Northern lakes are the largest natural sources of methane, a potent greenhouse gas, but it is unclear how and whether feedbacks from warming in Arctic regions will exacerbate or mitigate lake methane emissions. This proposal investigates two potential drivers of methane emissions, which are rapidly changing as the Arctic warms: (1) the composition and quantity of dissolved organic matter (DOM) transported into lakes from the land as vegetation changes and permafrost melts, and (2) the increasing quantities of windblown (aeolian) dust that is released from glacial discharge as the Greenland ice sheet melts. We hypothesize that DOM and dust are the key drivers of methane emissions. DOM is the dominant external source of carbon to lakes with the potential to fuel the methane cycle. Aeolian dust is a source of nutrients that drive microbial activity and, particularly, rare earth elements (REE) from the lanthanide group which are enzymatically-linked to methanotrophy. Understanding how such changes and interactions between DOM and dust/REE influence methane emissions requires approaches from different scientific fields. Methane cycling is powered by microbes and their interactions, but the lake conditions, trophic structure and environmental situation will modify the supply, distribution and bioavailability of elements that support the methane cycle over a variety of timescales and climatic conditions. This consortium focuses on a well-studied lake district as a living laboratory in West Greenland, and assembles experts in the microbiology of lanthanide-dependent methanotrophs, microbial and lake ecology to investigate respectively how microbial interactions and higher trophic levels of the food web modify methane production. Combining limnology and paleolimnology (sediment core analysis) with citizen scientist work will allow linkages between DOM, dust/ REE supply and methane production to be quantified at the landscape-scale and across timescales of decades to centuries as a means of evaluating their broader biogeochemical significance.

• prof. dr. Friederike Wagner-Cremer
• dr. Wim Hoek
• dr. Charlie Beard
• prof. dr. Suzanne McGowan