The outbreak of Drupella snails and its catastrophic effects on coral reefs: a comprehensive review

Abstract

The recurring outbreaks of Drupella snails are a significant threat to coral reef ecosystems on a global scale. However, research on Drupella snails is currently very fragmentary. This article explores the ecological impacts and mitigation methods of Drupella snails and its outbreaks, and draws the following main conclusions. 1) Drupella snails inhabit the tropical oceans of the Indo-Pacific, utilizing their specialized radula to feed on coral polyps, and they predominantly spawn during summer, attaching egg capsules onto coral skeletons. 2) An outbreak of Drupella snails is defined by a density of > 2 ind/m2, but large aggregations alone do not necessarily indicate an outbreak. 3) The damage of coral reef ecosystem is the primary cause of Drupella snail outbreaks, with the hypotheses of “terrestrial nutrient input” and “overfishing of predator” being widely accepted but not fully explaining all outbreak events. 4) Countering Drupella snail outbreaks involves improving the health of coral reef ecosystems, protected areas, biological control and manual removal, though manual removal is the most direct and effective in short-term. 5) The understanding of the physiological and ecological characteristics of Drupella snails is inadequate at present, with larval development and population ecology being areas of particular under-investigation. 6) Studies of Drupella snail outbreaks have focused mainly on mid-outbreak stages, with little attention to early warnings beforehand or adverse outcomes afterwards. Despite significant challenges, addressing knowledge gaps in the biology of Drupella snails is crucial to determine the true causes of their outbreaks and identify corresponding solutions.