Anchoring damages to benthic organisms in a subtropical scuba dive hotspot

Abstract

The physical damages to benthic organisms caused by boat anchorages were assessed in the Arraial do Cabo Marine Extractive Reserve (ACMER), Brazil. It is one of the most visited scuba diving sites along the southwestern Atlantic. Through underwater visual observations, we analyzed if benthic organisms were damaged by anchors and/or anchor cabling at two dive sites. A total of 112 anchorages were sampled. Damages to benthic organisms were observed 139 times, mainly affecting epilithic algal matrix, the zoanthid Palythoa caribaeorum, and the fire coral Millepora alcicornis. Damages caused by anchor cables were significantly higher than those caused by anchors at one site. A significant difference between benthic organisms damaged was observed only for P. caribaeorum, caused by the anchor’s cable. We present evidence that, at current visitation levels, anchors are a relevant stressor to benthic organisms at dive sites in ACMER.