Extreme hydrological events destabilize aquatic ecosystems and open doors for alien species

The number of alien species invasions steadily grows worldwide, as well as the frequency of extreme climatic/hydrological events (ECEs/EHEs). ECEs and the invasion of alien species are among the main reasons for catastrophic transformations of aquatic ecosystems, watersheds, and human activities worldwide. Along with other negative results ECE may facilitate biological invasions. The objective of this review paper is to summarize how extreme climatic events may improve the likelihood of successful invasions in aquatic ecosystems and analyze some of the mechanisms. The morphometric characteristics of water bodies and their positions in the landscape connectivity may influence lake processes. ECE may result in an extreme ecological response - destabilization of an ecosystem and abrupt shift towards an alternative new state. Lakes' peculiarities mediate the effect of ECE influences on a lake ecosystem and determine whether the ecosystem response will be catastrophic or not. Different ecosystem alternative stable states have different levels of ecosystem immunity to invasions. ECEs can destabilize ecosystems and push them towards a tipping point where an ecosystem is most vulnerable. In a destabilized ecosystem near tipping point, ecosystem immunity is sharply decreased and the 'door' for alien species opens. The invasion process has several steps, and ECEs influence all of them. We are beginning to understand the association of ECE with invasions; to gain a deeper understanding of this we should integrate and coordinate the joint efforts of climatologists, hydrologists, limnologists, ecologists and biologists in this direction.