and DIC concentrations were determined on discrete samples according to Dickson et al. (2007). Concentrations of the major macronutrients (nitrate, phosphate and orthosilicic acid) were determined with a segmented flow AutoAnalyzer model 3 (Seal 230 Analytical, Germany) using standard colorimetric methods adapted from Grasshoff et al. (1999). Nitrate concentration in the water column was also determined during each CTD cast using an In situ ultraviolet spectrophotometer (ISUS, Satlantic Inc., Halifax NS Canada) profiler mounted on the rosette. Concentrations varied between 0 and non-limiting concentrations over the entire cruise, with concentrations gradually increasing from the surface to bottom. Surface waters showed higher concentrations of macronutrients in the western half of the transects than in the eastern half of the transects, indicating surface 235 waters nutrients had been used by the developing PSB.
Organic elemental composition of total and dissolved matter (nitrogen, carbon and phosphorus) was measured on water samples taken from the Niskin bottles. Samples were immediately poisoned with sulfuric acid and brought back to the lab for analysis using wet oxidation, as described in Raimbault et al. (1999). Subtracting signals obtained for filtered samples (dissolved matter) from non-filtered samples (total matter) rendered calculated values for particulate organic matter. Particulate 240 organic carbon and nitrogen were also analysed on filtered samples (Whatman™ glass fiber GF/F, GE Healthcare USA) using high-temperature oxidation combined with gas chromatography.

Light Field and Bio-optics
The characteristics of the light field (quantity and quality) passing through snow and sea ice into the water column were assessed, as light is the most important parameter triggering the PSB. From the top of the CCGS Amundsen wheelhouse, the 245 total solar downwelling radiation was measured using a pyranometer (0.3 to 300 µm wavelength) and a radiometer (visible range 300 to 750 nm). Surface radiometry was performed using HyperSAS (Hyperspectral Surface Acquisition System, SeaBird Scientific USA) placed at the bow of the ship, including simultaneous measurements of hyperspectral above-water downward irradiance (Ed(0+,λ)),sky and surface radiance (Lsky(0+,λ) or Ltot(0+,λ)). Data were recorded at each FULL and BASIC station in open waters. Above-water hyperspectral remote sensing reflectance (Rrs(λ)) was calculated from the 250 radiometric quantities following the ocean optics protocols (Mueller et al., 2003;Mobley, 1999). In-water vertical profiles of downward irradiance (Ed(z)) and upward radiance (Lu(z,λ) or irradiance (Eu(z,λ)) in the water column were measured using was deployed during ice sampling through an auger hole carefully filled with fresh snow to avoid, as much as possible, 255 disturbing the underwater light field. A reference sensor provided simultaneous measurements of downward irradiance in the air. All measurements were made at 19 different wavelengths between 320 and 875 nm.
A profiling optical package was deployed at 28 stations to measure the inherent optical properties (IOPs) of seawater. The measured properties (and sensors) included: fluorescence of chlorophyll a and fluorescent dissolved organic matter (FDOM) (WetLabs, Eco Triplets), spectral total non-water absorption coefficients between 360 and 764 nm (Hobilabs, a-sphere), 260 particle backscattering coefficient at six different wavelengths (Hobilabs,394,420,470,532,620 and 700 nm)  together with CTD data (SeaBird sbe19+ attached to the package). In addition, discrete water samples were taken at each FULL and BASIC station to measure in the lab the CDOM absorption coefficient (aCDOM) between 200 and 722 nm using an Ultrapath (World Precision Instruments), and the phytoplankton and non-algal particle absorption coefficients between 200 and 860 nm determined from the "inside sphere" filter-pad technique (Rottgers and Gehnke, 2012;Stramski et al., 2015) using 265 a spectrophotometer equipped with a 155-mm integrating sphere (Perkin Elmer Lambda 19). Note that aCDOM, phytoplankton and non-algal particle absorption coefficients were also measured on the bottom slice of thawed ice cores. The data revealed that the minimum light amount required for net phytoplankton growth (0.415 mol m-2 d-1; Letelier et al., 2004) can be reached deeper under the ice than expected . Further details of the light field measurements can be found in

