ArticlePDF Available

Impacts of changing ocean circulation on the distribution of marine microplastic litter


Abstract and Figures

Marine plastic pollution is currently a major scientific focus, with attention paid to its distribution and impacts within ecosystems. With recent estimates indicating that the mass of plastic released to the marine environment may reach 250 million metric tons by 2025, the effects of plastic on our oceans are set to increase. Distribution of microplastics, those plastics measuring less than 5 mm, are of increasing concern because they represent an increasing proportion of marine litter and are known to interact with species in a range of marine habitats. The local abundance of microplastic is dependent on a complex interaction between the scale of local plastic sources and prevailing environmental conditions; as a result, microplastic distribution is highly heterogeneous. Circulation models have been used to predict plastic distribution; however, current models do not consider future variation in circulation patterns and weather systems caused by a changing climate. In this study, we discuss the potential impacts of global climate change on the abundance and distribution of marine plastic pollution.
Content may be subject to copyright.
Invited Commentary
Impacts of Changing Ocean Circulation on the Distribution of
Marine Microplastic Litter
Natalie AC Welden*
and Amy L Lusher
Faculty of Science, Technology, Engineering and Maths, Open University, Milton Keynes, United Kingdom
Department of Animal Ecology I, University of Bayreuth, Bayreuth, Germany
This is 1 of 15 invited commentaries in the series “Current Understanding of Risks Posed by Microplastics in the
Environment.” Each peer-reviewed commentary reflects the views and knowledge of international experts in this field and,
collectively, inform our current understanding of microplastics fate and effects in the aquatic environment.
Marine plastic pollution is currently a major scientific focus, with attention paid to its distribution and impacts within
ecosystems. With recent estimates indicating that the mass of plastic released to the marine environment may reach 250 million
metric tons by 2025, the effects of plastic on our oceans are set to increase. Distribution of microplastics, those plastics
measuring less than 5 mm, are of increasing concern because they represent an increasing proportion of marine litter and are
known to interact with species in a range of marine habitats. The local abundance of microplastic is dependent on a complex
interaction between the scale of local plastic sources and prevailing environmental conditions; as a result, microplastic
distribution is highly heterogeneous. Circulation models have been used to predict plastic distribution; however, current
models do not consider future variation in circulation patterns and weather systems caused by a changing climate. In this study,
we discuss the potential impacts of global climate change on the abundance and distribution of marine plastic pollution. Integr
Environ Assess Manag 2017;13:483–487.
Keywords: Marine debris Microplastic Vertical distribution Sea-temperature rise Climate change
The plastics circulating in the world’s oceans have rich and
diverse histories. In the wake of the Second World War,
disposable plastic items were developed and marketed as a
tool to kick-start global economies. The perpetuation of this
mind-set, in combination with the popularity of single-use
products, uncontrolled disposal, and poor waste manage-
ment and recycling practices, has resulted in the addition of
large volumes of plastic to the environment (Bergmann et al.
2015). Becauseof technological advances,population growth,
and economic expansion, plastic production has increased;
since its development as an industrial component in the 1950s,
the annual production of plastics hasrisen to 322 million metric
tons (PlasticsEurope 2016). With greater volumes of consumer
plastic in circulation, loss to the environment has also
increased. One estimate of future plastic input suggests that
input of plastic waste from coastal countries will increase from
its current level of approximately 12.7 million metric tons to as
high as 250 million metric tons by 2025 (Jambeck et al. 2015).
Plastic pollution has been divided into 2 functional
subcategories: macroplastic debris, measuring more than
5 mm, and microplastic debris, which fall below this
boundary. Microplastics are further divided into primary
microplastics, which are manufactured to measure less than
5 mm, and secondary microplastics, which achieve these
dimensions through the breakdown of macroplastic litter
once in the environment. The abundance of macroplastic
debris and the scale of weathering factors have a great
influence on the local level of secondary microplastics. The
pathways through which these plastics enter our oceans are
varied, including littering, landfill runoff, and loss at sea
(Browne 2015). Although the scale and number of local
sources of debris are of obvious importance, a number of
factors are responsible for the distribution of plastics in the
marine environment.
In addition to being highly resistant to degradation (known
as recalcitrant), the density of the polymer greatly influences
its distribution (e.g., Ivar do Sul et al. 2013). Polymers with a
density higher than that of the surrounding water will sink,
and those that are lower will float. These differences influence
* Address correspondence to
Published 25 April 2017 on
Integrated Environmental Assessment and Management — Volume 13, Number 3—pp. 483–487
Received: 15 November 2016
Returned for Revision: 24 January 2017
Accepted: 9 February 2017 483
Integr Environ Assess Manag 2017:483–487
C2017 SETACDOI: 10.1002/ieam.1911
whether plastics remain in surface waters, become beached
in coastal areas and estuaries, or sink to deep-sea sediments
(Galgani et al. 2015) (Figure 1). In areas with high levels of
macroplastic debris, weathering may result in elevated local
levels of microplastics. This breakdown is dependent on
local environmental conditions including latitude, UV, and
temperature (Andrady 2015).
Some areas accumulate both macroplastics and micro-
plastics from a vast catchment because of prevailing
conditions. Suspended microplastics may be transported
from their point of release to remote areas (Ivar do Sul et al.
2013) or accumulate in central ocean regions (or gyres) (C
et al. 2014) (Figure 1). Studies in the North Pacific Subtropical
Gyre and the South Pacific Gyre have shown densities of small
plastic particles of 334 271 and 26 898 km
, respectively (e.g.,
Moore et al. 2002; Eriksen et al. 2014), and circulation models
suggest that plastics can be present in all ocean gyres,
because the gyres act as a conveyer to collect and
accumulate plastic items (Lebreton et al. 2012). C
ozar et al.
