Ecologia e Fisiologia - Comunicações orais

Reef environments are one of the most biodiverse ecosystems on the planet. However, they have been threatened by increasing anthropogenic disturbances. Studying the dynamics of reef communities on isolated oceanic islands can help to understand their natural temporal variations and those derived from global climate changes. In this work, we identify and compare the dynamics of the benthic reef coverage of Fernando de Noronha (FN) and Rocas Atoll (RA) from 2013 to 2019, sampled annually through photoquadrats. The coverage percentage of organisms was categorized into functional groups. On both islands, the most abundant groups were turf and macroalgae, followed by calcifiers. Temporally, turf showed an opposite trend from 2017-2019, with a decrease in FN and an increase in RA. Macroalgae demonstrated a similar trend between islands, with a slight increase from 2015-2017 and a decrease from 2017-2019. Calcifiers showed different temporal trends, oscillating over the years in FN and decreasing in RA from 2013-2014 and 2018-2019. Cyanobacteria, despite the predominant low coverage, exhibited an increasing trend only for FN in 2017 and 2019. Therefore, FN presents low coverage of turf and macroalgae between 2018-2019, with a cyanobacteria increase in 2017 and 2019. RA presents low macroalgae and calcifiers coverage, with high turf between 2018-2019. Results suggest possible growth trends of opportunistic groups in recent years, coinciding with climate disturbances, which may indicate the impact of global anthropic drivers. This may suggest the beginning of an alteration of these benthic communities, culminating in the loss of biodiversity, structural complexity and ecosystem functions and services. Thus, we highlight how important long-term monitoring the Brazilian oceanic islands is to better understand and predict environmental and structural changes in the southwest Atlantic’s reefs.