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Plastic marine debris: Sources, distribution and impacts on coastal and ocean biodiversity

Authors:
  • Veer Wajekar A. S. C. College, Phunde (Navi Mumbai) 400 702 India

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Marine debris is a globally recognized environmental issue of increasing concern. Marine ecosystems worldwide are affected by human-made refuse, much of which is plastic. Marine debris includes consumer items such as glass or plastic bottles, cans, bags, balloons, rubber, metal, fiberglass, cigarettes, and other manufactured materials that end up in the ocean and along the coast. It also includes fishing gear such as line, ropes, hooks, buoys and other materials lost on or near land, or intentionally or unintentionally discarded at sea. Debris in oceans and seas is an aesthetic problem, it incurs considerable costs and can have severe impacts on marine organisms and habitats. This review focuses on plastic marine debris with respect to: (1) definition and types; (2) sources and distribution; (3) environmental impacts on coastal and ocean biodiversity; and (4) effective solutions to tackle the plastic marine debris.
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PENCIL Publication of Biological Sciences Vol. 3(1):40-54
ISSN: 2408-5561
Available at:
www.pencilacademicpress.org/ppbs
(c)2016 PENCIL Academic Press
OCEANOGRAPHY
Review
Plastic marine debris: Sources, distribution and impacts
on coastal and ocean biodiversity
Prabhakar R. Pawar*, Sanket S. Shirgaonkar and Rahul B. Patil
Authors' Affiliations
Veer Wajekar Arts, Science and
Commerce College, Mahalan Vibhag,
Phunde, Tal. -Uran, Dist. - Raigad, Navi
Mumbai - 400 702, Maharashtra, India.
*Corresponding author.
E-mail: prpawar1962@gmail.com
Accepted: 18th January, 2016.
Published: 27th January, 2016.
ABSTRACT
Marine debris is a globally recognized environmental issue of
increasing concern. Marine ecosystems worldwide are affected by
human-made refuse, much of which is plastic. Marine debris
includes consumer items such as glass or plastic bottles, cans, bags,
balloons, rubber, metal, fiberglass, cigarettes, and other
manufactured materials that end up in the ocean and along the
coast. It also includes fishing gear such as line, ropes, hooks, buoys
and other materials lost on or near land, or intentionally or
unintentionally discarded at sea. Debris in oceans and seas is an
aesthetic problem, it incurs considerable costs and can have severe
impacts on marine organisms and habitats. This review focuses on
plastic marine debris with respect to: (1) definition and types; (2)
sources and distribution; (3) environmental impacts on coastal and
ocean biodiversity; and (4) effective solutions to tackle the plastic
marine debris.
Key words: Plastic marine debris, entanglement, ingestion, marine environment, pollution.
INTRODUCTION
The National Oceanic and Atmospheric Administration
(NOAA) defines marine debris 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…
(http://marinedebris.noaa.gov/) (Brander et al., 2011).
While this definition encompasses a very wide range of
materials, most items fall into a relatively small number
of material types such as plastic/polystyrene pieces,
rope/cord/nets, cotton swabs, and light weight food
packaging (GEF, 2012b).
Marine debris is a problem along shorelines, and in
coastal waters, estuaries, and oceans throughout the
world. It is any man-made, solid material that gain
entrance into waterways either directly or indirectly. In
India, it gained entrance into oceans and coasts through
a number of land- and ocean-based sources. Yearly, more
people move near the coastal area of the country, and
the production of trash and the potential for marine
debris continues to increase. It is necessary to better
control the disposal of trash and other wastes, or
continue to find marine debris in our rivers, streams, and
oceans (Factsheet: Marine Debris, 2012).
The geographies of countries play an important part in
their contribution to marine debris. Among the top 20
ocean polluters are Sri Lanka, Philippines, Indonesia and
countries with long coastlines, such as China and
Vietnam (Jambeck, 2015).
Marine litter is found in all oceans of the world, from
the poles to the equator, and from continental coastlines
to small remote islands. It occurs not only close to
densely populated coasts, but also in remote places far
away from any obvious sources. It consists of slow
degrading materials and however, the continuous input
41. PENCIL Pub. Biol. Sci.
of large quantities of such items from many land- and
sea-based sources results in a gradual build-up in the
marine and coastal environment, which spoils beaches,
floats on the surface, drifts in the water column, and is
even found on the deep seabed. Over the past five or six
decades, contamination and pollution of the world’s
enclosed seas, coastal waters and the wider open oceans
by plastics and other synthetic, non-biodegradable
materials has been an ever-increasing phenomenon. The
environmental and other problems that may arise from
the indiscriminate disposal of marine debris into global
oceans and seas are chronic in nature rather than acute,
and are long-recognized international problems
(Thompson et al., 2009; Gregory, 2009).
Plastic and synthetic materials are the most common
types of marine debris and are the major cause of
problems for marine animals and birds. At least 267
different species are known to have suffered from the
entanglement or ingestion of marine debris, including
seabirds, turtles, seals, sea lions, whales and fish
(Sheavly, 2005).
Debris sizes can broadly be divided into the following
generally accepted categories: macro-debris (>20 mm
diameter), meso-debris (520 mm) and micro-debris (<5
mm). The term mega-debris (>100 mm) is also used and
can be applied to large debris items such as derelict
fishing nets (Barnes et al., 2009).
TYPES OF MARINE DEBRIS
Marine debris may consist of plastic, glass, metals,
styrofoam, rubber, derelict fishing gear and derelict
vessels. Plastics are the predominant type of marine
debris in the Pacific Gyre; it represents between 60 and
80% of the total marine debris in the world’s oceans
(Gregory and Ryan, 1997; EPA, 2011a). It also consists of
rope and netting, fragments, packaging, other fishing
debris, microplastics, paper, glass and metal (GEF, 2012).
