The Impact of Marine Debris:


“Marine debris is defined as any persistent solid material that is manufactured or processed and directly or indirectly, intentionally or unintentionally, disposed of or abandoned into the marine environment or the Great Lakes” – National Oceanic and Atmospheric Administration (NOAA)

Pipe fish sailing in a straw in Koh Tao (Thailand)


In short, marine debris can include anything— ranging from fishing nets, lines, plastic bottles, to glass.

And it has a catastrophic effect on marine life.


But first of all, where does it come from?


The overwhelming majority of marine debris results from human activity, and nearly 80% of marine debris originates from land-based sources. There are no confirmed estimates about how much marine debris is in the ocean, but research voyages across the globe have found expansive patches of garbage accumulating in the ocean as a result of ocean currents.

One of the most prominent garbage patches found in the North Pacific Gyre, referred to as the Great Pacific Garbage Patch, has increased 5-fold in the last 10 years. It is estimated to be one to two times the size of Texas, USA.

Marine debris may enter water sources directly from a ship, or indirectly when washed out to sea via rivers, streams and storm drains. It can travel for hundreds of thousands of miles on ocean currents, posing a threat to ocean ecosystems and wildlife along the way. People may contribute to the accumulation of marine debris by:


  • The inappropriate disposal of trash from land-­based activities;
  • Release of waste from shore­based solid waste disposal and waste processing facilities;
  • Abandoning fishing gear, including line, nets, ropes, bait boxes, fish tags and trawl floats;
  • Intentional or inadvertent discharge of trash, galley waste and boating materials;
  • Inappropriate handling of undersea exploration and oil and gas extraction items.




Much of the marine debris found in oceans do not decompose in seawater and can remain in the marine environment for many, many years. Depending on the material, some products may even remain in the ocean for tens of thousands of years!

In coastal areas, especially in coral reefs, fishing gear is prone to trap and even kill marine animals, a phenomenon known as “ghost fishing. Fishing line or nets, strapping bands or even plastic, six-pack rings can greatly affect the mobility of marine animals. Once entangled within marine debris, the animals can have trouble eating, breathing or swimming, all of which can have fatal results. Many animals can choke on small, everyday items, mistaking them for food. A prime example is plastic bags; sea turtles often mistake the plastic bags for jellyfish and attempts to eat them, eventually choking and suffocating to death. Furthermore, many endangered albatross birds and chicks have been found dead with stomachs full of plastic, including bottle caps and cigarette lighters. Even if the animal does not immediately choke to death, the debris within their stomachs can give them a false feeling of being full, and so the animal may die of starvation as a result.



Furthermore, marine debris can provide a habitat for marine species, such as oysters, barnacles, or plants, to collect upon. As debris is carried away by the currents, the organisms living on the debris are carried along far distances and may potentially end up in a completely new environment. Some of these organisms can become an invasive species in the new area they are in, and thus have a negative effect on the native species.


Marine debris also leads to microplastics— an issue that is recently gaining traction across the world; they are classified as plastic particles less than five millimeters in length, and they have a huge negative impact within the marine ecosystem, and for humans. Because is is still an emerging field of study, not a lot is known about microplastics and their long-term impacts yet. However, the current findings show a growing problem.


The worst part, the microplastics:

Plastics degrade incredibly slowly, often over hundreds, and if not, thousands of years. The biggest problem is that they are ingested by many marine organisms, and therefore the plastics have a tendency to move within the food web. Contaminated plastics can break down into small pieces resembling food—such as plankton—for the animals to eat, become embedded in animals’ tissue through ingestion or respiration, and sink towards the bottom of the ocean, from where they may be ingested by bottom feeders. The plastic debris ingested by animals can absorb many toxic, hormone-disrupting chemicals like Polychlorinated biphenyls (PCBs) and Dichloro-Diphenyl-Trichloroethane (DDT) which resides in seawater. When the plastics are ingested by marine species, they are spread into the food chain and can affect many marine animals. Studies in the North Pacific Central Gyre, where the Great Pacific Garbage Patch is, found that approximately 35% of the fish had ingested plastic.


Unfortunately, corals are also affected by microplastics. Recent experimentation shows that Scleractinian corals, which are primary reef-builders, may ingest microplastics under laboratory conditions. While the effects of ingestion on these corals has not been conclusive, corals can easily become stressed and bleach; microplastics have been shown to stick to the exterior of the corals after exposure in the laboratory, which can potentially be harmful as corals cannot handle sediment or any particulate matter on their exterior. The coral, in turn, slough it off by secreting mucus, and they expend a large amount of energy in the process, increasing the chances of mortality.

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By Ning Jiang