Slugging it out for science: volunteers provide valuable data on the diversity and distribution of heterobranch sea slugs

There is increasing interest in participation by volunteers in data collection for marine ecosystems. Here we evaluate the contribution that citizen scientists can make to documenting marine biodiversity through underwater photography of targeted taxa. In a series of 13, 24-hr censuses of sea slugs, at intervals of three months from December 2013 to December 2016, volunteers recorded similar species richness (89%) to scientists at Port Stephens, NSW, Australia. Volunteer numbers only partially (24.9% of variation) explained the relative performance of volunteers against scientists, or the number of species found by volunteers (20.5%). Species richness in censuses was similar (97%) to estimates obtained during four-week lead-up periods. The programme provided novel information on diversity and seasonality of sea slugs, revealing strong seasonal patterns for chromodorid nudibranchs, and cyclical temporal change at the assemblage level. The programme inspired many of the participants to take part in multiple events, generated educational material, and led to the extension of the programme to other locations. The potential benefits of programmes such as this go beyond the generation of data to address specific research questions and, combined with extension activities, can help to deliver and reinforce messages about the importance of marine ecosystem health.