High quantities of marine debris may be found on the
shoreline close to urban areas. UNEP/IOC has included
the following items in the list of marine debris:
-Plastic (moulded, soft, foam, nets, ropes, buoys,
monofilament line)
-Fisheries related equipment,
-Smoking related items such as cigarette butts or
lighters,
-Metal (drink cans, bottle caps, pull tabs),
-Glass (buoys, light globes, fluorescent globes, bottles)
-Processed timber (including particle board),
-Paper rubber and cloth.
The highest percentage of item of marine debris consists
Pawar et al. (2016)
of cap, spoon, small sachets, syringe, paste tube, straw,
pen assorted, plastic bits, bead, hair clips and the plastic
and nylon ropes followed by thermocol and sponge
(Sulochanan et al., 2013).
SOURCES OF MARINE DEBRIS
The United Nations Joint Group of Experts on the
Scientific Aspects of Marine Pollution (GESAMP)
estimated that land-based sources are responsible for up
to 80% of marine debris and the remainder was due to
sea-based activities (Sheavly, 2005). The main land and
sea-based sources of marine debris are thus listed and
explained
Land-based sources
Marine debris from land-based sources is blown into the
sea, washes into the sea or is discharged into the sea
(Sheavly, 2005). Land-based sources include the
following:
-Storm water discharges: Storm drains collect runoff
water generated during heavy rain events. The drains
directly discharge this wastewater into nearby streams,
rivers or the ocean. Rubbish from streets can be washed
into storm drains and is then discharged straight into the
ocean or to streams/rivers which, in turn, may carry the
rubbish to the ocean.
-Combined sewer overflows: Combined sewers carry
sewage, as well as storm water. During heavy rains, the
handling capacity of the wastewater treatment system
may be exceeded and the sewage plus storm water is
directly discharged into nearby rivers or oceans. This
waste can include rubbish such as condoms, tampon
applicators, syringes and street litter (Sheavly, 2005).
-Littering: Beachgoers may carelessly leave litter at the
coast and this will become marine debris, thus the debris
includes food packaging and beverage containers,
cigarette butts and plastic beach toys. Fishermen may
leave behind fishing gear. Litter from inland areas can
become marine debris if it gets into streams or rivers. In
this way marine debris may result from rubbish left by
workers in forestry, agriculture, construction and mining
operations. (Sheavly, 2005).
-Solid waste disposal and landfills: Run-off from
landfills located in coastal areas or near to rivers may
find its way into the marine environment. In addition to
loss from landfills, garbage may be lost to the marine
42. PENCIL Pub. Biol. Sci.
environment during its collection or transportation.
Illegal dumping of domestic or industrial wastes into
coastal and marine waters is another source of marine
debris (Sheavly, 2005).
-Industrial activities: Industrial products may become
marine debris if they are improperly disposed of on land
or if they are lost during transport or loading/unloading
at port facilities (US EPA, 2002). Small plastic resin
pellets, about 2-6 mm in diameter, are the raw material
for the manufacture of plastic products (Derraik, 2002).
These pellets have been released into the marine
environment from accidental spillage during production
and processing, transport and handling. Plastic pellets
have become ubiquitous in ocean waters, sediments and
on beaches and are ingested by marine wildlife (Redford
et al., 1997).
Ocean-based sources
All types of boats, ships and offshore industrial platforms
are potential sources of marine debris. The debris may
originate from accidental loss, indiscriminate littering or
illegal disposal. It may also due to the waste
management disposal practices carried out in the past
(Sheavly, 2005). Ocean-based sources of marine debris
include:
-Commercial fishing: Commercial fishermen generate
marine debris when they fail to retrieve fishing gear or
when they discard fishing gear or other rubbish
overboard. Debris resulting from commercial fishing
includes nets, lines and ropes, strapping bands, bait
boxes, bags, gillnet or trawl floats plus galley wastes and
household trash (Sheavly, 2007, Morishige e al., 2007;
Pichel et al., 2007).
-Recreational boaters: Boaters may deposit garbage
overboard such as bags, food packaging and fishing gear
(Sheavly, 2005).
-Merchant, military and research vessels: Rubbish
from vessels may be accidentally released or blown into
the water or may be deliberately thrown overboard.
Large vessels with many crew members, generate solid
wastes daily which may end up as marine debris if it is
not secured and stored properly (US EPA, 1992a;
Sheavly, 2005).
-Offshore oil and gas platforms and exploration:
Activities on oil and gas platforms may generate items,
which are deliberately or accidentally released into the
Pawar et al. (2016)
marine environment including hard hats, gloves, 55-
gallon storage drums, survey materials and personal
waste. Undersea exploration and resource extraction
also contribute to marine debris (US EPA, 1992a;
Sheavly, 2005).
PLASTIC MARINE DEBRIS
Introduction and definition
Plastic is a synthetic material that is made by
polymerizing molecules of monomer, materials that are
derived from coal, petroleum or natural gas (Selukar et
al., 2014). At present, plastic has achieved a pivotal
status, with extensive commercial, industrial, medicinal
and municipal applications. Demand is considerable;
annual plastic production has increased dramatically
from 1.5 million tonnes in the 1950s to approximately
280 million tonnes in 2011 (Plastics Europe, 2012).
Plastic has become the most common form of marine
debris since it entered the consumer arena less than 60
years ago, and presents a major and growing global
pollution problem (Andrady, 2011). The current global
annual production, estimated at 245 million tonnes
represents 35 kg of plastic produced annually for each of
the 7 billion humans on the planet, approximating the
total human biomass (Zettler et al., 2013).
