Nutrients and organic matter in a glacial river—floodplain system (Val Roseg, Switzerland)

Abstract

Nutrient and organic matter dynamics were evaluated for a glacial river-floodplain system in the Swiss Alps (Val Roseg). Glacial melt water was the primary source of particulate organic and inorganic matter; hillslope groundwater was richest in DOC and SiO 2 ; and pulses in dissolved nitrogen were identified during spring snowmelt. Calculations of temporal coherency revealed that hydrological processes within the catchment-floodplain complex controlled nutrient and organic matter species along the main channel; however, local hydrological and/or biogeochemical processes played a major controlling role in most floodplain channels. DON and NO 3 -N were the only variables that were in average significantly correlated across all sampling sites. Comparisons of measured concentrations and concentrations based on a two end member mixing model indicated that the floodplain served as a major sink for particulate phosphorous and suspended matter but was never a source for nutrients or organic matter. Annual areaspecific export rates from the Val Roseg catchment were 7.6 kg ha Ϫ1 yr Ϫ1 for TOC (47% DOC), 4.3 kg for TP (98% particulate phosphorus), and 4.1 kg for TN (78% NO 3 -N).Quantification of nutrient and organic matter sources, transformations, and sinks at the catchment/floodplain scale is a major challenge in ecology. This is in particular true for remote arctic and high alpine streams that have received much less attention compared to more accessible areas (Milner and Petts 1994;Wissmar et al. 1997). Alpine and arctic streams appear resource limited in terms of both nutrients and organic matter. For example, Lock et al. (1990) showed that the addition of phosphorous to an arctic river resulted in a substantial stimulation of both heterotrophic and autotrophic processes. Robinson and Gessner (2000) demonstrated that nutrient addition accelerated leaf breakdown in a glacial stream. Further, there is strong evidence that zoobenthic communities in glacial streams are not solely structured by temperature and channel stability (cf. Milner and Petts 1994), but are strongly influenced by seasonal shifts in water sources and corresponding availability of nutrients and or-1 Corresponding author (tockner@eawag.ch). AcknowledgementsThis study was supported by a research grant from the Swiss National Science Foundation (SNF 21-49243). We appreciate the field support of Tina Boesch, Birgit Klein, Chris Robinson, Rainer Zah, and Peter Burgherr, and we are especially grateful to Richard Illi and Bruno Ribi for the chemical analyses. We express our sincere thanks to Plenio Testa and his crew at the 'Hotel Roseg' for their hospitality and to the communes of Pontresina and Samedan for providing access to the sampling area. We also appreciate helpful comments by Jürg Zobrist, Edith Kaiser, and Chris Robinson. Thoughtful comments by two anonymous reviewers are gratefully acknowledged.

Bacterial structures and ecosystem functions in glaciated floodplains: contemporary states and potential future shifts

“…The waters of the Roseg and Loetschental catchments are partly fed by valley glaciers, which have retreated continuously over the past century (Maisch, 1988;Tockner et al, 1997Tockner et al, , 2002Malard et al, 2000). Permanently flowing first-order tributaries contribute groundwater and snowmelt to kryal main channels, which have peak flows during spring and summer (Malard et al, 2000).…”

Culturable bacteria community development in postglacial soils of Ecology Glacier, King George Island, Antarctica

“…Distance from a retreating glacier reflects soil age, with vegetation-free sandy deposits at the front of the glacier contrasting with more differentiated soils further away (Schmidt et al 2008). Antarctic soils that only recently became ice-free are considered to be nutrient limited (Sigler et al 2002;Darmody et al 2005), despite the influence of local meltwater streams, organic and inorganic inputs from marine aerosols, guano deposits in penguin and other seabird rookeries, slow-growing cryptogamic plants, and marine algae deposited on the shore and dispersed by wind (Orchard and Corderoy 1983;Tibbles and Harris 1996;Beyer et al 1999;Tockner et al 2002;Grzesiak et al 2009). Therefore, an urgent need exists to understand nutrient-and carbon-cycling processes in these recent and emerging environments.…”

The High Arctic glacial ecosystem: new insights from nutrient budgets

“…In recent years, ecologists have given major emphasis to the quantification of nutrient sources, transformations, and sinks at the catchment scale (Tockner et al 2002). However, little attention has been given to the biogeochemical processes operating in cold regions, despite their sensitivity to climate change.…”