(2014) suggested that accumulation as a result of gyre
circulation has led to the Pacific Ocean containing 33% to
35% of the global ocean plastic load. However, the vast
majority of the sea surface, outside of subtropical gyres, has
not been surveyed, and therefore introduces potential errors
to the global estimates.
Plastics and microplastics not entrained in gyre systems
may reach remote oceanic regions and shorelines as a result
of ocean transport, that is, surface currents and bottom-
water transport (Figure 1). Movement of water between
ocean basins is the product of a complex interaction of
forces, the key drivers of which are the temperature and
salinity of water, known as thermohaline circulation, the
frictional effects of air currents, and the Coriolis force
(Jonasson et al. 2007). Observations of cargo lost from
container ships have shown a strong relationship between
the patterns of global circulation and those of debris
distribution (Ebbesmeyer et al. 2007).
A more subtle influence on the distribution of floating
plastics is that of the wind. Plastic debris riding at the water’s
surface is subject to the frictional effect of air currents that
alter the path of the object, known as windage (Shaw and
Mapes 1979). The impact of windage on debris may result in
the course of an object differing from that of the current alone
(Figure 1). Comparisons of windward and leeward beaches
have shown a distinct disparity in plastic abundance, with
windward beaches experiencing greater plastic abundance
of up to 24.2% (Debrot et al. 1999). Similarly, in the Tamar
estuary, England, downwind sites had higher levels of
fragmented plastic debris (Browne et al. 2010).
The combination of factors that influence plastic distribu-
tion have been used to develop models to provide an
overview of the expected plastic load at a given time (e.g.,
ozar et al. 2014; Eriksen et al. 2014). In this way, researchers
may predict areas of high plastic accumulation and potential
threats of plastic debris to ecosystems. A Lagrangian tracking
model, NEMO, was used to predict the movement of
particles in the Mediterranean. This model assumed a
homogeneous initial distribution of marine debris, with
repeated 1-year predictions separated by 24 hours. This
model has been used to predict both the accumulation of
floating debris and its beaching points (Mansui et al. 2015).
The model MEDSLIK-II was used to predict the movement of
plastic debris in the Adriatic Sea, using an estimate of 10 000
tons of litter released each year. This model predicted
increased volumes of plastic in the northwest boundary of the
Adriatic, but no defined aggregation points; as a result, the
Figure 1. Factors that influence the distribution of plastics and microplastics within and between the zones of the marine environment. Figure adapted from
Lusher (2015).
484 Integr Environ Assess Manag 13, 2017—NAC Welden and AL Lusher
Integr Environ Assess Manag 2017:483–487
authors suggest that the main sinks are the seafloor and
shoreline stranding (Liubartseva et al. 2016).
Although many of these models have proven effective in
mapping current plastic distribution, they are subject to
sources of uncertainty, such as variation in wind direction and
force. Reconstructions of a decade of oceanic conditions in
the North Sea were used to simulate both pre-existing and
subsequent distribution of floating debris. A Lagrangian
particle tracking model, PELETS-2D, was used to predict the
90-day trajectories of debris from various locations. In that
study wind drift was seen to greatly affect the distribution of
particles away from the prevailing circulation patterns
(Neumann et al. 2014). In addition to the variability caused
by short-term variation in abiotic factors, our oceans are
currently undergoing a more marked period of uncertainty
brought about by global climate change. These changes may
not only affect the ability of models to predict the location of
plastic aggregations, but also alter the geographic areas and
habitats at risk for the negative effects of marine plastic
Changing climate and ice melt
Since the mid-19th century, there has been a mean
increase in atmospheric temperature of 0.6 0.2 ˚C (Solomon
et al. 2007). This warming has subsequently been linked to a
range of effects on the marine environment, manifesting in
the increasing reports of coral bleaching (Hoegh-Guldberg
1999), ocean acidification (Doney et al. 2009), and reduced
sea ice (Comiso et al. 2008). The symptoms of climate change
are not solely the result of a warmer atmosphere, but relate to
an interaction between the thermal properties of the air, land,
and sea. This relationship adds to an already complex picture
of emissions and mitigation methods, which cause uncer-
tainty in both climate change projections and its impacts on
the environment (Intergovernmental Panel on Climate
Change 2013). One of the most widely discussed effects of
temperature on circulation, salinity, and sea temperatures is
the increasing rate of ice melt and reducing glacier extent.
Increased freshwater input from terrestrial glaciers and
the thermal expansion of seawater result in global rises in
sea level. Previous projections of sea level change by
2099 indicated increases of 18 to 38 cm under the B1 and
26 to 59 cm under the A1FI climate scenarios (Solomon et al.
2007). More recent estimates range from a conservative 28
to 56 cm to a potentially disastrous 57 to 131 cm (Mengel
et al. 2016).
Ice melt in polar regions is predicted to have a range of
effects on the distribution of marine plastics. First, seasonal
expansion and contraction of the ice sheets is believed to
contribute to the flux of microplastics, because particles are
trapped as water freezes and are released when it melts
(Lusher et al. 2015) (Figure 2). It has been suggested that
melting ice may result in the release of entrained plastic
(Obbard et al. 2014); however, the bulk of the large ice sheets
and glaciers formed before the proliferation of plastics and
plastic litter, and the scale of such releases are predicted to
be relatively minimal. Second, the density of many polymers
is equal to or lower than that of seawater, causing plastics to
float and be carried for long distances on ocean currents.
Reduction in the density of seawater at sites of freshwater
Figure 2. Schematic diagram of the predicted effects of climate change on the marine environment and the potential impacts of such variation on plastic input,
distribution, and accumulation.
Changing Ocean Circulation and Marine Microplastic Litter—Integr Environ Assess Manag 13, 2017 485
Integr Environ Assess Manag 2017:483–487
C2017 SETACDOI: 10.1002/ieam.1911
input is expected to reduce the relative buoyancy of marine
debris, increasing the rate at which plastics sink (Figure 1).
