Glacial Streams Research Articles

Physical and biological changes to a lengthening stream gradient following a decade of rapid glacial recession

AbstractIn mountains, environmental gradients are steep in both terrestrial and aquatic systems, and climate change is causing upward shifts of physical and biological features of these gradients. Glacial streams are an interesting system to evaluate such shifts both because streams have a linear nature (for simplicity of analysis), and because the stream habitat will at least temporarily lengthen as it follows receding glaciers upward. The Tschierva Glacier, Swiss Alps, receded 482 m upstream from 1997 to 2008. We tested the null hypothesis that the physical and biological stream gradient below this glacier maintained the same structure between these time periods, but simply shifted upward following the glacial source. We compared longitudinal patterns of water temperature and zoobenthic community structure in 1997 and 2007–2008 during three seasons (spring, summer, fall) along the uppermost ca. 5 stream km. Upward shifts were evident, including colonization of the newly exposed stream reaches by cold‐adapted taxa, and the appearance in 2007/2008 of four lower‐altitude species that were previously absent. Overall, however, results rejected the null hypothesis, instead revealing significant changes in gradient structures. These included a more steeply increasing temperature profile downstream of the glacier and increased amplitude of seasonal community turnover in 2007/2008 vs. 1997. Long‐term (1955–2007) flow records revealed increasing short‐term and seasonal hydrologic variability, which might have influenced the increased intra‐annual community variability. The steepening of the temperature gradient was likely caused by a warming lake‐outlet tributary upon which glacial influence was diminished between 1997 and 2007/2008. These results suggest that upward‐shifting gradients in glacial streams can involve complex interactions with other landscape elements and that local‐scale climate response can progress even more rapidly than the rate of glacial recession.

Foreword: Global change and river ecosystems—implications for structure, function, and ecosystem services

Foreword: Global change and river ecosystems-implications for structure, function, and ecosystem services.- Understanding effects of global change on river ecosystems: science to support policy in a changing world.- Biogeochemical implications of climate change for tropical rivers and floodplains.- Dynamics of a benthic microbial community in a riverine environment subject to hydrological fluctuations (Mulargia River, Italy).- Global changes in pampean lowland streams (Argentina): implications for biodiversity and functioning.- Factors regulating epilithic biofilm carbon cycling and release with nutrient enrichment in headwater streams.- Periphyton biomass and ecological stoichiometry in streams within an urban to rural land-use gradient.- The physico-chemical habitat template for periphyton in alpine glacial streams under a changing climate.- The periphyton as a multimetric bioindicator for assessing the impact of land use on rivers: an overview of the Ardieres-Morcille experimental watershed (France).- Discharge and the response of biofilms to metal exposure in Mediterranean rivers.- Effects of eutrophication on the interaction between algae and grazers in an Andean stream.- Comparing fish assemblages and trophic ecology of permanent and intermittent reaches in a Mediterranean stream.- Global change and food webs in running waters.- Effects of hydromorphological integrity on biodiversity and functioning of river ecosystems.- Organic matter availability during pre- and post-drought periods in a Mediterranean stream.- Flow regime alteration effects on the organic C dynamics in semiarid stream ecosystems.- A multi-modeling approach to evaluating climate and land use change impacts in a Great Lakes River Basin.- Implications of global change for the maintenance of water quality and ecological integrity in the context of current water laws and environmental policies.

Geometry and drainage of a retreating glacier overlying and recharging a karst aquifer, Tsanfleuron-Sanetsch, Swiss Alps

