Plastic and metal ingestion in three species of coastal waterfowl wintering in Atlantic Canada

Article (PDF Available)inMarine Pollution Bulletin 98(1-2) · June 2015with 257 Reads
DOI: 10.1016/j.marpolbul.2015.05.063
Abstract
Relatively little attention has been paid to the occurrence of anthropogenic debris found in coastal species, especially waterfowl. We examined the incidence of ingested plastic and metal in three waterfowl species wintering in Atlantic Canada: American black ducks (Anas rubripes) and mallards (A. platyrhynchos), two species that use marine and freshwater coastal habitats for foraging in the winter, and common eider (Somateria mollissima), a coastal marine species that feeds on intertidal and subtidal benthic organisms. Plastic was found in the stomachs of 46.1% (6/13) of mallards and 6.9% (6/87) of black ducks, the first report of ingested anthropogenic debris in these species, while 2.1% (1/48) of eider stomachs contained plastic. Metal was found in the stomachs of 30.8% (4/13) of mallards, 2.3% (2/87) of black ducks, and in 2.1% (1/48) of eiders. Our results indicate that species using coastal marine and freshwater environments are exposed to and ingest anthropogenic debris. Copyright © 2015 Elsevier Ltd. All rights reserved.
Baseline
Plastic and metal ingestion in three species of coastal waterfowl
wintering in Atlantic Canada
Matthew D. English
a,
, Gregory J. Robertson
b
, Stephanie Avery-Gomm
b
, Donald Pirie-Hay
b
, Sheena Roul
b
,
Pierre C. Ryan
c
, Sabina I. Wilhelm
c
, Mark L. Mallory
a
a
Department of Biology, Acadia University, Wolfville, NS B4P 2R6, Canada
b
Wildlife Research Division, Environment Canada, 6 Bruce Street, Mount Pearl, NL A1N 4T3, Canada
c
Canadian Wildlife Service, Environment Canada, 6 Bruce Street, Mount Pearl, NL A1N 4T3, Canada
article info
Article history:
Received 9 April 2015
Revised 26 May 2015
Accepted 28 May 2015
Available online xxxx
Keywords:
Plastic ingestion
Metal ingestion
Mallard
American black duck
Common eider
Waterfowl
abstract
Relatively little attention has been paid to the occurrence of anthropogenic debris found in coastal spe-
cies, especially waterfowl. We examined the incidence of ingested plastic and metal in three waterfowl
species wintering in Atlantic Canada: American black ducks (Anas rubripes) and mallards (A.platyrhyn-
chos), two species that use marine and freshwater coastal habitats for foraging in the winter, and com-
mon eider (Somateria mollissima), a coastal marine species that feeds on intertidal and subtidal benthic
organisms. Plastic was found in the stomachs of 46.1% (6/13) of mallards and 6.9% (6/87) of black ducks,
the first report of ingested anthropogenic debris in these species, while 2.1% (1/48) of eider stomachs con-
tained plastic. Metal was found in the stomachs of 30.8% (4/13) of mallards, 2.3% (2/87) of black ducks,
and in 2.1% (1/48) of eiders. Our results indicate that species using coastal marine and freshwater envi-
ronments are exposed to and ingest anthropogenic debris.
Ó2015 Elsevier Ltd. All rights reserved.
Debris in the marine environment has been identified as one of
the leading threats to the health of the world’s oceans (UNEP,
2011), and emerging evidence suggests that freshwater systems
are similarly affected (Eriksen et al., 2013; Driedger et al., 2015).
In 2010, it was estimated that 4.8–12.7 million metric tons of plas-
tic entered the ocean from land-based sources, and if waste man-
agement practices do not improve on a global scale, this number
could increase by an order of magnitude by 2025 (Jambeck et al.,
2015).
Plastics and other debris enter aquatic systems through direct
or accidental dumping, and transport from land by wind or mis-
management of waste disposal (Jambeck et al., 2015). Most plastics
that enter aquatic systems are broken down through physical and
chemical stress into small fragments that persist in the environ-
ment, and many surface-feeding animals experience high rates of
plastic ingestion in areas of high plastic contamination. The occur-
rence of plastics in many surface-feeding pelagic seabirds in
Canadian waters has been recently summarized (Avery-Gomm
et al., 2013; Provencher et al., 2014a,b), and is an issue garnering
considerable media attention in Canada.
