The High Arctic glacial ecosystem: new insights from nutrient budgets

Abstract

Abstract. This paper describes detailed budgets of water, Cl ) , dissolved Si and both inorganic and organic forms of nitrogen and phosphorus for two small glacier basins in Arctic Svalbard (Midre Love´nbreen and AustreBrøggerbreen). Rates of nutrient deposition are modest, dominated by inorganic nitrogen and episodically enhanced by extreme events. Hence deposition rates are also variable, ranging from 20 to 72 kg NO 3 -N km )2 a )1 and 10-37 kg NH 4 -N km )2 a )1 over just two consecutive years. Deposition of dissolved organic and particulate forms of nitrogen (DONand PN respectively) also appears significant and therefore requires further investigation (3-8 kg DON-N km )2 and 7-26 kg PN-N km )2 during winter -no summer data are available). Evidence for microbially mediated nutrient cycling within the glacial system is clear in the nutrient budgets, as is the release of large phosphorus, Si and organic/particulate nitrogen fluxes by subglacial erosion. The latter is entirely dependent upon the presence of subglacial drainage, promoting silicate mineral dissolution and the erosion of largely unweathered apatite. The large DON and PN fluxes are surprising and may relate to young organic nitrogen associated with microbial life within the glaciers. This is because wide spread assimilation of NH 4 + and perhaps even nitrification occurs on the glacier surface, most likely within abundant cryoconite holes. Further microbial activity also occurs at the glacier bed, where denitrification and sulphate reduction is now known to take place. Thus a two component 'glacial ecosystem' is proposed that is highly sensitive to climate change.

Microbial Cell Retention in a Melting High Arctic Snowpack, Svalbard

“…This model has previously been used in a snowmelt study at this site and is described by Hodson et al (2005). It uses radiation, humidity, and temperature data from Ny-Ålesund that was provided by the Alfred Wegener Institute (AWI) through S. Debatin.…”

“…If particles and bacteria remain in the snowpack rather than following the meltwater, as our results suggest, an elevated concentration of associated chemicals (such as NO 3 -) might be expected in the remaining snow. This is because both nitrification, which is typical among bacteria associated with debris (Hodson et al, 2005), and cell-lysis, which may be caused by osmotic stress in the very diluted meltwater (Harding et al, 2011), might release solutes to the surrounding snow and meltwater. Furthermore, chemical dry deposition and sublimation of snow-water could also influence the snowpack concentrations and thereby the elution response.…”

Chemical and isotopic characteristics of weathering and nitrogen release in non-glacial drainage waters on Arctic tundra

“…No data are available for the snowpack at Site 1, but analyses of snow on nearby glaciers found that concentrations of DON were generally less than those of inorganic N (Hodson et al 2005). In contrast, and in common with many low N systems, concentrations of DON in the stream generally exceeded those for total inorganic N (Table 2b).…”

“…focused on glacial catchments Wadham et al 2004;Hodson et al 2005;Wynn et al 2006). These systems have major roles in (i) regulating the biogeochemical cycling of nutrients that may impact both freshwater and marine ecosystems and (ii) in our understanding of cryosphere-atmosphere interactions and the potential feedbacks that contribute to climate regulation .…”

“…These systems have major roles in (i) regulating the biogeochemical cycling of nutrients that may impact both freshwater and marine ecosystems and (ii) in our understanding of cryosphere-atmosphere interactions and the potential feedbacks that contribute to climate regulation . The evolution of snowmelt chemistry in these glacial catchments is largely influenced by the presence of meltwater derived from stored glacial ice and snow and the substantial contribution of solutes released during the weathering and leaching of underlying rock and glacial tills (Hodson et al 2005). In contrast, relatively little published work exists regarding the chemistry of soil-water interactions in those parts of the polar tundra free of the complications of glacial systems in the European High Arctic.…”