Plastic debris at the micro and potentially at the nano-
scale, are widespread in the environment. Microplastics
have accumulated in oceans and sediments worldwide in
recent years, with maximum concentrations reaching
100 000 particles m3. Due to their small size,
microplastics may be ingested by low trophic fauna, with
uncertain consequences for the health of the organism
(Wright et al., 2013). Sediment from densely populated
coastal areas can be heavily contaminated with
microplastics. Industrial coastal areas have also been
identified as microplastic hotspots; concentrations of
approximately 100 000 plastic particles m3 of seawater
have been reported in a Swedish harbour area adjacent
to a PE production plant (Noren and Naustvoll, 2010).
Worldwide, about 280 million t of plastic are produced
annually for the manufacturing of products such as
storage containers, packaging material, or even
automobiles. Plastic has become an optimal medium
used in vast amounts of consumer products because it is
lightweight, durable, inexpensive, and a good insulator
(Shaw and Sahni, 2014).
It is difficult to eliminate plastic waste due to the fact
that it does not biodegrade in nature, but only photo
degrades into smaller pieces. The percentage of plastics
that make up the total municipal solid waste has
43. PENCIL Pub. Biol. Sci.
increased by 12% over the last four decades (EPA,
2014). Almost one third of the plastic produced is used
to manufacture single-use plastics (DiGregorio, 2012)
such as coffee cup lids, stirrers, or straws.
Plastics are synthetic organic polymers, although they
have only existed for just over a century (Gorman, 1993).
The versatility of these materials has lead to a great
increase in their use over the past three decades, and
they have rapidly moved into all aspects of everyday life
(Hansen, 1990). Plastics are lightweight, strong, durable
and cheap, characteristics that make them suitable for
the manufacture of a very wide range of products. These
same properties happen to be the reasons why plastics
are a serious hazard to the environment (Laist, 1987).
Plastics do not disappear and will remain in our
environments indefinitely affecting wildlife, until the
pollution is reduced (Sigler, 2014).
Plastic marine debris has become a pervasive pollution
problem affecting all the world’s oceans, and it is the
direct cause of injuries and death to marine animals and
birds, either because they become entangled in it or
mistake plastic for food (Allsopp et al., 2006). Fauna in
case study beaches are affected by marine debris,
especially microplastics (Vlieststra and Parga, 2002;
Endo et al., 2005).
The environmental and other problems that arise from
the indiscriminate disposal of plastics and other
persistent synthetic materials (marine debris) into the
global oceans and seas are chronic in nature rather than
acute, and are long-recognized international problems
(Thompson et al., 2009). It has recently been estimated
that the 1982 report of 8 million marine debris items
entering the world’s oceans and seas each day now
needs to be updated by being multiplied several fold
(Barnes, 2005).
Types of plastic marine debris
Plastics are synthetic organic polymers, and though they
have only existed for just over a century (Derraik, 2002).
Since plastics are buoyant, an increasing load of plastic
debris is being dispersed over long distances, and when
they finally settle in sediments, they may persist for
centuries (Goldberg, 1997). Some common types of
plastic wastes are shown in Table 1.
Sources and distribution of plastic marine debris
The ever-growing problem of marine debris begins on
land, where streams and rivers carry debris to the coast.
Ocean currents then transport the debris to remote
Pawar et al. (2016)
areas, where it may take centuries to break down
(Goldberg, 1997). The Eastern Pacific Garbage Patch
(EPGP), an area between California and Hawaii, contains
a large quantity of small “microplastic” pieces derived
from the breakdown of larger plastic items (Marks and
Howden, 2008).
The sources of marine debris are both land- and
marine-based, their origins may be local or distant, and
the environmental consequences are many and varied
(Gregory, 2009). Some fraction of the increasing amount
of postconsumer plastic trash inevitably escapes the
recycling and waste streams and makes its way to the
global oceans (Zettler et al., 2013). Additionally,
tsunamis and storms can result in large pulses of plastic
entering the ocean from coastal areas. Plastic
accumulates not only on beaches worldwide, but also in
“remote” open ocean ecosystems (Andrady, 2011).
Through accidental release and indiscriminate discards,
plastic waste has accumulated in the environment at an
uncontrollable rate, where it is subjected to wind and
river-driven transport, ultimately reaching the coast
(Wright et al., 2013).
Annually, more than 35 million plastic bottles and 500
billion plastic bags are used by consumers, many of
which end up in oceans and along beaches (What a
Waste, 2010). The accumulation of plastics in the
environments is a result of improper disposal or
shipping spills. Since they are lightweight and durable,
plastics are capable of travelling long distances; ending
up in terrestrial environments, along shorelines, or
floating in the open ocean (Zbyszewski and Corcoran,
2011).
Plastic materials also end up in the marine
environment when accidentally lost, carelessly handled
or left behind by beachgoers. They also reach the sea as
litter carried by rivers and municipal drainage systems.
There are major inputs of plastic litter from land-based
sources in densely populated or industrialized areas,
most in the form of packaging (Gregory, 1999).
Drifter buoys and physical oceanographic models have
shown that surface particles such as PMD can passively
migrate from Eastern Seaboard locations all the way to
the interior of the North Atlantic Subtropical Gyre in less
than 60 days, illustrating how quickly human-generated
debris can impact the gyre interior that is more than
1000 km from land (Zettler et al., 2013).
-Lost and discarded nets and lines from fishing vessels
are important contributors to marine debris, especially
in heavily fished areas. These vessels also lose plastic
floats, traps, pots, and other gear (UNEP and NOAA).
-Other sea-based sources of plastic pollution include oil
and gas platforms, aqua culture facilities, and cargo ships
44. PENCIL Pub. Biol. Sci. Pawar et al. (2016)
Table 1. Some common types of plastic wastes.