Correspondingly, areas of high evaporation will experience
increased water densities, resulting in plastics persisting in
the water column and/or surface waters. When predicting the
movement of plastics at the water’s surface, researchers must
take into account the residence time of plastics in the
neustonic zone; in low-water-density areas, the transport
time of plastics will be reduced, and in high-density areas it
will be increased.
Climate and circulation
Freshwater inputs from melting glaciers are predicted to
have effects beyond increasing the volume of water in our
oceans. In addition to its role in the transport of heat from
low-latitude upwelling areas to high-latitude sites of over-
turning (Wunsch 2002), thermohaline circulation is directly
affected by climate. Meridional overturning circulation is
caused by the cooling of warm water, which increases its
density and causes it to sink. Freshwater inputs in polar
regions reduce the salinity, and therefore the density, of
surface waters. This lessens the rate at which these waters
sink, slowing formation of cold deep waters (Broecker 1987).
Further freshwater inputs result from changes in the
hydrological cycle, including increased rain events at higher
latitudes (Rahmstorf 1995). It is believed that a 4-fold increase
in CO
is required to cause a collapse of thermohaline
circulation (Manabe and Stouffer 1994); however, a reduction
in transport of up to 50% has been observed in a number of
models (Rahmstorf 1999), and Atlantic water overturning is
thought to be slower now than at any point in the previous
century (Rahmstorf et al. 2015). Reducing the speed of deep-
water formation also slows down the rate at which freshwater
is removed from these sinking regions, again reducing the
seawater density (Toggweiler and Key 2001).
In addition to the effect of salinity on deep-water
formation, overturning is also influenced by the circulation
of surface waters (Pasquero and Tziperman 2004). Surface
water movement is primarily wind driven, which is the result of
uneven heating of the earth’s surface. Climate change is
predicted to influence the pattern of global heating, one
result of which will be altered wind patterns. Melting of the
sea ice will reduce the albedo effect (the heat-reflective
capacity of the earth’s surface) (Ingram et al. 1989); these
areas will be more readily heated, resulting in the formation
of new low-pressure areas as the newly heated—less dense—
air rises upward. Because wind patterns are governed by the
movement of air from areas of high to low pressure, this
change will alter prevailing wind conditions. Variation in wind
patterns will affect the movement of surface waters, as well as
the position of eddies and convergences, changing the
distribution of floating macroplastics and microplastics. In
addition to altering the effect of windage on plastic at the
water’s surface, increased wind speeds will result in increased
vertical mixing, raising the abundance of plastics found at
depth (Kukulka et al. 2012; Reisser et al. 2014) (Figure 1).
Debris that has previously settled in the sediment may also be
resuspended by wind-driven mixing in nearshore waters
(Floderus and Pihl 1990), increasing their abundance in the
water column. These changes in coastal systems could also
facilitate the transport of plastics to offshore areas (Figure 2).
Climate and weather
Changes in sea surface temperature may also affect the
scale and patterns of precipitation, in particular, tropical
storms, cyclones, and tornadoes. Global warming intensifies
alongshore wind stress on the ocean surface, resulting in
accelerated coastal upwelling (Bakun 1990). It has been
suggested that, as temperatures increase, torrential rain,
flooding droughts, and storms will become more frequent
(Coumou and Rahmstorf 2012). Furthermore, ocean subsur-
face temperatures and thermohaline depths and thickness
are predicted to affect the activities of natural climatic
variations, an effect currently believed to be visible in the
increasing frequency of El Ni~
no events (Cai et al. 2014). Rising
sea surface temperatures also increase the frequency of
hurricanes, which form over warm tropical waters. Uncertainty
in wind conditions may best be addressed by increasing the
integration time of models, smoothing the effect of this short-
term variation (Liubartseva et al. 2016).
In addition to the increasing annual mass of plastic released
from land or lost at sea, the input, distribution, and
accumulation of marine plastic debris will also be affected
by changes to global circulation and the morphology of
coastal regions (Figure 2). Not only is increased wind strength
predicted to facilitate the transport of windblown plastics
from terrestrial environments into waterways, but more
frequent rain events will increase flooding and surface water
runoff, further increasing plastic input (Moore et al. 2002).
Movement of plastic from the terrestrial to the marine
environment is also enabled by coastal flooding, as sea levels
rise in response to melting ice and changes in water density.
Debris that is littering shorelines will also become available
for transport as these areas are inundated by rising seas.
Distinct relationships have previously been recorded
between microplastic aggregation and both marine circula-
tion and weather conditions. The impacts of a changing
climate on ocean salinity and volume, and on the movement
of air and water, suggest that there will be significant changes
to the current pattern of distribution. The predicted increase
in the mass of marine plastic debris indicates that the threat
posed by microplastics will only increase in the coming
decades. The ability to predict areas of plastic input and
deposition would enable the identification of at-risk species
and enable efforts to reduce and remove plastic debris to be
targeted to specific locations. The current uncertainty as to
the effects of global warming on our oceans is the greatest
challenge in predicting the future patterns of plastic
aggregation and accumulation in relation to global circula-
tion. With future models of climate–ocean feedback
expected to produce more accurate predictions of circulation
patterns, including the impacts of a variable climate is vital in
486 Integr Environ Assess Manag 13, 2017—NAC Welden and AL Lusher
Integr Environ Assess Manag 2017:483–487
forecasting potential microplastic hot spots and “garbage
AcknowledgmentWe thank Rebekah Cioffi and Gema
Hernandez-Milian for their valued comments on an earlier
draft of the manuscript.
Andrady AL. 2015. Persistence of plastic litter in the oceans. In: Bergmann M,
Gutow L, Klages M, editors. Marine anthropogenic litter. Berlin (DE):
Springer International Publishing. p 57–72.