Biodiversity 280
The Green Edge project also aimed to understand the related potential impacts of evolving environmental conditions on Arctic food-webs in the context of climate change. Hence, great care was taken to sample the entire size spectrum of particulate matter and living organisms ( Fig. 9) from the tiniest viruses and bacteria to demersal fishes, seabirds and marine mammals. A wide variety of sampling techniques and analyses, from visual observation to highly automated underwater imaging systems, allowed us to ensure that almost all the levels of the trophic network were examined. 285

Viruses and bacteria
Abundance of viruses and bacteria was determined on fresh and preserved (glutaraldehyde 4 % final concentration) water samples taken from the rosette at each FULL and BASIC station (10 depths) using two different flow cytometers. On board, fresh samples were counted using an Accuri™ C6 and preserved samples were counted back in the lab using a FACSCanto (both machines from Becton Dickinson Biosciences, San Jose CA, USA). Samples were processed according to Marie et al. 290 (1999). Bacteria (and viruses) are ubiquitous in the oceans, and in Baffin Bay we measured bacterial abundances up to 2.9x106 cells ml-1.
For bacterial diversity analysis, water samples were filtered sequentially by means of a peristaltic pump onto 20 µm and 3 μm polycarbonate filters (Millipore) and then onto a 0.22 μm filter cartridge (Sterivex-GV, Millipore). The filters and Sterivex were stored at -80 °C with RNAlater (Qiagen) until analyzed. The DNA/RNA co-extraction was carried out using the AllPrep 295 DNA/RNA kit (Qiagen). The V4-V5 hypervariable region of the 16S rRNA gene of the DNA and cDNA samples was then amplified by PCR using primers 515F-Y and 926R covering a broad spectrum of diversity including Archaea and Bacteria (Parada et al., 2016). PCR, as well as sequencing settings and bioinformatic of sequence data, can be found in Dadaglio et al.

(2018).
A comparison of the bacterial diversity as a function of geographic location and size fractions (free living bacteria, bacteria 300 attached to particles smaller than 20 µm and larger than 20 µm) was made at a relatively broad taxonomic level (Fig. 10)