Alpine glaciers store large amounts of freshwater contributing to groundwater recharge during warmer periods, but the inter­actions between glaciers and aquifers have rarely been inves­tigated in detail. The Tsanfleuron-Sanetscharea, Switzerland, is an ideal test site to study glacier-aquifer interactions. It con­sists of a rapidly retreating glacier (2.8 km 2 ) overlying a karst aquifer drained by a spring (mean discharge 600–700 L/s) used for drinking water supply and irrigation. The geometry and structure of the glacier were assessed by means of geophysical surveys, using radiomagnetotellurics (RMT). The estimated ice volume is 1.0 x 10 8 m 3 (0.92 x 10 8 m 3 water equivalent), but the glacier currently loses 1.5 m ice thickness per year. Field obser­vations, flow measurements and tracer tests allowed character­isation of glacier drainage and aquifer recharge. Three recharge pathways have been identified: 1) The main glacial stream sinks into the aquifer via swallow holes 3 km downstream of the glacier mouth; 2) Numerous small meltwater streams sink underground shortly below the glacier front; 3) Subglacial meltwaters and supraglacial streams sink into the glacier via moulins and contribute to aquifer recharge throughfractures and swallow holes underneaththe glacier. Recharge and spring discharge display strong diurnal and seasonal variability, witha general high-flow period during snow and glacier melt from spring to autumn. Preliminary predictions of the future avail­ability of spring water after disappearance of the glacier suggest that the discharge may decrease by 20–30%. Nearly all of this loss will occur in summer and autumn, presumably resulting in temporary water shortage.

Longitudinal zonation of macroinvertebrates in an Ecuadorian glacier‐fed stream: do tropical glacial systems fit the temperate model?

Summary1. The ecology of glacier‐fed streams at temperate latitudes has been intensely studied in recent years, leading to the development of a well‐validated conceptual model on the longitudinal distribution of macroinvertebrate communities downstream of the glacier margin (Freshwater Biology, 2001a; 46, 1833). However, to our knowledge, the ecology of tropical glacier‐fed streams has not yet been studied.2. We sampled benthic macroinvertebrates and measured environmental variables at nine sites between 4730 and 4225 m altitude along a 4.3 km stretch of a glacier‐fed stream 40 km south of the equator in the Ecuadorian Andes. Our goal was to study the longitudinal distribution of the fauna in relation to environmental factors and to compare this with the conceptual model based on temperate–arctic glacier‐fed streams.3. Total density of invertebrates differed considerably at the two highest altitude sites; 4600 m−2 at a pro‐glacial lake outlet and only 4 m−2 at a site originating directly from the glacier snout. Otherwise, there was a downstream decrease in density to about 825 m−2 at the three lowest sites. Taxon richness increased with distance from the glacier, very similar to the pattern predicted. A total of 28 taxa were collected; two at the glacier snout, seven at the nearby pro‐glacial lake outlet, 13 at site 2 (<400 m from the glacier) and 20 at the lowest sites.4. The numerical percentage of Chironomidae (Diptera) decreased downstream from 100 to 44%. The subfamily Podonominae was numerous at the highest sites but became much less important further downstream. The Orthocladiinae were important both in numbers and species at all sites, while Diamesinae were numerous only in the middle of the reach studied and were completely absent from the upper three sites. The limited importance of the Diamesinae, and its replacement by Podonominae, is different from the pattern typically observed in north‐temperate glacier‐fed streams. This could be because of the fact that the genus Diamesa is missing from the Neotropics.5. Stream temperature and channel stability explained most of the variability in faunal composition and richness, supporting the model. Stability increased systematically downstream while temperature did not. Surprisingly, no classical kryal zone (Tmax < 4 °C) was found, as even the site closest to the glacier snout (50 m) had a Tmax of 15 °C and no site had Tmax < 8 °C. We propose that this might be a general feature of equatorial glacial streams.

The physico-chemical habitat template for periphyton in alpine glacial streams under a changing climate

The physico-chemical habitat template of glacial streams in the Alps is characterized by distinct and predictable changes between harsh and relatively benign periods. Spring and autumn were thought to be windows of favorable environmental conditions conducive for periphyton development. Periphyton biomass (measured as chlorophyll a and ash-free dry mass) was quantified in five glacial and three non-glacial streams over an annual cycle. One glacial stream was an outlet stream of a proglacial lake. In all glacial streams, seasonal patterns in periphyton were characterized by low biomass during summer high flow when high turbidity and transport of coarse sediment prevailed. With the end of icemelt in autumn, environmental conditions became more favorable and periphyton biomass increased. Biomass peaked between late September and January. In spring, low flow, low turbidity, and a lack of coarse sediment transport were not paralleled by an increase in periphyton biomass. In the non-glacial streams, seasonal periphyton patterns were similar to those of glacial streams, but biomass was significantly higher. Glacier recession from climate change may shift water sources in glacier streams and attenuate the glacial flow pulse. These changes could alter predicted periods of optimal periphyton development. The window of opportunity for periphyton accrual will shift earlier and extend into autumn in channels that retain surface flows.

