Drivers of temporal variation in benthic cover and coral health of an oceanic intertidal reef in Southwestern Atlantic

Abstract

Intertidal environments and shallow reefs are subject to natural disturbances and impacts by humans that influence their dynamics and therefore their conservation. These environments are among the most subject to anthropogenic impacts worldwide, ranging from global warming to local pollution and disordered tourism. Fernando de Noronha Marine National Park is an important Marine Protected Area that covers marine habitats up to 50 m deep of an oceanic archipelago off North East Brazil. It is a no-take area, so the main potential impacts in intertidal and shallow environments there are related to tourism, pollution and climate change. One of the chief tourist attractions in this Park is a tide pool where snorkelers can dive under a series of regulations. We monitored corals and benthic organisms in this tide pool for two years and evaluated their response to different disturbances: burial by sand, temperature anomalies, and tourism. We observed high temporal variability in the benthic cover in the Atalaia pool, with an important role of the sand being naturally brought by waves coming from the southeast to south-southeast direction on a seasonal basis. Despite the highly variable environment of this pool leading to periodic visual coral cover decrease when sand accumulated, coral health was not significantly affected neither by burial nor by the number of visitors accessing the pool. However, sea temperature anomaly played a role, being the main environmental driver affecting coral health, leading to increased paleness, bleaching and unhealthy purple/pink color and causing changes on the associated symbionts. Regardless of the local scope of this monitoring, this is an interesting study case to be used by other marine parks, explicitly showing how biological monitoring can aid the evaluation and potential adjustments to management strategies.