Abstract
Plastic pollution is nowadays a relevant threat for the ecological balance in marine ecosystems. Small plastic debris (PD) can enter food webs through various marine organisms, with possible consequences on their physiology and health. The loggerhead sea turtle (Caretta caretta), widespread across the whole Mediterranean Sea, is a “flagship species,” useful as indicator of the general pollution level of marine ecosystems. Ingested PD accumulate in the final section of turtles’ digestive tract before excretion. During their transit and accumulation, PD also interact with the residing microbial community, with possible feedback consequences on the host’s health. To explore the possible relationship between fecal microbial composition and PD ingestion, we collected fecal samples from 45 turtles rescued between 2017 and 2019 in the Northwestern Adriatic Sea (Italy), assessing occurrence and content of PD in the samples and in parallel the microbiome structure by 16S rRNA gene sequencing. According to our findings, almost all samples contained PD, mirroring the high level of plastic pollution in the area. We identified phylotypes associated to a high amount of PD, namelyCetobacterium someraeand other taxa, possibly responding to contamination by plastic-associated chemicals. Furthermore, putative marine pathogens were found associated to higher plastic contamination, supporting the hypothesis that PD can act as a carrier for environmental pathogenic bacteria into marine organisms. Besides confirming the role of the sea turtle as relevant flagship species for plastic pollution of the marine environment, our study paves the way to the exploration of the impact that PD ingestion can have on the microbial counterpart of large marine organisms, with potential feedback consequences on the animal and ecosystem health.
Highlights
With a global mass production of more than 350 million tons per year (PlasticsEurope, 2019), plastic is nowadays one of the major emerging pollutant in marine environments (UNEP, 2014)
To shed light on this perspective, we explored the amount of plastic debris found in the feces of live loggerhead sea turtles (Caretta caretta) rescued from the Northwestern Adriatic Sea, along with possible relationships between occurrence of PD and changes in the animal gut microbiota
The present study explored the plastic debris (PD) amount in the feces of wild captured loggerhead sea turtles (C. caretta), dwelling in the Northwestern Adriatic Sea, collected after their arrival at a local rescue center for their rehabilitation
Summary
With a global mass production of more than 350 million tons per year (PlasticsEurope, 2019), plastic is nowadays one of the major emerging pollutant in marine environments (UNEP, 2014). The amount of PD is reported to increase progressively from the esophagus to the stomach and the intestine, and that debris can remain in the last part of the gut for more than 40 days before being defecated (Hoarau et al, 2014), gradually accumulating if the ingestion is not sporadic. This highlights the need to include feces as target samples in studies focused on the plastic ingestion by sea turtles (Pham et al, 2017)
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