Distribution and diversity of polychaetes collected by trawling in Admiralty Bay: an Antarctic glacial fiord

The aim of the study is to determine patterns of distribution, species richness and diversity of polychaetes collected by trawling in Admiralty Bay. Forty-seven species of polychaetes were found in 75 samples collected in 1988 along a depth range from 15 to 500 m. Four polychaete assemblages were distinguished. The most diverse and peculiar assemblage was found in the deepest sublittoral of the central basin from ca. 300–500 m with main constant species Laetmonice producta, Sternaspis sp. and Thelepus cincinnatus. Shallow water assemblages had low diversity and species richness. The most common and eurytopic epifaunal polychaetes were Aglaophamus trissophyllus, Barrukia cristata, Harmothoe spp., Flabelligera mundata and Perkinsiana littoralis. The low species richness in shallow waters of Admiralty Bay is probably associated with depth, influence of glacial streams and suspended matter inflow which is particularly distinct in the shallow water fiord areas.

Crustal Structure of Palmer Deep (West Coast of The Antarctic Peninsula) by Geophysical Data

The Ukrainian Antarctic expeditions acquired new geoelectrical data ('short-impulse electromagnetic field formation' – FSPEF, and 'vertical electric-resonance sounding' – VERS) along profiles across Drake Passage and continental shelf of Antarctic Peninsula. The electromagnetic experiments yielded new data set with unique information about the inner structure and new values of the depth of the Moho discontinuity of West Antarctica region. Deep crustal heterogeneities of the Palmer Deep Basin that were obtained from the VERS- profiles data could be connected with processes of tectonic transformations of the Antarctic Peninsula shelf structures. Possibly, the conformities of continental shelf glacial streams may be explained exactly by a tectonic factor of recent geological past. New information about sediment distribution and inner crustal structure has an important value for searching and prospecting the hydrocarbon deposits of Palmer Deep region

When and how did the continental ice retreat from Estonia?

The territory of Estonia was freed from the continental ice in Gotiglacial time, which was charaterized by high activity of the glacial streams and lobes and a highly variable glacial morphogenesis. Glaciers left behind different landforms and deposits, up to 200 m thick. Glacial accumulation was concentrated in the interlobate subglacial uplands. During the course of the thinning of the ice sheet, the movement and dynamics of its individual lobes was controlled by the underlying subglacial topography. The deglaciation history has been dated using 14C, varve chronology, palynology, electron spin resonance (ESR), thermoluminescence (TL), optically stimulated luminescence and the 10Be methods. The majority of the radiocarbon dates obtained from submorainic and intermorainic sequences are younger than would be expected. The obtained OSL and cosmogenic beryllium dates are extremely heterogenous, and cannot be readily used to improve the existing stratigraphical charts for the late-glacial period. In varve years Estonia became ice free at about 14 000–12 600 years ago.

Comparison of glacial and non-glacial-fed streams to evaluate the loading of persistent organic pollutants through seasonal snow/ice melt

The release of persistent organic pollutants (PCBs, HCB, HCHs and DDTs) accumulated in Alpine glaciers, was studied during spring-summer 2006 on the Frodolfo glacial-fed stream (Italian Alps). Samples were also taken on a non-glacial stream in the same valley, to compare POP contribution from different water sources (glacier ice, recent snow and spring). In late spring and early summer (May, June) recent snow melting is the most important process. POP contamination is more affected by local emissions and transport, and comparable levels have been measured in both streams for all studied compounds. In late summer and autumn (July–October), the contribution of ice melting strongly increases. In the glacial-fed stream the concentration of chlorinated pesticides (HCHs and DDTs) is about one order of magnitude higher than in the non-glacial-fed. A different behaviour was observed for PCBs, characterised by a peak in June showing, in both streams, concentrations three orders of magnitude higher than the background levels measured in May and in October. This result should be attributed to local emissions rather than long range atmospheric transport (LRAT). This hypothesis is supported by the PCB congener profile in June strictly comparable to the most commonly used Aroclor technical mixtures. The different seasonal behaviour observed for the different groups of chemicals indicates the POP loading in glacial streams is a combined role of long range atmospheric transport and local emission.

