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Plastic waste can promote microbial colonization by pathogens implicated in outbreaks of disease in the ocean. We assessed the influence of plastic waste on disease risk in 124,000 reef-building corals from 159 reefs in the Asia-Pacific region. The likelihood of disease increases from 4% to 89% when corals are in contact with plastic. Structurally complex corals are eight times more likely to be affected by plastic, suggesting that microhabitats for reef-associated organisms and valuable fisheries will be disproportionately affected. Plastic levels on coral reefs correspond to estimates of terrestrial mismanaged plastic waste entering the ocean. We estimate that 11.1 billion plastic items are entangled on coral reefs across the Asia-Pacific and project this number to increase 40% by 2025. Plastic waste management is critical for reducing diseases that threaten ecosystem health and human livelihoods.
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Plastic waste associated with disease
on coral reefs
Joleah B. Lamb,
*Bette L. Willis,
Evan A. Fiorenza,
Courtney S. Couch,
Robert Howard,
Douglas N. Rader,
James D. True,
Lisa A. Kelly,
Awaludinnoer Ahmad,
Jamaluddin Jompa,
C. Drew Harvell
Plastic waste can promote microbial colonization by pathogens implicated in outbreaks of
disease in the ocean. We assessed the influence of plastic waste on disease risk in 124,000
reef-building corals from 159 reefs in the Asia-Pacific region. The likelihood of disease
increases from 4% to 89% when corals are in contact with plastic. Structurally complex corals
are eight times more likely to be affected by plastic, suggesting that microhabitats for
reef-associated organisms and valuable fisheries will be disproportionately affected.
Plastic levels on coral reefs correspond to estimates of terrestrial mismanaged plastic
waste entering the ocean. We estimate that 11.1 billion plastic items are entangled on coral
reefs across the Asia-Pacific and project this number to increase 40% by 2025. Plastic
waste management is critical for reducing diseases that threaten ecosystem health and
human livelihoods.
Outbreaks of disease on coral reefs threaten
one of the most biodiverse ecosystems
on the planet (1), jeopardizing the U.S.
$375 billion in goods and services that
they provide to people each year through
fisheries, tourism, and coastal protection (2). Plas-
tic waste can host pathogens that are frequently
implicated as triggers of disease outbreaks on
coral reefs (39). For example, microbial commu-
nities colonizing polypropylene marine debris
were dominated by the genus Vibrio (10), an
opportunistic pathogenic bacteria of a globally
devastating group of coral diseases known as
white syndromes (11). Although an estimated
4.8 million to 12.7 million metric tons of plastic
waste enter the ocean in a single year (12), the
resulting influence on disease susceptibility in
the marine environment is unknown. Microbial
rafting on plastic debris has been shown to
strongly control surface longevity (13)andis
pared with more polar regions (14), suggesting
that coral reef ecosystems could have high levels
of colonized plastic waste.
We surveyed 159 coral reefs spanning eight
latitudinal regions from four countries in the
Asia-Pacific for plastic waste and evaluated
the influence of plastic on diseases that affect
keystone reef-building corals (15)(benthicarea=
12,840 m
) (Fig. 1). The Asia-Pacific region con-
tains 55.5% of global coral reefs (2)andencom-
passes 73.0% of the global human population
residing within 50 km of a coast (12) (table S1).
Overall, we documented benthic plastic waste
(defined as an item with a diameter >5 0 mm)
on one-third of the coral reefs surveyed, amount-
ing to 2.0 to 10.9 plastic items per 100 m
of reef
area [95% confidence interval (CI), n=8survey
regions]. The number of plastic items observed on
each reef varied markedly among countries, from
Lamb et al., Science 359, 460462 (2018) 26 January 2018 1of3
2010 2025
2000 km
1 Myeik Archipelago
2 Koh Tao
3 Sulawesi
4 Bali
5 West Papua
6 Palm Islands
7 Whitsunday Islands
8 Keppel Islands
Survey Regions
Estimated mismanaged plastic waste
entering the ocean (thousand metric tons)
Plastic debris on coral reefs (100 m-2)
Plastic debris on
coral reefs (100 m
N = 159
No coast
55.5% of global
coral reefs
73.0% of global coastal human population
within 50 km of coral reefs
0250 500
Fig. 1. Estimated plastic debris levels on coral reefs. (A) Modeled association
between plastic debris on coral reefs from surveys of 159 reefs in eight regions [red
squares in (B)] from 20112014 and estimated levels of mismanaged plastic waste
(thousand metric tons), assuming that 25% of waste entered the ocean in 2010
from human populations living within 50 km of the coast for each country (12).
