A Sea of Garbage: Ocean Floor Landfills

JAMSTEC Deep sea Debris Database

Marine litter ten years after the great 2011 tsunami in Japan. Credit: JAMSTEC [De S. Chiba]

The Long Journey of Litter to the Seafloor

The Messina Strait, a submarine bridge separating the island of Sicily from the Italian Peninsula, is the area with the largest marine litter density worldwide — more than a million objects per square kilometer in some parts — as reported in a new review paper published in the journal Environmental Research Letters.

Also, over the next thirty years, the volume of rubbish in the sea could surpass three billion metric tons (Mt), as cited in the study, whose corresponding authors are the experts Miquel Canals, from the Faculty of Earth Sciences of the University of Barcelona, and Georg Hanke from the European Commission’s Joint Research Centre (JRC), where scientists carry out research in order to provide independent scientific advice and support to EU policies.

Led by the University of Barcelona, this paper gathers the results of the scientific meeting on macrolitter that took place in May 2018, promoted by the European Commission’s Joint Research Centre (JRC) and the German Alfred Wegener Institute (AWI). A team of twenty-five scientists from across the world treated issues such as data needs, methodologies, harmonization, and needs for further development.

The study provides a synthesis of current knowledge on human-sourced materials lying on the seafloor and goes through the methodologies to improve future studies, “highlighting the need to understand litter occurrence, distribution, and quantities in order to provide insight for appropriate (policy) measures,” notes Georg Hanke, who adds that “the paper also shows the need to employ new methodologies — i.e. imaging approaches — to cover areas that had not been considered previously, and provides tools to enable quantitative assessments such as those under the EU Marine Strategy Framework Directive (MSFD).”

Strait of Messina

A litter hotspot at 415 m depth in the Strait of Messina, Mediterranean Sea. Credit: M. Pierdomenico D. Casalbore and F. Chiocci/National Research Council/La Sapienza University in Rome

Among other signatories of the article are experts from the University of Açores (Portugal), Alfred Wegener Institute (Germany), Utrecht University (Netherlands), the Norwegian Institute of Marine Research (Norway), the Secretariat of the Barcelona Convention on the protection of the Mediterranean Sea, Monterey Bay Aquarium Research Institute (MBARI, California, United States), the Institute for Global Change of the Japan Agency for Marine Earth Science and Technology Research (JAMSTEC, Japan), IFREMER (France) and Oxford University (United Kingdom), among other institutions.

When litter arrives before humans do

The ocean floor is increasingly accumulating marine litter. Whereas the largest seafloor litter hotspots — likely in the deep sea — are still to be found, plastics have already been found in the deepest point on Earth, the Mariana Trench — at a depth of 10,900 meters — in the Pacific Ocean. In some cases, litter concentrations reach densities comparable to large landfills, experts warn.

Calypso Deep

A plastic bag on the bottom of Calypso Deep, at 5109 m, the deepest place in the Mediterranean Sea. Credit: Caladan Oceanic

Despite the scientific community efforts, “the extent of marine litter on our seas and oceans is not yet fully known. The marine regions most affected by this problem are in landlocked and semi-enclosed seas, coastal bottoms, marine areas under the influence of large river mouths, and places with high fishing activity, even far from land,” says Professor Miquel Canals, head of the Consolidated Research Group on Marine Geosciences at UB.

Canals highlights that “the level of waste treatment in coastal countries is decisive: the less treatment — or the more deficient — the more waste reaching the ocean, and therefore, the ocean floor, which is a problem that affects specially third world countries.”

The long journey of litter to seafloor

Plastics, fishing gears, metal, glass, ceramics, textiles and paper are the most abundant materials in seafloor litter hotspots. Geomorphological features, the submarine relief and the nature of the seafloor determine the distribution of litter items on the seabed. Ocean dynamics, — that is, processes such as dense water cascades, ocean currents and storms — ease the transport and dispersal of litter across the ocean, from coasts to abyssal plains, thousands of meters deep. However, these factors do not occur in all ocean ecosystems and also vary over time and in intensity where they take place.

Due to a gravitational effect, light waste is usually transported along and into marine regions where dense currents flow — i.e. submarine canyons and other submarine valleys — and where flow lines concentrate, such as nearby large submarine reliefs. Finally, materials transported by ocean dynamics accumulate in depressions and quiet marine areas.

