Assessing DNA damage in sentinel crabs as indicators of tourist impact in the Fernando de Noronha Archipelago, a Marine Protected Area and World Natural Heritage Site in Brazil

Abstract This study investigates the genotoxic effects of tourism on two sentinel crab species (Johngarthia lagostoma and Grapsus grapsus) in the Fernando de Noronha Archipelago, Brazil, a Marine Protected Area and World Natural Heritage Site—sampling (October 2020–June 2022) covered periods of varying tourist influx due to COVID-19 restrictions. Genomic damage was assessed using micronucleus (macrolesions) and comet assays (microlesions) in hemolymph samples from crabs at two sites: Dolphin Trail (low visitation) and Porto de Santo Antônio Beach (high visitation). DNA damage increased with tourist numbers. In J. lagostoma, macrolesions rose from 3.2 MN/1000 cells (October 2020, 3261 tourists) to 8.8 MN/1000 cells (February 2022, 10,918 tourists), while microlesions increased from a damage index (DI) of 119.1 to 231.5. Grapsus grapsus was a more susceptible species, with macrolesions rising from 5.4 to 10.2 MN/1000 cells and microlesions from 184.7 to 303.1 DI (October 2020–October 2021, 12,085 tourists). Regression analysis revealed a strong correlation between tourist numbers and DNA damage, particularly in J. lagostoma (R2 = 0.99; p < 0.001). G. grapsus experienced more significant genomic damage due to its exposure at Porto de Santo Antônio Beach, a major tourist site, while J. lagostoma presented lower damage in the less disturbed Dolphin Trail. On average, G. grapsus had a 1.5-fold higher microlesion index (240.1 DI) than J. lagostoma (159.0 DI), highlighting interspecific differences. These findings highlight island ecosystems’ vulnerability and the urgent need for conservation strategies to mitigate tourism-induced genomic damages in biota.