Reef locations can be found in table S14. The Asia-Pacific region encompasses 9 of
10 countries with the highest global levels of estimated mismanaged plastic waste
entering the ocean (table S3). Gray shading represents the upper and lower 95%
CIs for the model. (Band C) Modeled plastic debris levels on coral reefs (100 m
as projected using the association between estimated mismanaged plastic waste
entering the ocean in 2010 for each sovereign country (12) and plastic debris
surveys between 20112014 [shown in (A)].The color scale represents the minima
and maxima model estimates of mismanaged plastic waste on coral reefs from
2010 (table S5). Projections of plastic debris on coral reefs for Indonesia and China
in 2025 were set to the maxima from 2010, owing to the limitations of the
model range. Countries without a coastline are shown in white.
Department of Ecology and Evolutionary Biology, Cornell
University, Ithaca, NY 14853, USA.
Australian Research
Council Centre of Excellence for Coral Reef Studies, James
Cook University, Townsville, Queensland 4811, Australia.
College of Science and Engineering, James Cook University,
Townsville, Queensland, Australia.
School of Aquatic and
Fishery Sciences, University of Washington, Seattle, WA
98195, USA.
Hawaii Institute of Marine Biology (HIMB),
University of Hawaii at Manoa, Kaneohe, HI 96744, USA.
Ecosystem Sciences Division, National Oceanic and
Atmospheric Administration (NOAA) Pacific Islands Fisheries
Science Center, Honolulu, HI 96818, USA.
Programme, Fauna & Flora International, Yangon, Myanmar.
Oceans Program, Environmental Defense Fund, New York,
NY 10010, USA.
Center for Biodiversity in Peninsular
Thailand, Prince of Songkla University, Hat Yai, Songkhla,
Fish Ecology and Conservation Physiology
Laboratory, Department of Biology and Institute of
Environmental Science, Carleton University, Ottawa,
Ontario, Canada.
The Nature Conservancy, Raja Ampat
Field Office, North Sorong, West Papua, Indonesia.
of Marine Science and Fisheries, Hasanuddin University,
Makassar, South Sulawesi, Indonesia.
*Corresponding author. Email:
on January 26, 2018 from
maxima in Indonesia [25.6 items per 100 ± 12.2 m
(here and elsewhere, the number after the ± sym-
bol denotes SEM)] to minima in Australia (0.4
items per 100 ± 0.3 m
) (table S2).
Terrestrially derived pollutants have been
implicated in several disease outbreaks in the
ocean (16). However, no studies have examined
the influence of plastic waste on disease risk in
a marine organism. In this work, we visually ex-
amined 124,884 reef-building corals for signs of
tissue loss characteristic of active disease lesions
(15) (fig. S1). We found plastic debris on 17 genera
from eight families of reef-forming corals. When
corals were not in contact with plastic debris, the
likelihood of disease was 4.4 ± 0.2% across all
eight regions (range = 2.8 to 8.4%, generalized
linear mixed model, likelihood ratio test among
regions: c2
7¼10:382, P=0.168) (Fig. 2A). In con-
trast, in the presence of plastic debris, the like-
lihood of disease occurrence in corals increased
significantly by more than a factor of 20 to 89.1 ±
3.2% (generalized linear mixed model: zscore =
27.24, P<0.001, n= 331 transects) (Fig. 2B and
table S3).
Human population size in coastal regions and
the quality of waste management systems largely
determine which countries contribute the
greatest plastic loads entering the ocean, given
that an estimated 80% of marine plastic debris
originates from land (12). Accordingly, we mod-
eled the relationship between our documented
levels of plastic debris on coral reefs (n=437
transects from Australia, Myanmar, Thailand, and
Indonesia) and Jambeck et al.s estimated levels of
mismanaged plastic waste entering the ocean (12)
from these four countries in 2010 (15)(generalized
linear mixed model: Akaike information crite-
rion = 662.3, z=3.95,P< 0.001) (Fig. 1A, fig. S2,
and table S4). Our model encompasses the range
of mismanaged plastic waste entering the ocean
introduced by coastal populations from 15 of the 17
(88%) sovereign countries in the Asia-Pacific re-
gion (maximum = 804,214 metric tons, minimum =
3472 metric tons), of which 9 are among the top 10
plastic-polluting countries globally (table S5).