The properties of materials dumped in the marine environment also affect their dispersion and accumulation on the ocean floor. It is estimated that 62% of the dirt accumulated on seabeds is made of plastics, “which is relatively light and easy to transport over long distances. On the other hand, heavy objects such as barrels, cables or nets are usually left at the point where they are initially fell or got entangled,” says Canals.

Litter drowns marine life

Litter is a new threat to marine biodiversity. It is already known that nearly 700 marine species, 17% of which are on the IUCN red list, have been affected by this problem in several ways. Seabed entangled fishing gears can cause serious ecological impacts for decades because of ghost fishing. The slow decomposition of fishing nets — usually made of high-strength polymers — aggravates the detrimental effects of this type of waste on the marine ecosystem.

Other human activities — dredging, trawling, etc. — trigger secondary dispersal by remobilization and fragmentation of seafloor litter. In addition, seabed waste concentrations can easily trap other objects, thus generating larger and larger litter accumulations. It is paradoxical that waste may increase the heterogeneity of the substrate, which can benefit some organisms. Some xenobiotic compounds — pesticides, herbicides, pharmaceuticals, heavy metals, radioactive substances, etc. — associated to litter are highly resistant to degradation and endanger marine life. However, the extent of the effects of litter on the habitats of the vast expanses of the deep ocean still is a chapter to be written by the scientific community.

“In the Mediterranean Sea,” says Miquel Canals, “seafloor marine litter already is a serious ecological problem. In some places of the Catalan coast, there are large accumulations of waste. When there are strong storms, such as Gloria, in January 2020, waves throw this waste on the beach. Some beaches in the country were literally paved with rubbish, thus showing to which extent the coastal seabed is littered. There are also noticeable concentrations of waste in some submarine canyons outside Catalonia.”

Robotic technology for large depths

Beach litter and floating garbage can be identified and monitored by simple, low-cost methods. In contrast, the study of seafloor litter is a technological challenge, the complexity of which increases with water depth and remoteness of the marine area to be investigated. The study reviews both methodologies allowing physical sampling of seafloor waste and in situ observations.

New technologies have enabled major advances in the study of the environmental status of the seabed worldwide. The use of unmanned remotely operated vehicles (ROVs) is critical for in situ observation, despite the limitations for physical sampling. Classic technologies such as bottom trawling also have limitations, as they do not allow determining the precise location of the bottom-sampled objects. “Future methodologies should aim at easing the comparison of scientific data from different places. It should also be easier for observation and sampling efforts to generate consistent data sets, something that we are still far from achieving,” says Canals.

Avoiding excess waste generation to take care of the planet

Knowledge and data about seafloor litter are necessary for the implementation of the Marine Strategy Framework Directive (MSFD) and other international policy frameworks, including global agreements. The publication shows how research on seafloor macrolitter can inform these international protection and conservation frameworks to prioritize efforts and measures against marine litter and its deleterious impacts.

The authors warn about the need to promote specific policies to minimize such a serious environmental problem. The study also addresses the debate on the removal of litter from the seabed, a management option that should be safe and efficient. In relation to this, the Joint Research Centre (JRC) is co-chairing the MSFD Technical Group on Marine Litter, which provides an information exchange and discussion platform to provide agreed guidance for MSFD implementation.

“Marine litter has reached the most remote places in the ocean, even the least (or never) frequented by our species and not yet mapped by science,” says Miquel Canals. “In order to correct something bad, we must attack its cause. And the cause of the accumulation of waste on the coasts, seas and oceans, and all over the planet, is the excess waste generation and spillage in the environment, and poor or insufficient management practices. As humans, we have little or no care at all to prevent litter from accumulating everywhere.”

Reference: “The quest for seafloor macrolitter: a critical review of background knowledge, current methods and future prospects” by Miquel Canals, Christopher K Pham, Melanie Bergmann, Lars Gutow, Georg Hanke, Erik van Sebille, Michela Angiolillo, Lene Buhl-Mortensen, Alessando Cau, Christos Ioakeimidis, Ulrike Kammann, Lonny Lundsten, George Papatheodorou, Autun Purser, Anna Sanchez-Vidal, Marcus Schulz, Matteo Vinci, Sanae Chiba, François Galgani, Daniel Langenkämper, Tiia Möller, Tim W Nattkemper, Marta Ruiz, Sanna Suikkanen, Lucy Woodall, Elias Fakiris, Maria Eugenia Molina Jack and Alessandra Giorgetti, 19 January 2021, Environmental Research Letters.
DOI: 10.1088/1748-9326/abc6d4

20 Comments on "A Sea of Garbage: Ocean Floor Landfills"

  1. stephen schaffer | February 21, 2021 at 10:00 am | Reply

    out of sight, out of mind; especially so when the human race seems to be cursed with infantile emotional brain development

  2. God help us!!! Its time for you to come back. And rid this planet of the disgusting greedy filthy uncaring stupid and worthless humans that dont care that we have destroyed this planet beyond repair. And instead of working as hard as we can to correct any of it we just continue to destroy and abuse what once was paradise..

