Passive Sampler Derived Profiles and Mass Flows of Perfluorinated Alkyl Substances (PFASs) across the Fram Strait in the North Atlantic

Per- and polyfluorinated alkyl substances (PFAS) are a family of pollutants of high concern due to their ubiquity and negative human health impacts. The long-range marine transport of PFAS was observed during year-long deployments of passive tube samplers in the Fram Strait across three depth transects. Time weighted average concentrations ranged from 2.4 to 360 pg L–1, and 10 different PFAS were regularly observed. PFAS profiles and concentrations were generally similar to those previously characterized for polycyclic aromatic hydrocarbons (PAHs) at these sites. The detection of several anionic PFAS in “old” water demonstrated that they are not perfect water mass tracers but are also transported to depth via settling particles. Mass flows of PFAS through the Fram Strait in and out of the Arctic Ocean were basically similar (112 ± 82 Mg year–1 northward flow, 100 ± 54 Mg year–1 southward flow). For perfluorooctane sulfonamide (FOSA), export from the Arctic Ocean via the Fram Strait exceeded import by Atlantic Water, likely due to preferential transport and deposition in the Arctic Ocean. These observations suggest that PFAS in the Arctic are governed by the feedback loop previously described for polycyclic aromatic hydrocarbons (PAHs) in the regionwith additional atmospheric transport delivering volatile PFAS to the Arctic, which then get exported via Arctic water masses

Passive Sampler Derived Profiles and Mass Flows of Perfluorinated Alkyl Substances (PFASs) across the Fram Strait in the North Atlantic

Per- and polyfluorinated alkyl substances (PFAS) are a family of pollutants of high concern due to their ubiquity and negative human health impacts. The long-range marine transport of PFAS was observed during year-long deployments of passive tube samplers in the Fram Strait across three depth transects. Time weighted average concentrations ranged from 2.4 to 360 pg L–1, and 10 different PFAS were regularly observed. PFAS profiles and concentrations were generally similar to those previously characterized for polycyclic aromatic hydrocarbons (PAHs) at these sites. The detection of several anionic PFAS in “old” water demonstrated that they are not perfect water mass tracers but are also transported to depth via settling particles. Mass flows of PFAS through the Fram Strait in and out of the Arctic Ocean were basically similar (112 ± 82 Mg year–1 northward flow, 100 ± 54 Mg year–1 southward flow). For perfluorooctane sulfonamide (FOSA), export from the Arctic Ocean via the Fram Strait exceeded import by Atlantic Water, likely due to preferential transport and deposition in the Arctic Ocean. These observations suggest that PFAS in the Arctic are governed by the feedback loop previously described for polycyclic aromatic hydrocarbons (PAHs) in the regionwith additional atmospheric transport delivering volatile PFAS to the Arctic, which then get exported via Arctic water masses

Environmental parameter of the water column at the chlorophyll <i>a</i> maximum of sampling sites^a.

<p>Environmental parameter of the water column at the chlorophyll <i>a</i> maximum of sampling sites<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0148512#t001fn001" target="_blank">^a</a>.</p

Community assemblage based on 454-NGS sequencing of selected samples representing the grouping in the MetaMDS-plot.

<p>Community assemblage based on 454-NGS sequencing of selected samples representing the grouping in the MetaMDS-plot.</p

Temperature-salinity diagram of the CTD stations.

<p>Profiles shallower than 50 m are shown as black lines and profiles deeper than 50 m as gray lines. The biological samples are marked where they were taken in the water column and named according to the labelling in the metaMDS plot from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0148512#pone.0148512.g004" target="_blank">Fig 4</a>. The surface freezing line is shown in blue and the isopycnals in black.</p

Diagram illustrating the spatial distribution of chlorophyll <i>a</i> biomass in the observation area in Fram Strait, Nansen Basin and Amundsen Basin.

<p>Data are interpolated based on point measurements and do not reflect measurements in between the sampling sites. A: Spatial distribution of total chlorophyll <i>a</i> biomass including micro-, nano-, and pico-plankton. B: Spatial distribution of pico-eukaryotic chlorophyll <i>a</i> biomass. C: Relative contribution of pico-eukaryotic chlorophyll <i>a</i> biomass to total chlorophyll <i>a</i> biomass.</p

Biogeography of pico-eukaryote communities determined by ARISA.

<p>A: Meta MDS plot displaying similarity between pico-eukaryote communities based on the Jaccard Index. B: Allocation of grouping in the MDS-plot to sampling locations. Modified after Rudels et al. (2012), major ocean currents were sketched into the map. Atlantic inflow is sketched in black, while modified Atlantic Water is sketched in orange.</p

Assemblage of the abundant biosphere, representing operational taxonomic units (OUTs) that constitute >1% of sequences in a sample.

