In 2019, a major coral bleaching event affected reefs worldwide, including marginal reefs within the Abrolhos Bank (16°40′–19°40′S, 39°10′–37°20′W), the largest and richest coral reefs in the South ...Atlantic. Between March and May 2019, this area was affected by the strongest heatwave since 1985. The health trajectories of the branching hydrocoral
Millepora alcicornis
and the endemic reef-building coral
Mussismilia braziliensis
were recorded during this thermal stress event. The degree heating week value reached its historical maximum (DHW 19.65), causing bleaching in 100% of
Millepora alcicornis
and 80% of
Mussismilia braziliensis
colonies. Bleached
Millepora alcicornis
were rapidly covered by cyanobacteria, followed by algal turfs and calcareous algae, leading to 90% mortality. Conversely, 90% of
Mussismilia braziliensis
colonies recovered to a healthy state after bleaching. The high post-bleaching recovery capacity and resistance to mortality of this massive reef-building coral suggests these marginal reefs can be resilient to thermal stress events, despite losing structural complexity due to high mortality of branching and less abundant hydrocorals.
Hybridization between sea turtle species occurs with particularly high frequency at two adjacent nesting areas in northeastern Brazil. To understand the outcomes of hybridization and their ...consequences for sea turtle conservation, we need to evaluate the extent of hybridization occurrence and possible deleterious effects in the hybrid progeny. Thus, we investigated the hypothesis of the existence of a new hybrid spot offshore of Brazil's northeastern coast. The Abrolhos Archipelago is surrounded by the largest and richest coral reefs in the South Atlantic and is known to be a nesting site for loggerhead turtles (Caretta caretta). In this study, we performed a multidisciplinary investigation into levels of hybridization in sea turtles and their reproductive output in the Abrolhos beaches. Genetic data from mitochondrial DNA (mtDNA) and six autosomal markers showed that there are first-generation hybrid females nesting in Abrolhos, resulting from crossings between hawksbill males (Eretmochelys imbricata) and loggerhead females, and backcrossed hatchlings from both parental species. The type and extent of hybridization were characterized using genomic data obtained with the 3RAD method, which confirmed backcrossing between F1 hybrids and loggerhead turtles. The reproductive output data of Abrolhos nests suggests a disadvantage of hybrids when compared to loggerheads. For the first time, we have shown the association between hybridization and low reproductive success, which may represent a threat to sea turtle conservation.
Invasive predators on islands impact organisms they consume and lead to cascading effects that disrupt ecosystem functioning. Black rats (
Rattus rattus
) are a prevalent threat on tropical islands. ...Here, we used stable isotopes to reveal patterns in the foraging ecology of black rats (
n
= 43) on two tropical islands in the Abrolhos archipelago, southwestern Atlantic Ocean. Contrary to our predictions, rats from the smaller island (3 ha), with greater seabird density, relied more on terrestrial resources than rats from the larger (31 ha) island, which were highly dependent (~ 50% of diet) on seabird resources. We attribute this finding to varying levels of spatial segregation among habitats between the islands. On the smaller island, only rats sampled inside the colony had a high contribution from seabirds, while those sampled outside the colony had their foraging apparently constrained within the small patch of grassland habitat. On the larger island, however, individuals consumed seabird resources regardless of the sampling area, although the sampling locations were farer apart, suggesting lower spatial segregation. A greater foraging segregation in the smaller island could be related to a higher population density of rats, increasing competition and territoriality. Rats inside seabird colonies were larger and heavier than in grassland areas, likely by having access to marine-derived resources, suggesting these individuals could defend their prime foraging territory against others. Our results highlight the capacity of black rats to rely either on marine or terrestrial resources on tropical islands, providing population resilience for this island invader.