Abstract
Lakes are a dominant feature of the Arctic landscape and a focal point of regional and global biogeochemical cycling. We collected a sediment core from a High Arctic Lake in southwestern Svalbard for multiproxy paleolimnological analysis. The aim was to find linkages between the terrestrial and aquatic environments in the context of climate change to understand centennial-long Arctic biogeochemical cycling and environmental dynamics. Two significant thresholds in elemental cycling were found based on sediment physical and biogeochemical proxies that were associated with the end of the cold Little Ice Age and the recent warming. We found major shifts in diatom, chironomid and cladoceran communities and their functionality that coincided with increased summer temperatures since the 1950s. We also discovered paleoecological evidence that point toward expanded bird (Little Auk) colonies in the catchment alongside climate warming. Apparently, climate-driven increase in glacier melt water delivery as well as a prolonged snow- and ice-free period have increased the transport of mineral matter from the catchment, causing significant water turbidity and disappearance of several planktonic diatoms and clear-water chironomids. We also found sedimentary accumulation of microplastic particles following the increase in Little Auk populations suggesting that seabirds potentially act as biovectors for plastic contamination. Our study demonstrates the diverse nature of climate-driven changes in the Arctic lacustrine environment with increased inorganic input from the more exposed catchment, larger nutrient delivery from the increased bird colonies at the surrounding mountain summits and subsequent alterations in aquatic communities.
Highlights
Climate change alters biogeochemical cycling of major elements and nutrients, especially in regions with sparse vegetation, which are sensitive to changes in surface energy and water balance (Zepp et al 2007)
Of the collection of several sediment cores from Lake Revvatnet by Ojala et al (2016), a 30-cm sediment profile RE2, taken from the southern part of the main basin, was used in the present study. We selected this specific core for the present study because of its distant location from the network of streams in the north (Revbotnen, Fig. 1) to avoid the dominant effect of stream sediments and to capture a variety of environmental changes and lake-catchment dynamics
The present study showed major changes in the physical, biogeochemical and ecological environment of the High Arctic Revvatnet and its catchment
Summary
Climate change alters biogeochemical cycling of major elements and nutrients, especially in regions with sparse vegetation, which are sensitive to changes in surface energy and water balance (Zepp et al 2007). In addition to increasingly productive freshwater systems in the Arctic (Michelutti et al 2005; Holmgren et al 2010), in some regions, changes in the water balance and cryogenic processes have caused disappearance of lakes (Bouchard et al 2013; Linderholm et al 2018) as well as formation of new freshwater ecosystems known as permafrost thaw ponds (Vonk et al 2015). Climate-driven biological reorganizations in the Arctic include increased primary production owing to longer summer growing seasons, increased algal habitat availability and enhanced catchment nutrient fluxes (Wrona et al 2016). Melting permafrost will likely cause a release of nutrients into inlet streams driving changes in the ecosystem structure of lakes (Hobbie et al 1999; Thienpont et al 2013)
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