2014 MARINE DEBRIS INGESTION REPORT 

Ingestion

Occurrence and Health Effects of 

Anthropogenic Debris Ingested by 

Marine Organisms

2014 NOAA Marine Debris Program Report 
April 2014

National Oceanic and Atmospheric Administration

National Ocean Service

National Centers for Coastal Ocean Science – Center for Coastal Environmental Health and Biomolecular Research

219 Fort Johnson Road

Charleston, South Carolina 29412

Office of Response and Restoration

NOAA Marine Debris Program

1305 East-West Hwy, SSMC4, Room 10239

Silver Spring, Maryland 20910

Cover photo courtesy of the United States Fish and Wildlife Service/ Pete Leary.

For citation purposes, please use: 

National Oceanic and Atmospheric Administration Marine Debris Program. 2014 Report on the Occurrence and Health Effects of Anthropogenic Debris Ingested 

by Marine Organisms. Silver Spring, MD. 19 pp

For more information, please contact: 

NOAA Marine Debris Program

Office of Response and Restoration

National Ocean Service

1305 East West Highway

Silver Spring, Maryland 20910

301-713-2989

www.MarineDebris.noaa.gov
Acknowledgements

The National Oceanic and Atmospheric Administration (NOAA) Marine Debris Program would like to acknowledge Jared Ragland for conducting this research, 

and Courtney Arthur and Jason Paul Landrum for providing guidance and support throughout this process. Special thanks go to Mike Fulton (National Centers for 

Coastal Ocean Science – Center for Coastal Environmental Health and Biomolecular Research) and Marie E. DeLorenzo (National Centers for Coastal Ocean Science 

– Center for Coastal Environmental Health and Biomolecular Research) for reviewing this paper and providing helpful comments. An additional thank you goes to 

John Hayes (NOAA National Ocean Service, National Centers for Coastal Ocean Science) for a copy/edit review of this report and Asma Mahdi for design and layout. 

Funding for this project was provided by the NOAA Marine Debris Program.

This publication does not constitute an endorsement of any commercial product or intend to be an opinion beyond scientific or other results obtained by the 

National Oceanic and Atmospheric Administration. No reference shall be made to NOAA, or this publication furnished by NOAA, to any advertising or sales 

promotion which would indicate or imply that NOAA recommends or endorses any proprietary product mentioned herein, or which has as its purpose an interest 

to cause the advertised product to be used or purchased because of this publication.
Executive Summary 1

Introduction 2

What we know 3

The extent of the issue 3

Where does marine debris accumulate? 4

Affected Wildlife 5

Microbes and Invertebrates 5

Fishes 6

Sea Turtles 7

Birds 7

Marine Mammals 9

Health Impacts 10

Physical Effects 10

Lacerations and Lesions 10

Blockage 10

Retention 11

Physiological Effects 12

Toxicants 12

What we need to learn 13

Conclusions 15

Cited References 16

TABLE OF CONTENTS
2014 MARINE DEBRIS INGESTION REPORT 

EXECUTIVE SUMMARY

Pollution of the marine ecosystem with anthropogenic debris 

has been an acknowledged issue for some time. Such debris 

can be ingested by marine organisms either directly or through 

the consumption of debris-contaminated prey. Debris ingested 

by marine organisms is predominantly plastic; whether from 

industrial, recreational, or personal care products. These items 

range in size from microscopic beads to large sheets over a meter 

long and can persist in the environment for decades. The research 

efforts to date have sought to characterize the types, sources, 

and impacts of such ingestible debris, yet the overall effects of 

ingesting such items remain poorly understood.

Globally, many types of marine organisms—from invertebrates 

and fish to turtles and whales—have been confirmed to ingest 

debris. Direct health impacts include dietary dilution, gut 

blockage, starvation, laceration, ulceration, and secondary 

infection. More subtle effects such as hormone disruption, 

reproductive impairment, immune system impairment, and 

disease development also have been postulated as likely results, 

but the role of debris ingestion in disease is poorly understood. 

Other aspects, such as the ability of plastic to concentrate 

persistent pollutants, such as PCBs and pesticides, are only now 

being investigated. Ingestion of debris affects the entire food web, 

and while the larger questions of ecological impact are difficult 

to address experimentally, such studies will provide the most 

valuable information toward understanding the issue.

The likelihood of any given organism ingesting debris is largely 

driven by debris concentration and feeding behavior. Buoyant 

plastic debris is concentrated by physical factors in many of the 

same areas that stimulate the base of the food web and serve as 

feeding grounds for many marine organisms. This combination 

likely enhances the chances of non-food items being ingested.

Progress has been made to characterize the types of marine 

debris available for ingestion, its sources, where it collects in 

the environment, and the physical forces driving its availability. 

However, many aspects of the health and ecological impacts from 

ingestible debris are poorly understood. Key areas where answers 

are needed include (but are not limited to):

updated estimates of ingestion by sea turtles and marine 

mammals;

better tools for detecting and quantifying debris;

assessments on the role of debris in altering uptake, 

distribution, and effects of toxic chemicals;

assessments of the chronic health effects caused by debris (as 

opposed to acute health impacts);

assessments of the trophic transfer of debris and associated 

chemicals between different levels in food webs; and

assessments of the population- and community-level effects of 

debris.

In addition, targeted science from interconnected disciplines (e.g., 

physical oceanography, aquatic toxicology, materials science, and 

veterinary science) is needed to identify the factors associated with 

ingestible debris that are most likely to impair the health of marine 

ecosystems, and hence are the most useful to understand to guide 

the development of effective policies.

This report reviews the state of the science regarding the 

occurrence and known health effects of marine debris. A broadlevel synthesis is provided. The presence and accumulation of 

ingestible anthropogenic debris in the marine environment, 

records of ingestion for a wide range of organisms, as well as 

observed and postulated health effects from field and laboratory 

studies are discussed. Knowledge gaps in the literature are 

identified, and suggestions for how they may be addressed are 

provided.

Please report stranded or entangled marine mammals and sea turtles by calling the stranding network member for 

your area (U.S. only). Hotline numbers are listed online at http://www.nmfs.noaa.gov/pr/health/stranding.htm.
2014 MARINE DEBRIS INGESTION REPORT 

INTRODUCTION

Anthropogenic debris in the marine 

environment is an acknowledged global 

issue with broad impacts. Millions of tons 

of debris enter the oceans each year from 

trash, damaged fishing gear, or shipping 

accidents. While far from every animal will 

encounter debris over its lifespan, the sheer 

amount of debris collecting on beaches, in 

ocean gyres, and on the ocean floor suggests 

that many types of marine wildlife cannot 

avoid encountering debris. The majority 

of debris items are small enough to be 

ingested by wildlife, and ingestion has been 

confirmed from the ocean surface to great 

depths. Whether debris is confused with, or 

accidentally ingested alongside, preferred food 

sources, debris is ingested by what increasingly 

appears to be nearly all types of marine 

organisms.