Acronym
Full Name
Common Examples
PETE/PET
Polyethylene terephthalate
Soda bottles, Films,
HDPE
High density polyethylene
Milk jugs, Packaging,
Shampoo bottles, Yogurt containers,
Detergent bottles, Shopping Bags
PVC
Polyvinyl chloride
Clear food packaging,
Candy wrappers, Some bottles,
Water pipes, Curtains, Credit card, Packaging
films, Water films
LDPE
Low density polyethylene
Plastic bags, Wire cloth,
Squeezable bottles, Shopping bags,
PP
Polypropylene
Caps, straws, Some bottles,
Plastic bag and toy, Drinking straws,
PS
Polystyrene
Takeout food containers,
Disposable cups & plates,
Fast food boxes, CD cases,
PC
PA
Other
Polycarbonate
Polyamide/Nylon
Acrylonitrile butadiene styrene
Water jugs, DVDs, Sunglasses,
Toothbrushes
that lose containers to the sea.
-Plastic debris from land comes primarily from two
sources: first, ordinary litter; and, second, material
disposed in open dumps or landfills that blows or
washes away, entering the ocean from inland
waterways, wastewater outflows, and the wind (Ambeck
et al., 2015; Lechner et al., 2014).
Environmental impacts of plastic marine debris
Countless marine animals have been killed or harmed by
marine debris primarily because they either become
entangled in it, or mistake plastic debris for food and
ingest it. Marine debris emanates from both land and
sea-based sources and can travel immense distances. It
can pose a navigation hazard, smother coral reefs,
transport invasive species and negatively affect tourism.
It also injures and kills wildlife, has the potential to
transport chemical contaminants, and may pose a threat
to human health.
Marine litter is a complex and multi-dimensional
problem, with significant implications for the marine and
coastal environment and human activities all around the
world. Plastic poses a major threat to marine mammals,
birds, turtles and fish due to entanglement and ingestion.
Plastics and polystyrene account for approximately 75
per cent of marine litter. Another emerging threat is the
ingestion by marine organisms of microscopic plastic
particles accumulating in the pelagic zone and
sedimentary habitats at concentrations of 150-2,400
particles per m3. Marine litter causes further ecological
damage by dispersing invasive alien species, which
‘hitch-hike’ on floating debris. The benthos is likely to be
a sink for high density microplastics. Benthic
suspension- and deposit- feeders are therefore likely to
ingest sinking and sedimentary microplastics. Fibres are
the most commonly encountered form of microplastics
in the marine environment. Benthic holothurians were
found to selectively ingest microplastics, showing a
preference for fibrous shapes. Microplastics may not
only affect species at the organism-level; they also have
the capacity to modify population structure (Wright et
al., 2013).
Not only the aesthetically distasteful plastic litter, but
also less conspicuous small plastic pellets and granules
45. PENCIL Pub. Biol. Sci.
are a threat to marine biota. The latter are found in large
quantities on beaches (Redford et al., 1997), and are the
raw material for the manufacture of plastic products that
end up in the marine environment through accidental
spillage during transport and handling, not as litter or
waste, but as other forms of plastics. Their sizes usually
vary from 26 mm, though occasionally much larger
ones can be found. Durability of Plastic pellets in the
marine environment is still uncertain but they seem to
last from 3 to 10 years, and additives can probably
extend this period to 3050 years (Gregory, 1978).
Countless marine animals have been killed or harmed
by marine debris primarily because they either become
entangled in it, or, they mistake plastic debris for food
and ingest it (Gregory, 2009). Entanglement and
ingestion of seabirds, marine mammals and fish may
lead to death from starvation and debilitation, with a
reduced quality of life and lowered reproductive
performance (Laist, 1987). Other impacts to receive
limited attention are of no less importance, e.g. damage
to subsistence fisheries; hazards to recreational boating
and larger commercial vessels; impact of plastic sheeting
that blankets the biota of soft sediment, reef and rocky
substrata, as well as anoxia and hypoxia induced by
inhibition of gas exchange between pore waters and
overlying sea water (Gregory and Andrady, 2003).
Marine debris travels throughout the world’s oceans,
accumulating on beaches and within gyres, and this
debris can degrade physical habitats, transport chemical
pollutants, threaten marine life, and interfere with
human uses of marine and coastal environments. Plastic
marine debris is considered to have the greatest
potential to alter the environment and impact biota and
humans, since it floats at the surface, is widely
transported by ocean currents, persists in the
environment for years, and is not readily digestible
when consumed. Therefore, the impact of plastic marine
debris is much more than a mere aesthetic problem
(EPA, 2011b).
Physical habitat impacts of plastic marine debris
Physical habitat alteration is caused by the following:
1. Accumulation of debris: As debris accumulates in
oceanic convergence zones, on beaches, and submerged
benthic habitats, habitat structure may be modified, light
levels may be reduced in underlying waters, and oxygen
levels may be depleted. These changes can undermine
the ability of open water and benthic habitats to support
marine life (EPA, 2011b).
2. Habitat degradation: Degradation of habitat occurs
Pawar et al. (2016)
due to smothering, abrasion, and fragmentation of
sensitive habitats and habitat forming species, such as
macro algal beds and coral reefs (Asoh et al., 2004).
3. Damage and degradation of coral reef and soft
sediment: Derelict fishing gear, including nets and lines,
can settle on coral reefs as currents and waves transport
them to shallow habitats. It can entangle branching
species of corals resulting in fragmentation and
abrasion, potentially reducing habitat heterogeneity and
providing open substrate for macroalgal colonization
(Chiappone et al., 2005).
4. Smothering: Plastic marine debris can smother the
benthos, reducing light penetration and oxygen
exchange (Uneputty and Evans, 1997).
5. Decline in species: Decline of benthic habitat-
forming species and modification of the physical
structure of the habitats, indirect impacts of marine
debris may cause declines in species that are dependent
on the habitats for foraging and shelter (EPA, 2011a).
