Strandings of sea turtles on beaches around the oil capital in Brazil

The south-western region of the Atlantic Ocean has feeding and nesting areas for the five species of sea turtles registered in Brazil, which are in different degrees of extinction threat, mainly due to anthropogenic factors. Fishing and the ingestion of solid waste, were identified as causing stranding and the mortality of sea turtles. In this work, data from the monitoring of beaches in the Municipalities of Macaé and Rio das Ostras, important oil zone in Brazil, in the north-central region of the State of Rio de Janeiro, were used in order to analyse the effects of seasonality on the sea turtle stranding. The monitoring was carried out daily from September 2017 to June 2019, in a study area covering 23.8 km long beach. Stranding data were obtained from active (n = 126) and passive (n = 66) monitoring of beaches and included the records of Chelonia mydas (n = 151), Caretta caretta (n = 23), Lepidochelys olivacea (n = 14), Dermochelys coriacea (n = 2) and Eretmochelys imbricata (n = 1). The largest stranding record occurred in the summer (n = 61) and spring (n = 60), a period compatible with the reproductive season of the species. The results obtained in this study emphasise the importance of the analysis of strandings of sea turtles, which provide relevant data on the biology of the group, the intra and interspecific dynamics and the state of conservation of these animals.

Environmental and anthropogenic factors affecting nesting site selection by sea turtles

Understanding the environmental and anthropogenic factors that affect nesting site selection by sea turtles is key to maintaining priority conservation areas. The species Lepidochelys olivacea, Caretta caretta, and Eretmochelys imbricata nest annually on the island of Comandatuba (Una, northeastern Brazil), where this survey was conducted. We evaluated the temporal and spatial distribution of nests during the seasons 2008/2009 to 2014/2015 and 2017/2018. In the last season, we further examined the environmental and anthropogenic factors that influence different nesting performances. We selected six sample areas with different nesting events (high, medium, and low), and recorded the following characteristics: beach slope, sediment grain size, vegetation richness, type of dune, anthropization, and final nest condition. A significant occurrence of nesting was observed in November and December . The spatial distribution of the nests varied over the seasons, with a greater tendency to nest in the south of the island. Higher frequency of anthropization and low slope of the beach were significant factors for areas with a smaller number of nests. Predation of turtle nests may be associated with areas of greater anthropization. Our findings have implications for the conservation and monitoring of nesting sites during reproduction seasons and provide further insight into the nesting dynamics of marginal sea turtle populations.

Genomic evidence of recent hybridization between sea turtles at Abrolhos Archipelago and its association to low reproductive output

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 (Carettacaretta). 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 (Eretmochelysimbricata) 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.

Ocular spirorchiidiosis in sea turtles from Brazil

The causes of the beaching and death of sea turtles have not been fully clarified and continue to be studied. Mild, moderate and severe lesions caused by spirorchiidiosis have been seen for decades in different organs and were recently defined as the cause of death of a loggerhead turtle. In the present study, eyes and optic nerves were analysed in green sea turtles with spirorchiidiosis and no other debilitating factors. Injuries to the optic nerve and choroid layer were described in 235 animals (90%) infected with spirorchiids. Turtles with ocular spirorchiidiosis are approximately three times more likely to be cachectic than turtles with spirorchiidiosis without ocular involvement.

First satellite tracks of South Atlantic sea turtle 'lost years': seasonal variation in trans-equatorial movement

In the South Atlantic Ocean, few data exist regarding the dispersal of young oceanic sea turtles. We characterized the movements of laboratory-reared yearling loggerhead turtles from Brazilian rookeries using novel telemetry techniques, testing for differences in dispersal during different periods of the sea turtle hatching season that correspond to seasonal changes in ocean currents. Oceanographic drifters deployed alongside satellite-tagged turtles allowed us to explore the mechanisms of dispersal (passive drift or active swimming). Early in the hatching season turtles transited south with strong southward currents. Late in the hatching season, when currents flowed in the opposite direction, turtles uniformly moved northwards across the Equator. However, the movement of individuals differed from what was predicted by surface currents alone. Swimming velocity inferred from track data and an ocean circulation model strongly suggest that turtles' swimming plays a role in maintaining their position within frontal zones seaward of the continental shelf. The long nesting season of adults and behaviour of post-hatchlings exposes young turtles to seasonally varying ocean conditions that lead some individuals further into the South Atlantic and others into the Northern Hemisphere. Such migratory route diversity may ultimately buffer the population against environmental changes or anthropologic threats, fostering population resiliency.