Assuming that improvements in waste manage-
ment infrastructure did not occur during our
survey period (20112014) and that the plastic
waste emanated from adjacent terrestrial point
sources, we estimate that levels of plastic debris
on coral reefs for each country in the Asia-Pacific
ranged from 0.9 to 26.6 plastic items per 100 m
in 2010 (95% CI) (Fig. 1B and table S5). This
amounts to an estimated 11.1 billion items of
plastic on coral reefs across the Asia-Pacific (95%
CI = 1.2 billion to 105.5 billion items, n=15
countries), which is likely underestimated owing
to the exclusion of China and Singapore because
they fall outside of the model range (table S5).
By 2025, the cumulative quantity of plastic
from land is predicted to increase by one order of
magnitude (12). Using this projection and assuming
that the area encompassed by coral reefs remains
constant, we estimate that 15.7 billion plastic
items will be entangled on coral reefs across the
Asia-Pacific by 2025 (the business-as-usualsce-
nario for global infrastructure: 95% CI = 1.7 billion
to 149.2 billion items) (Fig. 1C and table S5). Ac-
cording to our model, the predicted geographic
distribution of plastic debris on coral reefs does
not change substantially between now and 202 5
(Fig. 1, B and C), but the disparity in quantities of
accumulated plastic waste between developing
For example, plastic debris on coral reefs in-
creases by only ~1% in high-income countries
such as Australia but nearly doubles in a similarly
populated low-income country such as Myanmar
(Fig. 1C and table S5).
Comparative analyses of disease prevalence
among different diseases in the presence versus
absence of plastics can offer insights into poten-
tial mechanisms that increase disease suscepti-
bility in corals. Reef-building corals in contact
with plastic debris were affected by four of six
common diseases globally (17), whereas corals
without plastic debris were affected by all six
diseases but at much lower prevalence levels
(table S6). Disease assemblages on reef-building
corals differ distinctly when contact with plastic
waste is present versus absent, as visualized by a
principal coordinates ordination analysis (15)
(permutational multivariate analysis of variance:
F= 11.86, P<0.001,n= 75 paired transects) (Fig. 3).
In particular, three key diseases associated with
rapid coral mortality increased markedly when
plastic debris was in contact with coral tissues:
Skeletal eroding band disease increased from
1.2 ± 0.1% to 43.9 ± 5.1% (increased likelihood =
24%), white syndromes increased from 1.9 ± 0.2%
to 19.0 ± 4.0% (increased likelihood = 17%), and
black band disease increased from 0.6 ± 0.1% to
14.7 ± 3.9% (increased likelihood = 5%) (tables S7
to S10).
Given the widespread distribution of plastic
debris on coral reefs and the consequent increased
Lamb et al., Science 359, 460462 (2018) 26 January 2018 2of3
Likelihood of disease (%)
Without plastic debris
0 10025 50 75
With plastic debris
Plastic debris on
coral reefs (100 m
Group Mean
0 10025 50 75
Fig. 2. Plastic waste influences disease susceptibility of reef-building corals. (Aand B)Box
(median and 50% quantile) and whisker (95% quantile) plots of coral disease likelihood for each of
eight regions in four countries in the Asia-Pacific when no plastic waste is present (A) (n= 362
transects) and when plastic waste is present (B) (n= 75 transects). The red line represents the mean
and the light red bar denotes ±1 SEM across all eight regions. Boxes are shaded according to model
estimates of plastic debris on coral reefs per 100 m
from Fig. 1C. MYAN, Myanmar; THAIL, Thailand;
INDO, Indonesia; AUST, Australia.
Fig. 3. Reef-building corals with plastic
debris have different disease assem-
blages than corals without plastic
debris. Multivariate spatial representation
of the relative abundance and composition
of coral disease assemblages, as determined
by a principal coordinates analysis (PCoA)
(n= 75 paired transects). Vectors for each
group illustrate the median spatial distance
within the group. Disease assemblages
represent six diseasesskeletal eroding
band, white syndromes, black band,
growth anomalies, brown band, and
atramentous necrosisrecorded commonly
across the globe.
