The functional roles of surgeonfishes on coral reefs: past, present and future

Surgeonfishes have had a long evolutionary history that has been closely linked with coral reef ecosystems. Today they are a key component of reef fish assemblages, playing a pivotal role in a variety of ecosystem functions. However, coral reefs are at the forefront of environmental change with a suite of stressors pushing these ecosystems towards alternative configurations. The role of surgeonfishes in these ecosystems may be changing and our understanding of these fishes must now be considered within a context of change. To explore these issues, we review the literature on surgeonfishes and examine (1) how their functional roles on coral reefs have evolved over the past 50 million years, (2) the key functions performed by surgeonfishes on present-day coral reefs, and (3) predict how the nature and importance of these roles may change in the near future (similar to 30 years). Specifically, we draw on recently clarified functional frameworks to categorise surgeonfishes into six broad functional groups (browsers, brushers, croppers, concealed croppers, sediment-suckers, water-column feeders) using morphological and behavioural traits. Subsequently, we explore how these functional groups make critical contributions to the ecosystem processes of macroalgal removal, algal turf removal, detritus removal, sediment dynamics, plankton harvesting and cross-habitat trophic linkages Furthermore, using this framework we consider how environmental factors, anthropogenic stressors, as well as other behavioural and morphological traits can shape the delivery of key functions by surgeonfishes. Finally, we highlight how surgeonfishes may play increasingly important roles in supporting key functions and services on current and future, highly-altered, coral reefs. [GRAPHICS] .