Kenyon and Kridler first turned systematic 

attention to the ingestion of marine debris in 

1969, reporting that 74% of fledgling Laysan 

Albatross (Diomedea immutabilis) carcasses 

from Hawai’i, USA, had plastic debris (e.g., 

bottle and tube caps, toys, polyethylene 

bags, etc.) in their gut. Two articles followed 

shortly in the journal Science (Carpenter 

et al. 1972, Carpenter and Smith 1972) 

reporting the presence of polystyrene (a type 

of plastic) spherules in the coastal waters of 

New England, USA, and on the surface of the 

Sargasso Sea in the North Atlantic Ocean. 

These reports highlighted the capacity for 

organisms to ingest plastic debris particles, as 

well as the bacteria and plankton attached to 

debris. The authors speculated that attachment 

by encrusting organisms could make the 

particles more attractive for ingestion, and 

noted that polychlorinated biphenyls (PCBs, 

a known persistent organic pollutant) were 

associated with the plastic particles.

Over the last four decades, increasing 

attention has been paid to the source, 

distribution, and fate of marine debris—the 

scale of the problem—while the effects of 

ingesting debris have only recently been 

investigated. As reports of dead “charismatic 

megafauna” (e.g., whales, seals, sea turtles, 

etc.) that ingested large amounts of marine 

debris became more frequent, public interest 

in the issue rose and more targeted studies 

were conducted. Despite the relatively recent 

interest, reports over the last two decades on 

the incidence and effects of ingested debris 

have been described by Gregory (2009) as 

“voluminous and often repetitive.” 

This review seeks to summarize the “state 

of the science” regarding the effects of ingested 

marine debris and highlight areas where 

knowledge is currently lacking.

2

“... the sheer amount 

of debris collecting 

on beaches, in 

ocean gyres, and 

on the ocean floor 

suggests that many 

types of marine

wildlife cannot avoid 

encountering with 

debris.”
WHAT WE KNOW

The extent of the issue

To understand the risks associated with 

ingested marine debris, it is necessary to 

understand the extent and distribution of 

materials encountered by marine organisms. 

Many studies have examined the incidence, 

sources, factors influencing distribution, 

and trends in marine debris on seashores 

and estuaries (Ribic et al. 1989, 2010, 2011, 

2012a, 2012b; Thornton and Jackson 1998; 

Morishige et al. 2007; Rosevelt et al. 2013), 

sea floor (Moore and Allen 2000; Bauer et al.

2008; Wei et al. 2012), and open water (Mace 

2012; Howell et al. 2012 and sources therein; 

Eriksen et al. 2013) of the United States. These 

studies indicate significant regional differences 

in type, source, and abundance. These results 

are now close to being comparable with other 

countries due to long-term monitoring efforts 

targeting the same methods to assess debris 

(Cheshire et al. 2009).

Due to spatial variability of marine debris, 

efforts to detect, characterize, and quantify the 

extent of marine debris have increased over 

the last decade (see Mace 2012 and sources 

therein). Several techniques leveraging recent 

advances in technology are being explored 

to expand the knowledge of which areas 

accumulate marine debris. These include 

airborne sensors (Kataoka et al. 2012; Veenstra 

and Churnside 2012), satellite imagery (Pichel 

et al. 2012), and webcams (Kataoka et al.

2012), as well as numerical models predicting 

likely accumulation locations under both 

normal (Maximenko et al. 2012; Lebreton et 

al. 2012; Pichel et al. 2012; Potemra 2012) and 

storm conditions (Bagulayan et al. 2012; Miller 

and Brennan 2012; Lebreton and Borrero 

2013). Additionally, statistical techniques have 

been refined that can tie field observations 

of debris with their source(s) (Tudor et al.

2002, Ribic et al. 2010, 2011, 2012). New 

detection techniques can better characterize 

microplastics in sediment (Harrison et 

al 2012) and should be investigated for 

applicability to the water column. Studies 

have also begun to characterize microplastic 

pollution in large water bodies of the U.S. 

(Eriksen et al. 2013).

Several studies outside the United States 

have also examined the sources, distribution, 

and transport of marine debris (Galil et al.

1995; Galgani et al. 1995, 1996; Gregory and 

Ryan 1997; Mfilinge et al. 2005; Shiomoto and 

Kameda 2005; Quintela et al. 2012; Thiel et al.

2013). While these are not direct observations 

within U.S. waters, the dynamics of debris 

distribution and fate are the same, and these 

observations can inform our expectations 

in areas where oceanographic processes 

are similar. These studies are important to 

understanding ingestion of marine debris 

because the overwhelming majority of 

ingestible marine debris is plastic, due to its 

ubiquitous use in manufacturing since the 

1970s (see Derraik 2002 and sources therein). 

While many species will ingest non-plastic 

debris (e.g., hooks and line, metallic trash, 

etc.), ingestible plastic marine debris has 

become a serious ecological issue affecting 

hundreds of marine species (SCBD & STAP 

2012). Certain characteristics (e.g., color, size, 

shape) of debris items can stimulate feeding 

behaviors. Derraik (2002) and more recently 

Hammer et al. (2012) reviewed the types of 

debris and potential hazards from that debris 

in marine wildlife. Annual production of 

plastics topped 265 million tons in 2010 with 

an expected 40% increase in consumption per 

capita worldwide by 2015 (Hammer et al. 2012 

and sources therein). It has been estimated 

that 10% of globally produced plastics in 1997 

ended up as plastic oceanic waste (UNEP 

2005). If these estimates are correct and these 

trends continue, an estimated 38 million tons 

of debris will enter the marine environment in 

2015 alone. Approximately half of all produced 

plastics are buoyant and collect mainly at the 

water’s surface, although surface observations 

may be underestimating the total amount 

available for ingestion given the effect of winddriven mixing in the water column, which may 

push debris items below the surface (Kukulka 

et al. 2012). Additionally, plastics become 

brittle over time and fragment (reviewed 

by Andrady 2011). Physical and chemical 

processes can degrade some types of plastic in 

as little as a few weeks, while other pieces last 

for decades. Pieces that may be too large to be 

consumed by organisms when initially thrown 

away may gradually degrade, becoming 

smaller and more likely to be ingested. This 

means most plastic debris is ingestible by 

marine life over the course of its multi-decade 

lifetime at sea.

UNEP estimated that 

10% of globally 

produced plastics in 

1997 ended up in the 

ocean. If these estimates 

continue, potentially 

38 million tons

of debris will enter the 

marine environment in 

2015 alone. 
Debris from the fishing industry (e.g., 

floats, sinkers, hooks, monofilament line, 

lures) generally appears to be ingested by 

species in close proximity to fishing activities 

(Macfadyen et al 2009). Due to its buoyant 

nature, however, lower density debris (e.g., 

foamed plastics, bags, wrappers, etc.) can be 

transported extremely long distances by wind, 

wave, and currents. It has been estimated in 

the North Sea that, eventually, 15% of plastic 

debris washes ashore, 15% floats at the surface, 

and 70% will sink to the sea floor over an 

extended amount of time (Barnes et al., 2009). 

Storms can greatly affect the location of plastic 

debris in the short term (Moore et al. 2002).