PCoA 1
PCoA 2
−0.4 −0.2 0.0 0.2 0.4
With plastic debris
Without plastic debris
on January 26, 2018 from
likelihood of coral mortality from disease, we
evaluated the potential for plastic debris and
disease to affect structural complexity provided
by habitat-forming corals. The structural com-
plexity formed by corals underpins the avail-
ability of microhabitats for coral reefassociated
organisms (18). We grouped coral species into
three broad classifications based on the increas-
ing structural complexity of their colony mor-
phologies (massive < branching < tabular) (table
S11) and determined that plastic debris is eight
times more likely to affect reef corals with greater
structu ral complexity (tabular and branching
versus massive, n= 348 transects; posterior prob-
ability functions) (Fig. 4A and table S12). Massive
coral morphologies are less likely to maintain
contact with plastic debris; however, they exhibit
the greatest increase in disease risk when this
occurs (likelihood is increased by 98%) (Fig. 4, B
to D, and table S13).
Our study shows that plastic debris increases
the susceptibility of reef-building corals to dis-
ease. Plastics are a previously unreported cor-
relate of disease in the marine environment.
Although the mechanisms remain to be inves-
tigated, the influence of plastic debris on dis-
ease development may differ among the three
main global diseases that we observed. For ex-
ample, plastic debris can cause physical injury
and abrasion to coral tissues by facilitating in-
vasion of pathogens (19) or by exhausting resources
for immune system function during wound-healing
processes (20). Experimental studies show that
artificially inflicted wounds to corals are fol-
lowed by the establishment of the ciliated pro-
tozoan Halofolliculina corallasia, the causative
agent of skeletal eroding band disease (21).
Plastic debris could also directly introduce
resident and foreign pathogens or may indirectly
alter beneficial microbial symbionts. Cross-ocean
bacterial colonization of polyvinylchloride (PVC)
is dominated by Rhodobacterales (22), a group
of potentially oppo rtunistic pathogens asso-
ciated with outbreaks of several coral dis-
eases (23). Additionally, recent studies have
sh ow n t hat experimental shading and low-light
microenvironments can lead to anoxic conditions
favoring the formation of polymicrobial mats
characteristic of black band disease (24).
By disproportionately reducing the composi-
tion or abundance of structurally complex reef-
building coral species through disease, widespread
distribution of plastic waste may have negative
consequences for biodiversity and people (25).
For example, on coral reefs, the loss of structural
habitat availability for reef organisms has been
shown to reduce fishery productivity by a factor
of 3 (26).
Climate-related disease outbreaks have already
affected coral reefs globally and are projected to
increase in frequency and severity as ocean tem-
peratures rise (27). With more than 275 million
people relying on coral reefs for food, coastal
protection, tourism income, and cultural impor-
tance (2), moderating disease outbreak risks in
the ocean will be vital for improving both human
and ecosystem health. Our study indicates that
decreasing the levels of plastic debris entering
the ocean by improving waste management in-
frastructure is critical for reducing the amount of
debris on coral reefs and the associated risk of
disease and structural damage.
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This research was supported by The Nature Conservancy NatureNet
Science Fellowship, an AIMS@JCU (Australian Institute of Marine Science
at James Cook University) Postgraduate Scholarship, the NSF Ecology of
Infectious Marine Disease Research Coordination Network [Division of
Ocean Sciences (OCE) award 1215977], the Capturing Coral Reef and
Ecosystem Related Services (CCRES) Project funded by the Global
Environment Facility and the World Bank (project ID P123933), NOAA/
National Ocean Service (NOS)HIMB agreement code MOA-2009-039,
Australian Research Council (grant CEO561435), and the Environmental
Defense Fund Innovation for Impact partnership with the At kinson Center
for a Sustainable Future at Cornell Univ ersity. Surveys in Australia were
conducted under Great Barrier Reef Marine Park Authority permi ts G10/
33393.1 and G12/35232.1. All data and cod e to understand and assess
the conclusions of this research are available in the main text,
supplementary materials, and via the Dryad Digital Repository (https://
Materials and Methods
Figs. S1 and S2
Tables S1 to S14
References (2830)
31 October 2017; accepted 21 December 2017
Lamb et al., Science 359, 460462 (2018) 26 January 2018 3of3
2.2 2.8 4.2
0.02 0.1 0.4 44 91 98 85 99
Disease likelihood
without plastic debris (%)
Likelihood of contact
with plastic debris (
Increase in disease likelihood
with plastic debris (%)
Disease likelihood
with plastic debris (%)
0100 100
Fig. 4. Coral morphological complexity influences risk to plastic debris
and disease. (Ato D) Posterior probability density functions of coral species
grouped into three broad morphological classifications. Structural complexity is
determined by coral species (18); see table S11 for classifications. Minimum,
maximum, and peak values are shown for each structural complexity classification
group: massive (dark red), branching (medium red), and tabular (light red). For
ease of comparison, the inset in (C) represents the likelihood of disease without
plastic debris [as shown in (B)].
