A sea of rubbish: Ocean floor landfills
The long journey of litter to seafloor

Date:
January 19, 2021
Source:
University of Barcelona
Summary:
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 kilometre in some parts, according to a new review paper.



FULL STORY ==========================================================================
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 kilometre 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 UB, 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, harmonisation 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)." Among other signatories
of the article are experts from the University of Ac,ores (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.



========================================================================== 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 situobservation, 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."

========================================================================== Story Source: Materials provided by University_of_Barcelona. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. 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, Francois Galgani,
Daniel Langenka"mper, Tiia Mo"ller, Tim W. Nattkemper, Marta Ruiz,
Sanna Suikkanen, Lucy Woodall, Elias Fakiris, Maria Eugenia Molina
Jack, Alessandra Giorgetti. The quest for seafloor macrolitter:
a critical review of background knowledge, current methods and
future prospects. Environmental Research Letters, 2020; DOI:
10.1088/1748-9326/abc6d4 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/01/210119114320.htm

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