Phytoplankton community 305
Flow cytometry was used (same protocols as for viruses and bacteria, Sect. 4.5.1) to count and differentiate the smallest cells (picophytoplankton, nanophytoplankton, cryptophytes and Synechococcus) according to their fluorescence and scattering properties at each FULL station. At the surface, picophytoplankton and nanophytoplankton cell concentrations could reach 60,000 (station G719) and 9000 (station G515) cell ml-1, respectively while cryptophytes were always below 360 cell ml-1.
Synechococcus cyanobacteria were never observed. 310 Some samples were used to start phytoplankton cultures, which were brought back to the Roscoff laboratory for purification using flow cytometry sorting, serial dilution and single-cell pipetting. Pure cultures were characterized by microscopy and 18S rRNA gene sequencing. Most cultures isolated during the cruise belonged to diatoms, especially to the genera Attheya and Chaetoceros (Gérikas Ribeiro et al., 2020) All cultures were deposited to the Roscoff Culture Collection and available for distribution (http://www.roscoff-culture-collection.org/strains/shortlists/cruises/green-edge). 315 To study the phytoplankton community composition, an Imaging FlowCytobot (IFCB, McLane Research Laboratories Inc., East Falmouth MA, USA) was used during Leg 1b. The IFCB is best used for the study and identification of cells between 1 and 150 µm. Fresh samples (5 mL) taken from the rosette at each FULL station (all depths) and some BASIC and NUT stations (2 to 7 depths) were analyzed, as well as samples from the 2 bottom-most slices of ice cores once melted. The IFCB takes pictures at a resolution of around 3.4 pixels per µm. Image descriptors/features were extracted with Matlab®, using scripts 320 developed by Heidi Sosik . Taxonomic determination was achieved using Ecotaxa (Picheral M France) installed on the frame of the rosette carousel. The UVP5 collects in-focus images in the small seawater volume lit by its light emitting diodes (LEDs), as it is lowered in the water column. An automated computer system (https://ecotaxa.obsvlfr.fr/) was used to sub-sample images of individual objects and sort them into the appropriate category (marine snow or various taxa of zooplankton). The UVP has been mainly developed to count and identify particles larger than 100 µm. Samples for taxonomic analyses of micro-algae by microscopy were taken at each FULL and BASIC station at ten sampling depths. Half a litre of seawater was preserved with Lugol and kept at 4 °C until it was analyzed in the laboratory. Visual observation and taxonomic determination were done using an inverted microscope (Eclipse TS100, Nikon Instrument Inc.) according to the Ütermohl method (Ütermohl, 1958), using 25 or 50 ml columns. Three transects of 26 mm at 400x were 340 systematically observed for identification and counting of Bacillariophyceae, Dinophyceae, flagellates and ciliates. Larger phytoplankton cells and colonies were observed in all chambers at 100x. Diatoms (Bacillariophyceae) were found at every station, primarily at the surface of the water column, along with flagellates (both at the surface and at the SCM) (Fig. 12). The reaching 60 to 90 % of the cell counts (and to a lesser extent at the surface) across a wide range of ice cover conditions (OWD 345 values between -12 and 12 days).
Phytoplankton and ice-algae pigments were measured to derive indices of micro-algae biomass and taxonomic composition, and to get information on processes such as photoacclimation, senescence and grazing activities (Roy et al., 2011). Rosette water samples were filtered onto GF/F filters (Whatman™, GE Healthcare Life Sciences) and quickly frozen in liquid nitrogen.
Back in the land-based laboratory, samples were thawed and extracted in 100% methanol, separated and identified by HPLC, 350 as described by Ras et al. (2008). Twenty-five individual pigments or groups of pigments were identified and quantified at each FULL and BASIC station (10 depths sampled each time). Figure 13 shows the distribution of total chlorophyll a and pheophorbide concentrations along transects 300 and 500. The high chlorophyll a concentrations close to the surface in the MIZ, and deepening towards open waters in the east, confirmed the evolution of the PSB from an under-ice bloom to an SCM.
Note that highest concentrations of pheophorbide were systematically found underneath the accumulation of chlorophyll a, 355 indicating the sinking of degrading phytoplanktonic material.

Zooplankton and Fish
Zooplankton represents the second level of the food chain. The UVP5 and the Imaging FlowCytobot (see previous sections) both rendered valuable information on small zooplankton specimens (below 150 µm).   Figure 14 shows an example of the diversity of benthic organisms.
More than 220 species of macrofauna were identified during the Green Edge cruise from more than 25 classes (Grant and Yunda-Guarin Unpublished data). A box corer was used to sample sediment from each FULL station. The sediment samples were then divided among the research teams for diverse analyses (see Table 3 for a complete list) including (but not limited to) identification of organisms living inside the sediment, incubations for respiration and nutrient utilization or chemical 405 analysis.