Bakun A. 1990. Global climate change and intensification of coastal ocean
upwelling. Science 247(4939):198–201.
Bergmann M, Gutow L, Klages M. 2015. Preface. In: Bergmann M, Gutow L,
Klages M, editors. Marine anthropogenic litter. Berlin (DE): Springer
International Publishing. p ix–xiv.
Broecker W. 1987. Unpleasant surprises in the greenhouse? Nature 328:
Browne MA. 2015. Sources and pathways of microplastic to habitats. In:
Bergmann M, Gutow L, Klages M, editors. Marine anthropogenic litter.
Berlin (DE): Springer International Publishing. p 229–244.
Browne MA, Galloway TS, Thompson RC. 2010. Spatial patterns of plastic
debris along estuarine shorelines. Environ Sci Technol 44:3404–3409.
Cai W, Borlace S, Lengaigne M, Van Rensch P, Collins M, Vecchi G,
Timmermann A, Santoso A, McPhaden MJ, Wu L, and England MH. 2014.
Increasing frequency of extreme El Ni~
no events due to greenhouse
warming. Nature Climate Change 4(2):111–116.
Comiso JC, Parkinson CL, Gersten R, Stock L. 2008. Accelerated decline in the
Arctic sea ice cover. Geophysical Research Letters 35:L01703.
Coumou D, Rahmstorf S. 2012. A decade of weather extremes. Nature Climate
Change 2(7):491–496.
ozar A, Echevarra F, Gonz
alez-Gordillo JI, Irigoien X,
Ubeda B, Hern
on S, Palma AT, Navarro S, Garca-de-Lomas J, Ruiz A, et al. 2014. Plastic
debris in the open ocean. Proc Natl Acad Sci U S A 111(28):10239–10244.
Debrot AO, Tiel AB, Bradshaw JE. 1999. Beach debris in CuraScao. Mar Pollut
Bull 38:795–801.
Doney SC, Fabry VJ, Feely RA, Kleypas JA. 2009. Ocean acidification: The
other CO2 problem. Annual Review of Marine Science 1:169–192.
Ebbesmeyer CC, Ingraham Jr WJ, Royer TC, Grosch CE. 2007. Tub toys orbit
the Pacific Subarctic gyre. Eos 88(1):1–4.
Eriksen M, Lebreton LC, Carson HS, Thiel M, Moore CJ, Borerro JC, Galgani F,
Ryan PG, Reisser J. 2014. Plastic pollution in the world’s ocea ns: More than
5 trillion plastic pieces weighing over 250,000 tons afloat at sea. PLoS One
Floderus S, Pihl L. 1990. Resuspension in the Kattegat: Impact of variation in
wind climate and fishery. Estuar Coast Shelf Sci 31:487–498.
Galgani F, Hanke G, Maes T. 2015. Global distribution, composition and
abundance of marine litter. In: Bergmann M, Gutow L, Klages M, editors.
Marine anthropogenic litter. Berlin (DE): Springer International Publishing.
p 29–56.
Hoegh-Guldberg O. 1999. Climate change, coral bleaching and the future of
the world’s coral reefs. Mar Freshw Res 50:839–866.
Ingram WJ, Wilson CA, Mitchell JFB. 1989. Modeling climate change: An
assessment of sea ice and surface albedo feedbacks. Journal of
Geophysical Research: Atmospheres 94(D6):8609–8622.
Intergovernmental Panel on Climate Change. 2013. IPCC, Summary for
Policymakers. In: Stocker TF, Qin D, Plattner G-K, Tignor M, Allen SK,
Boschung J, Nauels A, Xia Y, Bex V, Midgley PM, editors. Climate change
2013: The physical science basis. Contribution of Working Group I to the
Fifth Assessment Report of the Intergovernmental Panel on Climate
Change. Cambridge (UK): Cambridge University Press. p 3–29.
Ivar do Sul JA, Costa MF, Barletta M, Cysneiros FJA. 2013. Pelagic
microplastics around an archipelago of the Equatorial Atlantic. Mar Pollut
Bull 75(1):305–309.
Jambeck JR, Geyer R, Wilcox C, Siegler TR, Perryman M, Andrady A, Narayan
R, Law KL. 2015. Plastic waste inputs from land into the ocean. Science
Jonasson JP, Thorarinsdottir G, Eiriksson H, Solmundsson J, Marteinsdottir G.
2007. Collapse of the fishery for Iceland scallop (Chlamys islandica)in
Breidafjordur, West Iceland. ICES J Mar Sci 64:298–308.
Kukulka T, Proskurowski G, Mor
et-Ferguson S, Meyer DW, Law KL. 2012. The
effect of wind mixing on the vertical distribution of buoyant plastic debris.
Geophys Res Lett 39(7):L07601.
Lebreton LM, Greer SD, Borrero JC. 2012. Numerical modelling of floating
debris in the world’s oceans. Mar Pollut Bull 64(3):653–661.
Liubartseva S, Coppini G, Lecci R, Creti S. 2016. Regional approach to
modeling the transport of floating plastic debris in the Adriatic Sea. Mar
Pollut Bull 103(1):115–127.
Lusher AL. 2015. Distribution and interactions of microplastics in the North
Atlantic [PhD thesis]. Galway (IE): Galway-Mayo Institute of Technology,
Lusher AL, Tirelli V, O’Connor I, Officer R. 2015. Microplastics in Arctic polar
waters: The first reported values of particles in surface and sub-surface
samples. Scientific Reports 5:14947.
Manabe S, Stouffer RJ. 1994. Multiple-century response of a coupled ocean-
atmosphere model to an increase of atmospheric carbon dioxide. Journal
of Climate 7:5–23.
Mansui J, Molcard A, Ourmieres Y. 2015. Modelling the transport and
accumulation of floating marine debris in the Mediterranean basin. Mar
Pollut Bull 91(1):249–257.