6. Alien species invasions: Marine litter items can
assist in alien species invasions as they drift on litter
across great distances (Factsheet 1, 2013). The
introduction of alien species can have major
consequences for marine ecosystems (Grassle et al.,
1991). This biotic mixing is becoming a widespread
problem due to human activities, and it is a potential
threat to native marine biodiversity (McKinney, 1998).
Drift plastics can increase the range of certain marine
organisms or introduce species into an environment
where they were previously absent (Winston, 1982). The
arrival of unwanted and aggressive alien taxa could be
detrimental to littoral, intertidal and shoreline
ecosystems (Gregory, 1999).
Rapid and heavy fouling of floating plastic (and other
objects) may increase the density of plastic object
causing them to sink to the sea floor (Ye and Andrady,
1991). Blanketing effects of plastic sheeting on the sea
floor could lead to anoxia and hypoxia induced by the
inhibition of gas exchange between pore water and sea
water (Goldberg, 1997).
Chemical impacts of plastic marine debris
-Accumulation and transport of persistent organic
pollutants (POPs): Accumulation and transport of POPs,
such as polychlorinated biphenyls (PCBs) and pesticides,
have been found at concentrations that are in orders of
magnitude greater than the surrounding environment
(Rios et al., 2007). Teuten et al. (2009) reported that the
46. PENCIL Pub. Biol. Sci.
highest PCB concentrations in plastics occurred in areas
with the highest production and use patterns, as well as
concentrations in the environment.
Plastic debris accumulates pollutants such as PCBs
(polychlorinated biphenyls) up to 100,000 to 1,000,000
times the levels found in seawater (NOAA, 2010). It is
apparent that plastics have the potential to adsorb
chemicals of concern from the environment, and serve as
a potential global transport mechanism for contaminants
of concern (EPA, 2011b).
-Leaching of constituent contaminants from plastics:
Contaminants can be released from plastics to the
environment and biota by the breakdown of plastics
through ultraviolet (UV) radiation, mechanical forces,
and weathering, as well as by ingestion by biota (EPA,
2011b). For example, the accumulation of POPs from
plastics has been documented in seabirds (Ryan et al.,
1988), and benthic organisms (Teuten et al., 2009).
Two broad classes of plastic-related chemicals are of
critical concern for human health, that is, Biphenyl-A
(BPA) and additives used in the synthesis of plastics,
which are known as phthalates.:
A. BPA: It is a common synthetic chemical found in
plastics, foods can linings, beverage can linings, and
other consumer products, which interferes with human
hormones (Sarkar et al., 2012).
B. Phthalates: They are chemicals used to soften
plastics, to carry fragrance and scent, and are used in
other everyday products. They linked to birth defects
and are harmful to reproductive system (Selukar et al.,
2014).
These aforementioned chemicals have a detrimental
effect on marine organisms even at very low levels and
plastic pellets could be a route for PCBs into marine food
chains. PCBs lead to reproductive disorders or death;
they increase risk of diseases and alter the hormone
levels (Ryan et al., 1988; Lee et al., 2001). The toxic
chemicals added to make plastics more flexible, known
as plasticizers, can leach out into the environment and in
turn into organisms that ingest plastic (Rahman ant
Brazel, 2004). Other dangerous chemicals can
concentrate on plastic surfaces (Mato et al., 2001),
increasing the toxicity of plastics.
The toxic compounds in or associated with plastics,
their uses and effects are shown in Table 2 (Brander et
al., 2011).
Biological impacts of plastic marine debris
Plastic marine debris has deleterious effects on marine
Pawar et al. (2016)
biota (Derraik, 2002). It has been estimated that plastic
marine debris adversely affects 267 species globally,
including 86% of sea turtles, 44% of seabirds, and 43%
of marine mammals (Laist, 1997). The most common
threats to biota include ingestion and entanglement
(Laist, 1997; Quayle 1992).
Microplastics resemble phytoplanktons, which are
eaten by fish and cetaceans (Boerger et al., 2010).
Ingested plastic debris has been found to reduce
stomach capacity, hinder growth, cause internal injuries,
and create intestinal blockage (Plot and Georges, 2010).
Plastic entanglement with fishing nets or other ring
shaped materials can result in strangulation, reduction
of feeding efficiency, and in some cases drowning (Allen
et al., 2012). Globally, at least 23% of marine mammal
species, 36 % of seabird species, and 86 % of sea turtle
species are known to be affected by plastic debris
(Stamper et al., 2009).
The consumption of plastic by marine organisms adds
persistent, bioaccumulative, and toxic substances to the
aquatic food chain (Pascall et al., 2005). The
entanglement in and ingestion of macroplastic items is
widely recognised in vertebrates. Over 250 marine
species are believed to be impacted by plastic ingestion
(Laist, 1997). Over 80% of reported incidents between
organisms and marine debris were associated with
plastic whilst 11% of all reported encounters are with
microplastics (GEF, 2012a).
Microplastics can be ingested by low trophic
suspension, filter and deposit feeders, detritivores and
planktivores (Murray and Cowie, 2011). Toxicity could
also arise from leaching constituent contaminants such
as monomers and plastic additives, capable of causing
carcinogenesis and endocrine disruption (Talsness et al.,
2009). A major concern about the toxic compounds
associated with plastics is that they can disrupt hormone
regulation in the cells of organisms (Oberdörster &
Cheek, 2001). Hormone disruption occurs when a
chemical acts as a natural hormone in a cell; it can
change reproductive ability and mating behaviour,
contribute to tumour development, and negatively affect
offspring (Wuttke et al., 2010).
Ingestion:
The threats to marine life are primarily mechanical due
to ingestion of plastic debris (Quayle, 1992). The
potential for plastic ingestion is largely associated with
foraging strategies and prey types (EPA, 2011b).