on January 26, 2018 from
Plastic waste associated with disease on coral reefs
A. Kelly, Awaludinnoer Ahmad, Jamaluddin Jompa and C. Drew Harvell
Joleah B. Lamb, Bette L. Willis, Evan A. Fiorenza, Courtney S. Couch, Robert Howard, Douglas N. Rader, James D. True, Lisa
DOI: 10.1126/science.aar3320
(6374), 460-462.359Science
, this issue p. 460Science
and anoxia, giving pathogens a foothold for invasion.
increased 20-fold once a coral was draped in plastic. Plastic debris stresses coral through light deprivation, toxin release,
entangled in the reefs. The more spikey the coral species, the more likely they were to snag plastic. Disease likelihood
surveyed 159 coral reefs in the Asia-Pacific region. Billions of plastic items wereet al.effects of plastic waste. Lamb
Coral reefs provide vital fisheries and coastal defense, and they urgently need protection from the damaging
Corals wrapped in plastic
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on January 26, 2018 from
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The occurrence of polypropylene and polyethylene bags in the coral reefs of the Mandapam group of Islands has become a concern. These plastic bags pose a potential threat to corals, reef-associated animals, and divers. Field surveys were conducted to track the source of origin of these plastics along the islands and mainland beaches. This study indicated that these plastics are carried by the fishers from the mainland and deployed in the reefs around the islands to catch squids. Finding alternative substitutes to replace plastic bags is an important concern without impacting the livelihoods of fishers. Additionally, awareness among fishers regarding the impact of plastics on marine life needs to be generated and encourage their participation in conservation programs.
... Irrespective of this, previous studies have reported dFADs with coral fragments entangled in the netting, as well as entanglement over coral colonies (Zudaire et al., 2018). The detrimental effects for corals of ALDFG have been widely acknowledged in the literature, including the introduction of disease through tissue abrasion, fragmentation, light and oxygen deprivation, mortality, and in more severe cases, death of the entire reef (Balderson and Martin, 2015;Lamb et al., 2018;Baske and Adams, 2019;Mueller and Schupp, 2020). Given the large size, longdistance transport capabilities of dFADs and their complex mix of material types, beached dFADs can undoubtedly contribute to these threats to sensitive coral habitats and our analysis indicates that a large fraction of dFAD beachings in the Seychelles occur in coral reef areas. ...
Purse-seine fisheries use drifting Fish Aggregating Devices (dFADs), human-made floating objects, to facilitate the capture of tropical tunas. Currently, the majority of dFADs are constructed primarily of highly durable non-biodegradable materials and there is no legal obligation to recover dFADs after deployment, leading to beaching events and potentially negative environmental impacts. We assessed beachings as a function of intra- and inter-annual trends, water depth, distance from land, seasonality, and benthic habitat within the local context of the Seychelles Archipelago using trajectories of dFADs deployed by French purse seiners over 2008–2020. Overall, 3842 beaching events associated with 2371 distinct dFAD tracking buoys were identified. Beachings occurred most frequently during the winter monsoon (December–March). Due to the shallow Mahé Plateau, beachings occurred in both nearshore (≤ 5 km from land) and offshore (> 5 km) regions, predominantly in estimated depths less than 60 m. Despite representing < 20% of overall mapped habitat, the benthic habitat “Coral/Algae” had the highest beaching rate (35.3% of beachings), and therefore, beachings pose a significant concern for conservation. Our results provide a detailed view of the spatio-temporal pattern of beachings in the Seychelles, supporting the development of mitigation and prevention methods to reduce marine debris and perturbations to the marine environment.
... In recent years, more and more attention has been paid to the fact that significant amounts of plastic end up in the ecosystem where it harms living organisms. It has been emphasised in particular that marine ecosystems are vulnerable to nano-/micro-and macroplastic waste (Lamb et al. 2018). According to recent estimates, 11 million tons of plastic end up in the ocean each year (Ocean Conservancy 2021). ...