Even without extreme weather events, the 

physical processes of the ocean (e.g., wind, 

waves, salinity gradients, and currents) play a 

large role in where debris accumulates in the 

ocean and along coastlines. Buoyant plastic 

debris remains at sea for an extended period 

of time and becomes entrained in dominant 

surface currents. This often results in larger 

amounts of debris accumulating in ocean 

gyres over time—large areas where currents 

swirl, forming regions from which buoyant 

items cannot easily escape. Trash from the 

2011 Tohoku tsunami in Japan was tracked 

along one such path and was headed toward 

the North Pacific subtropical gyre (Bagulayan 

et al. 2012). This area is commonly known 

as “Great Pacific Garbage Patch” due to the 

gyre’s ability to collect a very large proportion 

of floating trash entering the North Pacific 

Ocean. Moore et al. (2001) noted that while 

plankton numerically outnumbered plastic 

in this region by a factor of almost five, the 

mass of plastic debris was almost six times 

that of the plankton. In reality, while such 

areas contain high concentrations of debris for 

the open ocean, floating debris is constantly 

moving and dispersed along the water’s surface 

or to shallow depths. Such zones also shift 

location seasonally, making them difficult to 

study.

Plastics transported by surface currents 

will also reach higher concentrations in 

areas where dominant currents meet (i.e., 

convergence zones); these are zones where 

nutrient sources are plentiful, stimulating 

growth of algae and phytoplankton (plants) 

at the base of the complex marine food web. 

As areas with readily available food sources, 

they attract marine life across the food web, 

from zooplankton to large cetaceans. Higher 

debris concentrations are then located in 

areas where animals are most likely to forage, 

incidentally increasing the likelihood of 

encounters between wildlife and ingestible 

debris. Salinity fronts in estuarine systems 

can also serve as a similar barrier to debris 

entering the ocean from riverine systems and 

are likewise common foraging grounds for the 

same reasons as convergence zones (Acha et 

al. 2003).

Buoyant plastic debris gradually sinks as 

physical degradation processes increase the 

density of the plastic or as organisms decrease 

its buoyancy by colonizing debris items. Algae 

(Maso et al. 2003), bacteria (Webb et al. 2009, 

Zettler et al. 2013), and barnacles (Minchin 

1996) have all been studied for their impact 

on buoyancy, each with a slightly different 

effect. In reality, it is rare to observe only a 

single species attached to debris pieces, and 

effects can vary greatly between pieces. Plastics 

with encrusting organisms attached may also 

become more attractive to grazing fishes or 

invertebrates, and thus contribute to higher 

grazing rates on debris items (Carson 2013). 

The increased presence of such grazing species 

at the ocean surface also makes birds more 

likely to forage in such areas; this often means 

birds will peck at, and ingest, plastic at sea as 

well as on beaches (Cadée 2002).

As debris sinks through the water column, 

it becomes available to different species living 

at depth. While some species may be present 

in areas or depths where debris is also present, 

unless those species are actively feeding, it 

is unlikely they will ingest debris from that 

location. Ingestion may still occur indirectly, 

however, if prey items have ingested and 

retained debris. Some species feed in the 

middle of the water column, such as airbreathing divers (e.g., seals, walrus, penguins, 

baleen whales) and mid-water residents (e.g., 

sharks, squid, tuna). If enough encrusting 

organisms are removed from the debris, the 

debris may once again rise to the surface and 

the entire process can repeat. Eventually, it will 

sink to the sea floor and become available for 

another community to ingest (e.g., shrimps, 

crabs, echinoderms). Although ingestion in 

the deep ocean has been confirmed by several 

studies, much is still unknown regarding the 

distribution and ingestion of debris by benthic 

and deep water organisms.

Where does marine debris accumulate?

A map of the Eastern and Western 

Garbage patches. These regions have 

higher debris concentrations because of 

ocean circulation patterns.
2014 MARINE DEBRIS INGESTION REPORT 

Affected Wildlife

To date, more than 660 marine 

species (SCBD & STAP 2012) have 

been confirmed to be affected by 

marine debris, and the number 

is likely to increase with future 

studies. While some are limited to 

other impacts (e.g., entanglement 

and “ghost fishing”), a significant 

majority have been confirmed to 

ingest marine debris, primarily 

plastics. The amount and type 

of ingested debris often relates 

directly to the species’ foraging 

behavior. Passive feeders (i.e., filter 

and deposit feeders) ingest debris 

(mainly microplastics) with food. 

Active feeders (i.e., those searching 

for and capturing mobile prey) 

ingest debris not only incidentally 

while feeding, but also any debris 

ingested by their prey if the prey 

is taken whole. Some species 

are able to expel debris without 

passing it fully into the digestive 

system, while debris is also able 

to pass completely through the 

digestive system over an extended 

period of time for many species. 

The ability to expel debris once 

ingested is highly dependent on 

the anatomy and physiology of 

the organism, as well as the type 

of debris. It is apparent that the 

likelihood of debris ingestion is 

largely determined by the overlap 

of debris accumulation and 

foraging behavior. If an organism 

preferentially feeds in a nonselective manner in areas where 

debris accumulates, ingestion of 

debris becomes much more likely.

Microbes 

and Invertebrates

Microorganisms are known to colonize 

debris and form biofilms (Bonhomme et al.

2003; Webb et al. 2009), but the ways in which 

this affects the debris and the base of the food 

web is poorly understood (Harrison et al.

2011). Ingestion of microscale plastic debris 

in the wild has been confirmed for a wide 

array of invertebrates, including: amphipods 

(Thompson et al. 2004), barnacles (Goldstein 

and Goodwin 2013), lobster (Murray and 

Cowie 2011), sea cucumbers (Graham and 

Thompson 2009), and zooplankton (Cole 

et al. 2013), among others. Furthermore, 

the presence of debris on soft bottom areas 

appears to stimulate settling and colonization 

by invertebrates (Katsanevakis et al. 2007; 

Renchen and Pittman in Clark et al. 2012). 

This likely causes sea life to congregate in 

areas with debris, increasing the chances 

and frequency of debris ingestion. Sea 

cucumbers appear to preferentially select 

for plastic fragments while feeding (Graham 

and Thompson 2009), and this selectivity 

is not likely to be limited to one type of 

deposit feeder. Invertebrates not only ingest 

microscopic plastic debris, but they can also 

facilitate debris degradation. For example, 

some invertebrates bore into Styrofoam floats, 

which accelerates fragmentation and produces 

enormous amounts of microplastic debris. A 

single isopod burrow can generate thousands 

of such particles, while a colony can generate 

millions (Davidson 2012).

5
2014 MARINE DEBRIS INGESTION REPORT 

Fishes

Ingestion of debris by bony fishes and 

sharks has not historically been as widely 

reported as ingestion by birds, mammals, 

and turtles, although the attraction of fish 

to man-made objects is the underpinning of 

artificial reef and fish aggregation programs. 

Planktivorous fishes eat in areas where their 

food source and buoyant plastic debris are 

often mixed together. Boerger et al (2010) 

noted that approximately 35% of fishes had 

ingested types of debris consistent with that 

in the water from which they were feeding. 

