Plastic debris decrease fish feeding pressure on tropical reefs

Abstract

Fish feeding on the benthos mediate important ecological processes in reef ecosystems that are threatened by several anthropogenic activities, including plastic pollution. The impacts of plastic pollution on reef ecological processes, such as herbivory, is still unclear. We experimentally tested in the field how the presence of plastic on the benthos affects fish feeding by using a blocked design to compare fish feeding within 1m² plastic-free areas and areas with either clean plastic or plastic colonized with biofilm in reefs of NE Brazil. Each area was videoed for 10 min, through which we identified fish species, estimated sizes and quantified the number of bites and feeding frequency. The presence of plastic reduced fish feeding on the benthos, regardless of the biofilm presence, and fish barely interacted with plastic debris. Our results demonstrate that the impact of plastic goes beyond entanglement and ingestion, affecting species behavior and ecological role.

Keywords: Herbivory; Plastic pollution; Trophic interactions; Tropical reefs.