Mengel M, Levermann A, Frielder K, Robinson A, Marzeion B, Winkelmann R.
2016. Future sea level rise constrained by observations and long-term
commitment. Proc Natl Acad Sci U S A 11(10):2597–2602.
Moore CJ, Moore SL, Weisberg SB, Lattin GL, Zellers AF. 2002. A comparison
of neustonic plastic and zooplankton abundance in southern California’s
coastal waters. Mar Pollut Bull 44(10):1035–1038.
Neumann D, Callies U, Matthies M. 2014. Marine litter ensemble transport
simulations in the southern North Sea. Mar Pollut Bull 86(1):219–228.
Obbard RW, Sadri S, Wong YQ, Khitun AA, Baker I, Thompson RC. 2014.
Global warming releases microplastic legacy frozen in Arctic Sea ice.
Earth’s Future 2(6):315–320.
Pasquero C, Tziperman E. 2004. Effects of a wind-driven gyre on thermoh aline
circulation variability. J Phys Oceanogr 34:805–816.
PlasticsEurope. 2016. Plastics, the facts: An analysis of European plastics
production, demand and waste data. Brussels (BE): PlasticsEurope. http://
Rahmstorf S. 1995. Bifurcations of the Atlantic thermohaline circulation in
response to changes in the hydrological cycle. Nature 378:145–149.
Rahmstorf S. 1999. Shifting seas in the greenhouse? Nature 399:523–524.
Rahmstorf S, Box J, Feulner G, Mann M, Robinson A, Rutherford S,
Schaffernicht E. 2015. Exceptional twentieth-century slowdown in
Atlantic Ocean overturning circulation. Nature Climate Change 5:475–480.
Reisser J, Slat B, Noble K, du Plessis K, Epp M, Proietti M, de Sonneville J,
Becker T, Pattiaratchi C. 2014. The vertical distribution of buoyant plastics
at sea. Biogeosciences Discussions 11(11):16207–16226.
Shaw DG, Mapes GA. 1979. Surface circulation and the distribution of pelagic
tar and plastic. Mar Pollut Bull 10:160–162.
Solomon S, Qin D, Manning M, Chen Z, Marquis M, Averyt KB, Tignor M,
Miller HL, editors. 2007. Climate change 2007: The physical science
basis. Working Group I contribution to the Fourth Assessment Report
of the IPCC. Vol V 4 Cambridge (UK): Cambridge University Press.
996 p.
Toggweiler JR, Key RM. 2001. Thermohaline circulation. In: Steele JH, Thorpe
SA, Turekien KK, editors. Encyclopedia of ocean sciences. Amsterdam
(NL): Elsevier. p 2941–2947.
Wunsch C. 2002. What is the thermohaline circulation. Science 298(5596):
Changing Ocean Circulation and Marine Microplastic Litter—Integr Environ Assess Manag 13, 2017 487
Integr Environ Assess Manag 2017:483–487
C2017 SETACDOI: 10.1002/ieam.1911
... As stated previously, microplastics with density greater than that of the marine/ region water may sink to the seabed. This process is mediated by vertical turbulent mixing, biota transfer (via fishes or other marine organisms), biological fouling (also known as biofouling), and aggregate formation [61,101]. Biofouling is the accumulation of existing marine microorganisms, planktons, algae, microalgae, and small marine organisms on the plastic debris/microplastics [102]. This process depends on the polymer type, surface area, and size of the microplastic, as well as the microorganisms present in the marine environment, temperature, salinity, pH, nutrient/ metals, and oxygen concentration of the water [66,[103][104][105][106]. ...
... The fate of the microplastics accumulated in the marine sediments is affected by the disturbance in the sediment zone, resulting in releasing the accumulated microplastics back into the water zone [111]. Also, similar to surface water currents, bottom water currents can also lead to the transportation of the microplastic to remote regions (Figure 2) [101]. ...
Full-text available
Global plastic production is on the rise, and improper plastic management leads to the disposal of plastic in the environment, wherein it enters the environment, after degradation, as microplastics (size < 5 mm) and nanoplastics (size < 1 μm). The most common sink for the microplastics is the marine environment, including the sediment, deep sea, shorelines, and oceans. The objective of this study is to collate the environmental impact assessment of the microplastics in the marine habitat, focusing on the following main elements: (a) source and type of microplastics, specifically leading to the marine sink; (b) degradation pathways; (c) ecotoxicological impact on marine biota, since the smaller-sized microplastics can be digested by the marine biota and cause threats to them; (d) fate of microplastic in the marine environment, including the modes of transport and deposition. This chapter aims to provide a deeper insight into the fate of microplastics once it enters the marine environment, and the information could be a useful reference for the development of microplastic risk management strategies.
... Since jellyfish and their carcasses ('jelly-falls'), but possibly also excreted mucus (Hubot et al., 2022), are an important food source for various marine organisms, including fish and benthic seafloor communities (Sweetman and Chapman, 2015), the trophic transfer and possible bioaccumulation of microplastics in pelagic and benthic food webs of coastal marine ecosystems remain to be examined. Recent approaches assessing the environmental risk of microplastic pollution in the world's oceans further indicate harmful effects for marine species due to a predicted rise in microplastic abundances by a factor ≤ 50 until the end of the 21st century (Everaert et al., 2020, Everaert et al., 2018Isobe et al., 2019, Welden andLusher, 2017). In all our experimental treatments with microplastic concentrations exceeding present-day observations in marine ecosystems approximately 35-fold, medusae reproduced sexually after reaching an umbrella diameter of ~50 mm which is comparable to the minimum size of mature A. aurita from temperate coastal regions (Goldstein and Riisgård, 2016;Lucas, 1996) and provides further evidence for strong adaptation of jellyfish to microplastic contaminations. ...