  3. We are quick to point out the third world countries that pollute with untreated waste, but almost the entire coast of the USA dumps most if not all the street drains straight into the oceans. I live in a beach town on east coast and all of our street drains flow untreated into the Atlantic Ocean. All the plastic bottles and trash right in the water. Our sewage goes there also, but is piped further out so as not to pass off the tourist.

  4. Leslie Wimpfheimer | February 21, 2021 at 7:00 pm | Reply

    What’s the matter with KEEP AMERICA CLEAN (the whole Planet) we are so worried about climate change, Good God Mother Earth has been around for 4.8 billion years, maybe some pulsar or any thing that can shoot radition at us is doing that right now. We need of course to keep all the woundeful Science plugging away for a cleaner world, we will eventually get to the JETSON WORLD!

  5. Ever seen the movie

  6. I grew up in Fort Bragg CA and my favorite thing to do was go to the beach, not just any beach but one now famous beach called glass beach. Instead of sand the beach is covered in glass. This is because up until the 70s the garbage trucks would collect everyone’s weekly trash and once the truck was full it would head down to the beach, back up to the cliff and dump it right into the ocean. Although now a beautiful mixture of glass and large chunks of rusted metal that marine life uses as shelter I’m sure it wasn’t so pretty 40 years ago when it was the city’s garbage dump.

  7. They should make every boat capt and engineer and owner share the cost to clean it up.Marine traffic has records,so let them all that passed through share the cost.There it is,I’ll never eat anything from the Med,or for that matter, anything from the 7 seas.I was a shipboard Chief Eng.and know there’s rules against littering at sea. COME ON PEOPLE!!!

  8. The ocean is a garbage dump and has been used this way since man had rubbish to get rid of
    I take a bag of rubbish out of the the waterways I dive in
    whenever I dive in third world countries with pristine waterways I noticed a lot more plastics in the water
    I think it’s an education thing ie teaching recycling and bio degradable
    It’s a shame humans have the out of sight out of mind approach. IMO
    Cheers. Diving with AOS episodes

  9. When alien life does discover earth, lets hope they don’t classify it as a dump planet, since it is already so trashed out.

  10. That’s people. treat the. Earth. With their trash they should clean it up. That’s awful

  11. I am an avid scuba diver and ocean lover. This article literally made me feel nauseated. I did cry.

  12. You see what is under water. Why close your eyes to what is on earth to what is in Africa, in the Arab countries and beyond.
    you are the ones who are the devils on earth and among the water you are “angels”. You must first worry about the earth so that the water will be calm.May Allah help us and remind us.

  13. This is nothing compared to what USA have done.. believe me nothing

  14. You are all morons

  15. This is why I started the Vortex Man Universe to educate the children and adults of the cause and effects of our disposable society.

  16. Chris Anderson | March 25, 2021 at 8:13 pm | Reply



  17. It’s very depressing to see what we’ve done to our home our planet. Leaving this for our future is very, very irresponsible if us as humans. So we now try to locate another planet that can sustain life, only to ruin it yet again. When will we ever learn? Nothing like hoping from planet to planet to see which one we can live on and then after we use it up move on to the next planet.

  18. Melinda Bolchoz | March 26, 2021 at 10:46 am | Reply

    The government of this area should be heavily funded by the world and given an SHORT amount of time to clean this atrocities up…LIKE NOW..SHOW ME ACTION NOT DESOLATION

  19. Most dont realize that every coastal city in the USA has the city drains dumping right into the ocean. I live in a popular beach town and have always found it fascinating to see tourists allowing their children to play in the water coming out of the sewers that exit on the beaches.ill go ahead and say I live in Myrtle Beach. Our real sewer (toilet)waste dumps farther out to sea, but all the street drains flow into the ocean, trash,bottles,oil and dead animals end up in the water.

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