Investigating changes of electrical characteristics of the saturated zone affected by hazardous organic waste

The Picillo Farm, EPA Superfund Site, in western Rhode Island was an unauthorized disposal site of hazardous organic chemicals. Predominantly organic contaminants have entered an aquifer comprised of layered glacial deposits and fractured bedrock and spread past the site boundaries with groundwater flow. Hydraulic conductivities in the glacial deposits range over two orders of magnitude and fractures and faults in the granitic bedrock further complicate the spreading of contaminants. Monitoring wells delineate two plumes that extend towards a fault-controlled valley with lakes and wetlands; one to the northwest and the other to the southwest. In this investigation we studied the electrical characteristics of both plumes. One dimensional Schlumberger depth soundings were conducted along several profile lines over the plumes and compared to those over non-contaminated sections of the site. With regard to the southwestern plume, high formation factors (ratio of bulk layer to pore water resistivity) between 12 and 45 were observed compared to values between 2.5 and 7.7 measured over the non-contaminated sections. Also, high values (> 5) of vertical electrical anisotropy (ratio of geoelectrically determined depth to high resistivity bedrock to drilled depth to bedrock) were measured over the contaminated part of the site. These values are extremely high compared to other non-contaminated sites (range: 2 to 3) in glacial stream channels of southern Rhode Island. Geoelectric measurements were affected by lateral effects. However, the consistency of high formation factors (11 to 35) and high vertical anisotropies (3 to 5) over the southwestern plume in comparison to low formation factors (3 to 8) and vertical anisotropies (1 to 1.5) over non-contaminated sites represents a marked difference between both sites. Overall, the Schlumberger depth soundings are less susceptible to near-surface lateral inhomogeneities than expected from other geoelectrical methods. Also, the disadvantage of a 1D interpretation was compensated by estimating resistivity and thickness ranges within the concept of non-uniqueness using the Dar Zarrouk parameters (Maillet, R., 1947. The fundamental equations of electrical prospecting. Geophysics, 12(4): 529–556.). The results over the northwestern plume, i.e. an area with higher contaminant concentration than the southwestern plume, were mixed and showed no consistent trends. Predominantly reducing conditions, as indicated by the presence of soluble ferric (FeII) iron hydroxides in ground water samples, increased the electrical conductivity. This is believed to have compensated the effect of high formation factors on the bulk saturated layer resistivity within the affected area.

Mayfly production in a New Zealand glacial stream and the potential effect of climate change

In contrast to the northern hemisphere where species of Chironomidae are usually the dominant benthic invertebrates in the coldest upper reaches of glacial streams, mayflies (Deleatidium spp.: Leptophlebiidae) predominate in equivalent conditions in New Zealand. We examined the life histories and annual production of Deleatidium spp. at two sites on the Matukituki River (South Island, New Zealand) and at three sites in its glacier-fed tributary, Rob Roy Stream. Mean annual water temperature at the five sites ranged from 2.1 to 7.0°C. Monthly sampling showed that mayfly populations were poorly synchronised at all sites but were probably univoltine. The large Deleatidium cornutum was the dominant mayfly species found at the upper sites (Sites 1 and 2) on Rob Roy Stream, whereas above the confluence with Matukituki River (Site 3) it co-existed with a complex of smaller species we refer to as D. “angustum”. Deleatidium “angustum” also dominated at the Matukituki sites. Deleatidium production calculated for the five sites, assuming an 11-month nymphal life, ranged from 0.48 g dry weight/m2/year (Site 1) to 3.07 g dry weight/m2/year (Site 3). The values for D. cornutum at Sites 2 and 3 are high for a species of Deleatidium and reflect its large size. This species appears to be strongly adapted for growth at low temperatures. Climate change scenarios for New Zealand predict the gradual and ultimate loss of small South Island glaciers and a consequent warming of streams as runoff from rainfall and snow melt becomes more dominant in spring. As a result, suitable habitats will be lost for cold-water specialists such as D. cornutum, and they are likely to suffer reductions in their distributional range and local extinction. In contrast, species such as those in the D. “angustum” complex may extend their ranges into streams formerly dominated by glacial meltwater.

