Exposure to global change pressures and potential impacts on ecosystem services of mountain lakes in the European Alps

Reconstructing the environmental impact of mining on mountain lakes

Mountain lakes are particularly fragile ecosystems undergoing important ecological and depositional transformations associated with ongoing global change. However, the history of anthropogenic impacts on mountain lakes and their catchments is much longer, in many cases featuring millennia of summer pastoral farming. More recently, the growing demand for raw materials and energy linked to industrialization, particularly accelerated since the 19th century CE, meant a further increase in human impact on mountain areas. The Cantabrian Range (northern Spain) constitutes a paradigmatic case of southern European mountain range experiencing intense human impact during the past millennia and particularly the past two centuries. Here, we have reconstructed the environmental dynamics of this area during the last millennium, with a particular focus on the impact of mining, based on the multidisciplinary analysis (sedimentology, biogeochemistry, magnetic susceptibility, diatoms, pollen, charcoal and dung fungal spores) of sediment cores from Lago de La Cueva (43°03'N, 6°06'W, 1550 m a.s.l.). Fire induced deforestation during the 15th century CE increased erosion during the Little Ice Age. The onset of iron mining in the catchment 200 years ago significantly impacted the lake, increasing sedimentation rates and mining waste containing hematite and potentially toxic elements. Diatoms showed that lake regulation since the early 20th century CE severely altered the natural hydrological regime introducing rapid seasonal lake-level oscillations and increasing lakeshore erosion, water turbidity and nutrient loads. The recent environmental restoration, finished in 2006, involved the re-deposition of mine tailings. Although mining wastewater still reaches the lake, restoration effectively reduced erosion and nutrient loads. This study illustrates the complex interactions between human activities (grazing, mining, hydropower) and climate change in shaping mountain landscapes through time. Our findings highlight the usefulness of Paleolimnology to quantitatively assess the effectiveness of lake restoration programs.

Influence of water chemistry and contaminant occurrence on the oxidative stress ecology of Cottus gobio in a high-mountain lake (Carnic Alps)

Understanding oxidative stress in high-mountain lake fish offers crucial insights into their health, resilience, and adaptation to extreme environmental changes. This study investigates the oxidative stress response of Cottus gobio in a high-mountain lake (Dimon Lake) located in the northeast Italy during the ice-free season, focusing on the relationship between oxidative stress biomarkers and physicochemical water parameters, as well as persistent and emerging contaminants. Significant seasonal variations were observed in water parameters, with lower oxygen, pH, conductivity, and phosphate levels in summer compared to autumn, while temperature, ammonium, and nitrate were higher in summer. Metal concentrations in C. gobio muscle were higher in autumn, with Zn showing the most significant increase. PAHs, NDL-PCBs, and pesticides were all below the limit of quantification in the fish muscle samples. No microplastics items were found in the gastrointestinal tracts of fish. Oxidative stress biomarkers revealed organ-specific and seasonal variations. The liver exhibited the highest activities of catalase (CAT), glutathione peroxidase (GPx), glutathione S-tranferase (GST), and glutathione reductase (GR), highlighting its central role in detoxification and metabolic processes. Superoxide dismutase (SOD) activity was notably higher in muscle tissue during summer, suggesting increased metabolic activity. A strong correlation was found between pH and the activities of SOD, CAT, GPx, GR, and metallothioneins (MTs), emphasizing the importance of water chemistry in influencing oxidative stress responses. This approach not only aids in understanding the local adaptations of these fish but also highlights the impacts of environmental stressors on high-mountain ecosystems. Continuous monitoring of water chemistry, particularly pH, is crucial for understanding and managing oxidative stress in aquatic organisms, especially in the context of global environmental changes.

Alps at risk: High-mountain lakes as reservoirs of persistent and emerging contaminants

Despite their remote locations, high-mountain lakes located in the Alps are vulnerable to chemical pollution. This discussion explores the important aspects of these lakes as repositories of Persistent Organic Pollutants (POPs) and Contaminants of Emerging Concern (CECs), elucidating their sources and implications for both the environment and human health. In terms of the presence of POPs in high-altitude lakes of the Alps, 14 studies have been identified examining the occurrence of polychlorinated biphenyls, dichlorodiphenyltrichloroethane an its metabolites, polybrominated diphenyl ethers, and polycyclic aromatic hydrocarbons. The bulk of research on POPs in high-mountain lakes is concentrated in the Italian Alps (63%), followed by Switzerland (22%), Austria (12%), and France (3%), respectively. Sediment is predominantly investigated (65%), followed by fish (33%) and water (2%). Similarly, in relation to the presence of CECs in high-mountain lakes of the Alps, six studies have been identified investigating the occurrence of musks, perfluorinated compounds, and microplastics. Investigations into CECs predominantly occur in Switzerland (42%), France (33%), and Italy (25%), with fish samples (muscle and liver) being the primary focus (46%), followed by sediment (17%) and water (17%). Other compartments like zooplankton, frog/tadpoles, and snow remain less explored. The discussion also shed light on various pathways through which pollutants reach these remote landscapes, including atmospheric transport, glacial meltwater, and human activities. Protecting these pristine peaks demands concerted efforts encompassing ongoing research, vigilant monitoring, and dedicated conservation initiatives.

