A new application of tracer-based methods to quantify nutrient uptake in the supraglacial drainage network of a cold-based Antarctic glacier
Abstract
Glacial systems have been recognized as important sources of organic and inorganic material to their downstream ecosystems. While much work has been done on exports from the subglacial environment, less is known about transport of nutrients from supraglacial systems to the surrounding landscape. It remains unclear how nutrients are processed in a supraglacial stream network, if it is a nutrient sink or source, and stoichiometric limitations on additional uptake. The alpine glaciers of the McMurdo Dry Valleys are the headwaters of the ecosystem and set the initial biogeochemical signature of the stream water. It is thus important to understand potential nutrient uptake and limitation in these supraglacial headwater systems. In this study we had two goals: to test a widely used method in a new setting and to determine nutrient uptake rates and potential limitation. We performed slug injections of nutrient and conservative tracers in three supraglacial stream reaches (62-123m long). On each reach we did two additions: nitrate and nitrate plus phosphate. We found that despite the differences in this stream type relative to the setting in which this method was developed (i.e., no hyporheic zone, near-freezing temperatures and variable cover of substrate on a bed of ice), it worked well for measuring nutrient uptake. Furthermore, we found that in two of our three reaches, N only additions resulted in N uptake. The third reach resulted in net N release during an N addition. However, this third reach had the highest measured N uptake rate across all three reaches when N and P were added together. Therefore, the third reach appears to be P limited or co-limited by N and P, while reaches one and two are N limited. Background concentrations of N and P were below detection limits, suggesting that known sources of nutrients (cryoconite holes and nitrate in ice from atmospheric deposition) are consistently depleted prior to reaching our study site. This novel application of the nutrient tracer slug injection has potential to be applied in other supraglacial systems and can help reveal the global importance of glaciers on processing nutrients.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.H42A..05B
- Keywords:
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- 1804 Catchment;
- HYDROLOGY;
- 1806 Chemistry of fresh water;
- HYDROLOGY;
- 1848 Monitoring networks;
- HYDROLOGY;
- 1895 Instruments and techniques: monitoring;
- HYDROLOGY