This milestone report describes the current capacity to monitor or otherwise observe selected indicators of marine litter pollution which have the potential to be reported consistently on a regional to global scale in support of the stakeholder needs., {"references":["Programmi di Monitoraggio per la Strategia Marina Art. 11, D.lgs. 190/2010","B. Wenneker, L. Oosterbaan, & Intersessional Correspondence Group on Marine Litter (ICGML), Guideline for Monitoring Marine Litter on the Beaches in the OSPAR Maritime Area. Edition 1.0 (London, UK, 2010). https://doi.org/10.25607/OBP-968","MSFD GES Technical Subgroup on Marine Litter (TSG-ML), Monitoring Guidance for Marine Litter in European Seas Draft Report. (2013)","Cheshire, A.C., E. Adler, J. Barbière, Y. Cohen, S. Evans, S. Jarayabhand, L. Jeftic, R. T. Jung, S. Kinsey, E. T. Kusui, I. Lavine, P. Manyara, L. Oosterbaan, M. A. Pereira, S. Sheavly, A. Tkalin, S. Varadarajan, B. Wenneker, & G. Westphalen, UNEP/IOC Guidelines on Survey and Monitoring of Marine Litter (2009)","MARLIN Baltic Marine Litter Project, Final Report of Baltic Marine Litter Project Marlin - Litter Monitoring and Raising Awareness 2011-2013 (2013)","T. Maes & F. Preston-Whyte, The African Marine Litter Outlook (2023)","S. Lippiatt, S. Opfer, & C. Arthur, Marine debris monitoring and assessment. NOAA Technical Memorandum, (2013)","H. K. Burgess, C. E. Herring, S. Lippiatt, S. Lowe, & A. V Uhrin, NOAA Marine Debris Monitoring and Assessment Project Shoreline Survey Guide. NOAA Technical Memorandum NOS OR&R 56, 20 (2021) 1–20. https://doi.org/10.25923/g720-2n18","EMODnet Chemistry, European floating micro-litter standardized, harmonized and validated datasets 2011/2020 v2021. (2023). https://doi.org/10.13120/q6t1-2r39","M. D. Wilkinson, M. Dumontier, Ij. J. Aalbersberg, G. Appleton, M. Axton, A. Baak, N. Blomberg, J. W. Boiten, L. B. da Silva Santos, P. E. Bourne, J. Bouwman, A. J. Brookes, T. Clark, M. Crosas, I. Dillo, O. Dumon, S. Edmunds, C. T. Evelo, R. Finkers, A. Gonzalez-Beltran, A. J. G. Gray, P. Groth, C. Goble, J. S. Grethe, J. Heringa, P. A. C. t Hoen, R. Hooft, T. Kuhn, R. Kok, J. Kok, S. J. Lusher, M. E. Martone, A. Mons, A. L. Packer, B. Persson, P. Rocca-Serra, M. Roos, R. van Schaik, S. A. Sansone, E. Schultes, T. Sengstag, T. Slater, G. Strawn, M. A. Swertz, M. Thompson, J. Van Der Lei, E. Van Mulligen, J. Velterop, A. Waagmeester, P. Wittenburg, K. Wolstencroft, J. Zhao, & B. Mons, The FAIR Guiding Principles for scientific data management and stewardship. Scientific Data, 3 (2016) 1–9. https://doi.org/10.1038/sdata.2016.18","NOAA/ National Centers for Environmental Information (NCEI), Microplastics Database. (2022)","K. L. Law, S. Morét-Ferguson, N. A. Maximenko, G. Proskurowski, E. E. Peacock, J. Hafner, & C. M. Reddy, Plastic accumulation in the North Atlantic subtropical gyre. Science, 329 (2010). https://doi.org/10.1126/science.1192321","K. L. Law, S. E. Morét-Ferguson, D. S. Goodwin, E. R. Zettler, E. Deforce, T. Kukulka, & G. Proskurowski, Distribution of surface plastic debris in the eastern pacific ocean from an 11-year data set. Environmental Science and Technology, 48 (2014). https://doi.org/10.1021/es4053076","W. P. de Haan, A. Sanchez-Vidal, & M. Canals, Floating microplastics and aggregate formation in