Impactos locais e globais sobre ambientes marinhos do Arquipélago de Fernando de Noronha

Abstract

Reefs and other marine ecosystems face significant threats from human impacts, including pollution, poorly regulated tourism and global climate change. Marine Protected Areas (MPAs) stand out among the most important strategies for marine conservation. In Brazil, the Fernando de Noronha archipelago (FN) is protected by two MPAs: a no-take area and a multiple-use area. However, the archipelago has been experiencing increasing impacts due to the expansion of tourism and human occupation, and climate change. In this context, the main objective of this thesis was to assess multiple local and global impacts on marine environments in FN, and the role of the MPAs in mitigating these impacts. In Chapter 1, we investigated the presence of marine litter on the beaches of FN and its distribution related to oceanographic factors and tourism. We found a higher abundance of plastics in uninhabited areas on the windward side, despite being within the no-take area, a more restricted MPA, while on the leeward coast, near urban areas and within a less restricted MPA, there were more disposable plastics and cigarette butts. In Chapter 2, we investigated the temporal dynamics of benthic organisms in a tide pool and observed that temperature anomalies were the main factor affecting coral health and their endosymbiont communities. Although seasonal burial caused high temporal variability in benthic cover, it did not affect coral health. The number of tourists diving in the area also did not influence coral health, indicating that proper management can reduce tourism impacts. In Chapter 3, we mapped and quantified marine pollution in FN (nutrients, metals, microplastics, sterols, and polycyclic aromatic hydrocarbons - PAHs), characterizing their sources and evaluating their impacts on reef communities. We detected pollutants both in the multiple-use and in the no-take area. While nutrient concentrations in the water were in accordance with legislation in most samples, effluents from wastewater treatment plants did not meet legal standards. The isotopic signature of macroalgae indicated the presence of sewage-derived nitrogen throughout the multipleuse area, and nutrient-enriched areas showed distinct benthic communities with higher algal biomass. Sediment analysis revealed generally low levels of PAHs and fecal sterols, except in samples from Porto. We observed relatively high metal concentrations in sediments at some sampling stations, which may be related to anthropogenic sources and the archipelago's volcanic origin. Microplastics were found in all sediment and water samples, from the multiple-use and the no-take area. We emphasize the urgent need to improve wastewater management to protect the marine ecosystem in FN, promoting its resilience facing climate change. We also highlight the vulnerability of the no-take area, with pollutants originating from the multiple-use area on the leeward coast and pollutants transported by currents from distant sources on the windward coast. The information generated by this work will serve as an important reference for monitoring initiatives and improving management strategies for conserving FN and other MPAs.