BioMARathons as a formula to reduce the gap of knowledge in marine biodiversity with volunteer participation

Bioblitzes have been proven a successful approach for biodiversity monitoring with volunteer participation. Bioblitzes are intense periods of biological surveying, in the framework of a friendly competition among all the participants, in an attempt to record all the living species within a designated area over a continuous time period (e.g., usually 24 hours). The use of citizen science platforms, which allow sharing photos of organisms among the participants and validating these observations in a collaborative way, facilitates the design of bioblitzes with a much larger number of volunteer participants and larger areas to explore. Many examples (Diaz-Calafat et al. 2024, Herrando, S. et al. 2012) have shown the success of bioblitzes in terrestrial ecosystems.However, designing a bioblitz to monitor marine biodiversity is too risky, as rough sea conditions can completely ruin this type of event designed for such short periods of time. To avoid these potential risks an extended bioblitz has been designed for monitoring the sea: the BioMARathons.The BioMARathon concept has been validated in the coastal region of Catalonia (North-East of Spain, with the local name of BioMARató) using MINKA (minka-sdg.org) as the citizen science observatory for reporting and validating observations.Over the past 4 years, the BioMARató has been promoted in the Catalan coast, extending the competition over the summer period (from late April to the mid October). More than 850 volunteer participants have contributed with almost 250.000 observations, more than 2900 species, some of them first records of alien species. The BioMARathon approach has been replicated in the north of Portugal in summer 2024 and also a pilot in the Liguria region in Italy. BioMARathons require more complex community structures for participation, following the conceptual Janus framework (Liñan et al. 2022): in addition to volunteers and academia, the framework includes the communities of enablers as well, with the role of mobilizing participants and providing resources (diving suits, guided snorkel tours, underwater cameras…) to facilitate volunteer participation. Three communities of enablers have participated in the different BioMARathons: the Catalan Federation of Underwater activities (FECDAS) along the Catalan coast, BIOPOLIS working in the North of Portugal, and the“Posidonia Green project” initiative in Italy. The results of the BioMARathons demonstrate to be a very powerful and cost-effective solution for engaging people to report observations in marine environments and could be extended to many coastal areas in the future for global monitoring of coastal areas.