Potentially bioavailable iron produced through benthic cycling in glaciated Arctic fjords of Svalbard

Katja Laufer-Meiser,Molly O Patterson,Markus Maisch,Hans Røy,James M Byrne,Andreas Kappler,Alexander B Michaud,Bo Barker Jørgensen

doi:10.1038/s41467-021-21558-w

Abstract

The Arctic has the highest warming rates on Earth. Glaciated fjord ecosystems, which are hotspots of carbon cycling and burial, are extremely sensitive to this warming. Glaciers are important for the transport of iron from land to sea and supply this essential nutrient to phytoplankton in high-latitude marine ecosystems. However, up to 95% of the glacially-sourced iron settles to sediments close to the glacial source. Our data show that while 0.6–12% of the total glacially-sourced iron is potentially bioavailable, biogeochemical cycling in Arctic fjord sediments converts the glacially-derived iron into more labile phases, generating up to a 9-fold increase in the amount of potentially bioavailable iron. Arctic fjord sediments are thus an important source of potentially bioavailable iron. However, our data suggests that as glaciers retreat onto land the flux of iron to the sediment-water interface may be reduced. Glacial retreat therefore likely impacts iron cycling in coastal marine ecosystems.

Highlights

The Arctic has the highest warming rates on Earth
It was found that irondelivery by glaciers is dependent on bedrock geology and that benthic iron cycling is active in these sediments, which could play a significant role in the production of bioavailable iron[17,18]
We find that the amount and reducibility of FeA and FeM from glacial sources is relatively low, while the amount and reducibility of FeA and FeM in the fjord sediments increases with distance from the fjord head

Summary

Introduction

The Arctic has the highest warming rates on Earth. Glaciated fjord ecosystems, which are hotspots of carbon cycling and burial, are extremely sensitive to this warming. The amount of FeM was about two times higher than FeA (Supplementary Table 1), consistent with what has been previously found[26] and attributed to the large surface area of these glacial sediments being favorable for microbial reduction, differences in the mineral phases available to biotic and abiotic processes, and differences in mechanisms of biotic and abiotic iron reduction[26].

Results

Conclusion