Mediterranean Biodiversity and Marine Litter An interaction knowledge base


Marine litter is at present a top ranked pollution menace to the conservation and sustainability of marine biodiversity and healthy and functional ecosystems. There is a growing evidence of global marine ecosystems impacted by marine litter as a result of our unsustainable lifestyles associated with the ‘plastic’ revolution. The way litter pollution (from macro down to micro and nano scales) is affecting marine life is not fully understood yet, especially beyond short spatial and temporal scales. As the global production of plastics has been growing exponentially since 1960s and as there are already huge quantities of marine litter in the oceans and seas; such studies need to be urgently prioritized to allow the understanding of potential future scenarios and to support finding solutions to guarantee functional marine ecosystems and so the provision of proper ecosystem services.

Five thematic projects within the Mediterranean Biodiversity Protection Community have pursued marine litter pollution knowledge objectives

Threats of marine litter on Mediterranean biodiversity

An integrated regional approach to a global threat

Marine litter, human-created waste discharged into and/or found on the coastal or marine environment, is listed among the main perceived threats to biodiversity, causing major concern due to its abundance, durability and persistence in the marine environment.

In order to improve our regional understanding on the degree of threat litter is imposing to the Mediterranean region, ETC-UMA developed under the PANACeA framework a clearinghouse mechanism to provide an overview of current efforts in place, including the creation of a Mediterranean marine litter and biodiversity interactions database known as MedBioLitter. MedBioLitter builds on an extensive literature search to review the current state of knowledge on the effects of marine litter on marine organisms in the Mediterranean region.

Marine litter is listed among the main perceived threats to biodiversity, causing major concern due to its abundance, durability and persistence in the marine environment.

The known and unknown in the Mediterranean region

Scientific research has revealed that many marine species are impacted by marine litter in all known habitat types in the Mediterranean Sea. According to literature, up to 134 species were reported to be affected by marine litter in the region (Deudero et al., 2015), and a recent study confirms 91 assessed species were affected by ingestion from different habitats, with most available studies conducted on demersal (32.9%), pelagic (27.7%) species, followed by benthic (14.7%), benthopelagic (16.5%), neritic (5.3%) and mesopelagic (2.9%) species (Fossi et al., 2018 and references therein). Entanglement and colonization interactions such as diverse blockage forms and physical functions impairment as well as rafting or provision of new habitats have been also investigated. Entanglement has been proposed to become a target indicator to be included in the upcoming policy (Galgani et al., 2018).

Figure 1. Assessment of interactions between marine litter and biota in the Mediterranean Sea

Discovering marine litter effects on biodiversity through scientific research

The Med Biodiversity Protection Community is contributing with new regional findings related to the interactions of marine litter with different marine species in almost all marine habitats and commonly known Mediterranean ecological groups. As mentioned elsewhere in this document, the MEDSEALITTER project activities have studied the ingestion of microplastics by pelagic fish (Boops boops) and by benthic invertebrates (polychaeta spp), the ingestion of micro- and macroplastics by the loggerhead turtle (Caretta caretta) in Greece, Italy, France and Spain; and have evaluated the plastic ingestion probability by marine macro fauna in the Western Mediterranean subregion, based on several surveys combining the measurement of amounts and occurrence of floating marine litter and marine organisms. In addition, MEDSEALITTER investigated the risk of exposure of marine species listed in the Habitats Directive (such as cetaceans and marine turtles) to marine litter in several Mediterranean areas. Similarly, the PLASTICBUSTERSMPAs project is studying the impacts of marine litter in several species from invertebrates (e.g. isopods, mussels, etc.), fish (Engraulis encrasicolus, Sardina pilchardus, etc.) and mammal species like the fin whale (Balaenoptera physalus), sperm whale (Physeter macrocephalus), as well as other groups in the whole Mediterranean region, and particularly in the Pelagos Sanctuary and several Mediterranean MPAs.

