Inshore coral reef sediment and turf dynamics unaffected by canopy-forming macroalgae.

Abstract

Nearshore coral reefs face an increasing abundance of fleshy macroalgae, an indicator of degradation and threat to ecosystem functioning. Removal of macroalgae is proposed to assist coral recovery, though the ecological and physical impacts have not been studied. Nearshore reefs are also confronted with sedimentation stress, influencing reef dynamics including algal turfs, with flow-on impacts to coral recruitment, fish diets, and trophic cascades. In this study, the interplay between macroalgal canopies, sediment deposition and algal turf environments was investigated on the nearshore Great Barrier Reef. Removal of fleshy macroalgae over two years had no significant effect on the amount or composition of sediment deposited on proxy coral (SedPods) and algal turf (TurfPods) surfaces, nor was the height of algal turfs impacted. Deposition on TurfPods was greater with high-energy currents, likely due to retention of sediment within turfs. Therefore, macroalgae removal is unlikely to exacerbate nor alleviate sediment-related stress on benthic communities.