Marine litter results from human activity, both accidental and intentional, with most coming from land-based activities including transportation by rivers, drainage, sewage systems or wind.
Any persistent, manufactured or processed solid material discarded in marine and coastal environments is considered marine litter and, although the term covers a wide range of materials, the majority (75%) are plastics which don't degrade rapidly (Galgani et al., 2010). Especially problematic for marine organisms are microplastics – products of the breakdown of larger items or directly discarded –which can easily be consumed inadvertently. Factoring in that ocean circulation greatly affects the redistribution and accumulation of marine debris, as do the mass, buoyancy, and persistence of the material (Moore et al. 2001), it is clear the potential impacts of marine litter can be widespread and long-lasting.
Over the past decades, the quantities and number of types of marine litter have increased dramatically following trends in human use, for example the intensive and continuous release of highly persistent materials which can result in the accumulation of synthetic debris. The detritus can be found on the seafloor, in the water column, or casted onto beaches.
Marine litter is not just an environmental but also economic, health, and aesthetic problem, harmful or deadly to the wildlife that can ingest or become entangled in it. In some cases it affects a sizeable part of the population. It threatens marine biodiversity and could increase the risk of transporting marine invasive species (UNEP, 2005). Such debris also incurs losses to coastal tourism and fishing industries, and clean-up costs can be substantial.
Around 373 species of marine wildlife are currently known to be affected by marine debris through entanglement or ingestion but in reality this number is probably much higher (GEF, 2012). Studies have discovered notable amounts of planktivorous fish from the North Pacific gyre and fish caught off the south-west coast of England to contain plasticised matter in some form. In addition, microplastics have been found in the guts of an ever-rising number of marine mammals, birds, and invertebrates.
Litter in the form of medical, toxic, and sewage related waste represents potential health hazards for humans and it can also have ramifications in both an aquaculture and a food chain context.
Across Europe, the distribution and abundance of marine litter on the seabed has been investigated in conjunction with existing ICES stock assessment surveys since the beginning of the 1990s (Galgani et al., 2010).
ICES scientific work involves delivering advice on the management of 135 separate finfish and shellfish stocks and conveying scientific information on how anthropogenic activity impacts the marine environment. Because of its nature, marine litter can be seen as the perfect example of an anthropogenic pressure which can easily be monitored on the back of existing ICES stock assessment surveys to determine potential influences on fish stocks and biodiversity.
ICES provides advice to OSPAR, HELCOM and the EU on the monitoring of marine litter in relation to the Marine Strategy Framework Directive (MSFD), and the organization has recently taken on a more coordinating role in this area. The occurrence and effects of marine litter in the ICES area and understanding of this vast problem is still yet incomplete.
Amongst others things, this has led to the inclusion of Theme Session A at the ASC in Reykjavík.
Moore C. J., Moore S. L., Leecaster M. K. and Weisberg S. B. (2001) A comparison of plastic and plankton in the north pacific gyre. Marine Pollution Bulletin Vol. 42 No. 12 pp. 1297-1300
Secretariat of the Convention on Biological Diversity and the Scientific and Technical Advisory
Panel - GEF (2012). Impacts of Marine Debris on Biodiversity: Current Status and Potential Solutions,
UNEP (2005). Marine litter, an analytical overview, United Nations Environment Programme, 47pp.