Birds and marine mammals
During the entire cruise, a systematic bird and marine mammals survey was carried out from the ship's wheelhouse (see LeBlanc et al., 2019 for detailed methodology). A total of 20 different bird species and a total of 8 different mammal species were identified. Northern Fulmar, Thick-billed murre and Little auk were the most common bird species observed. Ringed 410 seal, Hooded seal and Harp seal were the most common seals. The long-finned pilot whale was the most common whale species observed. A total of 10 polar bears were observed.
A total of 123 seabirds from 7 species were also collected from a zodiac deployed from the CCGS Amundsen in Greenland waters during Leg1 (10 June -8 July). This includes black-legged kittiwakes (n=8), glaucous gulls (n=6), great black-backed gull (n=1), little auks (n=19), northern fulmars (n=42) and thick-billed murres (n=36). Sampled birds were frozen at -20°C 415 until laboratory analyses. A first study aimed to investigate the co-distribution of seabirds and their fish prey along the MIZ (LeBlanc et al., 2019). To this end, stomach contents were examined for 74 birds (35 murres, 30 fulmars and 9 kittiwakes) under a dissecting microscope. Otoliths were retrieved and used to identify fish species, age and size. A second focus was recording of plastic in the stomachs. Plastic data are used in OSPAR monitoring and AMAP working groups on plastic pollution. A third study aimed to determine bird association to sea ice and ice-derived resources by the combination of different 420 trophic markers (Cusset et al., unpublished). Hence, liver, muscle and blood (from the cardial clot) samples were collected from a total of 52 bird carcasses (27 murres, 14 auks, 3 kittiwakes and 8 fulmars), on which Highly Branched Isoprenoids (HBIs), carbon and nitrogen stable isotopes and fatty acids were measured. Finally, a fourth study is looking at stable isotope data together with Hg data for both muscle and liver.

Bacterial production, respiration and viability
At each FULL station during the cruise, water samples were taken from 2-3 depths (surface, DCM and below DCM) to determine bacterial respiration. Oxygen concentration was determined using the Winkler method on 1-µm filtered samples before and after a 5-day incubation in the dark at 1.5 °C. Bacterial respiration varied overall between 0 and 1.63 µmol O2 l-1 d-1, with a mean value of 0.35 ± 0.41 µmol O2 l-1 d-1. For bacterial production determination, water was collected at each 430 FULL station from 8-10 depths. Bacterial production was measured by [H3]-Leucine incorporation (Kirchman et al., 1985) modified for microcentrifugation (Smith and Azam, 1992). Overall values varied between 0 and 1.51 µgC l-1 d-1 around a mean value of 0.17 ± 0.25 µgC l-1 d-1. The use of the propidium monoazide (PMA) method allowed to show a high bacterial mortality in sea ice (up to 90%) and in SPM material (up to 68%) collected in shallower waters at St 409 and St 418 (Burot et al., 2021). 435

Primary production and micronutrient cycling
To determine the fate of the phytoplankton spring bloom, one must first determine primary production. In situ simulated incubations were carried out at each FULL station on water sampled from the rosette at 8 to 10 depths determined as chosen percentages of surface photosynthetic available radiation (PAR, namely 100, 50, 25, 10, 6, 2.9, 1.2, 0.6 amd 0.1%). The melted bottom-most slices of ice cores were also incubated, when available. After spiking the water with a mix of 13C/15N tracers, 440 samples were incubated on deck at simulated light levels identical to the sampling light levels. The dissolved and particulate matter resulting from these incubations were analyzed by mass-spectrometry resulting in detailed nitrogen assimilation and regeneration values (see Table 3 for a complete list of parameters), as well as phytoplankton primary production (PP). Primary production varied between 0 and 88.13 ± 3.0 µgC l-1 day-1 over the entire cruise.
Photosynthetic parameters also allow calculation of primary production and provide insight into the efficiency and 445 characteristics of photosynthesis of a given sample. Onboard, photosynthetic parameters were determined by the P vs E curves method using NaH14CO3-spiked incubations of water samples (Lewis and Smith, 1983). Changes in the saturation parameter