Contrasting chironomid assemblages in two high Arctic streams on Svalbard

Chironomid communities were investigated twice in summer 1997 in a glacier-fed (Bayelva) and a non-glacial stream (Londonelva), fed by snowmelt and rainfall near Ny-Alesund (Svalbard Archipelago, 78°N). Environmental conditions (discharge, water temperature, suspended sediment) were harsher for the fauna in the glacial system than in the non-glacial one. In all, 29 chironomid species were identifi ed from larval, pupal and male adult material, including six species new to Svalbard. Diamesa was the best represented genus, showing contrasting distributional trends at the species level in the two streams: Diamesa aberrata and D. bohemani were more characteristic of the glacial stream, while D. arctica and D. bertrami colonised primarily the snowmelt-fed one. Total abundance of chironomid larvae was ten times greater in Londonelva than in Bayelva. The prevailing harsh conditions in glacial streams, such as high and fl uctuating discharge, high sediment transport and substrate instability, strongly infl uenced the abundance of the chironomid fauna, demonstrating the key importance of water source in Arctic streams.

Life at the Edge: Habitat Condition and Bottom Faunaof Alpine Running Waters

AbstractAlpine river systems are fed by glacial icemelt, snowmelt, and groundwater and share common features (e.g., steep gradients, high flow velocities and dynamics) but each source produces a characteristic discharge regime and a distinctive suite of physical and chemical characteristics. The distribution of snow, ice, and groundwater springs varies spatially from stream‐reach to catchment scale, resulting in stream segments with characteristics, reflecting the different runoff sources. In recent investigations we have been focusing on the large variety of natural freshwater ecosystems in the Hohe Tauern Nationalpark and, based on hydromorphological conditions at catchment and reach scale, we defined specific river types. Glaciation in the catchment turned out to be a major factor for defining the hydromorphological conditions. Subsequently, we tested the effect of glaciation on the bottom fauna in applying a preliminary set of species traits, indicating strategies and adaptations of resilience and resistance as well as to face environmental harshness. Our results demonstrated the high degree of adaptation of the bottom fauna in alpine streams but especially in glacial streams. As current climate change scenarios propose major impacts at both high altitude and latitudes, considerable changes within the faunal assemblages including species number, densities and the distribution of species traits are to be expected. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Macroinvertebrate assemblages in glacial stream systems: A comparison of linear multivariate methods with artificial neural networks

The distribution of 19 macroinvertebrate taxa was related to 36 environmental variables in 3 Alpine glacial streams. Principal component analysis (PCA) and a self-organising map (SOM) were used to ordinate sample sites according to community composition. Multiple linear regression (MLR) was carried out with the environmental variables as predictors and each macroinvertebrate taxon as criterion variable, a multilayer perceptron (MLP) used the environmental variables as input neurons and each taxon as output neuron. The contribution of each environmental variable to macroinvertebrate response was quantified examining MLR regression coefficients and compared with partial derivative (Pad) and connection weights approach (CW) methods. PCA and SOM emphasized a difference between glacial (kryal) and non-glacial (krenal and rhithral) stations. Canonical correlation analysis (CANCOR) confirmed this separation, outlining the environmental variables (altitude, distance from source and water temperature) which contributed most with macroinvertebrates to site ordination. SOM clustered kryal, rhithral and krenal in three well separated group of sites. MLR and MLP detected the best predictors of macroinvertebrate response. Pad sensitivity analysis and CW method emphasized the importance of water chemistry and substrate in determining the response of taxa, the importance of substrate was overlooked by linear multivariate analysis (MLR).