Assessment of marine litter interactions with Mediterranean biodiversity

Harmonized and more balanced knowledge on marine litter and biodiversity interactions in Mediterranean Marine Protected Areas (MPAs) is needed to support informed daily management priorities and policy making mechanisms. The MedBioLitter database recently developed is being used to set a baseline for a regional understanding on the impacts of marine litter on biodiversity in the Mediterranean region.

This Mediterranean-wide spatial assessment by ETC-UMA was performed using the MedBioLitter meta-analysis outcomes (September 2019). It aims at obtaining a regional understanding on the state of knowledge on biodiversity within Mediterranean MPAs, particularly those engaged by the projects co-financed by the Interreg Med Programme and within the ecological boundaries of the Mediterranean (i.e. Mediterranean ecoregions).

State of knowledge on marine litter impacts in Mediterranean MPAs

Monitoring and management plans in Marine Protected Areas (MPAs) require evidence and knowledge of the marine litter interactions with protected species and biodiversity.

Based on this assessment, out of the total MPAs in the Mediterranean (=1321 based on MAPAMED November 2017), only 2.6% have peer reviewed knowledge related to pressures and impacts from marine litter. Peer reviewed knowledge is only available for MPAs that belong to European Mediterranean countries while totally missing for non-EU MPAs in the Mediterranean. Participation of additional MPAs as partners and pilot sites in projects like PLASTICBUSTERSMPAs will allow for more updates to MedBioLitter in the near future.

Figure 3. Distribution of monitoring data between types of protected areas in the Mediterranean Sea (based on the MedBioLitter database, September 2019).

Figure 3 shows that, among the MPAs that have peer-reviewed information on marine litter interaction with biodiversity, the coincidence between the available monitoring sites information and protected geographical areas is larger for the Natura 2000 Sites designed under the EU Bird and Habitats Directives (42.51% of the area), followed by the data localized at nationally Designated areas (34.49%), SPAMIs (19.51%) and, to a lesser extent, FRAs (3.14%) and Ramsar sites (0.35%).

The assessment of marine litter impacts on MPAs shows that, despite the increase in published information on marine litter pollution occurrence, distribution and impacts on biodiversity in the Mediterranean Sea, the research efforts are not targeted and do not provide an understanding on the most common taxa in MPAs and beyond. This fact reveals the lack of a clear targeted policy that directs research efforts to contribute to a comprehensive regional assessment but rather research results coming from individual projects with different objectives. In brief, an integrated approach that targets common taxa in MPAs and in the Mediterranean ecoregions is still majorly lacking, except for cetaceans (under the leadership of ACCOBAMS in the Mediterranean) and would require further efforts to assess the environmental impacts and to guide regional remediation actions.

An integrated approach that targets common taxa in MPAs and in the Mediterranean ecoregions is still majorly lacking, except for cetaceans

State of knowledge on marine litter impacts on marine habitats

The information hosted by the MedBioLitter database has been overlaid with the EUNIS Habitat classification system to assess the linkages between the information on biodiversity impacted by marine litter and the different habitat types. The interactions between biodiversity and marine litter published were assessed in the pelagic and benthic ecosystems; this is reflected through some additional layers of information complementary to each of the ecosystems.

Marine litter and biodiversity interactions have been classified following international policy standards in four main categories: ingestion, entanglement, colonization and others, which collects studies with experimental information on interactions, such as forced field experiments, or information difficult to classify under the other three categories.

Figure 6. Distribution of knowledge on interaction types in benthic ecosystems in the Mediterranean Sea.
Waters belonging to the countries of the European Union present more than 90% of the data, which highlights the lack of information in the Southern part of the Mediterranean

MedBioLitter: The Mediterranean database on marine litter impacts – State and Outlook

Database and information gathering, integration and parameters

The MedBioLitter database summarizes the results of scientific studies on biodiversity and marine litter interactions in the Mediterranean Sea. To this end, information has been collected from different data sources; institutions and projects working on marine litter; and relevant peer-reviewed publications. The original main source of data has been the LITTERBASE (AWI) coverage within the Mediterranean. LITTERBASE follows a similar approach to MedBioLitter, summarizing global results from scientific studies in understandable maps and figures.