Even when items are not ingested whole, 

Carson (2013) noted that approximately 

16% of inspected debris items showed signs 

of attack by a wide variety of fishes, with a 

preference for cylindrical shapes of blue or 

yellow color, indicating fishes were confusing 

debris for possible prey or exploring it for 

edibility. Recent studies from around the 

world have shown relatively consistent results; 

36% of fish in the English Channel (Lusher 

et al 2013), 18–33% of marine catfish from 

Brazil estuaries (Possatto et al 2011), and 19% 

of pelagic piscivorous fishes from the North 

Pacific Central Gyre (Choy and Drazen 2013) 

ingested debris. Even in areas of lower debris 

accumulation, 5% of fish in the relatively 

unpolluted northern areas of the North Sea 

(Foekema et al 2013), and deep-water species 

in the Mediterranean (Anatasopoulou et al 

2013) ingested plastic debris. These findings 

suggest a relationship between foraging 

behavior, location and type of debris, area 

of origin, and aggregation forces, although a 

larger comparative study is needed to confirm 

this. It is likely that as fishes become larger 

and more selective in their prey items, they 

consume less debris incidentally.

Sharks are a diverse group of very small 

to very large predatory fishes and have a 

range of feeding behaviors. An assessment 

of stomach contents from sharks caught in 

beach protection nets in South Africa found 

a relatively low frequency of debris ingestion 

(<0.5% of over 15,600 individuals comprising 

fourteen large shark species from 1978–2000; 

Cliff et al 2002). Most sharks ingest items 

similarly to other fishes, mainly plastic 

fragments and fisheries-related items, such as 

monofilament line and hooks. Tiger sharks 

(Galeocerdo cuvier) are often considered the 

“goats of the sea” and will ingest nearly any 

item encountered, anecdotally ingesting tin 

cans, chunks of rubber, and even license plates. 

Cliff et al (2002) found tiger sharks had by 

far the highest frequency of ingestion among 

species (7.5%, almost ten times higher than 

the other 13 shark species in the study). Tiger 

sharks were roughly of the same size and 

oceanographic distribution as other species 

examined in the study, again indicating 

feeding behavior as the primary driver of 

whether or not debris is commonly ingested 

by fishes.

A cluster of macro and mico plastic debris accumulates at the ocean’s surface 

in Hawaii’s Hanauma Bay. 

Credit: NOAA PIFSC

6
Reports of sea turtles ingesting marine 

debris are numerous and consumed debris 

has been implicated in nutrient deficiency 

(McCauley and Bjorndal 1999). Geography, 

species, year, and life stage all appear to affect 

the frequency with which turtles ingest debris. 

Ingestion has been confirmed in all seven 

species of sea turtle, though ingestion by 

flatback turtles (Natator depressus) has been 

reported only once. This could be due to a 

lack of systematic studies or that the flatback’s 

range, restricted to the region around northern 

Australia, is in an area of relatively very little 

debris accumulation (Lebreton et al. 2012). 

A recent review examined 37 studies from 

around the globe published between 1985 

and 2012 (Schuyler et al. 2013). The authors 

concluded that green (Chelonia mydas) 

and leatherback (Dermochelys coriacea) sea 

turtles in all regions are ingesting plastic 

debris more often than in years past, and that 

hawksbill turtles (Eretmochelys imbricata) were 

overall most likely to ingest debris (~47% of 

individuals with plastic in the gut). Ingestion 

frequencies ranged from 0–100%, likely 

highly dependent upon location and feeding 

behavior. Their analysis, however, was limited 

to studies with systematic necropsies. While 

this is the most effective manner of accurately 

quantifying plastic ingestion, it necessarily 

biases results toward dead individuals. While 

direct mortality from ingestion of non-food 

items (typically debris) is usually only verified 

in approximately 1 in 10 animals, non-lethal 

health impacts are poorly understood. Feeding 

behavior is a very important driver as to 

the type and frequency of debris ingestion 

(Gramentz 1988; Mrosovsky et al. 2009; 

Schuyler et al. 2012). Turtles will ingest several 

types of debris, though plastic bags are widely 

considered the most commonly ingested and 

dangerous item due to the resemblance to 

jellyfish and the high potential of becoming 

lodged in the throat.

Interestingly, Schuyler et al. (2013) noted a 

poor relationship between estimated regional 

debris density and the observed frequencies 

of ingestion. This merits further investigation 

as their study was a high-level overlay of 

several stranding studies with Lebreton et 

al.’s (2012) global debris density model, but 

did not factor in behavioral factors such as 

migratory paths, mobility, or feeding location 

(e.g., preferred foraging grounds may be 

well outside capture or stranding areas). Life 

history differences may also be obscuring 

the expected relationship between debris 

concentrations and ingestion rates. Younger 

turtles in the open ocean often seek shelter in 

the same productive convergence zones where 

debris accumulates (e.g., the Sargasso Sea), 

and are less selective in what they ingest, thus 

increasing the likelihood of debris ingestion 

(Carr 1987). Schuyler et al. (2012) confirmed 

this by demonstrating that smaller oceanicstage turtles are more likely to ingest debris. 

González Carman et al. (2013), however, noted 

a large overlap in debris accumulation areas 

and preferred foraging grounds for green 

turtles in the Río de la Plata (a large estuary 

at the Argentina–Uruguay border). Behavior, 

then, appears again to be a primary driver of 

how likely it is that an organism ingests debris.

Sea Turtles Birds

Birds are by far the most studied marine 

organism with regard to ingested marine 

debris. It has been estimated that over onethird of sea bird species ingest plastic (Laist 

1997). This may be much higher in certain 

areas, such as North Carolina (55%) (Moser 

and Lee 1992), and as more studies are 

conducted, the number of affected species 

is expected to rise. Sea birds have, in fact, 

been proposed as good indicators of plastic 

pollution due to the ease with which such 

studies can be conducted (Nevins et al. 2005). 

Birds are easy to capture, congregate in large 

numbers, and can be prompted to regurgitate 

their stomach contents, making dietary studies 

much easier than in other species. Sea birds 

Plastic bags are the most

commonly ingested type of debris 

amongst sea turtles.

All seven species of sea turtles 

have been confirmed to eat debris. 
2014 MARINE DEBRIS INGESTION REPORT 

from as far apart as Alaska and the Antarctic 

(Auman et al. 2004) have been confirmed to 

ingest debris, making them ideal indicators to 

compare different geographic areas. Different 

species exhibit a wide variety of feeding 

behaviors, and many studies have highlighted 

the difference this makes for plastic ingestion 

(see Azzarello and Van Vleet 1987 and 

references therein).

Birds, particularly the Procellariformes 

(e.g., albatrosses, fulmars, and shearwaters), 

may also be more susceptible to physical 

health effects, as debris most often gets stuck 

in the gizzard and cannot easily pass through 

the digestive system. Ryan and Jackson (1987) 

suggested a half-life of approximately one 

year for plastic pellets ingested by whitechinned petrels. Compared with other animal 

groups, birds may be ingesting debris with a 

similar frequency, but retaining it for longer 

periods of time. This makes them excellent 

study organisms for health effects such as 

obstruction, ulceration, blockage of digestive 

enzymes, diminished feeding stimulus, 

lower steroid hormone levels, and decreased 

reproductive function (reviewed by Azzarello 

and Van Vleet 1987). Direct health effects 

from ingesting debris do not presently seem to 

be a significant issue (Ryan and Jackson 1987; 

Sileo et al. 1990; Moser and Lee 1992; Sievert 

and Sileo 1993), but weights at fledging were 

found to be significantly lower for Laysan 

Albatross chicks that ingested large amounts 

of plastic (Sievert and Sileo 1993). This may be 

a dietary dilution effect, where plastic in the 

stomach prevents the chicks from consuming 

a full meal. Adults not only build nests using 

collected debris (Hartwig et al. 2007), but 

pass any ingested debris on to their offspring 

when the chicks are fed (Pettit et al. 1981). 

