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This dataset includes concentrations of dissolved (<0.4 micrometers (µm)) and labile particulate (0.4-5 µm and >5 µm) phosphorus (P), vanadium (V), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), cadmium (Cd), and lead (Pb) in shipboard incubation samples collected during the EXports Processes in the Oceans from RemoTe Sensing (EXPORTS) North Pacific (NP) cruise RR1813 on the R/V Roger Revelle near Ocean Station PAPA (Station P). 

This dataset includes concentrations of dissolved (<0.2 micrometers (µm)) manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), cadmium (Cd), and lead (Pb) in depth profile samples collected on 8 September 2018 during the EXports Processes in the Oceans from RemoTe Sensing (EXPORTS) cruise aboard R/V Roger Revelle cruise RR1813 at Ocean Station PAPA (Station P). 

This dataset includes concentrations of dissolved (<0.2 micrometers (µm)) manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), cadmium (Cd), and lead (Pb) in surface (~2 meters) samples collected between 15 August 2018 and 6 September 2018 during the EXports Processes in the Oceans from RemoTe Sensing (EXPORTS) cruise aboard R/V Roger Revelle cruise RR1813 at Ocean Station PAPA (Station P). 

Abstract Synechococcus are the most abundant cyanobacteria in high latitude regions and are responsible for an estimated 17% of annual marine net primary productivity. Despite their biogeochemical importance, Synechococcus populations have been unevenly sampled across the ocean, with most studies focused on low-latitude strains. In particular, the near absence of Synechococcus genomes from high-latitude, High Nutrient Low Chlorophyll (HNLC) regions leaves a gap in our knowledge of picocyanobacterial adaptations to iron limitation and their influence on carbon, nitrogen, and iron cycles. We examined Synechococcus populations from the subarctic North Pacific, a well-characterized HNLC region, with quantitative metagenomics. Assembly with short and long reads produced two near complete Synechococcus metagenome-assembled genomes (MAGs). Quantitative metagenome-derived abundances of these populations matched well with flow cytometry counts, and the Synechococcus MAGs were estimated to comprise >99% of the Synechococcus at Station P. Whereas the Station P Synechococcus MAGs contained multiple genes for adaptation to iron limitation, both genomes lacked genes for uptake and assimilation of nitrate and nitrite, suggesting a dependence on ammonium, urea, and other forms of recycled nitrogen leading to reduced iron requirements. A global analysis of Synechococcus nitrate reductase abundance in the TARA Oceans dataset found nitrate assimilation genes are also lower in other HNLC regions. We propose that nitrate and nitrite assimilation gene loss in Synechococcus may represent an adaptation to severe iron limitation in high-latitude regions where ammonium availability is higher. Our findings have implications for models that quantify the contribution of cyanobacteria to primary production and subsequent carbon export. 

The growth of diatoms in the Southern Ocean, especially the region surrounding the West Antarctic Peninsula, is frequently constrained by low dissolved iron and other trace metal concentrations. This challenge may be overcome by mutualisms between diatoms and co-occurring associated bacteria, in which diatoms produce organic carbon as a substrate for bacterial growth, and bacteria produce siderophores, metal-binding ligands that can supply diatoms with metals upon uptake as well as other useful secondary compounds for diatom growth like vitamins. To examine the relationships between diatoms and bacteria in the plankton (diatom) size class (> 3 µm), we sampled both bacterial and diatom community composition with accompanying environmental metadata across a naturally occurring concentration gradient of macronutrients, trace metals and siderophores at 21 stations near the West Antarctic Peninsula (WAP). Offshore Drake Passage stations had low dissolved iron (0.33 ± 0.15 nM), while the stations closer to the continental margin had higher dissolved iron (5.05 ± 1.83 nM). A similar geographic pattern was observed for macronutrients and most other trace metals measured, but there was not a clear inshore-offshore gradient in siderophore concentrations. The diatom and bacteria assemblages, determined using 18S and 16S rDNA sequencing respectively, were similar by location sampled, and variance in both assemblages was driven in part by concentrations of soluble reactive phosphorous, dissolved manganese, and dissolved copper, which were all higher near the continent. Some of the most common diatom sequence types observed were Thalassiosira and Fragilariopsis , and bacteria in the plankton size fraction were most commonly Bacteroidetes and Gammaproteobacteria. Network analysis showed positive associations between diatoms and bacteria, indicating possible in situ mutualisms through strategies such as siderophore and vitamin biosynthesis and exchange. This work furthers the understanding of how naturally occurring gradients of metals and nutrients influence diatom-bacteria interactions. Our data suggest that distinct groups of diatoms and associated bacteria are interacting under different trace metal regimes in the WAP, and that diatoms with different bacterial partners may have different modes of biologically supplied trace metals.