Monitoring Floating Marine Macro Litter (FMML) is a global priority, stressed within international programs, and regulated for the European Seas by the Marine Strategy Framework Directive. Although some well-defined common protocols exist for the assessment of beach litter and ingested litter, methodologies for FMML monitoring still vary, leading to some inconsistent results and hampering the global assessment of this threat. Within the MEDSEALITTER project (2016–2019), field experiments were implemented to define optimal monitoring parameters for FMML visual monitoring at different spatial scales, by assessing the influence of platform speed, strip width, observers experience, weather conditions, and litter size on its detectability. Along with the results of these experiments, we present the FMML density ranges detected across the over 20,000 km surveyed, highlighting a decreasing gradient from river mouths to coastal areas and the open sea, and providing a valuable contribution to the assessment of FMML in the Mediterranean Sea.

监测浮动海洋宏观废弃物（FMML）是一项全球优先事项，在国际计划中得到强调，并且由海洋战略框架指令对欧洲海洋进行了监管。尽管存在一些定义明确的通用协议来评估沙滩垃圾和吞食垃圾，但FMML监控方法仍然不同，导致结果不一致，并妨碍了对该威胁的整体评估。在MEDSEALITTER项目（2016-2019年）内，通过评估平台速度，带材宽度，观察者的经验，天气条件和垫料尺寸对其影响，实施了野外实验以定义不同空间尺度上FMML视觉监测的最佳监测参数。可检测性。连同这些实验的结果，我们介绍了20多个检测到的FMML密度范围，