Both of these actions are likely to increase 

the incidence of debris ingestion by chicks 

through the exposure of adults to marine 

debris.

An exposed carcass of a Laysan albatross reveals ingested pieces of plastics which 

includes a cigarette lighter, plastic bottle caps and numerous pieces of microplastics. 

Credit: NOAA
2014 MARINE DEBRIS INGESTION REPORT 

Reports of debris ingestion by marine 

mammals have existed for well over a century 

(reviewed by Walker and Coe 1989), with 

over 26 species of odontocetes (toothed 

whales), manatees, and multiple seal species 

confirmed to ingest debris. Due largely to 

regulatory restrictions on research, very little 

scientifically reliable information exists on 

the frequency or amount of debris ingested 

by wild marine mammals (de Stephanis et al.

2013). Most data are collected from stranded 

and dead individuals, or from captive animals 

ingesting a variety of man-made materials 

not necessarily comparable to typical marine 

debris. Baleen whales may be particularly 

susceptible to large sheets of plastic debris 

that can become entangled in their baleen 

Marine Mammals

(feeding structure) (Lambertsen et al. 2005). 

Since baleen whales filter extremely large 

volumes of water while feeding, it is possible 

that they encounter (and consume) plastic 

sheets at higher rates than other animals. 

Plasticizer chemicals have been measured in 

both fin whales and their planktonic prey in 

the Mediterranean, and there is the potential 

that such plasticizers may be associated with 

microplastics from the same areas (Fossi et al.

2012).

Deaths of endangered manatees (Trichechus 

manatus) have been attributed to large pieces 

of ingested plastic (see Derraik 2002 and 

references therein). Reports from fur seal 

scat indicate transfer of plastic fragments 

from directly consuming prey items, and not 

incidental ingestion during feeding (Eriksson 

and Burton 2003). Ingested plastic is mostly 

retained by harbor seals, with younger 

animals more susceptible to debris ingestion 

(Rebolledo et al. 2013). It is possible that 

younger seals are less selective in their feeding 

behaviors, or that older animals are consuming 

larger prey items, which are in turn more 

selective. This highlights the nearly unknown 

role that transfer of ingested debris from prey 

to predator plays in the frequency and scale of 

debris ingestion for mammals.

A Hawaiian monk seal chews on consumer debris, a single-use plastic bottle, found in 

the Pacific ocean near the Northwestern Hawaiian Islands. 

9

Credit: NOAA Fisheries, Pacific Islands Fisheries Science Center, taken under Marine Mammal Permit #10137 (Ilana Nimz photographer)
The health impacts from ingested 

debris can be thought of as falling 

into two main categories—physical 

and physiological effects—

although both are intricately 

linked. Currently, acute dangers 

from sharp objects and sheet 

plastics (e.g., bags) appear to cause 

the most damage to larger animals 

in the shortest amount of time.

Physical Effects

The mere presence of ingested debris 

can have a variety of health effects. Among 

others, these include: laceration or ulceration 

of the digestive tract, leading to infection 

and internal bleeding; direct blockage of the 

digestive tract, reducing nutrient uptake; 

satiation, reducing the urge to feed; failure of 

digestive tract compartmentalization, allowing 

highly acidic gastric juices into areas not 

adequately shielded; and retention, leading to 

an increasing amount of debris in the digestive 

system of the organism.

Health Impacts

Fish hooks are commonly ingested in areas 

with active fisheries. These are commonly 

lodged in the mouth, but can pass further into 

the digestive system and often become lodged 

in the esophageal area. As plastic degrades 

in the environment, it often fragments into 

pieces with sharp corners. Once ingested, 

sharp debris objects can puncture the lining of 

the digestive system. This leads to ulceration, 

persistent lesions, secondary infection 

and parasitism, and inflammation of the 

surrounding tissue (Gregory 1991; Oros et al.

2005) leading to reduced fitness and disease.

Ingested debris has often been noted 

as a secondary item during necropsies of 

many cetaceans and turtles with factors 

such as parasitism or other pathological 

conditions as the listed cause of death. 

Identifying debris as a definitive cause of 

death is extremely tenuous; animals at this 

stage are often diseased and determining 

pathologically which came first—disease or 

debris ingestion—can be extremely difficult, 

except in rare cases. Plastic sheeting and large 

plastic bags are commonly ingested by larger 

animals, especially turtles (which mistake 

plastic bags for jellyfish) and cetaceans. Such 

items can become lodged while strands of 

the plastic extend into the gastric system, 

exposing organs to an onslaught of digestive 

fluids. Approximately half of the forestomach 

lining and protective mucosa was eroded in 

a bottlenose dolphin (Tursiops truncatus) 

Blockage

Laceration and Lesions

The longer debris resides in the digestive 

tract, the greater the potential for negative 

health effects. Retention timing is highly 

dependent on the nature of the debris and 

the anatomy and physiology of the affected 

organism. Some ingested debris can pass 

relatively quickly through the body, while 

other debris items are retained for extended 

periods of time. Browne et al. (2008) showed 

that microplastics ingested by mussels stayed 

in the animal’s blood for over six weeks. Crabs 

were able to clear microspheres more quickly 

(Farrell and Nelson 2013), but still distributed 

the debris throughout the body over four 

weeks prior to clearance. Lobsters were unable 

to effectively clear plastic microfibers over two 

weeks (Murray and Cowie 2011). The only 

study looking at how long ingested debris remains in the gut of sea turtles found that 85% 

of the mass of 5-mm diameter soft foam dishes 

passed after 13 days, and that plastic spheres 

took almost twice as long to pass (Valente et 

al. 2008).

that ingested plastic sheeting, resulting in 

necrosis and inflammation deep into the 

stomach musculature (Walker et al. 1989). 

Cetaceans have been often noted to suffer 

gastrointestinal blockage due to ingesting nonfood items (Laist 1997; Derraik 2002). It has 

been hypothesized that in sperm whales such 

blockages lead to malnutrition, starvation, and 

gastric rupture from ingesting large amounts 

of debris (Jacobsen et al. 2010; de Stephanis 

et al. 2013). Supporting this hypothesis, a 

stranded pygmy sperm whale showing extreme 

signs of malnutrition successfully recovered 

after a series of endoscopic procedures that 

removed several sheet-like pieces of plastic 

debris such as garbage bags, a mylar balloon, 

and cellophane wrappers (Stamper et al. 2006).

Regardless of the animal, indigestible 

debris in the digestive tract, particularly 

the stomach, likely leads to a false sense of 

satiation, reducing the animal’s urge to feed 

properly (Secchi and Zarzur 1999; Pierce et 

al. 2004) until it can be cleared. This has been 

shown in birds to reduce meal size and impair 

formation of fat deposits among other effects 

(see Derraik 2002 and references therein). 