Marine turtles: Globally, approximately one third of
marine turtles have likely ingested debris. Most items
eaten by turtles are plastic and positively buoyant.
47. PENCIL Pub. Biol. Sci. Pawar et al. (2016)
Table 2. Toxic compounds in or associated with plastics: their uses and effects.
Toxic compound
Use
Effects
Plastic Types
Bisphenol A (BPA)
Plasticizer, can liner
Mimics estrogen
PVC, PC
Phthalates
Plasticizer, artificial
Fragrances
Interferes with testosterone,
sperm motility
PS, PVC
Persistent organic
pollutants (POPs)
Pesticides, flame
retardants, etc.
Possible neurological
and reproductive damage
All plastics
Dioxins
Produced in manufacture of PVC,
during waste incineration
Carcinogen, interferes
with testosterone
All plastics
Nonylphenol
Antistatic, antifog,
Surfactant (in detergents)
Mimics estrogen
PVC
Polyaromatic
Hydrocarbons (PAHs)
Produced when fossil fuels are
burned
Developmental and
reproductive toxicity
All plastics
Polychlorinated
biphenyls (PCBs)
Electronics manufacture
Interferes with thyroid
function
All plastics
Styrene monomer
Structure of polystyrene
Forms DNA adducts
PS
Smaller oceanic turtles are more likely to ingest debris
than coastal foragers; herbivores are more likely to
ingest debris than carnivorous species; oceanic
leatherback turtles and green turtles are at the greatest
risk of ingested marine debris effects. Sea turtles readily
consume plastic bags and other floating debris that
appear similar to their gelatinous prey (Bugoni et al.,
2001; Tomas et al., 2002).
Debris including fishing line, ropes, nets, six pack rings,
Styrofoam, and plastic bags have been extracted from
turtle digestive tracts. Plastic bags floating in the water
strongly resemble the shape of jellyfish, a primary food
source for sea turtles, thus resulting in the ingestion of
the bags (Mascarenhas et al., 2004). For the past 40
years, of the 371 autopsies conducted on leatherback
turtles, it was shown that 37.2% of the turtle had plastic
in their gastrointestinal tracts (Mrosovsky et al., 2009).
Plastic has also been found to block the passage of
female eggs and cause internal damage (Plot and
Georges, 2010).
Green turtles (Chelonia mydas) and loggerheads
(Caretta caretta) have been found in similar
predicaments and of the acquired 52 loggerheads
through by-catch in the Atlantic Ocean, 35% were found
to have plastics in their digestive tracts (Parker et al.,
2005). Ingestion of plastics is of great concern because it
can impact on turtle populations and the green turtle,
leatherback turtle, hawksbill turtle, Kemp’s ridley and
olive ridley are listed as endangered species whilst the
loggerhead turtle is listed as threatened (NOAA, 2005).
According to research, high numbers of sea turtles ingest
marine debris and plastic is the most common sort of
debris ingested (Tomás et al., 2002).
The problems associated with ingestion of plastics and
microplastics in marine turtles are:
-Suppurating skin lesions and ulcerating sores;
-Reduction in quality of life and reproductive capacity;
-Drowning and limited predator avoidance;
-Development of internal and external wounds.
-Impairment of feeding capacity due to the buildup of the
digestive system.
-Decreased mobility and predatory avoidance, and
toxicity.
-Gastrointestinal blockages by plastics (Derraik, 2002).
-Block the passage of female eggs and cause internal
damage (Plot and Georges, 2010).
-Starvation due to accrue of plastics in the stomach
cavities.
-Satiation, starvation and general debilitation often
leading to death.
-Plastic resin pellets may adsorb and concentrate
potentially damaging water quality.
-Blockage of enzyme production;
-Diminished feeding stimulus; nutrient dilution;
-Reduced growth rates;
48. PENCIL Pub. Biol. Sci.
-Lowered steroid hormone levels;
-Delayed ovulation and reproductive failure and
absorption of toxins.
-To clog and block the feeding appendages of marine
invertebrates or even to become embedded in tissues.
Pelagic seabirds: The amount of plastic ingested by
different species of birds may be an indicator of the
accumulation of plastics in an area (Sigler, 2014).
Around the world, nearly half of all seabird species are
likely to ingest debris. Birds eat everything from
balloons to glow sticks, industrial plastic pellets, hard
bits of plastic, foam, metal hooks and fishing line. Small
plastics such as bottle caps are often mistaken by
seabirds for food. It was found that diving birds that fed
on fish in the water column had less plastic in their
stomachs as compared with those of surface eaters
(Provencher et al., 2010).
Birds such as the albatross and shearwater had more
plastic in the first region of their stomachs and gizzards
(Moser and Lee, 1992). Juvenile albatross and
shearwaters were found to ingest more plastics than
adults (Avery-Gomm et al., 2013). Blight and Burger
(1997) reported in the eastern North Pacific that, of the
353 ingested items recovered from 11 species of
seabirds, 29.2% were industrial pellets and 70.5% were
broken pieces of everyday use plastics.
Among sea birds, the ingestion of plastics is directly
correlated to foraging strategies and technique, and diet.
Some seabirds select specific plastic shapes and colors,
mistaking them for potential prey items (Moser and Lee,
1992). Seabirds with large plastic loads have reduced
food consumption, which limits their ability to lay down
fat deposits, thus reducing fitness (Ryan et al., 1988).
Plastic materials of varying kinds had spread to all
oceans and adjacent seas and wide concern was being
expressed over the amounts of cylindrical, virgin plastic
pellets together with fragmented plastic particles of
varying size and shape that were being ingested by
pelagic seabirds (Shomura and Yoshida, 1985).
