Citizen science projects for monitoring alien macrophytes

To understand the invasive potential and the spread dynamics of an alien species, any newly colonized area needs to be quickly detected. Therefore, regular monitoring programs and public awareness campaigns are essential. Since intensive monitoring activities involving scientists are expensive, the occurrence and spread of marine species could remain undetected or could be detected only years after the initial colonization. Citizen Science initiatives, a potential solution to this problem providing supplemental information that would otherwise be lost, are able to involve different groups of volunteers: students, tourists, divers, underwater photographers, amateurs and fishermen. Volunteers are encouraged to collaborate by providing data on the occurrence of alien species together with photos and environmental information which are published after validation by taxonomic experts. Websites and social networks play a fundamental role in the coordination, sharing and flow of all the collected data. The aim of this paper is to report the experience of two citizen science projects. The Participated Project “Caulerpa cylindracea – Egadi Islands” and the citizen science platform “Seawatchers”. The first one is a two-year Participated Project (sponsored by the Department of Biological, Chemical and Pharmaceutical Sciences and Technologies-STEBICEF, University of Palermo and the Egadi Islands Marine Protected Area) launched on 27th August 2014 and aimed at creating a database on the spread dynamics and the levels of threat of C. cylindracea within the Egadi Islands MPA. The second one is a platform of projects, coordinated by the Institute of Marine Sciences of Barcelona (CSIC, Spain), that relies on the collaboration among citizens and scientists. The results of these projects highlight how important the contribution of citizen scientists is for collecting new data and information on non-native marine species, and can be also used as an early-warning system. Moreover, they represent an opportunity to promote the creation of a permanent observatory “a warning system” for alien species within the Mediterranean Sea.