About this Research Topic
According to United Nations, 6.4 million tons of anthropogenic litter end up in the oceans every year. The majority of this litter (up to 83% according to some sources) is plastics. Continental plastic litter enters the ocean largely through storm-water runoff, is dumped on shorelines during recreational activities or directly discharged at sea from ships and trade activities. The deep-sea floor is probably the final global sink for marine litter. However, long-term data is scarce and does not show any clear or significant trends with regards to variations in debris quantities. In many coastal countries, mismanagement of solid waste caused 1.7% to 4.6% of the total plastic waste generated in 2010 in those countries to end up in the sea. Despite initiatives to reduce marine litter, such as from UNEP, the G20, and G7, the European Marine Strategy Framework Directive and action plans from the regional seas conventions, harm is still to be well understood. Moreover, standardization of sampling techniques, result units and metrics is still at an incipient stage, and harmonization is needed to achieve reliable monitoring.
The coastal landscape is frequently impacted by marine litter that impairs recreational uses and causes a loss of touristic value. Beyond the aesthetic impact, marine litter also bears potential economic implications to the fishery sector. It also strongly affects the marine environment. First, solid particles are ingested by fauna and may remain in the stomach undigested (most of them are excreted). Large differences among taxa, resulting from differences in size and feeding habits, have been described. Many studies have focused on selected species such as seabirds or sea turtles and have even been proposed as bioindicators of oceanic plastic pollution because they feed exclusively at sea, show a non-selective surface foraging, and the prevalence of plastics in their stomachs reaches 100% for certain populations. Second, plastic litter can represent a relevant source of chemical additives, some of them with suspected endocrine disrupting action, that easily leach into the water since they are not bound to the polymeric chains and become available to the estuarine and marine fauna. Third, intentionally or accidentally discarded fishing gear poses special risk for large, air-breathing marine animals, including endangered species, which get entangled in the nets. Estimated entanglement rates (percentage of individuals of the population observed to get entangled) for different species of seals ranged from 0.1 to 1.9%. Conventional plastics are non-biodegradable and they may persist in the environment for hundreds of years but also because of hydrodynamics and exposure to light, they may fragment into small particles readily taken up by marine organisms. Microplastics and nanoplastics are a specially feared component of marine litter since the smallest zooplankton species may uptake them, and they might play a role as vectors of hydrophobic pollutants (and plastic additives) into the trophic webs, although thermodynamic models and experimental data provide conflicting results and more research is needed on this field. Finally, plastic at sea may transport alien species for long distances or act as substratum for benthic species, providing a support to colonization.
This research topic will consider several feature of marine litter impacts from the ecological, ecotoxicological, economical and social impacts. Moreover, it also proposes a discussion forum to better understand all potential harms caused by Marine litter, both to marine organisms as well as to the whole marine/estuarine environment and communities.
Keywords: Marine Litter, plastic, microplastics, impacts, harm
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