The problems associated with ingestion of plastics and
microplastics in pelagic seabirds are:
-Reduced body weight (Spear et al., 1995),
-Inhibit fat deposition (Connors and Smith, 1982),
-Reduce reproductive capacity (Azzarello and Van Vleet,
1987).
-Swallowed plastic can obstruct and damage a bird’s
digestive system, reducing its foraging capabilities.
-Reduced food consumption, thus reducing fitness (Ryan
et al., 1988).
Cetaceans: Predatory organisms, such as fur seals, may
indirectly consume plastics through consumption of
Pawar et al. (2016)
pelagic fish and other prey (Eriksson and Burton, 2003).
Microplastics resemble phytoplanktons, which are eaten
by fish and cetaceans (Boerger et al., 2010).
Most cetaceans live far from the shoreline, which limits
the amount of research on the ingestion of marine debris
(Sigler, 2014). If plastic causes unnatural death,
cetaceans will most likely sink to the bottom of the
ocean. At least 26 species of cetaceans have been
documented to ingest plastic debris (Baird and Hooker,
2000). Ingestion is most likely because the debris was
mixed with the desired food. Jacobsen et al. (2010)
reported that two sperm whales (Physeter
macrocephalus) were found off the coast of northern
California in 2008 with a large amount of fishing gear in
their gastrointestinal tracts.
Currently, there have not been enough trends found in
collected data that prove ingested plastics are the
primary cause of death contributing to the decline of
cetaceans (Baulch and Perry, 2014). Plastic marine
debris can cause direct mortality of cetaceans or even
create debilitating scenarios that make the mammals
more prone to predation or disease (Sigler, 2014). Baird
and Hooker (2000) cited other cetaceans that have been
reported with ingested plastics, such as the killer whale
(Orcinus orca). The deaths of whales, manatees, and
dolphins have been attributed to gastrointestinal
blockages by plastics (Derraik, 2002).
Fish: Ingestion of plastic debris by fishes has been
widely documented and incidences of ingestion have
been reported for fishes by Carpenter et al. (1972).
There is plenty of evidence supporting that fish are
consuming plastics (Sigler, 2014). Of the 7 species
studied in the North Sea, only 2.6% of the 1203 collected
fish contained plastic pieces in the digestive tracts
(Foekema et al., 2013). When the gastrointestinal tracts
of 504 fish were studied in the English Channel, 36.5 %
contained plastics (Lusher et al., 2013). The inconsistent
results found among studies could possibly indicate
important variables such as location, accumulation of
plastics, and fish species (Sigler, 2014).
Most of the plastic pieces ingested by fishes were blue,
white or clear, which are of the same colors as plankton,
the primary food source of fish (Boerger et al., 2010).
Davison and Asch (2011) speculate that plastic between
12,000 and 24,000 t are consumed by fish each year.
Small fragments of plastic may facilitate the transport of
absorbed pollutants to predators within the food chain
(Dau, 2012).
Entanglement:
Over 250 species of marine animals impacted by
entanglement includes turtles; penguins; albatrosses,
49. PENCIL Pub. Biol. Sci.
petrels and shearwaters; shorebirds, skuas, gulls and
auks; coastal birds other than seabirds; baleen whales,
toothed whales and dolphins; earless or true seals, sea
lions and fur seals; manatees and dugong; sea otters; fish
and crustaceans (Laist, 1997; Gregory, 2009).
One of the greatest threats of entanglement to marine
life and seabirds is derelict fishing gear, including
monofilament line; trawl nets, and gill nets. Lost and free
floating fishing gear can continue to ―ghost fish for
months and even years, ensnaring a wide range of
species, particularly in areas adjacent to fishing grounds,
along current convergence zones, and along shorelines
where debris is deposited by currents and waves.
Seabirds, turtles, whales, dolphins, dugongs, fish, crabs
and crocodiles and numerous other species are killed
and maimed through entanglement (EPA, 2011b).
Entanglement in plastic debris, especially in discarded
fishing gear, is a very serious threat to marine animals
(Derraik, 2002). According to Vauk and Schrey (1987),
entanglement accounts for 1329% of the observed
mortality of gannets (Sula bassana) at Helgoland,
German Bight. Entanglement is a particular problem for
marine mammals, such as fur seals, which are both
curious and playful (Mattlin and Cawthorn, 1986).
Once an animal is entangled, it may drown, and its
ability to catch food or avoid predators is impaired, or
incur wounds from abrasive or cutting action of attached
debris. Lost or abandoned fishing nets pose a particular
great risk (Jones, 1995). These ‘‘ghost nets’’ continue to
catch animals even if they sink or are lost on the seabed
(Laist, 1987). Whales are also caught in their mouths or
wrapped around their heads and tails’’ (Weisskopf,
1988).
Accumulation:
There is a potential danger to marine ecosystems from
the accumulation of plastic debris on the sea floor
(Derraik, 2002). Kanehiro et al. (1995) documented that
plastics are made up 8085% of the seabed debris in
Tokyo Bay and accumulation of such debris can inhibit
the gas exchange. The accumulation of POPs from
plastics has been documented in seabirds (Ryan et al.,
1988),and benthic organisms (Teuten et al., 2009).
Accumulation of microplastic particles in marine
invertebrates could potentially cause blockages
throughout the digestive system, suppressing feeding
due to satiation. Alternatively, predation of microplastic-
contaminated marine invertebrates may present a
pathway for plastic transfer along the food chain. The
capacity for microplastics to accumulate within an
organism is likely to affect the associated physical
impact of microplastic ingestion (Wright et al., 2013).