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This review is the first part of a comprehensive review of hydrophobisation of lignocellulosic materials. The purpose of this review has been to compare physical hydrophobisation methods of lignocellulosic materials. We have compared molecular physical adsorption with plasma etching and grafting. Adsorption methods are facile and rely upon the simple mixing or coating of the substrate with the hydrophobing agent. However, none of the surfactant-based methods reviewed here reach contact angles above 90°, making them unsuitable for applications where a high degree of hydrophobisation is required. Nevertheless, surfactant based methods are well suited for compatibilising the lignocellulosic material with a hydrophobic matrix/polymer in cases where only a slight decrease in the hydrophilicity of the lignocellulosic substrate is required. On the other hand, wax- and lignin-based coatings can provide high hydrophobicity to the substrates. Plasma etching requires a more complex set-up but is relatively cheap. By physically etching the surface with or without the deposition of a hydrophobic coating, the material is rendered hydrophobic, reaching contact angles well above 120°. A major drawback of this method is the need for a plasma etching set-up, and some researchers co-deposit fluorine-based layers, which have a negative environmental impact. An alternative is plasma grafting, where single molecules are grafted on, initiated by radicals formed in the plasma. This method also requires a plasma set-up, but the vast majority of hydrophobic species can be grafted on. Examples include fatty acids, silanes and alkanes. Contact angles well above 110° are achieved by this method, and both fluorine and non-toxic species may be used for grafting. Graphical abstract
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The focus of this study is to examine the level of awareness, as well as the impacts of environmental information provision, regarding plastic bag consumption in Greece, taking into consideration the effects of plastic pollution in the marine environment within the framework of the environmental levy. This study was conducted through the use of two structured questionnaires as web-based surveys. The aim of both questionnaires was to explore citizen attitudes towards the marine environment in addition to their preferences with regard to the implementation of a program aimed at marine conservation and the reduction of plastic bag use. Data on plastic bag consumption at a national level were also incorporated. This research was carried out according to the contingent valuation method aimed at estimating citizen willingness-to-pay (WTP) on both structured questionnaires. The first questionnaire utilized the minimal legal WTP (ML-WTP) model resulting in 834 responses in total, while the second questionnaire applied a double-bounded dichotomous choice method and amassed 713 responses in aggregate. Based on the results of the first questionnaire, pre-existing environmentally friendly behaviour was further enhanced by the introduction of the environmental levy on plastic bags. The second questionnaire revealed that marine conservation is based both on collective as well as individual responsibility. This study provides evidence that the utilization of both economic and non-economic measures may be very effective in considerably reducing plastic bag consumption and its detrimental impact on the marine environment.
The present review is detailed on the microplastics occurrences and their size, types besides impacts of microplastics from phytoplankton to marine mammals. Hence, the previous studies stated that the impacts of microplastics in the marine environment have been compared with the interaction of microplastics into marine organisms such as primary and secondary producers, fish, crustaceans, molluscs, sponges, marine plants, coral reefs, marine mammals and humans. Lastly, there is a need to understand the ecotoxicological effects of environmentally relevant concentrations of microplastics on the health of aquatic organisms. The recycling and reuse of plastic products and the support for research and innovation to develop new products to replace single-use plastics are also necessary to prevent and reduce plastic pollution. Thus, a precautionary approach is urged to be considered and research supporting mitigation of plastic pollution should be prioritized by the policy makers.
Over recent years, awareness of the ecological consequences of marine plastic debris has increased considerably. This chapter focuses on the ingestion of plastics. It defines harm within the ecotoxicological context of impacts on organisms and ecosystems. Owing to the small size of microplastics and their near ubiquitous presence throughout the marine environment, concern for marine life arises from their ingestion. The result of the microplastic exposure can lead to effects at different levels of biological functioning, including those on the individual, at site‐specific target organs, on certain cell types, and even subcellular effects. To date, few studies have quantified the effects of microplastic pollution on ecosystem functioning. During production, chemicals are added to plastics to alter or improve their desired properties, such as plasticizers, flame‐retardants, antimicrobial agents, or UV inhibitors. These additive chemicals can subsequently leach from the plastic into the environment or, if ingested, into organisms.