Fate of the phytoplankton spring bloom 455
Some organic matter produced by the PSB was exported down the water column, as algal cells aggregated and sank, or were grazed upon by vertically migrating zooplankton. One ambitious experiment was conducted during the cruise to monitor the export of the PSB at a high temporal resolution. A sequential sediment trap (Technicap PPS4 France; 12 sampling cups) was anchored to an ice floe and deployed 25 m under the ice from June 15th to July 9th, 2016. Sediment trap collection cups were filled with filtered seawater adjusted to a salinity of 38 with NaCl and a formalin concentration of 4 % to preserve samples 460 during deployment and after recovery. The carousel holding the sampling cups was programmed to rotate every 2 days. The sediment trap was deployed in the marginal ice zone along transect 200 (Fig. 1), eventually drifted south with the ice, and was recovered on the way back to Iqaluit. The sediment trap was no longer anchored to its floe at recovery, but sea ice was still cells m-2 d-1) from June 15th to early July, when a 6-fold increase in diatom fluxes was observed from July 5th to July 7th 465 (~300 million cells m-2 d-1) along with a peak in chlorophyll a fluxes. More than half of the cells exported during the peak in algal fluxes were identified as the ice-associated pennate diatom Navicula spp.. Fluxes of the ice-obligate pennate diatom Nitzschia frigida, among the first species to be consistently exported from the melting sea ice in the Arctic Ocean (Lalande et al., 2019;Dezutter et al., 2021;Nadaï et al., 2021), peaked from June 23rd to June 25th, probably indicating the onset of sea ice melt. Fluxes of copepod fecal pellets collected in the sediment trap were higher prior to June 27th, suggesting under-ice 470 grazing of ice algae until the ice melted.

Benthic processes
Taken from the box corer, portions of the sediment were incubated at in situ simulated conditions of temperature and light in order to assess the consumption of oxygen and nutrients by endofauna. Oxygen use in the sediment cores allowed calculation of the benthic carbon demand (mgC m-2 d-1) which was found to be especially high at stations in open waters where the PSB 475 had already reached senescence and sinking organic matter had reached the bottom.

Other data
The exhaustive list of parameters measured during the cruise is presented in Table 3 along with principal investigator (PI) contact information.

Data availability 480
Raw data (and associated meta-data) are available on the LEFE-CYBER website at: http://www.obsvlfr.fr/proof/php/GREENEDGE/x_datalist_1.php?xxop=greenedge&xxcamp=amundsen. The formatted data are available on SEANOE (SEA scieNtific Open data Edition) under the CC-BY license (https://www.seanoe.org/data/00487/59892/, ). Detailed metadata associated with each data file contain the principal investigator's contact information. For specific questions, the PI associated with the data should be contacted directly. Dissolved inorganic carbon 485 (DIC), alkalinity, and O-18 data are also archived with the Ocean Carbon Data System (OCADS) https://doi.org/10.25921/719e-qr37. Navigation, ADCP, MVP and CTD data are also available on the Polar Data Catalog (https://www.polardata.ca/).

Lessons learned
As for any scientific cruise, a large amount of data was acquired by many people. Even though guidelines had been suggested 490 ahead of time for data formatting, merging and storage, a tremendous amount of effort was necessary to collect, assemble and standardize the data. It is important that a clear and streamlined data management plan be established ahead of time in order to avoid errors or loss of data in the merging process. For oceanographic CTD-rosette sampling-based cruises, depth of sampling necessitates special attention, as it is crucial to use Niskin bottle number instead of nominal depth in order to correctly merge the data. Furthermore, we cannot emphasize enough that data management specialists must be involved from the 495 beginning of such large-scale projects, to ensure that data is properly documented, in order to render the best quality data set possible and avoid loss of both valuable time and data.

Conclusion
The Green Edge cruise was of typical oceanographic design. In terms of goal achievement, the cruise was extremely successful and generated an impressive data set over a diverse set of disciplines, providing a global picture of the explored environment 500 https://doi.org/10.5194/essd-2022-41 and of all the processes fuelling the Arctic food-web. Figure 15 represents all interactions existing and/or measured during the cruise between compartments of the various trophic levels. The generated data set contains a much larger number of parameters than those presented in this paper. All data can be obtained from the data repository and provide an excellent opportunity for re-use and comparison with other Arctic data sets. A special issue of the Elementa journal entitled Green Edge -The phytoplankton spring bloom in the Arctic Ocean: past, present and future response to climate variations, and impact on carbon 505 fluxes and the marine food web contains a collection of research papers referring to this cruise.

Acknowledgments
The Green Edge project was funded by the following French and Canadian programs and agencies: Agence nationale de 520