Preface: Restoration of eutrophic lakes: current practices and future challenges

Eutrophication of lake ecosystems is a pervasive global environmental problem, exacerbated by urbanization, industrialization, and intensification of agriculture. Excess loading of the macronutrients nitrogen and phosphorus from a myriad of human activities in catchment areas has forced many lake ecosystems into turbid, eutrophic states from which natural recovery is slow. A wide array of tools is available to lake managers to accelerate the process of lake restoration. These range from external measures to reduce nutrient loading, to internal measures designed to either retain nutrients in sediments or remove them from the lake ecosystem. In this preface to the Special Issue Restoration of eutrophic lakes: current practices and future challenges, we briefly review the currently available approaches to lake restoration and assess their global prevalence through a literature survey. The results show that traditional restoration methods such as aeration and chemical inactivation of phosphorus by aluminum continue to be widely used and reported in the scientific literature. The popularity of biomanipulation appears to be in decline, while studies into newly developed, in-lake nutrient inactivation methods are expanding. Hypolimnetic withdrawal, on the other hand, remains a comparatively rare technique. The 16 original research articles in the Special Issue showcase the current state-of-the-art in knowledge of these approaches and their efficacy. We conclude by discussing the key relevant future challenges in the field of lake restoration science. Of these, the need to unite diverse fields of knowledge to develop quantitative models of lake ecosystem responses to restoration measures under a changing climate is paramount. We also emphasize the ongoing need for interaction between scientists, managers, and stakeholders in lake restoration.