Keeping up with introduced marine species at a remote biodiversity hotspot: awareness, training and collaboration across different sectors is key

Despite being a well-recognized issue, the introduction of non-native marine species is an underestimated topic in highly biodiverse developing countries. The Indonesian archipelago sits at the center of the Coral Triangle, extending over several biogeographic regions with unique benthic communities, where the extent of non-native species presence is largely unknown. It is also at the center of maritime traffic between Australasia and Asia, and therefore at risk of introduction of species that are carried on the hulls and ballast water of vessels. In the present study, we aimed to raise awareness on marine biological invasions across the Indonesian archipelago by fostering discussions among scientists, educating science students, generating media articles for the public and actively involving island communities. We also aimed to test the suitability of a range of methods commonly used in bioinvasion research (settlement arrays, DNA barcoding and environmental DNA metabarcoding, vessel surveys) to establish a baseline for biofouling species and potential threats, while developing much needed capacity for monitoring and application to other areas. We recorded 66 different non-coral specimens in the fouling communities of a remote group of islands of the Indonesian archipelago, represented mainly by the taxa Porifera, Tunicata and Mollusca, which are known to include notorious invasive species. None of the identified species was known to be invasive in the region but several were cryptogenic and/or were considered to have a very broad global distribution range that can potentially include part, or all, of the Indonesian archipelago. One species, the ascidian Didemnum molle, was found to quickly settle and spread on available blank substrates. While settlement plates (monitored every 5 months) proved suitable for early detection of potential incursions of these organisms, benthic surveys, DNA barcoding and eDNA metabarcoding provide valuable complementary baseline biodiversity information. A combination of sampling methods is therefore recommended for similar studies in understudied high biodiversity areas. Results from vessel surveys highlights the importance of civil society education in helping prevent bioinvasions. This study represents the first marine biological invasions baseline, awareness and capacity development training carried in the Indonesian archipelago. The lessons taken from the variety of methods explored in a simultaneously scientific and educational setting should prove useful and motivate similar work in other areas of the world.