AND WHAT ABOUT THE LITTER INTO OUR SEA?
Humans have been impacting the environment so intensely during the last centuries that biologists now suggest that a sixth mass extinction may be under way, given the estimated extinction rate, elevated to more than a 1.000 times than the rate at pre-human time (1). According to an IUCN analysis, life on earth is under serious threat and it has been shown that, out of around 45.000 species, a minimum of 16.928 are facing the risk of extinction (2). This current sixth extinction has almost nothing in common with the five massive past extinction events because of its anthropogenic nature. The main human activities which drive to species extinctions are the pollution, the landscape transformation, the overexploitation of sources and the introduction of alien species.
Our oceans, extending over three quarters of the earth surface, are increasingly bearing the brunt of direct and indirect impacts from human activities. Marine debris is a big part of the phenomenon of environmental pollution which can be directly caused in the sea (ocean-based) but can also have its source on the terrestrial ecosystem (land-based: account for up to 80 percent of the worldʼs marine pollution) and end up in the oceans (3). Most debris, especially plastic objects, cannot decompose and remains suspended in the oceans current for years.
Even if it is a common belief that the marine pollution “harms only the environment”, facing it completely isolated from the humans, and that sea could store and accumulate all the human debris, it is nowadays highly emphasized that marine pollution strongly affects the sector of economy and it can cause safety and human health problems in the long term.
Figure 1: Marine litter impacts on environment, economy and human health.
Direct environmental impacts
Marine debris is usually mistaken for food and thus it is being consumed by marine organisms with various effects. They can be consumed by a wide range of marine species, especially those that consume jellyfish or squid, which look similar when floating in the water column. Some common examples are the whales and sea turtles that often mistake plastic bags for squid or jellyfish, and the birds which often mistake plastic pellets for fish eggs. Ingestion of plastic can be deleterious for marine organisms in many different ways such as causing intestines blockage, stomach ulceration, distension of the stomach leading to a reduction in hunger, reduction of digestive capability (4).
Marine animals may be seriously harmed by marine debris when they get entangled. Prior to the 1950s, one of the main fishing equipment, the rope, was made of natural fibers (Indian hemp and cotton). These materials lose their resilience in usage and, if lost or discarded in the ocean, they tend to disintegrate quickly. These last years it has been replaced by nylon and synthetic materials that are by far more endurable and thus they create numerous problems to the marine ecosystem (5).
-natural habitat alteration
Alteration of natural habitat caused by marine litter can happen by a variety of ways as these objects are changing the composition of the marine ecosystem. Τhe litter objects can disperse toxic substances as they have usually accumulated these substances by land pollution sources. An illustrating example is the tyres which have been exploited for many marine construction applications like artificial reefs for fishery enhancement (6). However, according to several scientific investigations when considering the potential environmental impact of tyre reefs on the marine environment, the growth of organisms on the tyre surface may be revealing as they are exposed to chemical release (7).
Indirect environmental impacts
-disturbance from beach litter cleaning
Efforts which aim to remove the marine debris can also indirectly harm the ecosystems. The use of mechanical equipment (e.g. tractor) in the shoreline can end up causing adverse catastrophic impacts to the environment such as erosion and disturbances to aquatic vegetation, nesting sea turtles and birds. In addition, seabed smothering is a common impact coming from dredging activities which intent to remove the contaminated sediment (remediation dredging).
Marine litter has been found to contribute to the transfer of invasive species. There are several cases that aggressive invasive species were introduced to a region through attachment to plastic artefacts moving around the ocean. This can be particularly destructive to at-risk coastal environments.
The economic impacts of marine litter have several different fields. They can be pointed out as loss in tourism due to bad environmental conditions or due to bad reputation of one country. Another economic effect is the costly vessel repairs of damages caused by debris as well as the reduction of the fish stock when commercial fish become bycatch in lost fishing nets or other fishing gear. In addition, European legislation is particularly rigorous with environmental protection issues. Thus, the amounts of fines are not negligible and especially during these times of economic crisis.
Human health and safety impacts
Beachgoers can be injured by stepping on broken glass, cans, needles or other items. Similar to marine organisms, swimmers and divers can become entangled in abandoned fishing gear.
Humans are also affected by toxic substances and chemicals, transferred by marine litter, which come into the food chain and are being consumed through our daily food.
It is up to every one of us to deal with this issue at small or bigger scale!
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1. Wilson Edward O., Is humanity suicidal?, Biosystems, Volume 31, Issues 2–3, 1993, Pages 235-242
2. Wildlife in a Changing World – an analysis of the 2008 IUCN Red List of Threatened Species™ , 2008
3. GESAMP (Group of Experts on the Scientific Aspects of Marine Pollution), The state of the marine environment, Blackwell Scientific Publications, London, 1991, Pages 146
4. Ryan P.G., Connell A.D., Gardner B.D., Plastic ingestion and PCBs in seabirds: is there a relationship?, Marine Pollution Bulletin, Volume 19, 1988, Pages 174–176.
5. Gregory M. R., Environmental implications of plastic debris in marine settings—entanglement, ingestion, smothering, hangers-on, hitch-hiking and alien invasions, Philosophical Transactions of the Royal Society B, Volume 364, 2009, Pages 2013-2025
6. Collins, K. J., Jensen, A. C., and Albert, S., A review of waste tyre utilisation in the marine environment, Chemistry and Ecology, Volume 10, 1995, Pages 205–216
7. Risso-deFaverney C. , Guibbolini-Sabatier M.E.,Francour P., An ecotoxicological approach with transplanted mussels(Mytilus galloprovincialis)for assessing the impact of tyre reefs immersed along the NW Mediterranean Sea,Marine Environmental Research, Volume 70, 2010, Pages 87-94