The downstream health impact then becomes 

one of wasting and malnutrition, impacting 

migration distances and physical condition, 

often leading to secondary infections as the 

immune system becomes impaired.

Retention
The body of a Laysan albatross decays in the Northwestern Hawaiian Islands exposing 

its stomach, which contained several pieces of plastic, primarily plastic bottle caps. 

Credit: United States Fish and Wildlife Service/ Peter :eary
Most of the direct physical effects of 

ingesting debris lead directly to physiological 

impairment, whether that be nutritional, 

developmental, immunological, or 

toxicological. Debris in the digestive tract 

can have negative effects on gastric enzyme 

secretion, impairing the proper digestion 

of food and resulting in loss of body weight 

(Spear et al. 1995). Ingestion of debris has 

been indicated to cause poor production of 

steroid hormones in sea birds, leading to 

delayed ovulation and reproductive failure 

(Azzarello and Van Vleet 1987). Debris 

colonized by microbes can serve as a vector 

for harmful bacteria when ingested. Plastic 

microspheres similar in size to marine 

bacteria may stimulate hemocyte aggregation 

(an immune response) in crabs and become 

trapped in the gill microvasculature, reducing 

respiratory function (Johnson et al. 2011). 

Köhler (2010) reported pronounced immune 

response and formation of granulomas 

in blue mussels (Mytilus edulis) ingesting 

similar microspheres. Rochman et al. (2013b) 

reported hepatic stress in Japanese medaka 

(Oryzias latipes) ingesting virgin polyethylene 

fragments.

Although studies on the direct 

physiological impacts of ingested debris on 

marine organisms are relatively rare, studies 

from other research fields (e.g., veterinary 

science) give an indication of likely effects. 

For example, female goats fed plastic rope 

exhibited no clinical signs of disease over 

fifty days, yet serious damage to the digestive 

tract was observed on necropsy, including: 

lesions, increased thickness in the muscle 

tissue surrounding the plastic, and reduced 

thickness of mucosal layers (Raoofi et al.

2012). Considering the anatomical structure 

of goats, it is unsurprising the rope localized 

in the rumen; similar structures in marine 

organisms likely have similar effects. While 

these findings are not directly comparable 

to many marine organisms (none being 

ruminants), tissue damage can be expected to 

occur in a similar manner. Similar pathologies 

have been observed in the gastric tissues of 

marine mammals (Walker et al. 1989; Stamper 

et al. 2006; Jacobsen et al. 2010; de Stephanis 

et al. 2013). This also serves to highlight that 

non-invasive clinical measures may miss 

meaningful pathology resulting from ingested 

debris that cannot be observed until the health 

of the animal has deteriorated substantially, 

or the animal has died and a necropsy can be 

performed.

Physiological Effects

Toxicants

Chemical toxicants associated with marine 

debris (e.g., metals or metal oxides leaching 

from fish hooks and marine paints, legacy 

organic pollutants, halogenated compounds, 

and plasticizers) inevitably enter the body 

if the debris is ingested. Through direct 

ingestion of debris or through consuming 

polluted prey, these can have a variety of 

health impacts on marine organisms in 

addition to the physiological effects of 

debris presence. At high enough doses, such 

toxicants are well-documented to cause health 

effects such as cancer, endocrine disruption, 

immune impairment, neurological damage, 

reproductive failure, developmental delays, 

and muscle damage (see Jones and de Voogt 

1999 and references therein).

Plastic is essentially solidified oil. 

While current-market plastics are typically 

considered biologically inert (Teuten et al.

2009), properties considered desirable for 

consumer markets require the incorporation 

of various chemical additives. This includes 

(among others) phthalates and bisphenol A to 

alter the rigidity of the product, brominated 

flame retardants to increase heat resistance, 

antimicrobial agents such as triclosan to 

reduce biodegradation, or antioxidants to 

delay the plastic becoming brittle (see Cole et 

al. 2011 and references therein). Such additives 

are rarely completely incorporated into the 

polymer structure of plastics, causing them 

to leach out over time. Plasticizers represent 

up to half the total weight of plastic in the 

case of phthalates and therefore have been 

studied extensively (see Oehlmann et al. 2008; 

2009 and references therein) and are shown 

to cause a variety of negative health effects 

on reproduction and development. Mollusks, 

crustaceans, and amphibians appear to be 

particularly sensitive.

Added to this are a host of other 

anthropogenic pollutants, some banned from 

production for decades, which adsorb onto 

hydrophobic plastic in the environment. This 

is due partly to the relatively large surface 

area to volume ratio of plastics, which only 

increases as debris fragments into smaller 

pieces. Microplastics have a high surface area 

to volume ratio and a large potential to collect 

toxicants. Such adsorbed pollutants include 

aqueous metals, halogenated persistent organic 

pollutants (e.g., polychlorinated biphenyls 

(PCBs)), organochlorine pesticides (e.g., 

DDT), and polycyclic aromatic hydrocarbons 

(PAHs). Teuten et al. (2007) reported PCB 

concentrations in free-floating polystyrene 

pellets were 106 times greater than in the 

surrounding water. Pollution of this type 

adsorbed onto plastic debris has been widely 

reported in the literature at concentrations that 

may pose a significant health hazard (Cole et 

al. 2011 and references therein; Rochman et 

al. 2013a, b), though the evidence is currently 

not definitive regarding health risks. The 

same study confirmed the potential for these 

adsorbed compounds to disassociate once 

ingested and translocate to tissues; this has 

since been reinforced by a variety of studies. 

While plastic buried in the sediment may 

desorb such compounds, plastic remaining 

at the sea surface has no such capacity and 

continues to accumulate such toxicants. Since 

organisms are historically exposed to toxicants 

of this nature from non-plastic sources 

through the food web (primarily sedimentbound), this represents a new transfer pathway 

for lower trophic level organisms not typically 

associated with sediments. While the presence 

of adsorbed pollutants has been investigated 

heavily in the last decade, more research is 

needed to clarify transfer dynamics from 

plastics to primary, secondary, and tertiary 

consumers. As biological systems become 

more complex, potential disruptions from 

toxicants become more likely and more 

varied. As many toxicants bioaccumulate and 

biomagnify through the food web, tying plastic 

exposure or ingestion and the presence of 

toxicants to health effects in a given animal is 

extremely tenuous at this time. In the future 

more discriminatory indicators may be found. 

There is some thermodynamic model-based 

evidence that toxins associated with plastics 

may be of limited importance compared with 

other vectors (the total amount of plastic is 

currently still dwarfed by the total amount of 

organic carbon in the ocean) and that ingested 

plastic may, if excreted, reduce the total body 

burden of certain toxicants by adsorbing 

toxicants from the digestive system (Gouin 

et al. 2011; Koelmans et al. 2013). Presently, 

the presence of plastic debris and its potential 

role in mediating bioconcentration and 

bioaccumulation dynamics is an open question 

for which further study is warranted.
2014 MARINE DEBRIS INGESTION REPORT 

WHAT WE NEED TO LEARN

The concentration and distribution of 

ingestible marine debris in the world oceans 

is currently not well understood. While one 

section of the North Pacific Ocean has been 

most often studied, questions still remain 

about the full character of debris collecting 

in that gyre. Other areas have been studied 

only sparsely. Currently, the indication is 

what would be expected, that most ingestible 

debris is generated by urban areas, becomes 

entrained by surface currents, and collects 

along converging current boundaries. New 

technology focusing on passive airborne 

sensors, internet-enabled cameras, oceanic 

gliders, drones, and improved satellite imagery 

may be able to more quickly establish the 

true extent of marine debris, not only on 

beaches and at the ocean’s surface, but also 

at depth and throughout the water column. 