Stability and Persistence of Alpine Stream Macroinvertebrate Communities and the Role of Physicochemical Habitat Variables

Macroinvertebrate communities in alpine streams have rarely been examined over more than two consecutive years or at sub-monthly temporal resolution during the summer melt season, in relation to a range of stream physicochemical habitat measurements. This paper addresses these research gaps by investigating the inter- (late melt season, 1996–2003) and intra-annual (bi-weekly; June–September, 2002–2003) community compositional stability and persistence of three alpine streams fed from different water sources (snow, glaciers and groundwater) in the Taillon–Gabietous catchment, French Pyrenees. Inter-annual community stability and persistence decreased from 1996 to 2003; however, groundwater stream communities changed less than those in the main glacial stream. Intra-annual community stability varied spatially and temporally, particularly in relation to water quality variables (water temperature and suspended sediment concentration); water quantity (stream discharge) was less important perhaps due to taxa possessing adaptations to flow variability. The 15 most abundant taxa were consistently more stable and persistent than the entire stream community suggesting a common pool of taxa in these streams. Overall, the results support the view that streams originating from different alpine water sources are characterised by distinct benthic macroinvertebrate assemblages, and demonstrate the value of sampling at nested temporal scales (inter-annual to bi-weekly) for understanding how these stream ecosystems function.

Patterns of macroinvertebrate traits along three glacial stream continuums

Summary1. Glacier‐fed streams are characterised by low spatial but high temporal heterogeneity, manifested in seasonal and diurnal discharge and suspended sediment peaks induced by glacial runoff. These streams shelter macroinvertebrate communities adapted to such harsh environmental conditions. Studies relating macroinvertebrate traits to environmental conditions in glacial streams could provide important insights into the structure and function of glacial stream communities.2. From data collected in three glacial streams from the central Swiss and southern French Alps, we analysed the relationships among six biological traits to define five groups of macroinvertebrate taxa with similar suites of traits.3. The longitudinal distribution of the five groups and of individual traits was analysed, as well as their variation according to a glaciality index combining water temperature, conductivity, suspended solids and substrate stability.4. The trait diversity along the three streams showed a strong upstream‐downstream gradient. The upper reaches were dominated by a single group of taxa characterised by small, crawling, deposit feeders. The other trait‐based groups appeared progressively downstream.5. Changes in the relative frequency of trait‐based groups along the glaciality gradient highlighted the dominance of all‐rounder resistant/resilient traits in the three streams and confirmed that environmental conditions in the glacial streams are too harsh or uniform to allow macroinvertebrate communities to develop alternative suites of traits. The findings are discussed in relation to the question of trait coding in the available literature.

Hydroclimatological influences on water column and streambed thermal dynamics in an alpine river system

Few detailed studies of thermal dynamics exist for alpine river systems despite their high climatic sensitivity. This paper examines water column temperatures (15 min resolution) for snowmelt/glacier-fed streams and groundwater tributaries in the French Pyrénées. Streambed temperatures were monitored at: (1) the Taillon Glacier stream, (2) the Tourettes groundwater-fed tributary, and (3) the Taillon glacier stream downstream of the confluence with (2). Stream temperatures were analysed with reference to hydrological (snowline altitude, glacial ice exposure and river discharge) and climatological (air temperature, incident short-wave radiation and precipitation) data to infer key processes driving thermal variability. Mean water column temperature increased by 7 °C in 2002, and 8.6 °C in 2003, over a distance of 1 km from the Taillon Glacier snout. Groundwater springs punctuated longitudinal glacial stream thermal patterns by decreasing (karstic) and increasing (hillslope) temperatures. Bed temperatures at all depths were coldest (warmest) and most (least) variable for the Taillon (Tourettes) stream. Stream temperatures varied at sub-seasonal time-scales. In particular, extreme precipitation events decreased temperatures in the Taillon Glacier stream by up to 10 °C in the water column and 0.05 m depth, 7.5 °C at 0.20 m depth and 5 °C at 0.40 m depth. Key drivers of thermal variability were: (1) dynamic water source contributions (i.e. snowmelt, ice-melt and groundwater), (2) proximity to source, and (3) prevailing hydroclimatological conditions. The variability of water column and streambed temperatures indicates alpine river basins to be highly thermally heterogeneous.

