Multi-site experiments demonstrate that control of invasive corals (Tubastraea spp.) by manual removal is effective

Abstract

Sun corals Tubastraea spp. from the Indo-Pacific have invaded hard grounds in the Caribbean, Gulf of Mexico, Brazil and Canary Islands where they cause significant ecological and economic damage to native systems, industry and society. In Brazil the National Plan for the Prevention, Control and Monitoring of the Sun Coral requires that sun corals are reduced to acceptable levels in nature and eradicated from vectors. Here we tested the efficiency of manual removal as a management tool at three sites along 260 km of Brazil's coastline with different oceanographic conditions (Ilha Grande, Rio de Janeiro and Cabo Frio). Four treatments were applied to shorelines undergoing management: (a) community removal (the whole benthic community scraped and stripped to bare rock), (b) sun coral single removal (c) sun coral repeated removal at 2 mo revisit) and (d) control areas naturally devoid of Tubastraea spp. Benthic communities were sampled over time using cover estimated from underwater photographs and larvae quantified in plankton trawls during management. The act of manual removal had no significant effect on sun coral larval abundance. The repeated removal method reduced cover at all sites to zero but a single removal was sufficient at sites with low densities of sun coral. The treatment effects varied systematically between sites, depending on local propagule pressure and invasion history. Manual removal is efficient and readily available and should be implemented in synergy with other methods to slow the spread of invaders, promote ecosystem recovery and allow time for the development of additional tools.