Bacterioma dos ninhos de Tartaruga-de-Pente (Eretmochelys imbricata Linnaeus, 1766) em praias arenosas no município de Fortaleza-Ceará

Abstract

Marine turtles are cosmopolitan organisms that extensively inhabit the oceans and face various impacts due to their long life cycle and biological complexity. Along the Brazilian coast, five species of marine turtles are present. These animals face numerous threats to their health and survival, such as bycatch, climate change, and anthropogenic waste. A key aspect of conserving any species, especially those under threat, is protecting their reproductive cycle. Thus, a crucial conservation strategy for turtles is monitoring nests to understand hatching success, which is influenced by a combination of biotic and abiotic factors. Among the less studied biological factors, the microbiome stands out, with its role in establishing and maintaining the health of metazoans as a second genome being well recognized. The aim of this study was to characterize the bacteriome of Eretmochelys imbricata nests on two sandy beaches in Fortaleza, Ceará: one highly anthropized by coastal developments and tourism, and the other less anthropized and situated within a municipal conservation unit. The study investigated whether the microbiome is influenced by the surrounding environment during this specific life stage of the species and if it is possible to correlate the composition of the bacteriome with the environmental characteristics of these locations as well as hatching success. Nest monitoring was conducted weekly by the Instituto Verdeluz. After the hatching of the clutch, sediment samples were collected from five randomly selected nests on each beach post-hatching and stored at -20°C for later DNA analysis and sequencing. Additionally, aseptic samples of egg shells from two nests on each beach were also collected for molecular analysis to characterize the bacteriome. Microbial community analysis, performed through 16S rDNA gene sequencing, revealed the presence of 40 bacterial phyla in the nests. The predominant phyla included Proteobacteria, Bacteroidota, Crenarchaeota, Firmicutes, Actinobacteriota, and Acidobacteriota. On the egg shells, Proteobacteria and Bacteroidota were the most abundant, with Proteobacteria predominating at Praia do Futuro and Sabiaguaba showing a more balanced distribution between Proteobacteria and Bacteroidota. Sediments exhibited greater bacterial diversity and species richness compared to the egg shells. Ecological indices, such as Simpson and Shannon, indicated that sediments have significantly higher richness and diversity than egg shells. Beta diversity analysis, conducted using the NMDS method, showed that samples from Praia do Futuro are more similar to each other, while samples from Praia de Sabiaguaba exhibited greater variability. The study concludes that sediment microbiota influences egg shell microbiota and that the observed differences are related to environmental and anthropogenic factors. It highlights the importance of environmental preservation for maintaining the health 12 of marine turtle nests and hatching success and notes that further studies are needed for a better understanding of the microbiome.