Understanding which types of debris are most 

harmful, prioritizing the most polluted areas, 

and tracking the debris to identify sources 

will have a tremendous impact on targeting 

effective policies to reduce ingestible debris.

It is difficult to provide a single estimate 

for how long a piece of plastic takes to degrade 

in marine environments due to differences 

in research methodology and differences 

in environmental factors (e.g., temperature, 

salinity, colonization, etc.), and the limited 

number of studies conducted are at times 

contradictory. This is especially true when 

considering newer production formulas as 

polymer manufacturers attempt to improve 

their products, making them more cost 

effective and “green.” Similarly, the degradation 

of plastics in different digestive environments 

will play a key role in understanding health 

impacts for current and future plastic 

formulations. In part, this determines how 

quickly toxicants move into the body. Some 

programs are beginning to address this lack 

of information, and these efforts should be 

increased and more tightly coordinated.

Much of what we know about the ingestion 

of debris by mammals and turtles is based on 

reports that document mortality events. These 

observations, although useful, do little to 

address the amount and type of debris ingested 

by a typical member of these species. Given 

that mammals and turtles are reported to 

ingest debris at higher frequencies than some 

other more well-studied species, currently 

reported rates of ingestion are likely inflated 

by this bias. This represents a very large void 

in the current state of the science. There is 

an acknowledged difficulty in working with 

large, federally protected and relatively rare 

species (e.g., larger cetaceans and polar bears 

likely cannot be assessed using live animals), 

but routine monitoring projects around the 

country already capture many dolphin, seal, 

and turtle species. Esophageal lavage has been 

used successfully (Witherington et al. 2012), 

but only recovers items ingested recently. 

Similarly, fecal collection only recovers items 

passing through the gut within a limited time 

window. The addition of a brief endoscopic 

screen of stomach contents during captures 

would add tremendous value in verifying 

the accuracy of necropsy-based studies for 

relatively little added difficulty, cost, or health 

impact to the animal.

These and other basic questions about 

the ingestion and health effects of ingested 

marine debris remain unanswered (and largely 

unasked), including:

As mentioned above, debris can be 

found floating on the surface of the 

ocean, but it can also be found at 

depth. If high concentrations of debris 

overlap with preferred foraging areas 

for many mid-water species (e.g., 

deep chlorophyll maximum), current 

estimates may be underestimating the 

overall impacts of debris on organisms 

in the world’s oceans. Future work 

should identify the location and 

concentration of debris at depths where 

organisms are actively feeding in order 

to assess the potential impacts on those 

animals actively feeding in these areas.

Detection and quantification of plastics 

and plastic-associated contaminants 

in the environment currently lacks 

sophistication (most studies are 

microscopy or type-identification 

based). Drawing conclusions regarding 

trophic uptake and transfer is 

important; however the available data 

are tenuous at this time (Fossi et al.

2012). More discriminating analyses 

based on analytical chemistry would 

advance the science tremendously by 

allowing more directed questions and 

more easily eliminating alternative 

hypotheses.

Very little information exists on how 

long plastic stays in the body and how 

it becomes distributed throughout the 

body once ingested. Residence time 

and distribution likely varies greatly 

from species to species, but has been 

addressed only by a handful of studies 

on birds (Ryan and Jackson 1987), crabs 

(Farrell and Nelson 2013), mussels 

(Browne et al. 2008), turtles (Valente et 

al. 2008), and zooplankton (Cole et al.

2013). More studies are warranted along 

the lines of those from Browne et al.

(2008), which examined the relocation 

of microplastics throughout the body, 

and Farrell and Nelson (2013), which 

noted a specific clearance rate.

How filter and deposit feeders select 

what they consume and what they 

reject is not well understood (Ward and 

Shumway 2004). Indications point to a 

very complex system, and the ability of 

these organisms to separate their food 

from microplastic debris could alter 

understanding of the system.

Bacterial microflora and -fauna in the 

gut environments of larger animals 

likely play a mediating role in plastic 

digestion and toxicant effect. This has 

not been well addressed and represents 

a knowledge gap.

Desorption and uptake of debrisassociated toxicants is known to occur 

in ways inconsistent with standard 

theory (Voparil and Mayer 2000; Endo 

et al. 2013), but the dynamics are poorly 

understood. How do toxicants distribute 

through the body? How does the gut 

environment of different organisms 

alter desorption, degradation, and 

toxicant uptake rates? Is this altered by 

the plastic carrier, and in what ways? A 

wealth of information exists for acute 

toxicology regarding such chemicals, 

but currently the desorption dynamics 

of a gut environment containing debris 

and multiple co-occurring factors such 

as adsorption of non-plastic pollutants, 

sediment, and species-specific gut 

environment is poorly understood. 

Toxicological and chemical studies 

using debris (particularly plastic debris 

and microplastics) as a vector should 

therefore be given a high priority.

13
2014 MARINE DEBRIS INGESTION REPORT 

In contrast to acute toxicology, relatively 

little is known regarding chronic 

exposures for longer-lived organisms. 

Similarly, almost no information exists 

regarding the mixtures of toxicants to 

which organisms are actually exposed. 

This may alter the toxicity of individual 

chemicals. The interface of toxicant and 

debris presence and health interactions 

between these exposures is also poorly 

understood.

Minimal useful information exists 

regarding trophic transfer of ingested 

marine plastics and associated 

chemicals; that is, if prey ingests 

plastic, what effect does that have on 

the predator? How much (plastic and 

chemical load) transfers? How does 

this affect digestion of the prey? Only 

two studies examining this issue were 

identified. Farrell and Nelson (2013) 

showed that plastic microspheres fed to 

mussels were observed in the blood of 

crabs. Toxic effects were not evaluated 

although no overt mortality was 

reported. The clearance rate (21 days) 

was also a key observation, as faster 

clearance rates may decrease the plastic 

load transferred to predators. Murray 

and Cowie (2011) noted that when 

lobsters ingested rope fibers contained 

in fish, they could not excrete the 

fibers. Information of this type is vital, 

and more attention should be turned 

to answering questions about transfer 

dynamics throughout the food web.

No studies to date have attempted to 

tackle the larger question of interspecies 

ecological effects of ingested debris. 

Studies at the population and 

community levels would necessarily 

be observational and correlative, but 

data sets large enough to evaluate 

such effects may be available if data 

from enough single studies could be 

combined. These could be augmented 

by targeted mesocosm studies to 

understand the health impacts of 

debris entering the ecological system 

at different levels. What role does 

submerged aquatic vegetation play in 

ingestion mediation? Is ingested debris 

leading to a higher incidence of sick 

animals more susceptible to predation 

and at what rates?

