Contemporary limnology of the rapidly changing glacierized watershed of the world’s largest High Arctic lake

Abstract

Glacial runoff is predicted to increase in many parts of the Arctic with climate change, yet little is known about the biogeochemical impacts of meltwaters on downstream freshwater ecosystems. Here we document the contemporary limnology of the rapidly changing glacierized watershed of the world’s largest High Arctic lake (Lake Hazen), where warming since 2007 has increased delivery of glacial meltwaters to the lake by up to 10-times. Annually, glacial meltwaters accounted for 62–98% of dissolved nutrient inputs to the lake, depending on the chemical species and year. Lake Hazen was a strong sink for NO3−-NO2−, NH4+ and DOC, but a source of DIC to its outflow the Ruggles River. Most nutrients entering Lake Hazen were, however, particle-bound and directly transported well below the photic zone via dense turbidity currents, thus reinforcing ultraoligotrophy in the lake rather than overcoming it. For the first time, we apply the land-to-ocean aquatic continuum framework in a large glacierized Arctic watershed, and provide a detailed and holistic description of the physical, chemical and biological limnology of the rapidly changing Lake Hazen watershed. Our findings highlight the sensitivity of freshwater ecosystems to the changing cryosphere, with implications for future water quality and productivity at high latitudes.

Microbial genomes retrieved from High Arctic lake sediments encode for adaptation to cold and oligotrophic environments

“…Cores were maintained at ambient temperatures (∼ 4°C) throughout profiling. The microprofiles of these cores have also been described in an earlier study (St. Pierre et al ).…”

“…These pathways include, for example, nitrogen assimilation as and . Likely, because of the low concentration of inorganic nitrogen in Lake Hazen (St. Pierre et al ), it might be directly assimilated only by a small number of organisms. The majority of microbes might instead resort to recycling of existing organic nitrogen compounds or nitrogen fixation to fulfill their needs for this nutrient (Fig.…”

Climate change negatively impacts dominant microbes in the sediments of a High Arctic lake

“…Our findings are likely to apply 23 to other, smaller, glacierized watersheds typical of polar or high latitude / high altitudes 24 ecosystems; we can predict that such changes will have far reaching consequences on these 25 ecosystems by a↵ecting nutrient biogeochemical cycling, the direction and magnitude of 26 which are yet to be determined. 27 Keywords: High Arctic, microbial ecology, metagenome assembled genomes 28 (MAGs), high-throughput sequencing 29 3 Main 30 Climate change is amplified in polar regions, where near-surface temperatures have in-31creased almost twice as fast as elsewhere on Earth over the last decade [1,2, 3]. Climate 32 models predict that temperature will increase in the Arctic by as much as 8°C by 2100…”

“…creased almost twice as fast as elsewhere on Earth over the last decade [1,2, 3]. Climate 32 models predict that temperature will increase in the Arctic by as much as 8°C by 2100…”

“…Any remaining length of cores that were used for DNA analysis were discarded. These 38 uppermost layers in the sediment correspond to both the most recent sediment deposition 39 dates [2] and the region of greatest microbial activity [3]. The top of each core was 40 sectioned and placed into Whirlpack bags.…”