<p>An OTU represents a cluster of sequences with 97% similarity in the sequence of the 18S rRNA V4 region. The numbering of taxa reflects different sequences that fall into this branch of the phylogenetic tree, but that could not be annotated with higher taxonomic resolution.</p

Table_1_Seasonal Variation in Transport of Zooplankton Into the Arctic Basin Through the Atlantic Gateway, Fram Strait.pdf

<p>The largest contribution of oceanic heat to the Arctic Ocean is the warm Atlantic Water (AW) inflow through the deep Fram Strait. The AW current also carries Atlantic plankton into the Arctic Basin and this inflow of zooplankton biomass through the Atlantic-Arctic gateway far exceeds the inflow through the shallow Pacific-Arctic gateway. However, because this transport has not yet been adequately quantified based on observational data, the present contribution is poorly defined, and future changes in Arctic zooplankton communities are difficult to project and observe. Our objective was to quantify the inflow of zooplankton biomass through the Fram Strait during different seasons, including winter. We collected data with high spatial resolution covering hydrography (CTD), currents (ADCP and LADCP) and zooplankton distributions (LOPC and MultiNet) from surface to 1,000 m depth along two transects crossing the AW inflow during three cruises in January, May and August 2014. Long-term variations (1997–2016) in the AW inflow were analyzed based on moored current meters. Water transport across the inflow region was of the same order of magnitude during all months (January 2.2 Sv, May 1.9 Sv, August 1.7 Sv). We found a higher variability in zooplankton transport between the months (January 51 kg C s⁻¹, May 34 kg C s⁻¹, August 50 kg C s⁻¹), related to seasonal changes in the vertical distribution of zooplankton. However, high abundances of carbon-rich copepods were observed in the AW inflow during all months. Surface patches with high abundances of C. finmarchicus, Microcalanus spp., Pseudocalanus spp., and Oithona similis clearly contributed to the advected biomass, also in winter. The data reveal that the phenology of species is important for the amount of advected biomass, and that the advective input of zooplankton carbon into the Arctic Basin is important during all seasons. The advective zooplankton input might be especially important for mesopelagic planktivorous predators that were recently observed in the region, particularly during winter. The inflow of C. finmarchicus with AW was estimated to be in the order of 500,000 metric tons C y⁻¹, which compares well to modeled estimates.</p

Table_2_Seasonal Variation in Transport of Zooplankton Into the Arctic Basin Through the Atlantic Gateway, Fram Strait.pdf

<p>The largest contribution of oceanic heat to the Arctic Ocean is the warm Atlantic Water (AW) inflow through the deep Fram Strait. The AW current also carries Atlantic plankton into the Arctic Basin and this inflow of zooplankton biomass through the Atlantic-Arctic gateway far exceeds the inflow through the shallow Pacific-Arctic gateway. However, because this transport has not yet been adequately quantified based on observational data, the present contribution is poorly defined, and future changes in Arctic zooplankton communities are difficult to project and observe. Our objective was to quantify the inflow of zooplankton biomass through the Fram Strait during different seasons, including winter. We collected data with high spatial resolution covering hydrography (CTD), currents (ADCP and LADCP) and zooplankton distributions (LOPC and MultiNet) from surface to 1,000 m depth along two transects crossing the AW inflow during three cruises in January, May and August 2014. Long-term variations (1997–2016) in the AW inflow were analyzed based on moored current meters. Water transport across the inflow region was of the same order of magnitude during all months (January 2.2 Sv, May 1.9 Sv, August 1.7 Sv). We found a higher variability in zooplankton transport between the months (January 51 kg C s⁻¹, May 34 kg C s⁻¹, August 50 kg C s⁻¹), related to seasonal changes in the vertical distribution of zooplankton. However, high abundances of carbon-rich copepods were observed in the AW inflow during all months. Surface patches with high abundances of C. finmarchicus, Microcalanus spp., Pseudocalanus spp., and Oithona similis clearly contributed to the advected biomass, also in winter. The data reveal that the phenology of species is important for the amount of advected biomass, and that the advective input of zooplankton carbon into the Arctic Basin is important during all seasons. The advective zooplankton input might be especially important for mesopelagic planktivorous predators that were recently observed in the region, particularly during winter. The inflow of C. finmarchicus with AW was estimated to be in the order of 500,000 metric tons C y⁻¹, which compares well to modeled estimates.</p