Control of invasive marine invertebrates: an experimental evaluation of the use of low salinity for managing pest corals (Tubastraea spp.)

Abstract

This study investigated the use of low salinity as a killing agent for the invasive pest corals Tubastraea coccinea and Tubastraea tagusensis (Dendrophylliidae). Experiments investigated the efficacy of different salinities, the effect of colony size on susceptibility and the influence of length of exposure. Experimental treatments of colonies were carried out in aquaria. Colonies were then fixed onto experimental plates and monitored in the field periodically over a period of four weeks. The killing effectiveness of low salinity depended on the test salinity and the target species, but was independent of colony size. Low salinity was fast acting and prejudicial to survival: discoloration, necrosis, fragmenting and sloughing, exposure of the skeleton and cover by biofoulers occurred post treatment. For T. tagusensis, 50% mortality (LC₅₀) after three days occurred at eight practical salinity units (PSU); for T. coccinea the LC₅₀ was 2 PSU. Exposure to freshwater for 45–120 min resulted in 100% mortality for T. tagusensis, but only the 120 min period was 100% effective in killing T. coccinea. Freshwater is now routinely used for the post-border management of Tubastraea spp. This study also provides insights as to how freshwater may be used as a routine biosecurity management tool when applied pre-border to shipping vectors potentially transporting non-indigenous marine biofouling species.

Keywords:

• biological invasion
• control
• eradication
• invasive species management
• mortality trials
• Tubastraea spp.

Acknowledgements

JCC would like to thank Anna Maria Scofano (Petrobras) and Dr Ricardo Coutinho (Brazilian Navy/Petrobras) for raising questions answered by this study. The authors would like to thank the students and researchers that contributed to the present study with assistance in the laboratory and field and the Center for Environmental Studies and Sustainable Development – CEADS/UERJ for the use of its staff and facilities.

JCC acknowledges financial support from the Programa de Incentivo à Produção Científica, Técnica e Artística, UERJ and Conselho Nacional de Desenvolvimento Científico e Tecnológico and a grant from the Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro [No. E-25/170669/2004]; CAPES ‘Ciências do Mar’ [1137/2010]; and sponsorship of the Projeto Coral-Sol from Petrobras through the Programa Petrobras Ambiental.