Landscape-scale soil phosphorus variability in the McMurdo Dry Valleys

Heindel, Ruth C.; Spickard, Angela M.; Virginia, Ross A.

doi:10.1017/s0954102016000742

Cited by 14 publications

(8 citation statements)

References 40 publications

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“…Alternatively, due to the absence of vascular plants, Antarctic Dry Valley soils have some of the lowest soil organic matter concentrations on Earth ( Burkins et al, 2000 ; Jobbagy and Jackson, 2000 ) with much of the soil organic matter being “legacy” C accumulated over thousands of years by cryptoendolithic bacteria, paleolake deposition, and minor inputs of contemporary algae and cyanobacteria from lakes, intermittent streams and saturated zones ( Burkins et al, 2000 ). The concentrations of inorganic N and P are relatively low with N entering the system via atmospheric deposition ( Michalski et al, 2005 ), endolithic and hypolithic cyanobacterial N 2 fixation over millions of years ( Cowan et al, 2014 ), and from dust, while P enters soils through mineral weathering ( Barrett et al, 2007 ; Heindel et al, 2017 ). Both N and P concentrations vary among soils occurring on glacial tills with distinct exposure age and mineralogy ( Barrett et al, 2007 ).…”

Section: Introductionmentioning

confidence: 99%

Stoichiometric Shifts in Soil C:N:P Promote Bacterial Taxa Dominance, Maintain Biodiversity, and Deconstruct Community Assemblages

et al. 2018

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Imbalances in C:N:P supply ratios may cause bacterial resource limitations and constrain biogeochemical processes, but the importance of shifts in soil stoichiometry are complicated by the nearly limitless interactions between an immensely rich species pool and a multiple chemical resource forms. To more clearly identify the impact of soil C:N:P on bacteria, we evaluated the cumulative effects of single and coupled long-term nutrient additions (i.e., C as mannitol, N as equal concentrations NH4+ and NO3−, and P as Na3PO4) and water on communities in an Antarctic polar desert, Taylor Valley. Untreated soils possessed relatively low bacterial diversity, simplified organic C sources due to the absence of plants, limited inorganic N, and excess soil P potentially attenuating links between C:N:P. After 6 years of adding resources, an alleviation of C and N colimitation allowed one rare Micrococcaceae, an Arthrobacter species, to dominate, comprising 47% of the total community abundance and elevating soil respiration by 136% relative to untreated soils. The addition of N alone reduced C:N ratios, elevated bacterial richness and diversity, and allowed rare taxa relying on ammonium and nitrite for metabolism to become more abundant [e.g., nitrite oxidizing Nitrospira species (Nitrosomonadaceae), denitrifiers utilizing nitrite (Gemmatimonadaceae) and members of Rhodobacteraceae with a high affinity for ammonium]. Based on community co-occurrence networks, lower C:P ratios in soils following P and CP additions created more diffuse and less connected communities by disrupting 73% of species interactions and selecting for taxa potentially exploiting abundant P. Unlike amended nutrients, water additions alone elicited no lasting impact on communities. Our results suggest that as soils become nutrient rich a wide array of outcomes are possible from species dominance and the deconstruction of species interconnectedness to the maintenance of biodiversity.

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Section: Introductionmentioning

confidence: 99%

Stoichiometric Shifts in Soil C:N:P Promote Bacterial Taxa Dominance, Maintain Biodiversity, and Deconstruct Community Assemblages

et al. 2018

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“…The productivity of lentic and lotic ecosystems depends on fluxes of weathering‐derived solutes, particularly P and Si. Bioavailable P is primarily sourced from apatite weathering (Heindel et al, ) and can be the limiting nutrient for lake phytoplankton (Lizotte et al, ; Priscu, ) and stream cyanobacteria communities (Kohler et al, ). Similarly, Si is required for diatom growth and dissolved Si may influence diatom species composition in benthic microbial mats.…”

Section: Discussionmentioning

confidence: 99%

Transit Times and Rapid Chemical Equilibrium Explain Chemostasis in Glacial Meltwater Streams in the McMurdo Dry Valleys, Antarctica

Wlostowski

Gooseff

McKnight

et al. 2018

Geophysical Research Letters

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Fluid transit time is understood to be an important control on the shape of concentration‐discharge (C‐q) relationships, yet empirical evidence supporting this linkage is limited. We investigated C‐q relationships for weathering‐derived solutes across seven Antarctic glacial meltwater streams. We hypothesized that (H1) solute fluxes in McMurdo Dry Valley streams are reaction limited so that C‐q relationships are characterized by dilution and that (H2) transit time explains between‐stream variability in the degree of C‐q dilution. Results show that C‐q relationships are chemostatic because solute equilibrium times are shorter than stream corridor fluid transit times. Between‐stream variability in the efficiency of solute production is positively correlated with transit time, suggesting that transit time is an important control on the solute export regime. These results provide empirical evidence for the controls on weathering‐derived C‐q relationships and have important implications for Antarctic ecosystems and solute export regimes of watersheds worldwide.

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“…N is more readily available, as it can be sourced through fixation, internal cycling, and from melting of the surrounding ice, which is nitrate rich due to atmospheric deposition (Legrand & Mayewski, 1997). Phosphorus is not detectable in glacier ice (Bagshaw et al, 2013) and is primarily sourced from mineral weathering of sediment (Stibal et al, 2008), which is deposited on glaciers by wind lofting the Ross Sea Drift material from the valley floor (Heindel et al, 2017; Sabacka et al, 2012). Glaciers located closer to the coast may have higher concentrations of P‐bearing minerals and may not exhibit strong P limitation relative to those closer to the polar plateau.…”

Section: Discussionmentioning

confidence: 99%

Nutrient Uptake in the Supraglacial Stream Network of an Antarctic Glacier

et al. 2020

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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 colimitation. Coinjecting 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 worldwide 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. Plain Language Summary In polar regions most glaciers are frozen to their beds, meaning that meltwater from these glaciers comes from the surface, or "supraglacial" environment. Active biological communities exist in this supraglacial environment where they generate and recycle nutrients. However, it remains unclear whether nutrients are removed by the supraglacial streams, and what limits this removal process. We did experimental nutrient additions in three streams on Canada Glacier in the Taylor Valley of the McMurdo Dry Valleys, Antarctica. We found that nitrogen in the form of nitrate was quickly removed. In one of three locations, the addition of phosphorus stimulated more nitrogen removal than just adding nitrogen alone. We also found that at low nitrogen concentrations, the streams can be a net source of nitrogen. We confirmed these field experiment findings using laboratory nutrient incubation experiments on sediment collected from stream channels on Canada Glacier and two other glaciers in the Taylor Valley. Supraglacial streams act as a filter and can remove nitrogen from meltwater before it leaves the glacier and affect the quantity and type of nutrients transported to downstream ecosystems. This is important worldwide because glaciers are often the headwaters of the stream network.

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Landscape-scale soil phosphorus variability in the McMurdo Dry Valleys

Cited by 14 publications

References 40 publications

Stoichiometric Shifts in Soil C:N:P Promote Bacterial Taxa Dominance, Maintain Biodiversity, and Deconstruct Community Assemblages

Stoichiometric Shifts in Soil C:N:P Promote Bacterial Taxa Dominance, Maintain Biodiversity, and Deconstruct Community Assemblages

Transit Times and Rapid Chemical Equilibrium Explain Chemostasis in Glacial Meltwater Streams in the McMurdo Dry Valleys, Antarctica

Nutrient Uptake in the Supraglacial Stream Network of an Antarctic Glacier

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