Full-text available
Jellyfish blooms may be important bioindicators for marine ecosystem degradation, including the accumulation of microplastics in pelagic food webs. Here we show growth, respiration and filtration rates of the moon jellyfish (Aurelia aurita s.l.) when fed high concentrations (350 L-1) of zooplankton prey (Artemia salina nauplii) and polystyrene (PS) or reference particles (charcoal; size range 50-500 μm). Our controlled feeding experiments reveal that inedible particles are ingested less efficiently compared to prey (retention efficiency ~60 % for PS) and actively removed from the gastrovascular system of ephyrae and medusae. Increased metabolic demands for excretion of inedible material (up to 76.7 ± 3.1 % of ingested prey biomass) suggest that overloading with microplastics can decelerate growth (observed maxima 26.1 % d-1 and 12.6 % d-1, respectively) and reproductive rates when food is limited. Possible consequences of this selective feeding strategy in response to proceeding microplastic pollution in the world's future oceans are discussed.
... With this in mind, we employed a meta-analysis with existing literature data, incorporating macroecological tools to hypothesize that species' functional traits could influence bioaccumulation and that there is a relationship between the tissues and the exposure routes, so that accumulation patterns on crabs might depend on functional traits. In addition, from what we have exposed so far, we hypothesized that at lower latitudes, animals could accumulate more MPs due to ocean currents that carry plastic particles to lower latitudes and the presence of mangroves, which are ecosystems known for their high capacity to retain contaminants (Welden and Lusher, 2017). If this hypothesis holds true, regional-tocontinental accumulation patterns could be influenced mainly by the degree of local contamination. ...
Despite the increasing plastic discharge into the environment, few articles have dealt with the macroecological implications of microplastics (MPs) bioaccumulation on organisms. We performed a meta-analysis of MPs accumulation in true crabs and pseudocrabs worldwide and made use of macroecotoxicological approaches to know if: I) functional traits influence the bioaccumulation of MPs in the tissues of crabs; II) there is a latitudinal pattern of MPs bioaccumulation; III) there are tissues that can accumulate more MPs; IV) crabs can sort particles according to size, color, shape and type. Our results showed that functional traits influence the accumulation of MPs. Smaller crabs in size and weight and with shorter lifespans tended to exhibit more plastic particles. According to the environment, estuarine crabs from the intertidal and muddy substrates held more MPs. Also, burrowers exhibited significantly more particles in the tissues than omnivorous crabs. Besides, we recorded that crabs from low latitudes tended to exhibit more plastic particles, probably because of the mangroves' location that acts as traps for MPs. Non-human-consumed crabs accumulated significantly more MPs than human-consumed ones. Considering the tissues, gills were prone to accumulate more debris than the digestive tract, but without significant differences. Finally, colorless fibers of 1–5 mm of PA, PP and PET were the predominant characteristics of MPs, suggesting that crabs accumulated denser types but did not sort plastic according to color. These results indicate that functional traits might influence the accumulation of MPs and that there are coastal regions and geographical areas where crabs tend to accumulate more MPs. Analyzing MPs accumulation patterns with macroecological tools can generate information to identify the most affected species and define priorities for monitoring and implementing actions toward reducing plastic use globally.
... The existence of plastic allows the efficiency of the production of necessities to cut the cost of fuel distribution and buying and selling goods in everyday life. The cost of making plastic is cheap compared to other supporting materials, driving market demand and consumer interest, this can also raise the risk of public dependence on plastic [1,2]. Plastics are a collection of synthesis and semi-synthesis materials arranged on polymer long chains. ...
Full-text available
Microplastic contamination gain recognition in recent years. Microplastic is found within many parts of human tissue and thus provides potential health hazards. Although microplastic pollution ranges across the land, air, and water ecosystem, this review only exposes the existence of microplastic within the marine environment, which includes the marine territories of Kupang City, Indonesia, and its proximity. In this review, we assess any scientific literature related to microplastic issues in Kupang City. The purpose of this review article is to analyze and combine the results from the researchers who discuss the existence of microplastics and the characteristics of the microplastics studied in Kupang City. In order to achieve a comprehensive explanation, each aspect of expertise in previous research will be carried within a human health point of view. As a result, seven papers published in 2019 to 2022 referring to microplastic problems in Kupang City were found, proposing the presence of filament-shaped and black microplastics in almost all related studies.
... However, vertical mixing can bring the MPs into different layers . Nevertheless, the morphology of coastal regions, sea surface temperature changes, ocean circulation patterns, coastal upwelling, and weather conditions also influence the distribution and aggregation of MPs hot spots (Welden and Lusher, 2017). According to Liu et al. (2022), current velocity strongly affects the accumulation, abundance, and distribution of MPs, in addition to the seawater temperature and salinity, which affect the density and movement of water. ...
Full-text available
Microplastics (MPs) are ubiquitous pollutants in the ocean, and there is a general concern about their persistence and potential effects on marine ecosystems. We still know little about the smaller size-fraction of marine MPs (MPs <300 μm), which are not collected with standard nets for MPs monitoring (e.g., Manta net). This study aims to determine the concentration, composition, and size distribution of MPs down to 10 μm in the Kattegat/Skagerrak area. Surface water samples were collected at fourteen stations using a plastic-free pump-filter device (UFO sampler) in October 2020. The samples were treated with an enzymatic-oxidative method and analyzed using FPA-μFTIR imaging. MPs concentrations ranged between 11 and 87 MP m⁻³, with 88% of the MPs being smaller than 300 μm. The most abundant shape of MPs were fragments (56%), and polyester, polypropylene, and polyethylene were the dominant synthetic polymer types. The concentration of MPs shows a significant positive correlation to the seawater density. Furthermore, there was a tendency towards higher MPs concentrations in the Northern and the Southern parts of the study area. The concentration of MPs collected with the UFO sampler was several orders of magnitude higher than those commonly found in samples collected with the Manta net due to the dominance of MP smaller size fractions. Despite the multiple potential sources of MPs in the study area, the level of MPs pollution in the surface waters was low compared (<100 MP m⁻³) to other regions. The concentrations of MPs found in the studied surface waters were six orders of magnitude lower than those causing negative effects on pelagic organisms based on laboratory exposure studies, thus is not expected to cause any impact on the pelagic food web.