Pawar et al. (2016)
Between the overlying waters and the pore waters of
the sediments, the resulting hypoxia or anoxia in the
benthos can interfere with the normal ecosystem
functioning and alter the make-up of life on the sea floor
(Goldberg, 1997). Accumulation of plastic debris within
the waters and on the shorelines has impacts on 13
marine species that are listed as threatened or
endangered under the Endangered Species Act (ESA) as
shown in Table 3 (EPA, 2011b; Laist 1997).
Impacts of plastic marine debris on human
Plastic marine litter can also impact human health and
safety as follows:
1. Degradation of the habitats and ecosystem
services:
-Ghost fishing by lost nets and pots can remove fish and
invertebrates that are targeted by local commercial and
recreational fisheries (EPA, 2011b).
2. Impede commercial and recreational fishing:
-Fishing gear that is lost or discarded at sea may have
the greatest impact on humans due to impediments to
commercial and recreational fishing.
-Marine debris can block ship propellers or steering
systems and do direct damage to vessels.
3. Threaten health and safety:
-Entangling in nets and lines while swimming or being
injured by sharp debris that accumulates on beaches.
-Medical wastes, syringes, glass and other sharp
dangerous items that are washed up on beaches result in
direct risks to beachgoers.
-Swimmers, divers and snorkelers may become
entangled in submerged or floating debris.
-Solid waste associated with sewage such as sanitary
towels, condoms and cotton buds degrades the quality of
the bathing water and may present a health risk.
-Transfer of infections and disease due to medical waste,
such as punctures by hypodermic needles.
-Fish and shellfish meant for human consumption may
contain (micro) plastics and poses a human health risk.
-Marine litter poses a safety risk for sea vessels and their
crews.
-Burning of polystyrene polymers releases styrene gas,
which can readily be absorbed through the skin and
lungs and damage the eyes and mucous membranes. It
can increase the risk of heart disease; aggravate
50. PENCIL Pub. Biol. Sci. Pawar et al. (2016)
Table 3. List of threatened or endangered marine species listed under the Endangered Species Act (ESA).
S/N
Animals
Common Name
Species
1
Marine Mammals
Hawaiian monk seal
Monachus schauinslandi
2
Humpback whale
Megaptera novaengliae
3
Sperm whale
Physeter macrocephalus
4
Blue whale
Balaenoptera musculus
5
Fin whale
Balaenoptera physalus
6
Sei whale
Balaenoptera borealis
7
North Pacific right whale
Eubalena japonica
8
Marine Turtles
Olive Ridley turtle
Lepidochelys olivacea
9
Leatherback turtle
Dermochelys coriacea
10
Loggerhead turtle
Caretta caretta
11
Hawksbill turtle
Eretmochelys imbricate
12
Green turtle
Chelonia mydas
13
Seabirds
Short-tailed albatross
Phoebastria albatrus
respiratory ailments, such as asthma and emphysema,
and cause rashes, nausea or headaches, damages in the
nervous system, kidney or liver, in the development
system (Selukar et al., 2014).
4. Reduce tourism:
-Reduces the aesthetic and recreational values of
beaches and marine resources.
5. Interfere with navigation:
Marine debris can block ship propellers or steering
systems and do direct damage to vessels. A substantial
number of marine rescues have resulted.
Impacts of plastic marine debris on aesthetic values
-Plastic Marine Debris reduces the aesthetic and
recreational values of beaches and marine resources.
-Marine debris attracts considerable media and public
attention.
-Visual affront of unsightly, discarded and/or acci-
dentally lost plastic and other manufactured materials
that tend to strand and concentrate along shorelines and
sandy beaches - ones often of considerable recreational
importance.
-Concerns are commonly expressed about economic
losses, health issues and harm to local biota, and other-
wise general impressions of longer term deterioration in
beach aesthetic values (e.g. Gabrielides, 1995).
Effective solutions to tackle marine debris
-Plastic is now an integral part of the everyday activity of
human life and one cannot rule out the disadvantages of
plastic, but its disadvantages can be reduced to some
extent.
-The most effective way to reduce and mitigate the
harmful effects of marine debris is to prevent it from
entering the marine environment in the first place. This
requires incorporating an improved understanding of
debris at the local, regional and national levels;
improved waste management efforts; education and out-
reach activities; development of technology solutions;
anti-dumping campaigns; reducing losses of fishing gear
at sea; and incentives to reduce debris.
-Marine litter is entirely due to human activity and
therefore, has to be controlled by human management.
-Recycling is one of the most identified practices
available to reduce the impact of waste in landfills and in
the environment through the reuse of materials.
-Conversion of marine debris to adhesive is an
economical, eco-friendly and efficient technique.
-Other measures to address marine debris include ma-
nual clean-up operations of shorelines and the sea floor,
as well as school and public education programmes.
Conclusion
Recycling is the current solution to the overuse of
plastics. Thermal degradation may be the new solution
to recycling and repurposing plastics such as high-
51. PENCIL Pub. Biol. Sci.
density and low density polyethylene, polypropylene,
and polystyrene, without causing further environmental
degradation. ‘Thinking globally and acting locally is a
fundamental attitude to reduce such an environmental
threat. A combination of legislation and the enhance-
ment of ecological consciousness through education are
likely to be the best way to solve such environmental
problems. It is possible that biodegradable plastics could
be used where plastic is deemed necessary, but should
not be seen as an environmentally sound alternative
unless they are known to break down rapidly to non-
hazardous substances in natural environments. The
ultimate solution to waste prevention is to implement a
responsible waste strategy, namely the concept of Zero
Waste”.
ACKNOWLEDGEMENTS
The corresponding author is thankful to The Principal,
Veer Wajekar Arts, Science and Commerce College,
Mahalan Vibhag, Phunde (Uran), Navi Mumbai - 400 702
for providing the necessary facilities for the present
study. This work was supported by grant from the
University Grants Commission, New Delhi [File No: 42
546/2013 (SR) dated 22nd Mar 2013].
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