Detrimental effects of plastic ingestion include impaction and
physical damage to the digestive tract (Gregory, 2009; van
Franeker et al., 2011). As well, plastics can adsorb high concentra-
tions of organic contaminants and may act as vectors for contam-
inant transfer into marine food webs, when plastics are ingested
(Mato et al., 2001; Teuten et al., 2009). Negative effects of
plastic-related organic contaminants has not yet been explicitly
shown in birds, but has been demonstrated in fish (Rochman
et al., 2013). Lead and steel shot is the most reported type of
non-plastic anthropogenic debris ingested by waterfowl (Mateo
et al., 1998; Moore et al., 1998; Pain, 1990), and reports of other
types of metal ingested by waterfowl are limited (e.g., whooping
crane Grus americana research by Olsen and Wise, 2001). Lead poi-
soning as a result of lead shot ingestion has been
well-documented, and in many cases lead to the death of the
organism.
While numerous studies have focused on debris in the marine
environment, comparatively little attention has been paid to the
occurrence of anthropogenic debris in freshwater systems
(Wagner et al., 2014; Driedger et al., 2015). In the Laurentian
Great Lakes, microplastics reach surface concentrations as high or
higher than some ocean gyres (Eriksen et al., 2013; Driedger
et al., 2015). Remote lakes are also susceptible to plastic contami-
nation, and in some cases can be more polluted than the Great
http://dx.doi.org/10.1016/j.marpolbul.2015.05.063
0025-326X/Ó2015 Elsevier Ltd. All rights reserved.
Corresponding author.
E-mail address: matthew.english@acadiau.ca (M.D. English).
Marine Pollution Bulletin xxx (2015) xxx–xxx
Contents lists available at ScienceDirect
Marine Pollution Bulletin
journal homepage: www.elsevier.com/locate/marpolbul
Please cite this article in press as: English, M.D., et al. Plastic and metal ingestion in three species of coastal waterfowl wintering in Atlantic Canada. Mar.
Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.05.063
Lakes (Free et al., 2014). To date, only one study has reported plas-
tic ingestion in a freshwater species, a small fish (Sanchez et al.,
2014); most published studies on plastic pollution in freshwater
systems report on availability and distribution of microplastics,
not on ingestion or frequency of occurrence in biota (e.g.,
Driedger et al., 2015). Importantly, few studies have examined
the incidence of anthropogenic debris in species that use both
coastal freshwater and marine habitats seasonally, despite that
many species (e.g., shorebirds/waders, waterfowl) typically breed
near freshwater sites but winter along the ocean.
The ingestion of plastics and metal has rarely been reported in
waterfowl species, except for species that live at sea (Provencher
et al., 2014a). In this paper, we provide the first report of plastic
and metal ingestion in two species of common waterfowl in
Atlantic Canada: the mallard (Anas platyrhynchos) and the
American black duck (Anas rubripes), both of which overwinter
along coastal marine sites but use a wide-range of freshwater habi-
tats as well. We also document the occurrence of plastic and metal
ingestion in common eiders (Somateria mollissima).
Common eider were collected off Newfoundland’s northeast
coast from 21 Dec 2013 to 17 January 2014 during the annual
sea duck hunt. Mallards were collected during the winters of
2014 and 2015 in a rural area in New Brunswick (a tidal creek)
and two rural areas in Nova Scotia (a tidal cove and a pond in a
farmer’s field). American black ducks were collected during the
winter of 2014 in rural, coastal, and freshwater areas in Nova
Scotia and New Brunswick, and in an urban pond in the city of
St. John’s, Newfoundland and Labrador (Fig. 1). Since the urban
and rural black ducks came from very different habitats, they were
treated separately.
Birds were frozen after collection and shipped to Acadia
University, where they were subsequently thawed and dissected.
The proventriculus and gizzard contents of all birds were examined
under a dissecting microscope for the occurrence of any anthro-
pogenic debris. Methods used were consistent with the interna-
tionally standardized approach for quantifying plastic ingestion
among seabirds (e.g., van Franeker et al., 2011). When found, deb-
ris was weighed to the nearest 0.1 mg, measured to the nearest
0.25 mm, classified, and photographed. Plastics were identified as
either user or industrial plastics, and user plastics were further cat-
egorized (i.e., sheet-like, foam-like, fragmented, thread-like, and
other).
We analysed 87 American black ducks (all adults; 43 female, 44
male), 13 mallards (all adults; seven female, six male) and 48 com-
mon eiders (32 females, 16 males: 26 adult, 10 juvenile, 12
unknown age) in this study. We did not test for an effect of age
or sex on debris ingestion as our incidence rates were too low.