The main information used by MedBioLitter is the location and type of interaction, followed by the type of habitat, species and marine litter associated with the event. Location is extracted directly when the coordinates of the study area are provided or there are GIS layers available. Locations have also been digitized from existing maps. In particular cases, the location is estimated from the description of the study area. Information on the type of interaction, affected species, etc. is compiled based on the detailed reading of publications.

Key messages to policy makers


Science has demonstrated that most common species, ecological groups and ecosystem trophic levels (producers such as planktonic communities, consumers such as the commercial fish families and large predators and long-lived species such as turtles and cetaceans) interact with marine litter and are impacted to death in some cases.


More than 100 species in all common ecological groups have been identified in the scientific literature as impacted by marine litter and the numbers will increase in the Mediterranean region and globally because of increased scientific research initiatives funded in the last decade.


Though some peer reviewed information exists, the knowledge available on the status of biodiversity within MPAs is very low in terms of interaction with marine litter pollution; representativeness at a Mediterranean scale is lacking.


The geographical unbalance in terms of knowledge availability and the lack of consolidated routine networks and programmes in most of Mediterranean countries are perceived by the Mediterranean Biodiversity Protection Community as gaps that need to be urgently tackled at regional scale, accompanied by the corresponding financial and regulatory mechanisms.


Management plans for MPAs should consider measures to reduce litter pollution and include surveys on the marine biodiversity status, knowing that MPAs are also affected by external sources of litter and other distinct continuous pressures.


There is an opportunity to investigate marine pollution effects to biodiversity in selected species in MPAs, as those are meant to have reduced, controlled and monitored pressures and impacts from human activities.


Studies on biodiversity effects in controlled environments such as MPAs should not be extrapolated directly to larger scales (sub-regional or regional) as the impacts could be underestimated, despite the patchiness of drivers and known pressures in the Mediterranean.


Further science-practice-policy strategies to approach marine litter pollution effects in the Mediterranean Sea biodiversity still need to be refined, harmonized and aligned with ongoing policy developments (EU MSFD, UN MAP/IMAP) and scientific evidence.


It is an informative quantitative fact that monitoring strategies are more advanced for marine macro and micro litter monitoring in marine compartments than for monitoring litter impact on marine biodiversity. This fact impedes a full comprehension and understanding of marine litter effects on biodiversity, limiting therefore our current knowledge on the overall impact to take action.


An integrated approach that targets common species or group of species in MPAs and in the Mediterranean ecoregions is still majorly lacking and would require further efforts to assess the environmental impacts and to be able to guide regional remediation actions.


Such integrated approach would enable the consolidation of a regional mechanism to properly monitor and assess this transboundary pressure in the Mediterranean Sea and its trends over time, as partial solutions and actions taken only at local and country level have proved not to be fully effective.


A collaborative Mediterranean community representing around 200 institutions are bringing together their work to identify the most effective mechanisms to manage and protect Mediterranean biodiversity.

The results of eleven projects (ACT4LITTER, AMARE, CONFISH, ECOSUSTAIN, FISHMPABLUE2, MEDSEALITTER, MPA-ADAPT, PHAROS4MPAs, PLASTICBUSTERSMPA, POSBEMED, WETNET) are being streamlined by PANACeA to offer holistic solutions that bridge science, practice and policy to priority environmental challenges through an action roadmap implemented by several working groups.

This report is one of a series developed by PANACeA in the framework of Working Group 1 focusing on protected areas and biodiversity management, led by ETC-UMA and MedCities.

The overall aim of the Biodiversity Protection Community is to increase the current understanding, knowledge and awareness of multiple environmental threats and promote best practices and Ecosystem-based Management tools as a response to address cumulative pressures and impacts affecting protected areas and functional ecosystem units in the Mediterranean.