The distribution of Fe across the shelf of the Western Antarctic Peninsula at the start of the phytoplankton growing season

Seyitmuhammedov, Kyyas; Stirling, Claudine H.; Reid, Malcolm R.; Hale, Robert Van; Laan, Patrick; Arrigo, Kevin R.; Dijken, G. van; Alderkamp, Anne‐Carlijn; Middag, Rob

doi:10.1016/j.marchem.2021.104066

Cited by 3 publications

(2 citation statements)

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“…We grouped the samples into three depth horizons: shallow (0–40 m), medium (50–75 m), and deep (100–275 m). The depth categorization was done based on mixed layer depth, temperature, and salinity, as reported previously in Schofield et al (2018) and Seyitmuhammedov et al (2022) . There were 23 samples collected from the shallower depth, whereas 11 and 14 samples were collected from the medium-depth and deeper horizons, respectively.…”

Section: Methodsmentioning

confidence: 99%

Depth drives the distribution of microbial ecological functions in the coastal western Antarctic Peninsula

et al. 2023

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The Antarctic marine environment is a dynamic ecosystem where microorganisms play an important role in key biogeochemical cycles. Despite the role that microbes play in this ecosystem, little is known about the genetic and metabolic diversity of Antarctic marine microbes. In this study we leveraged DNA samples collected by the Palmer Long Term Ecological Research (LTER) project to sequence shotgun metagenomes of 48 key samples collected across the marine ecosystem of the western Antarctic Peninsula (wAP). We developed an in silico metagenomics pipeline (iMAGine) for processing metagenomic data and constructing metagenome-assembled genomes (MAGs), identifying a diverse genomic repertoire related to the carbon, sulfur, and nitrogen cycles. A novel analytical approach based on gene coverage was used to understand the differences in microbial community functions across depth and region. Our results showed that microbial community functions were partitioned based on depth. Bacterial members harbored diverse genes for carbohydrate transformation, indicating the availability of processes to convert complex carbons into simpler bioavailable forms. We generated 137 dereplicated MAGs giving us a new perspective on the role of prokaryotes in the coastal wAP. In particular, the presence of mixotrophic prokaryotes capable of autotrophic and heterotrophic lifestyles indicated a metabolically flexible community, which we hypothesize enables survival under rapidly changing conditions. Overall, the study identified key microbial community functions and created a valuable sequence library collection for future Antarctic genomics research.

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Section: Methodsmentioning

confidence: 99%

Depth drives the distribution of microbial ecological functions in the coastal western Antarctic Peninsula

et al. 2023

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“…Similar to the sediment tracers, one CDW tracer (dFe CDW ) was free to advect and diffuse over the entire model domain, and the second (dFe CDW_ZC ) was relaxed to zero (timescale of 10 days) within any ice shelf cavity. The CDW tracer concentration was related to dFe using an end member concentration of 0.32 nM, which is an average of measured CDW dFe concentrations just off the Antarctic continental shelf (McGillicuddy et al., 2015; Seyitmuhammedov et al., 2022; Sherrell et al., 2015; A. J. R. Smith et al., 2021).…”

Section: Model and Simulationsmentioning

confidence: 99%

Sensitivity of the Relationship Between Antarctic Ice Shelves and Iron Supply to Projected Changes in the Atmospheric Forcing

et al. 2023

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Upward advection or mixing of iron‐rich deep waters due to circulation changes driven by the rate of basal ice shelf melt was shown to be a primary control on chlorophyll a production in coastal polynyas over the Antarctic continental shelf. Here, the effects of atmospheric changes projected in 2100 on this relationship were examined with a 5‐km resolution ocean/sea ice/ice shelf model of the Southern Ocean with different simulated dissolved iron sources and idealized biological uptake. The atmospheric changes are added as idealized increments to the forcing. Inclusion of a poleward shift and strengthening of the winds, increased precipitation, and warmer atmospheric temperatures resulted in doubling of the heat advected onto the continental shelf and an 83% increase in the total Antarctic ice shelf basal melt. The total dissolved iron supply to the surface waters over the continental shelf increased by 62%, while the surface iron supply due just to basal melt driven overturning increased by 48%. However, even though the ice shelf driven contribution becomes less important to the total iron supply on average (29% of total), the ice shelf involvement becomes relatively even more important in some locations, such as the Amundsen and Bellingshausen Seas. The modified atmospheric conditions also produced a reduction in summer sea ice extent and a shoaling of the summer mixed layers. These simulated responses to projected changes suggest relief of light and nutrient limitation for phytoplankton blooms over the Antarctic continental shelf and perhaps an increase in annual production in years to come.

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Fe-binding organic ligands in coastal and frontal regions of the western Antarctic Peninsula

et al. 2021

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Abstract. Organic ligands are a key factor determining the availability of dissolved iron (DFe) in the high-nutrient low-chlorophyll (HNLC) areas of the Southern Ocean. In this study, organic speciation of Fe is investigated along a natural gradient of the western Antarctic Peninsula, from an ice-covered shelf to the open ocean. An electrochemical approach, competitive ligand exchange – adsorptive cathodic stripping voltammetry (CLE-AdCSV), was applied. Our results indicated that organic ligands in the surface water on the shelf are associated with ice-algal exudates, possibly combined with melting of sea ice. Organic ligands in the deeper shelf water are supplied via the resuspension of slope or shelf sediments. Further offshore, organic ligands are most likely related to the development of phytoplankton blooms in open ocean waters. On the shelf, total ligand concentrations ([Lt]) were between 1.2 and 6.4 nM eq. Fe. The organic ligands offshore ranged between 1.0 and 3.0 nM eq. Fe. The southern boundary of the Antarctic Circumpolar Current (SB ACC) separated the organic ligands on the shelf from bloom-associated ligands offshore. Overall, organic ligand concentrations always exceeded DFe concentrations (excess ligand concentration, [L′] = 0.8–5.0 nM eq. Fe). The [L′] made up to 80 % of [Lt], suggesting that any additional Fe input can be stabilized in the dissolved form via organic complexation. The denser modified Circumpolar Deep Water (mCDW) on the shelf showed the highest complexation capacity of Fe (αFe'L; the product of [L′] and conditional binding strength of ligands, KFe'Lcond). Since Fe is also supplied by shelf sediments and glacial discharge, the high complexation capacity over the shelf can keep Fe dissolved and available for local primary productivity later in the season upon sea-ice melting.

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The distribution of Fe across the shelf of the Western Antarctic Peninsula at the start of the phytoplankton growing season

Cited by 3 publications

References 97 publications

Depth drives the distribution of microbial ecological functions in the coastal western Antarctic Peninsula

Depth drives the distribution of microbial ecological functions in the coastal western Antarctic Peninsula

Sensitivity of the Relationship Between Antarctic Ice Shelves and Iron Supply to Projected Changes in the Atmospheric Forcing

Fe-binding organic ligands in coastal and frontal regions of the western Antarctic Peninsula

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