... Plastic pollution has gained recognition among the scientific community over the past decade because they pose a universal threat to the marine system (Fok and Cheung 2015;Zhang X et al. 2020). According to recent estimates, the mass of plastic discharged into the marine environment could reach 250 million metric tonnes (MMT) by 2025 (Welden and Lusher 2017). In recent years, global plastic production has been around 300 MMT, with Asia alone accounting for half of it. ...
Full-text available
Microplastics (MPs) are defined as plastic particles smaller than 5 mm in size. They are primarily derived from larger pieces of plastic debris that degrade into smaller pieces. The current study identified, characterized, and quantified MPs in Chennai coast coastal aquifers, seawater, and foreshore sediments. The spatial distribution and polymer composition of MP particles were studied to identify and evaluate their abundance and characteristics (composite, size, color, and shape of MPs). The foreshore and river mouth sediment samples were found to be contaminated by MPs with a total of 263 particles in 12 samples collected from different locations (average of 22 particles 5 g⁻¹ of dry sediment (d.s.)). The surface water and groundwater samples were also contaminated by MPs with a total of 315 particles in 25 samples collected from different locations (average of 13 particles/L). Size of majorities of MPs ranged from 1 mm to 300 μm. The study also confirmed the presence of MPs in sediments and water samples collected from the study area using Fourier transform infrared spectroscopy (FTIR). FTIR results revealed that nylon, polyvinylchloride, and polyethylene terephthalate were the predominant types of MPs. The spatial variation map showed that high concentration of MPs was observed on tourist beaches. Remediation technologies are highly effective in eliminating and preventing MPs pollution in our environment. The existence of MPs in water samples suggests that it is essential to take preventive steps to avoid MPs causing health issues like neurotoxicity, Alzheimer, and cancer.
... Since the first production of plastic in 1907, plastic production has increased approximately 200 fold. In 2019, global plastic production reached 368 million tons [2]. Hence, a large amount of plastic waste is released into the marine environment. ...
Full-text available
Microplastics (MPs) are ubiquitous pollutants that have potentially harmful and toxic effects. MPs are frequently ingested by aquatic animals, as microplastics share a similar size and color to their food. Heavy metals are harmful and difficult to degrade, have a wide range of sources and an extended residual time from exposure to recovery. Although the effects of MPs and heavy metals on the performance of aquatic species have been extensively studied, the molecular mechanisms of MP and heavy metal (Pb, Cd and Cu) exposure on aquatic organisms remain unclear. Here, the effects of MPs and heavy metal accumulation on the line seahorse, Hippocampus erectus, were investigated at the molecular level using transcriptome analysis. Using gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses, we found that immune, metabolic, and apoptotic pathways were affected in the heavy metal group, whereas the DNA damage repair and metabolism pathways were mainly involved in the MP group. Both types of stress caused significant changes in the genes related to the antioxidant pathway in H. erectus larvae. Transcriptome differences between the treatment groups were analyzed, and sensitive candidate genes (Hsp70, Hsp90, Sod, etc.) were screened. The response characteristics of seahorses to MP environmental stress were also investigated. Using seahorse as a biological model and candidate sensitive genes as a basis, our results provide a theoretical basis for detecting MPs and heavy metals pollution in coastal areas.
... This was expected as the water is well mixed from continuous wave and wind mixing and is not affected by circulating currents compared to the interior of the bay. Strong winds and waves create vertical mixing within the water column agitating particulates (Welden and Lusher 2017) which could affect the overall concentrations of surface microplastic abundance outside the bay. ...
Technical Report
Full-text available
A compilation of Coastal Carolina University undergraduate research project papers conducted as part of the 2018 Ecology of Coral Reefs short-term, study abroad program in Discovery Bay, Jamaica.
... Altered microbial biogeochemical function in the water column and in sediments; and shifts in nitrification and denitrification Changes in soil nutrient ratio: Soil Exacerbation of the effects of flooding events in urban and riverine areas Galgani et al. 2015, Welden and Lusher 2017, van Sebille et al. 2020 Land system change Changes in land-use Land clearing for the extraction of fossil fuel , Liboiron 2021 Land clearing to cultivate raw material for biobased plastics Zheng and Suh 2019, Escobar and Britz 2021 Change to place of landfills, dumpsites, and incineration facilities OECD 2022 ...
Plastics are novel entities that have exceeded the planetary safe operating space due to extensive and resource-intensive production, uncontrolled environmental releases, and failure to control the chemicals within the materials. This paper examines evidence and discusses how plastics pollution affects Earth-system processes along the impact pathway from production, to release, to environmental fate and impacts of plastics and their additives. Multiple lines of evidence are necessary to capture the complex reality of these substances and attempts to quantify a singular boundary would be detrimental to the global governance of plastics. We demonstrate causal links between plastics and other major environmental problems at the global scale, exacerbating the consequences of breaching other planetary boundaries, especially climate change and biodiversity loss. We propose ways to translate these assessments into control variables for the globally and biophysically defined planetary boundaries framework that can be utilized to tackle plastics pollution. Efforts should be oriented towards further developing and monitoring a set of control variables that describe the actual state of the system along the impact pathway. We call for experts and policymakers to take urgent action, considering plastics pollution not only as a waste management problem but as an integrative part of climate change, biodiversity and natural resource use policy.
