@article {4489, title = {Nutrient uptake in the supraglacial stream network of an Antarctic glacier}, journal = {Journal of Geophysical Research: Biogeosciences}, year = {2020}, month = {08/2020}, abstract = {

In polar regions, where many glaciers are cold-based (frozen to their beds), biological communities on the glacier surface can modulate and transform nutrients, controlling downstream delivery. However, it remains unclear whether supraglacial streams are nutrient sinks or sources and the rates of nutrient processing. In order to test this, we conducted tracer-injections in three supraglacial streams (62 to 123 m long) on Canada Glacier in the Taylor Valley, of the McMurdo Dry Valleys, Antarctica. We conducted a series of additions including: nitrate (N), N + phosphate (P), N+ P + glucose (C), and N+C. In two reaches, N-only additions resulted in N uptake. The third reach showed net N release during the N-only addition, but high N uptake in the N+P addition, indicating P-limitation or N+P co-limitation. Co-injecting C did not increase N-uptake. Additionally, in these systems at low N concentrations the streams can be a net source of nitrogen. We confirmed these findings using laboratory-based nutrient incubation experiments on sediment collected from stream channels on Canada Glacier and two other glaciers in the Taylor Valley. Together, these results suggest there is active biological processing of nutrients occurring in these supraglacial streams despite low sediment cover, high flow velocities and cold temperatures, modifying the input signals to proglacial streams. As glaciers world-wide undergo rapid change, these findings further our understanding of how melt generated on glacier surfaces set the initial nutrient signature for subglacial and downstream environments.

}, keywords = {LTER-MCM, McMurdo Dry Valleys, nitrogen, nutrient tracers, nutrient uptake, sediments, supraglacial streams}, doi = {10.1029/2020JG005679}, url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020JG005679}, author = {Bergstrom, Anna J. and Michael N. Gooseff and Singley, Joel G. and Cohen, Matthew J. and Kathleen A. Welch} } @article {3522, title = {Niche and metabolic principles explain patterns of diversity and distribution: theory and a case study with soil bacterial communities}, journal = {Proceedings of the Royal Society B: Biological Sciences}, volume = {282}, year = {2015}, month = {05/2015}, pages = {2630}, abstract = {

The causes of biodiversity patterns are controversial and elusive due to complex environmental variation, covarying changes in communities, and lack of baseline and null theories to differentiate straightforward causes from more complex mechanisms. To address these limitations, we developed general diversity theory integrating metabolic principles with niche-based community assembly. We evaluated this theory by investigating patterns in the diversity and distribution of soil bacteria taxa across four orders of magnitude variation in spatial scale on an Antarctic mountainside in low complexity, highly oligotrophic soils. Our theory predicts that lower temperatures should reduce taxon niche widths along environmental gradients due to decreasing growth rates, and the changing niche widths should lead to contrasting α- and β-diversity patterns. In accord with the predictions, α-diversity, niche widths and occupancies decreased while β-diversity increased with increasing elevation and decreasing temperature. The theory also successfully predicts a hump-shaped relationship between α-diversity and pH and a negative relationship between α-diversity and salinity. Thus, a few simple principles explained systematic microbial diversity variation along multiple gradients. Such general theory can be used to disentangle baseline effects from more complex effects of temperature and other variables on biodiversity patterns in a variety of ecosystems and organisms.

}, keywords = {LTER-MCM}, issn = {0962-8452}, doi = {10.1098/rspb.2014.2630}, url = {http://rspb.royalsocietypublishing.org/lookup/doi/10.1098/rspb.2014.2630}, author = {Okie, Jordan G. and David J. Van Horn and Storch, David and John E. Barrett and Michael N. Gooseff and Kopsova, Lenka and Cristina D. Takacs-Vesbach} }