Abstract
The Arctic is being disproportionally affected by climate change compared with other geographic locations, and is currently experiencing unprecedented melt rates. The Greenland Ice Sheet (GrIS) can be regarded as the largest supraglacial ecosystem on Earth, and ice algae are the dominant primary producers on bare ice surfaces throughout the course of a melt season. Ice-algal-derived pigments cause a darkening of the ice surface, which in turn decreases albedo and increases melt rates. The important role of ice algae in changing melt rates has only recently been recognized, and we currently know little about their community compositions and functions. Here, we present the first analysis of ice algal communities across a 100 km transect on the GrIS by high-throughput sequencing and subsequent oligotyping of the most abundant taxa. Our data reveal an extremely low algal diversity with Ancylonema nordenskiöldii and a Mesotaenium species being by far the dominant taxa at all sites. We employed an oligotyping approach and revealed a hidden diversity not detectable by conventional clustering of operational taxonomic units and taxonomic classification. Oligotypes of the dominant taxa exhibit a site-specific distribution, which may be linked to differences in temperatures and subsequently the extent of the melting. Our results help to better understand the distribution patterns of ice algal communities that play a crucial role in the GrIS ecosystem.
Highlights
The Greenland Ice Sheet (GrIS) is an important component of Earth’s cryosphere; it plays a crucial role as a freshwater reservoir and is an integral component of the Earth system processes driving current sea level rise and climate change [1, 2]
The availability of liquid water is restricted to the short summer melt season, resulting in ice algae having to cope with desiccation stress for most of the year
Ice algae are restricted to the ice surface, where they overwinter in a frozen state [12]
Summary
The Greenland Ice Sheet (GrIS) is an important component of Earth’s cryosphere; it plays a crucial role as a freshwater reservoir and is an integral component of the Earth system processes driving current sea level rise and climate change [1, 2]. Only in the last decade have we recognized their importance with regard to primary production and decrease in surface albedo [6,7,8,9]. After the onset of melting and the disappearance of the snow cover, ice algae are the dominant primary producers on bare ice surfaces [6, 10]. Together with airborne-delivered impurities such as mineral dust, black carbon and bacteria, this algal-derived pigment causes a darkening of the ice surface, which in turn decreases albedo and increases melt rates [6, 10, 15,16,17,18,19]. A. nordenskiöldii has so far 000159 ã 2018 The Authors
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