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The availability of habitat structure across spatial scales can determine ecological organization and resilience. However, anthropogenic disturbances are altering the abundance and composition of habitat-forming organisms. How such shifts in the composition of these organisms alter the physical structure of habitats across ecologically important scales remains unclear. At a time of unprecedented coral loss and homogenization of coral assemblages globally, we investigate the inherent structural complexity of taxonomically distinct reefs, across five ecologically relevant scales of measurement (4–64 cm). We show that structural complexity was influenced by coral species composition, and was not a simple function of coral cover on the studied reefs. However, inter-habitat variation in structural complexity changed with scale. Importantly, the scales at which habitat structure was available also varied among habitats. Complexity at the smallest, most vulnerable scale (4 cm) varied the most among habitats, which could have inferences for as much as half of all reef fishes which are small-bodied and refuge dependent for much of their lives. As disturbances continue and species shifts persist, the future of these ecosystems may rely on a greater concern for the composition of habitat-building species and prioritization of particular configurations for protection of maximal cross-scale habitat structural complexity.
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Marine protected areas can prevent over-exploitation, but their effect on marine diseases is less clear. We examined how marine reserves can reduce diseases affecting reef-building corals following acute and chronic disturbances. One year after a severe tropical cyclone, corals inside reserves had sevenfold lower levels of disease than those in non-reserves. Similarly, disease prevalence was threefold lower on reserve reefs following chronic exposure to terrestrial run-off from a degraded river catchment, when exposure duration was below the long-term site average. Examination of 35 predictor variables indicated that lower levels of derelict fishing line and injured corals inside reserves were correlated with lower levels of coral disease in both case studies, signifying that successful disease mitigation occurs when activities that damage reefs are restricted. Conversely, reserves were ineffective in moderating disease when sites were exposed to higher than average levels of run-off, demonstrating that reductions in water quality undermine resilience afforded by reserve protection. In addition to implementing protected areas, we highlight that disease management efforts should also target improving water quality and limiting anthropogenic activities that cause injury.
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Rising sea temperatures are likely to increase the frequency of disease outbreaks affecting reef-building corals through impacts on coral hosts and pathogens. We present and compare climate model projections of temperature conditions that will increase coral susceptibility to disease, pathogen abundance and pathogen virulence. Both moderate (RCP 4.5) and fossil fuel aggressive (RCP 8.5) emissions scenarios are examined. We also compare projections for the onset of disease-conducive conditions and severe annual coral bleaching, and produce a disease risk summary that combines climate stress with stress caused by local human activities. There is great spatial variation in the projections, both among and within the major ocean basins, in conditions favouring disease development. Our results indicate that disease is as likely to cause coral mortality as bleaching in the coming decades. These projections identify priority locations to reduce stress caused by local human activities and test management interventions to reduce disease impacts.
During 2015-2016, record temperatures triggered a pan-tropical episode of coral bleaching, the third global-scale event since mass bleaching was first documented in the 1980s. Here we examine how and why the severity of recurrent major bleaching events has varied at multiple scales, using aerial and underwater surveys of Australian reefs combined with satellite-derived sea surface temperatures. The distinctive geographic footprints of recurrent bleaching on the Great Barrier Reef in 1998, 2002 and 2016 were determined by the spatial pattern of sea temperatures in each year. Water quality and fishing pressure had minimal effect on the unprecedented bleaching in 2016, suggesting that local protection of reefs affords little or no resistance to extreme heat. Similarly, past exposure to bleaching in 1998 and 2002 did not lessen the severity of bleaching in 2016. Consequently, immediate global action to curb future warming is essential to secure a future for coral reefs.
Recent estimates suggest that roughly 100 times more plastic litter enters the sea than is found floating at the sea surface, despite the buoyancy and durability of many plastic polymers. Biofouling by marine biota is one possible mechanism responsible for this discrepancy. Microplastics (<5 mm in diameter) are more scarce than larger size classes, which makes sense because fouling is a function of surface area whereas buoyancy is a function of volume; the smaller an object, the greater its relative surface area. We tested whether plastic items with high surface area to volume ratios sank more rapidly by submerging 15 different sizes of polyethylene samples in False Bay, South Africa, for 12 weeks to determine the time required for samples to sink. All samples became sufficiently fouled to sink within the study period, but small samples lost buoyancy much faster than larger ones. There was a direct relationship between sample volume (buoyancy) and the time to attain a 50% probability of sinking, which ranged from 17 to 66 days of exposure. Our results provide the first estimates of the longevity of different sizes of plastic debris at the ocean surface. Further research is required to determine how fouling rates differ on free floating debris in different regions and in different types of marine environments. Such estimates could be used to improve model predictions of the distribution and abundance of floating plastic debris globally.