The type of debris ingested by the waterfowl we examined con-
sisted of user plastics and small metal fragments (Fig. 2). Except
for one piece of rope 10 cm long and found in a mallard, all other
debris measured in the black ducks and mallards was 0.5–5 mm
long and 0.25–3 mm wide. The eiders examined contained a piece
of rope measuring 2 52 mm and a piece of metal measuring
12 10 mm that likely would have sunk to the benthos where
these birds forage.
There were no significant differences between the overall
amount of debris found in rural or urban American black ducks
(Fisher Exact test, p= 0.29). Of the 49 rural black ducks examined,
three had some form of debris (6.2%), while five of the 38 urban
black ducks contained some form of debris (13.2%). Plastic was
found in one rural black duck (2.0%), and in five (13.2%) urban
black ducks, but this difference was not statistically significant
(Fisher Exact test, p= 0.08). Metal was found in two rural black
ducks (4.1%), and was not found in any urban black ducks (0%),
but this difference was not statistically significant (Fisher Exact
test, p= 0.50). Due to there being no statistically significant differ-
ences in debris in these two groups of black ducks, these groups
were pooled for further analyses.
Of the 148 waterfowl examined, 17 (11.5%) contained anthro-
pogenic debris (plastic and metal combined), but the proportions
differed among species (Table 1). Debris was most common in mal-
lards (7/13, 53.8%), lower in American black ducks (8/87, 9.2%) and
lowest in common eiders (2/48, 4.2%;
v
2
2
= 20.0, p< 0.001). These
differences were attributable to mallards having significantly higher
occurrence of debris than the other species (Fisher Exact tests, both p
< 0.003); frequency of occurrence in black ducks and eiders was not
statistically different (p= 0.32).
Fig. 1. The sample sites used for this study. NB: New Brunswick, NS: Nova Scotia, NL: Newfoundland.
2M.D. English et al. / Marine Pollution Bulletin xxx (2015) xxx–xxx
Please cite this article in press as: English, M.D., et al. Plastic and metal ingestion in three species of coastal waterfowl wintering in Atlantic Canada. Mar.
Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.05.063
User plastic was present in 13 of the 148 (8.8%) waterfowl
examined, and again, the proportions differed among species.
Plastic was most common in mallards (6/13, 46.1%), lower in black
ducks (6/87, 8.9%), and lowest in common eiders (1/48, 2.1%;
G-test; G
2
= 13.1, p< 0.01). Again, these differences were attributa-
ble to mallards having significantly higher occurrence than the
other species (Fisher Exact tests, both p< 0.001); frequency of
occurrence in black ducks and eiders was not statistically different
(p= 0.42). Overall, proportions of the different types of debris were
low and similar across species (Table 2).
Metal was present in 7 of the 148 (4.7%) waterfowl examined.
Metal was most common in mallards (4/13, 30.8%), less common
in black ducks (2/87, 2.3%), and lowest in common eiders (1/48,
2.1%; G
2
= 8.2, p< 0.05). Mallards had significantly higher occur-
rence than the other species (Fisher Exact tests, both p< 0.01); fre-
quency of occurrence in black ducks and eiders was not
statistically different (p= 1.00). Most of the ingested metal was
small aluminum fragments that appeared to be compacted in the
gizzard. None of the ingested metal was lead or steel shot pellets.
Our results on the incidence of plastic and metal consumed by
wintering waterfowl of Atlantic Canada highlight the need to
expand our sampling and considerations of the potential effects
of anthropogenic debris on wildlife. We recommend that any study
examining the gut contents of marine or freshwater organisms
adopt a screening method for plastics and other debris similar to
that of van Franeker and Meijboom (2002). In that study on north-
ern fulmars (Fulmarus glacialis), they evaluated sample variability,
and for their situation concluded that P40 individuals were rec-
ommended for a reliable sample average, and that with such
annual samples, depending on the type of plastic considered, 4–
8 years were needed to reliably assess trends. Our mallard sample
size (n= 13) was small, and we only had one year of collection data
for all species in this study, thus any conclusions drawn from this
paper should be carefully considered. As the three species studied
were harvested species, establishing collection points for digestive
tracts of harvested birds through the hunting season could be
essential in monitoring plastic and other debris ingestion in these
waterfowl.
