High-resolution simulations of coastal dispersion of Tubastraea spp. larvae from a large estuary in northeast Brazil

Abstract

Along more than 2,500 km of tropical coastline north of Rio de Janeiro, the invasive coral Tubastraea spp. has primarily been observed on shipwrecks and oil platforms located on the outer continental shelf or slope. An exception is Baía de Todos os Santos (BTS), a large estuary near 13°S, where Tubastraea spp . has been repeatedly documented since its first occurrence in 2012. These reports have raised concerns about BTS potentially serving as a source of Tubastraea larvae for nearby coastal areas with endemic coral populations. Here, we investigate population connectivity within BTS and evaluate whether Tubastraea larvae could reach and colonize mapped hard substrates within the bay and on the shelf using the biophysical model OpenDrift in conjunction with a high-resolution hydrodynamic model (ROMS). Instead of simply simulating larval dispersion potential using a passive particle approach, our model incorporated two critical larval traits: variable density and immediate settlement upon contact with the seafloor. Results revealed a significant reduction in larval spreading capability with the incorporation of those two key traits. There was minimal connectivity among the five larval release sites within BTS, with less than 1% of the 4.38 million larvae released annually successfully settling on suitable substrates. The maximum potential recruitment distance was found to be less than 50 km from the bay’s mouth, indicating that BTS plays a limited role in facilitating Tubastraea spp. dispersal along the open coast.

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