Drivers of litter ingestion by sea turtles: Three decades of empirical data collected in Atlantic Europe and the Mediterranean

Sea turtles are considered as bio-indicators for monitoring the efficiency of restoration measures to reduce marine litter impacts on health. However, the lack of extended and standardised empirical data has prevented the accurate analysis of the factors influencing litter ingestion and the relationships with individual health. Historic data collected from 1988 and standard data collected from 2016 were harmonised to enable such analyses on necropsied loggerhead turtles (Caretta caretta) in eight Mediterranean and North-East Atlantic countries. Litter was found in 69.24 % of the 1121 individuals, mostly single-use and fishing-related plastics. Spatial location, sex and life history stage explained a minor part of litter ingestion. While no relationships with health could be detected, indicating that all individuals can be integrated as bio-indicators, the mechanistic models published in literature suggest that the high proportion of plastics in the digestive contents (38.77 % per individual) could have long-term repercussions on population dynamics.

Automated summary

Sea turtles are considered as bio-indicators to evaluate the effectiveness of restoration measures in reducing the impact of marine litter on health. This study analyzed the factors influencing litter ingestion and its relationship with individual health using data from loggerhead turtles in the Mediterranean and North-East Atlantic. The results showed that litter was found in 69.24% of the turtles, mainly consisting of single-use and fishing-related plastics. Factors such as spatial location, sex, and life history stage had a minor effect on litter ingestion. Although no relationship with health was found, the high proportion of plastics in the turtles' digestive contents could have long-term consequences on population dynamics, as suggested by mechanistic models.