Leaf breakdown and the ecosystem functioning of alpine streams

AbstractLeaf breakdown, a key functional process, was examined in 3 glacial streams, 3 alpine springbrooks, and a rock-glacier stream in the Swiss Alps. Environmental conditions within each stream type were expected to significantly affect leaf breakdown rates among streams. Individual leaf packs (7 g fresh mass) of alder (Alnus viridis) were immersed in each stream and replicate samples were collected at periodic intervals over 49 d. Collected leaves were assessed for N and P, ergosterol (a measure of fungal biomass), % lignin (an indicator of recalcitrance), and aquatic macroinvertebrates. Leaf breakdown was faster in the springbrooks (k = −0.0085) and rock-glacier stream (k = −0.0073) than in the glacial streams (k = −0.0027) when expressed in terms of time. However, leaf breakdown rates based on degree days were similar among streams, ranging from k = −0.0011 to −0.0020. Leaf P levels increased over time in all sites, and reflected respective increases in ergosterol. Leaf ergosterol levels increased f...

Organochlorine compounds in ice melt water from Italian Alpine rivers

Organochlorine chemicals (OCs) (dichlorodiphenyltrichloroethanes, hexachlorocyclohexanes, and hexachlorobenzene) were measured in ice melt water from five glaciers in the Italian Alps. Even though the data collected may not be sufficient for a precise description of persistent organic pollutant release patterns from glacier melting, they have, however, highlighted the potential for surface water contamination. Concentrations were of the same order of magnitude in all glacial streams, indicating comparable contamination levels in different glaciers of the alpine region. OC levels in nonglacial springs sampled in the same areas are usually lower. Even if differences during the melting season (from spring to autumn) have been identified, a regular seasonal pattern in OC concentrations was not observed. Risk for the aquatic environment is excluded through direct water exposure, but it is likely to occur through biomagnification and secondary poisoning exposure.

A comparison of solute fluxes and sources from glacial and non‐glacial catchments over contrasting melt seasons

AbstractSolute and runoff fluxes from two adjacent alpine streams (one glacial and one non‐glacial) were investigated to determine how the inorganic solute chemistry of runoff responded to seasonal and interannual changes in runoff sources and volume, and to differences in physical catchment properties. Intercatchment differences in solute composition were primarily controlled by differences in catchment geology and the presence of soils, whereas differences in total solute fluxes were largely dependent on specific discharge. The glacial stream catchment had higher chemical denudation rates due to the high rates of flushing (higher specific discharge). The non‐glacial Bow River had higher overall concentrations of solutes despite the greater prevalence of more resistant lithologies in this catchment. This is likely the result of both longer average water–rock contact times, and a greater supply of protons from organic soils and/or pyrite oxidation. Increases in snowpack depth/snowmelt runoff reduced the retention of nitrate in the Bow River catchment (i.e. increased nitrate export), probably by reducing net biological uptake, or by reducing the proportion of runoff that had contact with biologically active soil horizons that tend to remove nitrate.The two streams exhibited opposite solute flux responses to climate perturbations over three melt seasons (1998, 1999, and 2000). The 1998 El Niño event resulted in an unusually thin winter snowpack, and increased runoff and solute fluxes from the glacial catchment, but decreased fluxes from the Bow River catchment. Solute fluxes in the Bow River increased proportionally to discharge, indicating that increased snowmelt runoff in this catchment resulted in a proportional increase in weathering rates. In contrast, the proportional variation in solute flux in the glacial stream was only ∼70–80% of the variation in water flux. This suggests that increased ablation of glacier ice and the development of subglacial channels during the 1998 El Niño year apparently reduced the average water–rock contact time in the glacial catchment relative to seasons when the subglacial drainage system was primarily distributed in character. Copyright © 2005 John Wiley & Sons, Ltd.