Green Edge ice camp campaigns: understanding the processes controlling the under-ice Arctic phytoplankton spring bloom

Abstract

Abstract. The Green Edge initiative was developed to investigate the processes controlling the primary productivity and fate of organic matter produced during the Arctic phytoplankton spring bloom (PSB) and to determine its role in the ecosystem. Two field campaigns were conducted in 2015 and 2016 at an ice camp located on landfast sea ice southeast of Qikiqtarjuaq Island in Baffin Bay (67.4797∘ N, 63.7895∘ W). During both expeditions, a large suite of physical, chemical and biological variables was measured beneath a consolidated sea-ice cover from the surface to the bottom (at 360 m depth) to better understand the factors driving the PSB. Key variables, such as conservative temperature, absolute salinity, radiance, irradiance, nutrient concentrations, chlorophyll a concentration, bacteria, phytoplankton and zooplankton abundance and taxonomy, and carbon stocks and fluxes were routinely measured at the ice camp. Meteorological and snow-relevant variables were also monitored. Here, we present the results of a joint effort to tidy and standardize the collected datasets, which will facilitate their reuse in other Arctic studies. The dataset is available at https://doi.org/10.17882/59892 (Massicotte et al., 2019a).

Spatial Heterogeneity as a Key Variable Influencing Spring-Summer Progression in UVR and PAR Transmission Through Arctic Sea Ice

“…Prior to melt pond onset during stage I of the seasonal progression of light transmittance, measured snow depth and the corresponding lowT(PAR) were similar to other observations on landfast and mobile FYI in the Canadian Arctic (Iacozza and FIGURE 8 | Change in total chlorophyll a (Tchl a) concentration (green circles) integrated over 100-m water column (Massicotte et al, 2020), and in isolume depth (z 0.415 ), extracted from Oziel et al (2019, white squares), as well as calculated from mean PAR transmittance (T (PAR), gray squares) and calculated fromT (PAR) and scalar irradiance using an inverse average cosine (µ d ) of 1.4 (blue squares) for each melt stage (I -III) at the ice camp site. Barber, 1999;Campbell et al, 2015).…”

“…However, the relationship between the sudden change in ice surface properties, the increase in the spatial heterogeneity of PAR transmittance, and the onset of algal growth during the spring melt are still not well understood. Figure 8 provides an overview of the measured increase in Tchl a concentration in the water column (Massicotte et al, 2020) at the ice camp site and the depth of the isolume, z 0.415 , where integrated PAR 24h (z) = 0.415 mol photons m −2 d −1 , a threshold used for positive net growth (Boss and Behrenfeld, 2010). The z 0.415 was extracted from Oziel et al (2019), and estimated fromT(PAR) from our study using the same daily incident PAR data and K d (PAR).…”

Arctic mid-winter phytoplankton growth revealed by autonomous profilers

“…In addition to using literature values for summer Baffin Bay photosynthetic parameters ( 15 ), photophysiological experiments were conducted off the fast ice in Baffin Bay in 2015 and 2016 during the Green Edge ice camps ( 54 ). Methods are described in ( 55 ), but briefly, we determined E k , the light saturation irradiance for photosynthesis, and P b, max , the chl-a specific light saturated growth rate, using the models P = P s · (1 − e −αE ) · e −βE + P 0 (when photoinhibition was apparent) and P = P s · (1 − e −αE ) + P 0 (when no photoinhibition was apparent). Here, P is the rate of photosynthesis and E is the light intensity; the rest are free parameters.…”

Culturable diversity of Arctic phytoplankton during pack ice melting

“…The development of the spring phytoplankton bloom at the IC site was monitored by flow cytometry (Massicotte et al, 2020), and its phases were defined as follows: 'prebloom' from 4 May to 23 May; 'bloom-development' from 24 May to 22 June and 'bloom-peak' from 23 June to 18 July. AM strains were not related to bloom phases due to spatial variability across the marginal ice zone during sampling.…”