Potential Small and Large-Scale Effects of Mechanical Beach Cleaning on Biological Assemblages of Exposed Sandy Beaches Receiving Low Inputs of Beach-Cast Macroalgae

Abstract

Mechanical beach cleaning occurs worldwide on heavily urbanised beaches to remove litter and decomposing macroalgae from impacting tourismand recreation. This study investigated the potential small- (100 s of metres) and largescale (kms) ecological impacts of beach cleaning in a region receiving low inputs of macroalgae with a focus on: levels of total nitrogen and nitrate; abundances of bacteria, meiofauna, macrofauna and ocypodid crabs; and assemblages of meiofauna and macrofauna. Results indicated that beach cleaning was not having an impact. Given beach cleaning occurred only weekly to twice-weekly on small sections of a few beaches, and that collected beach-cast macroalgae in the study region is relocated on the same beach for degradation, it is likely that nutrients are redistributed from surrounding areas to cleaned sites and that potential physical impacts to biota are short-term and sustainable. Impacts of beach cleaning may be evident in regions that experience more extensive beach cleaning operations or on beaches with high inputs of beachcast macroalgae. This study also highlights the importance of comparing sites at the same location to investigate the effects of beach cleaning, as ecological differences among distant locations may incorrectly be attributed to beach cleaning but may actually be driven by differences in their physical characteristics.