Sediment deposition in an upwelling rocky-reef in southwest Atlantic Ocean

Abstract

Sediment is highly related to coral reef degradation worldwide, and sedimentation is considered a critical cause of stress for coral communities. The current study focused on the Arraial do Cabo Marine Extractive Reserve (ACMER), recognized as a coralline oasis in the southwest Atlantic, which is facing multiple environmental pressures. Among them, mass tourism stands out, which enhances sedimentation. To address the scientific question of how sediment characteristics and rates vary across different sites, local sedimentation was monitored for about one year through sedimentation rates, granulometric composition, and the percentage of calcium carbonate (%CaCO₃) at five sampling sites, each exposed to varying levels of natural and anthropogenic activities. The results revealed distinct patterns linked to these activities and natural agents. For instance, Forno's Cove exhibited the highest percentage of fine sediment (about 70%) among all the other sampled points, suggesting the sedimentation to be strongly related to anthropogenic action. Although the overall sedimentation rates in Arraial do Cabo Bay were not high, the current findings highlight the sedimentation related to the increase in tourist activities and the need for continuous monitoring of ACMER. Such vigilance is crucial for ensuring the environmental health of coral environments and supporting the local human community's livelihoods.