Integrating ecosystem services closely related to human well-being into the restoration and management of deep lakes facing multiple stressors: Lessons from long-term practice in Qiandao Lake, China

Deep-lake (reservoir) ecosystems provide valuable ecosystem services (ES) and generate significant ecosystem service values (ESV); however, reservoir ecosystems have suffered great losses from environmental changes and human activities. Currently, studies on ES and its correlations with stressors remain insufficient and the integration of ES into ecological restoration and management poses numerous challenges. Here, we combined four types of stressors with six ES closely related to human well-being to discuss their interactions in Qiandao Lake (a representative deep lake in China). Our results indicate that all ESV showed a consistent growth trend throughout the study period, reaching 5203.8 million CNY in 2018, and the cultural service value surpassed the provisioning service value for the first time in 2004. Almost all the ESV were limited during the cyanobacterial bloom in Qiandao Lake. Redundancy analysis and partial least squares structural equation modeling jointly revealed that socioeconomic development was the most important direct driver of the increase in ESV (0.770) and that hydro-meteorological conditions (0.316) and pollutant loads (0.274) positively affected ESV by mediating lake trophic status. The trophic status of the lake is the result of the interaction of multiple stressors, which has a negative impact on ESV. Therefore, to continuously protect the provisioning and cultural service values of deep-lake ecosystems from damage, the government must rationally formulate SED goals and reduce pollutant loads during lake development, operation, and utilization. This work provides valuable insights into the interactions between ES, which are closely related to human well-being, and stressors in deep-lake ecosystems.

How does 2D and 3D of urban morphology affect the seasonal land surface temperature in Island City? A block-scale perspective

The global climate warming caused by urbanization has significantly affected the urban environment. Whilst land surface temperature (LST) is an important factor reflecting urban temperature, previous research on LST mostly focused on two-dimensional (2D) factors and rarely mentioned about the role of three-dimensional (3D) factors, particularly the LST variation characteristics of island cities. Therefore, this study examined the seasonal variation characteristics of urban LST by analyzing the impact of 2D and 3D urban morphology factors of different urban block types on LST in Xiamen Island. The main results are as follows. First, compact low layer (CL), a block type with a higher density of low-rise buildings, has a higher LST in any season. Under the same block density (BD), the higher the block average height (BH), the lower the LST. Second, among the 2D urban morphology factors, normalized difference vegetation index (NDVI) was the main factor for cities to reduce urban LST, especially in summer, while normalized difference built-up index (NDBI) was the opposite. Different from land cities, we found a positive correlation between modified normalized difference water body index (MNDWI) and LST in autumn and winter. Third, in the 3D urban morphology factors, sky view factor (SVF) was significantly positively correlated with LST, while building fluctuation (BF) was negatively correlated. The higher the SVF, the worse the radiation shielding effect between buildings. On the contrary, the higher the BF, the higher the building undulation, and the better the building radiation shielding. These findings should provide some quantitative insights for the future construction and planning of island cities, which can be used to improve the thermal environment of island cities and support the sustainable development of cities.

Spatial and temporal patterns of supply and demand risk for ecosystem services in the Weihe River Main Stream, NW China

The rapid development of society and economy in the post-industrial era has exacerbated the spatial matching contradiction between the demand of humans and the supply of the natural environment, while ecosystem service (ES) as a bridge linking nature and society, identifying and assessing its supply-demand risk, was beneficial to ecosystem management and promoted regional high-quality development. Based on the data of multi-source remote sensing and statistics, the supply and demand levels of four ESs, which contain food supply, carbon storage, soil conservation, and water yield in the main stem of the Weihe River in 2000, 2010, and 2020, were quantitatively measured. The spatial and temporal analysis of the supply, demand, and supply-demand ratio of each service was carried out using spatial mapping. The spatio-temporal pattern of the supply-demand risk was recognized by the method of spatial overlay, which means overlaying the supply and demand for material quality, ratio, trend, and the degree of trade-off coordination together between each service. The results showed that (1) the demand for water yield decreased slightly while the demand for food and the supply of carbon storage remained stable. In addition, the supply and demand of other services showed an upward trend. (2) The spatial distribution of the supply-demand ratio of each service shows "high in the south and low in the north" and "high in the east and low in the west," among which the supply-demand ratio of carbon storage is decreasing. (3) The overall supply-demand risk of soil conservation in the study area is low with characteristics of small range and high degree, the risk distribution characteristics of the other services are high in the east and low in the west, and the risk is high in the city center and low around. Otherwise, the supply-demand risk of food supply showed a downward trend, the risk of carbon storage showed an upward trend, the risk of soil conservation remained stable, and the risk of water yield showed a significant downward trend. Based on static supply-demand risk identification, this study assesses supply-demand risk over two periods and analyzes the trend of supply-demand risk changes over time. It clarifies the extent and direction of supply-demand risk shifts, as well as provides improved theoretical support for ecosystem service management.