Coupling of Carbon, Iron, and Microbial Dynamics Across a Glaciated, High-Latitude Wetland Landscape

Abstract:

High-latitude, coastal wetlands are particularly dynamic and responsive to climate, and yet we do not understand, and thus cannot fully predict, how crucial aspects of these systems will change in the future. The Northern Hemisphere has disproportionately experienced the largest increase in yearly average temperature over 50 years, with predicted seasonal extremes to be three times greater than mid-latitude areas. In areas where glaciers exist, increasing temperatures are causing deglaciation and associated changes to the down-gradient wetland geomorphology and biogeochemistry. The objective of this research is to assess key aspects of carbon and iron cycling and microbiomes in wetland sediments along a gradient reaching from the outwash plains near the glaciers to uplifted marshes distal to the glaciers. Using autonomous sampling techniques and 16S rDNA sequencing, we have begun to identify key processes that occur in the Copper River Delta, AK, a model system to study high-latitude watersheds experiencing climate change. We revealed spring melt-associated spikes of dissolved methane >250 µM in glacial outwash pond environments and identified a diverse yet deterministically structured, heterogeneous sediment microbiome community capable of influencing local carbon cycling. We calculated carbon accumulation rates upwards of 385 g C m²yr^-1 within outwash pond sediments nearest to the glaciers, which co-occurred with pronounced suboxic peaks in Fe³⁺ and Mn²⁺. High-latitude wetland ecosystems are not only influenced by the changing climate, but also have the potential to impact carbon cycling considering enormously high carbon burial rates. These findings bring to light the importance of understanding changing biogeochemical processes in high-latitude wetlands, as they have the potential to influence elemental cycling and are disproportionately sensitive to our changing climate.