PT Unknown
AU Mack, L
TI Surface waters under multiple stress
PD 07
PY 2022
DI 10.17185/duepublico/78112
LA de
AB Water is essential for life on earth. Fresh and marine surface waters not only provide a great variety of habitats for many aquatic plant and animal species, they also fulfil various essential ecosystem functions, such as the provision of clean drinking water or the regulation of the climate. However, the condition of surface waters is increasingly declining worldwide, which severely threatens their biodiversity and ecosystem functions. We are in the midst of a biodiversity crisis, with over 40,000 plant and animal species being at risk of extinction. In addition, the capacity of surface waters to provide essential functions is decreasing. This deterioration is driven by increasing human impacts, which have substantially modified the earth’s surface and atmosphere to exploit its functions. These impacts drive several stressors affecting biodiversity and ecosystem functions and nowadays, most areas are affected by multiple, co-occurring stressors. Such multiple stressors can act independently, but they can also interact with each other, enhancing or dampening their combined effect. The severe effects of multiple stressors on the global ecosystem require the conservation of intact and restoration of damaged ecosystems. For successful environmental management, multiple stressor interactions have to be taken into account, as they require specific management measures. However, understanding the stressoreffect relationships and predicting interactions and combined effects of multiple stressors remains a major challenge, making effective management of surface waters difficult. Assessing the current condition of surface waters and identifying the stressor effects and interactions that cause this condition are crucial for a successful environmental management. The aim of this work is supporting the future conservation and restoration of surface waters by addressing contemporary challenges in environmental assessment and stressor research: Chapter 1: The assessment of the condition of a specific water body, including potential stressors affecting the area, is the basis for environmental management. Hence, comprehensive monitoring programmes that acquire information on the environmental status of the system are essential. In this chapter, novel methods with the potential to enhance marine monitoring are identified and rated. The main benefits of these methods are the autonomous collection of realtime data with enhanced spatial and temporal resolution as well as data acquisition on ecosystem elements that have not yet been monitored. Chapter 2: The experimental study of multiple stressors can help to disentangle interactions and effects of specific stressor combinations. Thus, it helps to derive guidelines for effective management. In this chapter, a stream-mesocosm experiment to study the combined effects of fine sediment and a novel insecticide on the decomposition of organic matter as an important ecosystem function is evaluated. Results indicate that both stressors can inhibit organic matter decomposition. An interaction between the two stressors was not detected under the given conditions. Chapter 3: In order to detect and quantify possible stressor interactions, an understanding of the factors that influence stressor interactions and effects is essential. Several factors relating to ecological processes are already known, but the role of the sampling strategy has not been examined so far. In this chapter, the influence of sample size and stressor gradient length on observed multiple stressor effects is studied. The results indicate that both factors play a significant role in shaping observed multiple stressor effects. This highlights the need for cautious interpretation of observed effects and adaptive environmental management. For the future conservation and restoration of ecosystems, further research is needed. Shifting from descriptive frameworks towards a mechanistic understanding of multiple stressor effects might improve the prediction and promote the management of multiple stressors. In addition, further studies on stressor mitigation are needed to better assess restoration effects, as current studies mostly focus on the effects of increasing stressor levels. Global biodiversity as well as ecosystem functions are already severely threatened and trends are alarming, making immediate conservation and restoration measures urgently needed. The effects of measures cannot be predicted with certainty and therefore, they need to be constantly monitored in order to detect possible unintended consequences like adverse effects on the environment and to be able to revise the measures accordingly.
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