There has been much research and increased monitoring of
plastic in marine organisms over the past three decades (e.g.,
Laist, 1997; van Franeker et al., 2011; Avery-Gomm et al., 2012;
Provencher et al., 2014a,b; van Franeker and Law, 2015). The focus
on marine species is presumably a consequence of industrial plas-
tics being transported (and spilled) on the oceans, various forms of
garbage ending up in the ocean through waste management prac-
tices, flushing off the land in rivers, or movement by wind, and
some marine wildlife have been debilitated or killed through deb-
ris ingestion (Young et al., 2009). Although anthropogenic debris
clearly occurs in freshwater systems (e.g., Driedger et al., 2015),
it has generally not been considered as a ‘‘contaminant’’ that ends
up being a concern for wildlife. This may not be the case.
In their summary of the incidence of plastic debris in marine
birds of Canada, Provencher et al. (2014b) found that three of 17
species in Atlantic Canada had high incidences of debris ingestion
(petrels; 72–93%), but the other 14 species that they sampled had
lower incidences of 0–26%, a slightly higher rate than observations
reported here (8.8%). Marine species (especially albatrosses and
petrels), most of which consume fish, zooplankton, or squid, are
thought to mistake bits of debris for prey, or possibly ingest plastic
when they consume small fish that have, in turn, eaten plastic.
Common eiders are primarily benthic molluscivores foraging near-
shore in waters <20 m deep (Goudie et al., 2000), and we conclude
that eiders must be consuming debris that falls to the seafloor in
areas rich in benthic molluscs, perhaps incidentally while eating
molluscs.
Mallards and American black ducks are mainly herbivores
(notably eating seeds, including leftovers from agricultural prac-
tices), but also eat small invertebrates (pelagic and benthic mol-
luscs, worms and crustaceans) from brackish shallow waters,
riparian zones, or on land (Longcore et al., 2000; Drilling et al.,
2002). Our sampling was conducted principally in the winter,
meaning most freshwater habitats for rural mallards and
American black ducks were ice-covered, although the urban site
in St. John’s was open. For rural mallards and black ducks, they
were either foraging in fields where snow cover was minimal
and agriculture waste grains were exposed, or along brackish
Fig. 2. Photograph of some of the user plastic (top rows), and compacted metal
fragments (bottom rows) found in the stomachs of MALL (mallards) and COEI
(common eiders). Note: None of the debris found in American black duck stomachs
was saved, so it was not photographed.
Table 1
Sample sizes, bird mass ± SE (g), the frequency, mean number of pieces ± SE, and mean mass of debris ingested ± SE (mg) for plastic, metal, and any debris. Means represent all
birds studied, not just the birds with ingested debris. ABDU = American black duck; MALL = mallard; COEI = common eider.
Species nMean bird mass ± SE (g) Ingestion frequency (%) Mean pieces of debris/bird ± SE Mean mass of debris/bird ± SE (mg)
Plastic Metal Any debris Plastic Metal Any debris Plastic Metal Any debris
ABDU 87 1148 ± 16 6.9 2.3 9.2 0.07 ± 0.03 0.02 ± 0.02 0.09 ± 0.03 0.01 ± 0.005 0.04 ± 0.03 0.06 ± 0.03
MALL 13 1104 ± 28 46.1 30.8 53.8 1.00 ± 0.38 1.08 ± 0.55 2.08 ± 0.80 32.11 ± 30.66 2.00 ± 0.56 33.24 ± 30.58
COEI 48 1707 ± 28 2.1 2.1 4.2 0.02 ± 0.02 0.02 ± 0.002 0.04 ± 0.03 3.56 ± 3.56 1.73 ± 1.73 5.28 ± 3.92
Table 2
The amount of different types of plastic ingested in the three species studied.
ABDU = American black duck; MALL = mallard; COEI = common eider.
Species Industrial
plastic
User plastic
Thread-
like
Sheet-
like
Fragmented Foam-
like
Others
ABDU 0 0 2 2 2 0
MALL 0 2 2 6 1 2
COEI 0 1 0 0 0 0
M.D. English et al. / Marine Pollution Bulletin xxx (2015) xxx–xxx 3
Please cite this article in press as: English, M.D., et al. Plastic and metal ingestion in three species of coastal waterfowl wintering in Atlantic Canada. Mar.
Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.05.063
coastlines which were not frozen over, such as the large macrotidal
areas of the Bay of Fundy. The urban black ducks were collected
from a city pond, where they fed mainly on handouts from the
public (bread, corn), and likely did not leave the pond through
the winter to forage along the coast (GJ Robertson, pers. observ.).