The accumulation of plastic in the marine environment is a long-known issue, but the potential relevance of this pollution for the ocean has been recognised only recently. Within this context, microplastic fragments (<5 mm) represent an emerging topic. Owing to their small size, they are readily ingested by marine wildlife and can accumulate in the food web, along with associated toxins and microorganisms colonising the plastic. We are starting to understand that plastic biofilms are diverse and are, comparably with non-plastic biofilms, driven by a complex network of influences, mainly spatial and seasonal factors, but also polymer type, texture and size of the substratum. Within this context, we should raise the question about the potential of plastic particles to serve as vectors for harmful microorganisms. The main focus of the review is the discussion of first insights and research gaps related to microplastic-associated microbial biofilm communities.
Bacterial colonization of marine plastic litter (MPL) is known for over four decades. Still, only a few studies on the plastic colonization process and its influencing factors are reported. In this study, seafloor MPL was sampled at different locations across the Belgian part of the North Sea to study bacterial community structure using 16S metabarcoding. These marine plastic bacterial communities were compared with those of sediment and seawater, and resin pellets sampled on the beach, to investigate the origin and uniqueness of plastic bacterial communities. Plastics display great variation of bacterial community composition, while each showed significant differences from those of sediment and seawater, indicating that plastics represent a distinct environmental niche. Various environmental factors correlate with the diversity of MPL bacterial composition across plastics. In addition, intrinsic plastic-related factors such as pigment content may contribute to the differences in bacterial colonization. Furthermore, the differential abundance of known primary and secondary colonizers across the various plastics may indicate different stages of bacterial colonization, and may confound comparisons of free-floating plastics. Our studies provide insights in the factors that shape plastic bacterial colonization and shed light on the possible role of plastic as transport vehicle for bacteria through the aquatic environment.
Parks and protected areas have been instrumental in reducing anthropogenic sources of damage in terrestrial and aquatic environments. Pathogen invasion often succeeds physical wounding and injury, yet links between the reduction of damage and the moderation of disease have not been assessed. Here, we examine the utility of no-take marine reserves as tools for mitigating diseases that affect reef-building corals. We found that sites located within reserves had four-fold reductions in coral disease prevalence compared to non-reserve sites (80,466 corals surveyed). Of 31 explanatory variables assessed, coral damage and the abundance of derelict fishing line best explained differences in disease assemblages between reserves and non-reserves. Unexpectedly, we recorded significantly higher levels of disease, coral damage and derelict fishing line in non-reserves with fishing gear restrictions than in those without gear restrictions. Fishers targeting stocks perceived to be less depleted, coupled with enhanced site access from immediately adjacent boat moorings, may explain these unexpected patterns. Significant correlations between the distance from mooring sites and prevalence values for a ciliate disease known to infest wounded tissue (r = -0.65), coral damage (r = -0.64) and the abundance of derelict fishing line (r = -0.85) corroborate this interpretation. This is the first study to link disease with recreational use intensity in a park, emphasizing the need to evaluate the placement of closures and their direct relationship to ecosystem health. Since corals are modular, ecological processes that govern reproductive and competitive fitness are frequently related to colony surface area, therefore even low levels of cumulative tissue loss from progressing diseases pose significant threats to reef coral persistence. Disease mitigation through reductions in physical injury in areas where human activities are concentrated is another mechanism by which protected areas may improve ecosystem resilience in a changing climate.
Plastic debris in the marine environment is widely documented, but the quantity of plastic entering the ocean from waste generated on land is unknown. By linking worldwide data on solid waste, population density, and economic status, we estimated the mass of land-based plastic waste entering the ocean. We calculate that 275 million metric tons (MT) of plastic waste was generated in 192 coastal countries in 2010, with 4.8 to 12.7 million MT entering the ocean. Population size and the quality of waste management systems largely determine which countries contribute the greatest mass of uncaptured waste available to become plastic marine debris. Without waste management infrastructure improvements, the cumulative quantity of plastic waste available to enter the ocean from land is predicted to increase by an order of magnitude by 2025. Copyright © 2015, American Association for the Advancement of Science.