Clements M, Selvakumaraswamy P, Deaker D, Byrne M

Freshening of Great Barrier Reef waters is deleterious for larval crown-of-thorns starfish, counter to the terrestrial runoff hypothesis

The terrestrial runoff hypothesis (TRH) posits that river runoff plumes generate phytoplankton blooms, potentially increasing food for crown-of-thorns starfish (COTS) larvae and enhancing their success, thus leading to outbreaks. Plumes also freshen seawater with potential deleterious effects on larvae. Clements and colleagues show that decreased salinity across a range of food levels, commensurate with the TRH, negatively impacts COTS larval development and survival. Salinity performance curves showed that salinity was the dominant factor and that salinity tolerance narrowed with time. Swimming was also impaired, resulting in sinking. The sharp onset of deleterious effects occurred at levels that larvae would encounter in a river runoff plume impacting the Great Barrier Reef. These results counter the TRH which has underpinned decades-long management of COTS.

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