Nonetheless, the urban black ducks ingested similar proportions
of debris as wild, rural ducks.
We suggest two possible explanations as to how these water-
fowl ingested debris. First, the waterfowl ingested debris in remote
freshwater habitats during the breeding season and fall migration,
or secondly and more likely, debris was ingested in coastal winter-
ing areas. Residence times for ingested debris particles are
unknown, and we cannot explicitly relate the debris ingestion to
the areas which the waterfowl were collected. In either case, it sug-
gests that either the freshwater breeding habitats or the marine
coastal wintering habitats in which these birds were feeding were
polluted with anthropogenic debris, which are consumed by these
organisms. The mallards and American black ducks were either
actively ingesting plastic and metal because it looked like food
items, or as they strained materials while feeding in the shallows,
they were unable to discern plastic and metal from items that they
sought (e.g., small molluscs or crustaceans) and consumed the deb-
ris by accident.
Jambeck et al. (2015) reported that if waste management prac-
tices do not improve on a global scale, the amount of plastic enter-
ing the ocean will increase by an order of magnitude by 2025. A
similar analysis for plastic inputs to freshwater environments is
not yet available, but we suggest that plastic contamination in
freshwater systems may become a serious conservation issue, as
is the overlooked issue of birds foraging along marine coastlines.
Our baseline data provide alarming insights that these two habitats
may prove as problematic as pelagic areas for birds foraging and
consuming plastic debris.
Acknowledgements
Financial support for this project was provided by the Black
Duck Joint Venture, Environment Canada, the Natural Sciences
and Engineering Research Council of Canada, and the Canada
Research Chairs program. The hunters on the northeast coast of
Newfoundland made the common eider sample possible.
Collection and possession of waterfowl were made under appropri-
ate permits from Acadia University (Animal Care Permit 02-14)
and the Canadian Wildlife Service (Banding Permit 10694,
Scientific Permits ST2785 and SS2505).
Appendix A
Details on each bird that ingested anthropogenic debris in this
study. ABDU = American black duck; MALL = mallard;
COEI = common eider (data on all birds, including those that did
not ingest plastic, are available from the authors).
Species Location Sex Age nplastic
total
nsheet-like
plastic
nthread-like
plastic
nfoam-like
plastic
nfragmented
plastic
nother
plastic
nmetal
pieces
ABDU 43°28
0
10 N F Adult 1 1 0 0 0 0 0
64°45
0
11 W
ABDU 47°31
0
24 N F Adult 1 0 0 0 1 0 0
52°45
0
12 W
ABDU 47°31
0
24 N M Adult 1 0 0 1 0 0 0
52°45
0
12 W
ABDU 47°31
0
24 N M Adult 1 0 0 0 1 0 0
52°45
0
12 W
ABDU 45°53
0
41 N M Adult 0 0 0 0 0 0 1
64°20
0
20 W
ABDU 45°53
0
41 N M Adult 0 0 0 0 0 0 1
64°20
0
20 W
ABDU 47°31
0
24 N F Adult 1 1 0 0 0 0 0
52°45
0
12 W
ABDU 47°31
0
24 N M Adult 1 0 0 1 0 0 0
52°45
0
12 W
MALL 45°53
0
41 N F Adult 2 2 0 0 0 0 0
64°20
0
20 W
MALL 45°53
0
41 N F Adult 1 0 1 0 0 0 0
64°20
0
20 W
MALL 45°53
0
41 N F Adult 3 0 1 1 0 1 4
64°20
0
20 W
MALL 45°53
0
41 N M Adult 0 0 0 0 0 0 1
64°20
0
20 W
MALL 45°53
0
41 N F Adult 4 0 0 0 4 0 3
64°20
0
20 W
MALL 45°53
0
41 N M Adult 1 0 0 0 0 1 6
64°20
0
20 W
MALL 44°58
0
07 N F Adult 2 0 0 0 2 0 0
64°08
0
27 W
COEI 49°43
0
N F Juvenile 1 0 1 0 0 0 0
54°32
0
W
COEI 49°43
0
N F Unknown 0 0 0 0 0 0 1
54°32
0
W
4M.D. English et al. / Marine Pollution Bulletin xxx (2015) xxx–xxx
Please cite this article in press as: English, M.D., et al. Plastic and metal ingestion in three species of coastal waterfowl wintering in Atlantic Canada. Mar.
Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.05.063
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Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.05.063
  • ... lobatus), which eat freshwater zooplankton , also consume plastic debris (Day et al., 1985; Moser and Lee, 1992). English et al. (2015) examined mallard (Anas platyrhynchos), American black duck (A. rubripes), and common eider (Somateria mollissima) wintering in Atlantic Canada, and found an 11.5% prevalence of plastics in 140 birds. ...
    ... Therefore our microbead findings should be interpreted cautiously, because waterfowl are likely ingesting them. Our results on the prevalence of anthropogenic debris ingestion in waterfowl indicate that it is occurring at similar rates to historic trends in some marine birds (Laist, 1997) and current rates in some freshwater birds (English et al., 2015). Future studies examining gut contents of freshwater birds should adopt a screening method for anthropogenic debris similar to that of van Franeker and Meijboom (2002) and van Franeker (2004), and collection points for examination of harvested bird digestive tracts should be established. ...
    ... Our study adds to the limited but mounting evidence (Moser and Lee, 1992; Denuncio et al., 2011; Besseling et al., 2014; Sanchez et al., 2014; English et al., 2015; Moseman, 2015; Fischer et al., 2016 ) that anthropogenic debris may be a threat to aquatic biota in freshwater environments . We found debris in 55% of species collected from freshwater habitats in Canada, including from remote sites as far as 63°N. ...
  • ... Previous reports showing the presence of plastics in the guts of freshwater waterbirds are scarce and among the species analyzed the highest plastic prevalence has been found in seabirds (Provencher et al., 2015). However, English et al. (2015) have discovered a high prevalence of plastic in some waterfowl species, including the mallard that presented plastic in 46.1% of the in- dividuals analyzed, and therefore clearly showed that bird species using freshwater environments are also exposed to ingest plastic debris. Since the use of plastic in modern agriculture is widely distributed in the world this could be an overlooked emerging problem deserving further attention in other areas where wetlands are located in the middle of wide agricultural fields. ...
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  • ... Previous reports showing the presence of plastics in the guts of freshwater waterbirds are scarce and among the species analyzed the highest plastic prevalence has been found in seabirds (Provencher et al., 2015). However, English et al. (2015) have discovered a high prevalence of plastic in some waterfowl species, including the mallard that presented plastic in 46.1% of the in- dividuals analyzed, and therefore clearly showed that bird species using freshwater environments are also exposed to ingest plastic debris. Since the use of plastic in modern agriculture is widely distributed in the world this could be an overlooked emerging problem deserving further attention in other areas where wetlands are located in the middle of wide agricultural fields. ...
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    Background: While the use of plastic materials has generated huge societal benefits, the ‘plastic age’ comes with downsides: One issue of emerging concern is the accumulation of plastics in the aquatic environment. Here, so-called microplastics (MP), fragments smaller than 5 mm, are of special concern because they can be ingested throughout the food web more readily than larger particles. Focusing on freshwater MP, we briefly review the state of the science to identify gaps of knowledge and deduce research needs. State of the science: Environmental scientists started investigating marine (micro)plastics in the early 2000s. Today, a wealth of studies demonstrates that MP have ubiquitously permeated the marine ecosystem, including the polar regions and the deep sea. MP ingestion has been documented for an increasing number of marine species. However, to date, only few studies investigate their biological effects. The majority of marine plastics are considered to originate from land-based sources, including surface waters. Although they may be important transport pathways of MP, data from freshwater ecosystems is scarce. So far, only few studies provide evidence for the presence of MP in rivers and lakes. Data on MP uptake by freshwater invertebrates and fish is very limited. Knowledge gaps: While the research on marine MP is more advanced, there are immense gaps of knowledge regarding freshwater MP. Data on their abundance is fragmentary for large and absent for small surface waters.Likewise, relevant sources and the environmental fate remain to be investigated. Data on the biological effects of MP in freshwater species is completely lacking. The accumulation of other freshwater contaminants on MP is of special interest because ingestion might increase the chemical exposure. Again, data is unavailable on this important issue. Conclusions: MP represent freshwater contaminants of emerging concern. However, to assess the environmental risk associated with MP, comprehensive data on their abundance, fate, sources, and biological effects in freshwater ecosystems are needed. Establishing such data critically depends on a collaborative effort by environmental scientists from diverse disciplines (chemistry, hydrology, ecotoxicology, etc.) and, unsurprisingly, on the allocation of sufficient public funding.