the Western Mediterranean Sea. Marine Pollution Bulletin, 140 (2019). https://doi.org/10.1016/j.marpolbul.2019.01.053","M. C. Goldstein, A. J. Titmus, & M. Ford, Scales of spatial heterogeneity of plastic marine debris in the northeast Pacific Ocean. PLoS ONE, 8 (2013). https://doi.org/10.1371/journal.pone.0080020","G. Suaria, C. G. Avio, A. Mineo, G. L. Lattin, M. G. Magaldi, G. Belmonte, C. J. Moore, F. Regoli, & S. Aliani, The Mediterranean Plastic Soup: Synthetic polymers in Mediterranean surface waters. Scientific Reports, 6 (2016). https://doi.org/10.1038/srep37551","G. Suaria, V. Perold, J. R. Lee, F. Lebouard, S. Aliani, & P. G. Ryan, Floating macro- and microplastics around the Southern Ocean: Results from the Antarctic Circumnavigation Expedition. Environment International, 136 (2020). https://doi.org/10.1016/j.envint.2020.105494","J. Reisser, J. Shaw, C. Wilcox, B. D. Hardesty, M. Proietti, M. Thums, & C. Pattiaratchi, Marine plastic pollution in waters around Australia: Characteristics, concentrations, and pathways. PLoS ONE, 8 (2013). https://doi.org/10.1371/journal.pone.0080466","T. Tanhua, S. B. Gutekunst, & A. Biastoch, A near-synoptic survey of ocean microplastic concentration along an around-the-world sailing race. PLoS ONE, 15 (2020). https://doi.org/10.1371/journal.pone.0243203","A. P. W. Barrows, S. E. Cathey, & C. W. Petersen, Marine environment microfiber contamination: Global patterns and the diversity of microparticle origins. Environmental Pollution, 237 (2018). https://doi.org/10.1016/j.envpol.2018.02.062","A. Isobe, T. Azuma, M. R. Cordova, A. Cózar, F. Galgani, R. Hagita, L. D. Kanhai, K. Imai, S. Iwasaki, S. Kako, N. Kozlovskii, A. L. Lusher, S. A. Mason, Y. Michida, T. Mituhasi, Y. Morii, T. Mukai, A. Popova, K. Shimizu, T. Tokai, K. Uchida, M. Yagi, & W. Zhang, A multilevel dataset of microplastic abundance in the world's upper ocean and the Laurentian Great Lakes. Microplastics and Nanoplastics, 1 (2021) 1–14. https://doi.org/10.1186/s43591-021-00013-z","IMO/FAO/UNESCO-IOC/UNIDO/WMO/IAEA/UN/UNEP/UNDP/ISA, Guidelines for the monitoring and assessment of plastic litter in the ocean: GESAMP Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection (2019)","Y. Michida, S. Chavanich, S. Chiba, M. R. Cordova, A. Cozsar Cabanas, F. Glagani, P. Hagmann, H. Hinata, A. Isobe, P. Kershaw, N. Kozlovskii, D. Li, A. L. Lusher, E. Marti, S. A. Mason, J. Mu, H. Saito, W. J. Shim, A. D. Syakti, H. Takada, R. Thompson, T. Tokai, K. Uchida, K. Vasilenko, & J. Wang, Guidelines for Harmonizing Ocean Surface Microplastic Monitoring Methods. Ministry of the Environment Japan, (2020) 71","ICES, Manual for the International Bottom Trawl Surveys (Copenhagen, 2012)","MEDITS Working Group, MEDITS - Handbook. Version n.9 (2017)","ICES, Manual for the International Bottom Trawl Surveys. Series of ICES Survey Protocols. SISP 1-IBTS VIII. Series of ICES Survey Protocols.SIPS 1-IBTS VIII, (2012). https://doi.org/10.17895/ices.pub","ICES, SISP 2 Manual for the Midwater Ring Net sampling during IBTS Q1 (2013)","M. Bergmann, M. B. Tekman, & L. Gutow, LITTERBASE: An Online Portal for Marine Litter and Microplastics and Their Implications for Marine Life. Fate Impact Microplastics Mar. Ecosyst. (2017). https://doi.org/10.1016/b978-0-12-812271-6.00104-6"]}