Benthic Marine Litter in Three Greek Gulfs: Are Mean Density Estimates Truly Representative?

In this study, seafloor litter loads were compared across three major gulfs in Greece—Saronikos, Thermaikos, and Patras Gulf—by analyzing and synthesizing existing datasets from published research. Particular emphasis is placed on evaluating depth related spatial patterns, methodological differences, and potential sources of bias to provide a clearer understanding of the pollution status, highlight existing data gaps, and underscore the urgency for further research on the topic. Thermaikos appears to be the most heavily polluted, followed by Saronikos, with Patras Gulf showing the lowest litter levels. Plastic materials dominate the composition of marine litter, particularly food and beverage packaging, while a variable proportion of the litter is associated with fishing activities. Litter density tends to decrease with depth, with the dramatically higher concentrations observed in nearshore shallow waters (0–5 m) by scuba divers, whereas the lowest densities are recorded through trawling surveys in deeper areas.