Monitoring and assessment of anthropogenic activities in mountain lakes: a case of the Fifth Triglav Lake in the Julian Alps

Abstract

The Fifth Triglav Lake is a remote mountain lake in the Julian Alps. The area of the Julian Alps where the lake is situated is protected by law and lies within the Triglav National Park. Mountain lakes in Slovenia were considered for a long time as pristine, unpolluted lakes, but analyses in the last decade revealed considerable human impact even in such remote places. Eutrophication or excessive accumulation of nutrients is the main problem of most lakes in the temperate climatic zone, also in Slovenia. Since the introduction of fish in 1991, the lake is going through a series of changes for which we do not know exactly where they lead, so the monitoring and assessment of anthropogenic activities are of great importance. For this purpose, a qualitative multiattribute decision model was developed with DEX method to assess ecological effects on the lake. The extent of the ecological effects on the lake is assessed using four main parameters: the trophic state, lake characteristics, environmental parameters, and anthropogenic stressors. Dependence of environmental impact on various external factors beyond human control, such as temperature, precipitation, retention time, and factors on which we have influence, such as the amount of wastewater and the presence of fish in the lake, were also evaluated. The following data were measured: chlorophyll a, nutrients, TP, oxygen, C/N ratio, nutrients in sediment, temperature, precipitation, retention time, and volume. We made assumptions about fish and wastewater, which we could not measure. The main contributions of this work are the designed model and the obtained findings for the Fifth Triglav Lake that can help not only scientists in understanding the complexity of lake-watershed systems and interactions among system components but also local authorities to manage and monitor the lake aquatic environment in an effective and efficient way. The model is flexible and can be also used for other lakes, assuming that the used parameters are measured and anthropogenic stressors are adjusted to a specific situation. The results of assessment are of particular interest for decision makers in protected areas, providing a new approach to the management of the quality of the water environment.

Recent changes in major and trace elements in sediments from a remote mountain lake (6th Triglav Lake) in the Julian Alps, NW Slovenia

“…A frequently visited mountain hut on the shore of 5J may also contribute nutrients to the lake in the form of wastewater inflow. Whereas the introduction of fish has had a documented major impact on lake condition (Ravnikar et al 2016), the impact of the hut remains unclear (Muri et al 2013(Muri et al , 2018.…”

“…3 and 5). It was most likely caused by increased eutrophication, triggered by the introduction of fish in 1991, which is regarded as one of the major factors affecting the overall condition of the lake (Brancelj 1999;Muri et al 2013;Ravnikar et al 2016). The lake responded quickly with increased primary production (Brancelj 2002), as indicated by higher sediment OC and TN contents, lower C/N ratios, a change in the stable isotope composition of OC, and increases in total phosphorus and refractory organic phosphorus contents (ESM 1; Muri et al 2018).…”