Full-text available
Significance Anthropogenic sea level rise poses challenges to coastal areas worldwide, and robust projections are needed to assess mitigation options and guide adaptation measures. Here we present an approach that combines information about the equilibrium sea level response to global warming and last century's observed contribution from the individual components to constrain projections for this century. This “constrained extrapolation” overcomes limitations of earlier global semiempirical estimates because long-term changes in the partitioning of total sea level rise are accounted for. While applying semiempirical methodology, our method yields sea level projections that overlap with the process-based estimates of the Intergovernmental Panel on Climate Change. The method can thus lead to a better understanding of the gap between process-based and global semiempirical approaches.
Full-text available
The increasing global production and use of plastics has led to an accumulation of enormous amounts of plastic litter in the world’s oceans. Characteristics such as low density, good mechanical properties and low cost allow for successful use of plastics in industries and everyday life but the high durability leads to persistence of the synthetic polymers in the marine environment where they cause harm to a great variety of organisms. In the diverse marine habitats, including beaches, the sea surface, the water column, and the seafloor, plastics are exposed to different environmental conditions that either accelerate or decelerate the physical, chemical and biological degradation of plastics. Degradation of plastics occurs primarily through solar UV-radiation induced photo oxidation reactions and is, thus, most intensive in photic environments such as the sea surface and on beaches. The rate of degradation is temperature-dependent resulting in considerable deceleration of the processes in seawater, which is a good heat sink. Below the photic zone in the water column, plastics degrade very slowly resulting in high persistence of plastic litter especially at the seafloor. Biological decomposition of plastics by microorganisms is negligible in the marine environment because the kinetics of biodegradation at sea is particularly slow and oxygen supply for these processes limited. Degradation of larger plastic items leads to the formation of abundant small microplastics. The transport of small particles to the seafloor and their deposition in the benthic environment is facilitated by the colonization of the material by fouling organisms, which increase the density of the particles and force them to sink. © 2015, Springer International Publishing. All Rights Reserved.
Full-text available
Plastic, as a form of marine litter, is found in varying quantities and sizes around the globe from surface waters to deep-sea sediments. Identifying patterns of microplastic distribution will benefit an understanding of the scale of their potential effect on the environment and organisms. As sea ice extent is reducing in the Arctic, heightened shipping and fishing activity may increase marine pollution in the area. Microplastics may enter the region following ocean transport and local input, although baseline contamination measurements are still required. Here we present the first study of microplastics in Arctic waters, south and southwest of Svalbard, Norway. Microplastics were found in surface (top 16cm) and sub-surface (6 depth) samples using two independent techniques. Origins and pathways bringing microplastic to the Arctic remain unclear. Particle composition (95% fibres) suggests they may either result from the breakdown of larger items (transported over large distances by prevailing currents, or derived from local vessel activity), or input in sewage and wastewater from coastal areas. Concurrent observations of high zooplankton abundance suggest a high probability for marine biota to encounter microplastics and a potential for trophic interactions. Further research is required to understand the effects of microplastic-biota interaction within this productive environment.
Full-text available
Marine debris is commonly observed everywhere in the oceans. Litter enters the seas from both land-based sources, from ships and other installations at sea, from point and diffuse sources, and can travel long distances before being stranded. Plastics typically constitute the most important part of marine litter sometimes accounting for up to 100 % of floating litter. On beaches, most studies have demonstrated densities in the 1 item m−2 range except for very high concentrations because of local conditions, after typhoons or flooding events. Floating marine debris ranges from 0 to beyond 600 items km−2. On the sea bed, the abundance of plastic debris is very dependent on location, with densities ranging from 0 to >7700 items km−2, mainly in coastal areas. Recent studies have demonstrated that pollution of microplastics, particles <5 mm, has spread at the surface of oceans, in the water column and in sediments, even in the deep sea. Concentrations at the water surface ranged from thousands to hundred thousands of particles km−2. Fluxes vary widely with factors such as proximity of urban activities, shore and coastal uses, wind and ocean currents. These enable the presence of accumulation areas in oceanic convergence zones and on the seafloor, notably in coastal canyons. Temporal trends are not clear with evidences for increases, decreases or without changes, depending on locations and environmental conditions. In terms of distribution and quantities, proper global estimations based on standardized approaches are still needed before considering efficient management and reduction measures.
Full-text available
Possible changes in Atlantic meridional overturning circulation (AMOC) provide a key source of uncertainty regarding future climate change. Maps of temperature trends over the twentieth century show a conspicuous region of cooling in the northern Atlantic. Here we present multiple lines of evidence suggesting that this cooling may be due to a reduction in the AMOC over the twentieth century and particularly after 1970. Since 1990 the AMOC seems to have partly recovered. This time evolution is consistently suggested by an AMOC index based on sea surface temperatures, by the hemispheric temperature difference, by coral-based proxies and by oceanic measurements. We discuss a possible contribution of the melting of the Greenland Ice Sheet to the slowdown. Using a multi-proxy temperature reconstruction for the AMOC index suggests that the AMOC weakness after 1975 is an unprecedented event in the past millennium (p > 0.99). Further melting of Greenland in the coming decades could contribute to further weakening of the AMOC.
Identifying and eliminating the sources of microplastic to habitats is crucial to reducing the social, environmental and economic impacts of this form of debris. Although eliminating sources of pollution is a fundamental component of environmental policy in the U.S.A. and Europe, the sources of microplastic and their pathways into habitats remain poorly understood compared to other persistent, bioaccumulative and/or toxic substances (i.e. priority pollutants; EPA in U.S. Environmental Protection Agency 2010–2014 Pollution Prevention (P2) Program Strategic Plan. Washington, USA, pp. 1–34, 2010; EU in Official J Eur Union L334:17–119, 2010). This chapter reviews our understanding of sources and pathways of microplastic, appraises terminology, and outlines future directions for meaningfully integrating research, managerial actions and policy to understand and reduce the infiltration of microplastic to habitats. © 2015, Springer International Publishing. All Rights Reserved.