Evidence of corallivorous Drupella cornus breeding on the higher latitude reefs of Rottnest Island (32° S), Western Australia.

Abstract

Abstract With increasing seawater temperatures, higher latitude temperate and sub-tropical reefs are becoming increasingly tropicalised. Although these cooler areas might offer refuge to tropical species escaping the heat, the reshaping of ecosystems can have devastating effects on the biodiversity in these areas, especially when habitat structure is affected. Recently, feeding aggregations of corallivorous gastropod Drupella cornus, a tropical species capable of large-scale reef degradation, were found at Rottnest Island in Western Australia (32 °S). We provide evidence that D. cornus spawned at Rottnest Island for two consecutive years in 2020–2022. Drupella veligers are also shown to hatch and develop successfully at lower temperatures (17.5–23.2°C) in the laboratory, showing high plasticity in the early life stages of D. cornus. The spawning was possibly triggered by higher than usual La Niña-associated SSTs during the survey period, or the long period of high sea water temperature anomalies recorded around Rottnest Island. A spawning population of D. cornus can greatly affect these higher-latitude reef areas, especially when accompanied by increased heat stress. Monitoring and management should be implemented to further understand what effects a breeding, and potentially self-sustaining population of D. cornus has on Rottnest Island.