Glacier-fed rivers represents ideal aquatic ecosystem models to investigate the impact of climate change on aquatic life at a global scale, as these rivers are relatively pristine and are found worldwide from the Mediterranean region to the Alpine and up to the high Arctic. The current alarming change in climate induce glaciers retreats which are located in all these regions, altough distinct in amplitude, cause significant changes in rivers feed by the glaciers in terms of habitat conditions for the aquatic life. These alterations range from unstable physical habitat conditions of the riverbeds in the proximity of the glacier outlet (unstable river bed sediments, high sediments loads of water, high discharge with large daily fluctuations, low temperature) up to more friendly stable conditions downstream from the glacier terminus.
Foto 2: Aktru River, Altai Mountains (Russia) (by Sanda Iepure)
In the northwest reaches of the Altai Mountains in Siberia, most glaciers are showing signs of rapid retreat due to climate change that significantly affect the glacier feed rivers ecosystems downstream. Currently, there are about 1030 glaciers recorded in Altai with a total area of 805 km2 and volume of 42.5 km3. The Altai glaciers start to be investigated in the first half of the nineteenth century in 1835 by F. V. Gebler. Intensive studies have been devoted since then, reflecting trends of glacier regimes and mass balance, ice reserves, accumulation and distribution of snow and ablation (Narozhniy & Narozhniy, 2011).
One of the most comprehensive monitoring study on Altai glaciers states that in different regions the average summer air temperature has increased from 1952 to 2008 from about 0.2°C (Aktru) to 1.1°C (Akkem) (Narozhniy & Narozhniy, 2011). However, the increase was actually observed only over the last two decades, since 1985. Furthermore the annual atmospheric precipitation rate also increased by 8–10%, with a raise of summer precipitation by 4–5%, and winter precipitation by 10–12%. Therefore, the data indicate that since 1952 the glacier area in different regions of the Altai has decreased by 9–27% and their volume by 12–24%. By 2008, as a result of degradation, the total number of glaciers was 953 with an area of 724 km2 and volume of 38 km3.
Specifically in the Aktru valley the high extent of the glacier recession occurred in 2008 when the annual retreat was 16.1 m (Narozhniy & Narozhniy, 2011). This is an alarming situation for the Altai glaciers in the context of the long-term climate projections worldwide indicating the rise of temperatures by over 4 degrees Celsius above pre-industrial levels by 2100. The fast retreats of glaciers in the Altai will have a significant ecological but also socio-economic impact for the local population living in the high mountains with a nomadic way of life, that relay on pastoral animal husbandry and rain-fed agriculture.
One glacier river feed already under threat, located in the Kuray basin from southeastern Siberia in the Altai Mountains (at the borders with Mongolia and China in the south and Kazakhstan in the west) (Foto 4) is the focus of recent ecological study of the University of Gdansk (Poland).
Aktru River also named “Ak-Turu” selected to perform our study belong to Aktru – Chuya – Katun – Ob drainage network and is a left tributary of the Chuya River (Fotos 2, 5). The river has a length of 25 km and a catchment area of 161.4 km2 and its source is located at 2750 m.
Within the catchment area there are seven glaciers of total area 16.7 km2. The largest glacier among those of the catchment involved is mountain-valley glaciers of the Left, Right, and Small Aktru. The river Aktru has low mineralization, a very common state for glacier feed rivers (up to 0.1 g/dm) and a very alkaline pH (Savichev et al., 2016). Previous studies indicate that surface channel of the Aktru River mostly in the glacier zone has high concentrations of Ti, V, Zn, Hg, Pb. These elements in excess appear to be caused by natural and anthropic factors, i.e. intensive interaction of melt water with rocks and dust, the later being expected to be connected with transport of atmospheric pollutants to some extent, particularly in case of radioactive elements.
The water hydrochemistry besides other environmental factors characterizing the glacier feed rivers (i.e. habitat instability, low content in nutrients, and low water temperature with high daily fluctuations) are expected to influence the colonization, establishment and resilience of the aquatic fauna in Aktru River. Generally, the resilience of hyporheic biota in glaciarized landscapes is strongly controlled by long-lasting stress related to persistently low water temperatures, prolonged ice-cover, permafrost occurrence, strong freeze-thaw cycles, nutrient availability, and frequent disturbance of their physical habitats. Consequently, the structural pattern of hyporheic and benthic biota is distinct in biodiversity, ecology, morphological, life-cycle and behavior adaptations in order to ensure their resistance and persistence under adverse environmental conditions.
BIOCLIM, a project financed by the EU-INTERACT program aims to investigated the aquatic fauna beneath the stream channel of the Aktru River in the high Altai Mountains (Russia). The study is performed at the Aktru Research Station (AKR) (50°06‘03 N, 87°40‘14‘‘E, 2150 m a.s.l.) together with geomorphologists from Tomsk State University (TSU). BIOCLIM aims to depict the biodiversity, species distribution and ecological structure of aquatic invertebrates (at local and basin scales) on longitudinal gradient downstream from the glaciers outlets in Aktru valley and to detect the environmental factors involved in setting the aquatic invertebrates succession from the glacier outlet downstream, in two river compartments, benthic and the hyporheic zone. We expect that the increase of the discharge as the glaciers melt, influence the habitats conditions for the aquatic fauna settled in both benthic and the interstitial sediments beneath the stream, the so-called hyporheic zone.
The hydrological and chemical processes occurring in the hyporheic zone of glacier feed rivers have received increased attention in recent years, yet the studies on primary succession of biotic assemblage and their response to cope with extreme environmental conditions are still scarce. This river compartment that function as a refugee for benthic aquatic fauna during the floods events or intense droughts get more and more attention in the recent years, however the investigations from remote regions in the high Arctic or less accessible regions such is Siberia are just at the beginning.
BIOCLIM aims to fill this gap in knowledge and to advance our understanding of global warming impact on biodiversity and functional diversity of aquatic invertebrates from the hyporheic zone of rivers in glacierized related landscapes and to generate the basis for further development of long-term interdisciplinary monitoring programs of glacier-fed rivers ecosystems from remote regions worldwide.
Narozhniy Y., V. Zemtsov, 2011. Current State of the Altai Glaciers (Russia) and Trends Over the Period of Instrumental Observations 1952–2008. Ambio. 2011 Sep; 40(6): 575–588.
Savichev, O., I. S. Matveenko, V. Paromov, 2016. Chemical Composition of Bottom Sediments in Small Mountain Rivers (Altai, the Russian Federation). MATEC Web of Conferences, 85, 01031. DOI: 10.1051 matecconf/20168501031.