Marine Litter (EO 10)

Common Indicator 23: Trends in the amount of litter in the water column including microplastics and on the seafloor

Geographical scale of the assessment:
Mediterranean Sea
Contributing countries:
Mediterranean assessment based on existing regional and national surveys, research and publications and as appropriate data from national monitoring programmes of the Contracting Parties.
Mid-Term Strategy (MTS) Core Theme:
1-Land and Sea Based Pollution
Ecological Objective:
Ecological Objective 10 (EO10): Marine and coastal litter do not adversely affect the coastal and marine environment
IMAP Common Indicator:
Common Indicator 23 (CI23): Trends in the amount of litter in the water column including microplastics and on the seafloor
Indicator Assessment Factsheet Code:

GES Definition: Number/amount of marine litter items in the water surface and the seafloor do not have negative impacts on human health, marine life, ecosystem services and do not create risk to navigation  

GES Targets:

  • State: Decreasing trend in the number/amount of marine litter items in the water surface and the seafloor



The marine environment is directly linked to human life. Nowadays, marine litter is found widespread in the environment, from shallow water till the deep abyssal plains, posing one of the major threats for the marine environment.

The Mediterranean Sea has been described as one of the areas most affected by marine litter in the world. Human activities generate considerable amounts of waste, and quantities are increasing, although they vary between countries. Some of the largest amounts of municipal solid waste (MSW), generated annually per person occur in the Mediterranean Sea (208 – 760 kg/year, Plastic, which is the main marine litter component, has now become ubiquitous and may comprise up to 90% for seafloor litter.

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Assessment methods

The current assessment has been based on recent key assessments, reports and publications by the UN Environment/MAP, and other projects and initiatives. The UN Environment/MAP 2015 Marine Litter Assessment in the Mediterranean report has been used as the main source for this indicator assessment factsheet. For the moment, there is no reporting toUN Environment /MAP on floating and seafloor marine litter and the assessment is based on the available data and information from reports and scientific publications. Several approaches, protocols and units (items/km, items/km2, kg/km2, kg/h) have been used. However, the expression of the abundance of marine litter found float at sea or lying on the seafloor in items per surface are (m2, km2, ha2) coupled with information on weight seems to be the most appropriate. Nowadays the harmonization of all the sampling methodologies is among the top-priorities of the marine litter agenda.

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Results and Status, including trends

Floating Marine Litter

The abundance of floating macro and mega litter in Mediterranean waters has been reported at quantities measuring over 2 cm range from 0 to over 600 items per square kilometer (Aliani et al., 2003; UNEP, 2009; Topcu et al., 2010, Gerigny et al., 2011, Suaria and Aliani, 2015) (Figures 1, 2). Plastics are predominant among floating marine macro- and micro-litter items.

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Plastic is the main component of floating marine litter and also for those lying on the Mediterranean seafloor, from shallow water, the continental shelf, till the deep abyssal plains. Regarding marine litter (floating and on seafloor) that are accumulating in the Mediterranean basin, no safe conclusion can be drawn for the moment. Probably hydrodynamics and geomorphology favor the constant circulation. More consistent, interconnected and interlinked studies need to be promoted in order to have a better picture at basin scale. The comparability of the existing and future studies seem to be a key point towards an integrated assessment at basin scale.

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Key messages

  • The abundance of floating litter in Mediterranean waters has been reported at quantities measuring over 2 cm range from 0 to over 600 items per square kilometer (Aliani et al., 2003; UNEP, 2009; Topcu et al., 2010, Gerigny et al., 2011, Suaria and Aliani, 2015).
  • The 2015 UN Environment/MAP Marine Litter Assessment report states that approximately 0.5 billion litter items are currently lying on the Mediterranean Seafloor. Moreover, there is great variability in the abundance of seafloor marine litter items ranging from from 0 to over 7,700 items per km² depending on the study area.

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References included in the UN Environment/MAP (2015). Marine Litter Assessment in the Mediterranean 2015. UN Environment /Mediterranean Action Plan. ISBN: 978-92-807-3564-2.

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Gerigny O., Henry M., Tomasino C., F.Galgani (2011). Déchets en mer et sur le fond. in rapport de l'évalution initiale, Plan d'action pour le milieu marin - Mediterranée Occidentale, rapport PI Déchets en mer V2 MO, pp. 241-246 (

Güven O. Gülyavuz H., Deval M. (2013) Benthic Debris Accumulation in Bathyal Grounds in the Antalya Bay, Eastern Mediterranean. Turkish Journal of Fisheries and Aquatic Sciences 13: 43-49.

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Katsanevakis S, Katsarou A. (2004). Influences on the distribution of marine debris on the seafloor of shallow coastal areas in Greece (Eastern Mediterranean). Water, Air and Soil Pollution 159: 325-337

Koutsodendris A., Papatheodorou G., Kougiourouki O., Georgiadis M. (2008) Benthic marine litter in four Gulfs in Greece, Eastern Mediterranean; abundance, composition and source identification. Estuarine, Coastal and Shelf Science 77, 501-512.

Lebreton L., Greer S., J.Borrero (2012) Numerical modelling of floating debris in the world’s oceans, Marine Pollution Bulletin 64, 653-661.

Mansui, J., Molcard, A., Ourmieres, Y. (2015). Modelling the transport and accumu-` lation of floating marine debris in the Mediterranean basin. Mar. Pollut. Bull. 91, 249–257.

Mifsud R., Dimech M., Schembr P. (2013) Marine litter from circalittoral and deeper bottoms off the Maltese islands (Central Mediterranean). Mediterranean Marine Science 14: 298-308.

Pham C., Ramirez-Llodra E., Claudia H. S., Amaro T., Bergmann M., Canals M., Company J., Davies J., Duineveld G., Galgani F., Howell K., Huvenne Veerle A., Isidro E., Jones D., Lastras G., Morato T., Gomes-Pereira J., Purser A., Stewart H., Tojeira I., Tubau X., Van Rooij D., Tyler P. (2014). Marine Litter Distribution and Density in European Seas, from the Shelves to Deep Basins. Plos One, 9(4), e95839.

Ramirez-Llodra E., De Mol B., Company J.B., Coll M., Sardà F. (2013) Effects of natural and anthropogenic processes in the distribution of marine litter in the deep Mediterranean Sea. Progress in Oceanography, Volume 118, 273-287.

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Strafella P., Fabi G., Spagnolo A., Grati F., Polidori P., Punzo E., Fortibuoni T., Marceta B., Raicevich S., Cvitkovic I., Despalatovic M., Scarcella G. (2015). Spatial pattern and weight of seabed marine litter in the northern and central Adriatic Sea. Marine Pollution Bulletin 01/2015; 91(1):120-127.

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Topcu T., G.Ozturk (2013) Origin and abundance of marine litter along sandy beaches of the Turkish Western Black Sea Coast. Mar. Env. Res., 85, 21-28

UNEP (2009), Marine Litter A Global Challenge, Nairobi: UNEP. 232 pp.

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Additional references

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Galgani F., Burgeot T., Bocquéné G., Vincent F., Leauté J.P., Labastie J., Forest A., Guichet R. (1995b). Distribution and Abundance of Debris on the Continental Shelf of the Bay of Biscay and in Seine Bay. Mar. Pollut. Bull. 30: 58-62.

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