Degradation of plastics in the 

environment can be enhanced with 

emerging “green” formulations, such 

as compostable plastics, which degrade 

completely in less than six months 

(O’Brine and Thompson 2010). This 

reduces the amount of time the plastic 

is available for ingestion, but may 

relatively increase the short-term 

transmission of plasticizer chemicals 

into the environment. The trade-off 

regarding health effects has not been 

investigated.

Before the issues related to ingestion of 

marine debris can be fully addressed, each 

of these questions must be answered. The 

application of mesocosm and flow-through 

toxicology studies could answer several of 

the basic questions regarding ecological 

distribution, adsorption and desorption of 

contaminants in plastic debris, digestive 

transfer, and trophic relationships of debris 

transference.

14
2014 MARINE DEBRIS INGESTION REPORT 

CONCLUSIONS

Many types of marine organisms routinely 

ingest marine debris, whether from the water 

column, with target prey items, or picked up 

from the sea floor or beaches. The majority 

of this debris is plastic, buoyant at first and 

gradually sinking over time as degradation 

and colonization by encrusting organisms 

increases its density. The interaction between 

plastic formulation (i.e., initial density), 

degradation, and colonization that leads 

to the transfer of plastic from the ocean 

surface to the ocean floor is currently only 

loosely understood. Buoyant plastic debris 

is entrained in ocean gyres or aggregated by 

wind, wave, and currents onto beaches and 

along ocean convergence zones.

Plankton, shellfish, birds, fishes, marine 

mammals, and sea turtles from all parts of 

the globe and from various depths of the 

ocean have been confirmed to ingest debris. 

Birds appear to suffer the broadest impacts, 

particularly long-range surface foragers 

such as albatross, fulmars, and shearwaters. 

Impacts are seen not only in the individual 

ingesting the debris, but also in offspring 

due to the manner in which chicks are fed by 

adults. Effects and dynamics from transfer of 

debris, either directly (as in the case of birds) 

or indirectly through consuming prey items 

with debris in the gut, are currently poorly 

understood.

Behavior appears to be the driving factor 

determining the likelihood of ingestion when 

debris is present. Individual species of filter 

feeders, deposit feeders, grazing fishes, and 

active predators exhibit different frequencies 

of ingestion (and thus different potential 

health impacts) depending on species-specific 

feeding behaviors. Convergence zones, which 

concentrate floating debris, produce areas 

of abundant nutrients and aggregate sea life, 

likely increasing the probability of interactions 

between marine life and debris.

Direct health effects have been difficult 

to quantify, but there appears to be little 

direct mortality from the majority of small 

plastic items. Physical health effects typically 

include laceration, perforation, or fouling 

of the digestive system. Physiological effects 

resulting from such physical outcomes 

include inflammation, secondary infection, 

and potential toxicant transfer. It is likely that 

observations of health effects in large animals 

that have ingested debris are confounded by 

the unknown health status of the animal when 

it ingested the debris, as well as the duration of 

debris retention. Animals may be impaired by 

an initial insult, such as the ingestion of debris 

or infection, subsequently making them more 

susceptible to infections and inflammation. 

This can alter animal behavior, particularly 

energy-intensive feeding behaviors, leading 

to a cascade effect whereby each insult 

reinforces the others, leading to sickness and 

death. Debris is an easier target than actual 

prey items and may be more appealing to an 

impaired animal. This “chicken or the egg” 

style problem should be addressed in a more 

systematic manner controlling for behavior 

and states of physiological stress. Similarly, 

care must be taken to eliminate alternative 

hypotheses when observing debris-associated 

toxic chemicals in difficult-to-study animals.

Many different policies have been 

considered to reduce the overall input of 

marine debris in a natural setting. Any 

reduction in the amount of debris entering 

the environment will also generate long-term 

benefits by reducing the potential future 

impacts of newly-introduced debris on many 

organisms. However, while policies to reduce 

debris from entering the environment may be 

useful, fewer policies have been constructed 

to assess and address the overall impacts of 

existing debris in the environment. Since some 

debris items can last for decades or longer in 

the environment, they will likely be available 

for consumption and potential harm to 

organisms across multiple generations. Even if 

we stopped the flow of debris into the ocean, 

debris that has already made its way into the 

ocean will continue to impact the organisms 

therein for decades to come. Thus, future 

research should continue to quantify the 

concentrations of debris in the environment, 

while also assessing the impacts of that debris 

(including the most ”impactful” debris types) 

on marine wildlife. Policies should then use 

the information gleaned from this research to 

identify areas that require immediate action in 

reducing the impacts of debris in those areas. 

It is possible that additional baseline data can 

better inform numerical modeling exercises 

to provide broader and more accurate 

information regarding collection areas, source 

tracking, and amounts of debris. The recent 

improvements in modeling of debris patterns 

and increasing data on health effects are 

encouraging. Without a comprehensive toplevel understanding of the system and effects, 

however, crafting highly specific policies may 

be an overwhelming and premature exercise.

More targeted science from interconnected 

disciplines (e.g., physical oceanography, 

mesocosm toxicology, and veterinary science) 

is needed to identify the factors associated 

with ingestible debris that are most likely to 

impair the health of marine ecosystems, and 

hence most useful to help establish effective 

policies. Future studies on ingestible debris 

should connect with veterinary research 

centers for diagnosis and treatment of foreign 

body ingestion. These would benefit greatly 

from simple gastroscopic investigations to 

better quantify ingestion rates and amounts 

in larger animals that cannot be sacrificed for 

regulatory reasons (e.g., turtles and cetaceans). 

Refined analytical chemistry and toxicology 

methods could provide more useful insights 

into community-scale distribution of debrisassociated toxicants and indicate which parts 

of the food web are most at risk from direct 

ingestion and trophic transfer. Micro- and 

mesocosm studies could effectively model 

environmental partitioning, especially in 

estuarine systems where debris often becomes 

concentrated.

Broader policies, both national and 

international, established to reduce the amount 

of plastic debris entering the oceans will 

likely be the only effective approach moving 

forward. Policies to reduce the amount of 

plastics entering consumer and manufacturing 

markets are currently unlikely to gain traction. 

Formulation changes, for example increases in 

density or degradation rates, will likely reduce 

the chances of debris being ingested by surface 

or mid-water organisms but may have effects 

on the benthic community that are currently 

poorly understood. Incentives to contain 

and reduce the amount of plastic debris 

entering the environment will likely have 

more meaningful impact in the nearest term 

while these are investigated. Modifications 

to plastic formulation should be rigorously 

investigated prior to market entry, with 

environmentally beneficial formulations (e.g., 

those with lower toxicity and environmental 

persistence) being given regulatory priority 

and older formulations regulated out of the 

market. Likewise, some manufacturers have 

begun to recognize the environmental impacts 

of plastics, particularly in the personal care 

product market, and have started voluntarily 

to address the issue. Such responsible 

businesses should be encouraged and provided 

support to implement and expand these 

practices.

15
2014 MARINE DEBRIS INGESTION REPORT 

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2014 MARINE DEBRIS INGESTION REPORT 

Penny Pritzker

United States Secretary of Commerce 

Dr. Kathryn D. Sullivan

Under Secretary of Commerce for Oceans and Atmosphere

Dr. Holly A. Bamford

Assistant Administrator, National Ocean Service