Marine litter disrupts ecological processes in reef systems

Trapping of microplastics and other anthropogenic particles in seagrass beds: Ubiquity across a vertical and horizontal sampling gradient

Seagrass beds can trap large amounts of marine debris leading to areas of accumulation, known as 'sinks', of anthropogenic particles. While the presence of vegetation can enhance accumulation, less is known about how the trapping effect changes from vegetated to less vegetated patches. To test this, vegetation and sediment were sampled along a vegetation percent cover gradient from the centre of seagrass beds to nearby less vegetated patches. To determine whether trapped particles can lead to increased accumulation in associated fauna, gastropods were also collected from the transects laid across this gradient. Extracted anthropogenic particles were counted and characterised. Particles were detected in all sample types and reached quantifiable limits in at least 50% of sediment and gastropod samples. There was no significant difference in the distribution of particles found in seagrass beds compared to less vegetated patches, suggesting other factors contribute to the trapping efficiency of biogenic habitats besides simply the presence or absence of vegetation.

Identifying potential high-risk zones for land-derived plastic litter to marine megafauna and key habitats within the North Atlantic

The pervasive use of plastic in modern society has led to plastic litter becoming ubiquitous within the ocean. Land-based sources of plastic litter are thought to account for the majority of plastic pollution in the marine environment, with plastic bags, bottles, wrappers, food containers and cutlery among the most common items found. In the marine environment, plastic is a transboundary pollutant, with the potential to cause damage far beyond the political borders from where it originated, making the management of this global pollutant particularly complex. In this study, the risks of land-derived plastic litter (LDPL) to major groups of marine megafauna - seabirds, cetaceans, pinnipeds, elasmobranchs, turtles, sirenians, tuna and billfish - and a selection of productive and biodiverse biogenic habitats - coral reefs, mangroves, seagrass, saltmarsh and kelp beds - were analysed using a Spatial Risk Assessment approach. The approach combines metrics for vulnerability (mechanism of harm for megafauna group or habitat), hazard (plastic abundance) and exposure (distribution of group or habitat). Several potential high-risk zones (HRZs) across the North Atlantic were highlighted, including the Azores, the UK, the French and US Atlantic coasts, and the US Gulf of Mexico. Whilst much of the modelled LDPL driving risk in the UK originated from domestic sources, in other HRZs, such as the Azores archipelago and the US Gulf of Mexico, plastic originated almost exclusively from external (non-domestic) sources. LDPL from Caribbean islands - some of the largest generators of marine plastic pollution in the dataset of river plastic emissions used in the study - was noted as a significant input to HRZs across both sides of the Atlantic. These findings highlight the potential of Spatial Risk Assessment analyses to determine the location of HRZs and understand where plastic debris monitoring and management should be prioritised, enabling more efficient deployment of interventions and mitigation measures.

Environmental DNA metabarcoding reveals the effects of seafloor litter and trawling on marine biodiversity

Environmental DNA (eDNA) techniques are emerging as promising tools for monitoring marine communities. However, they have not been applied to study the integrated effects of anthropogenic pressures on marine biodiversity. This study examined the relationships between demersal community species composition, key environmental features, and anthropogenic impacts such as fishing effort and seafloor litter using eDNA data in the central Tyrrhenian Sea. The results indicated that both fishing effort and seafloor litter influenced species composition and diversity. The adaptive traits of marine species played a critical role in their response to debris accumulation and fishing. Mobile species appeared to use relocation strategies, while sessile species showed flexibility in the face of disturbance. Epibiotic species relied on passive transport. The use of eDNA-based methods is a valuable resource for monitoring anthropogenic impacts during scientific surveys, enhancing our ability to monitor marine ecosystems and more effectively assess the effects of pollution.

The plastic homes of hermit crabs in the Anthropocene

Plastic is the most pervasive element of marine waste, with harmful impact on wildlife. By using iEcology (i.e., internet Ecology, use of online data sources as a new tool in ecological research), we report on the emergence of a novel behaviour in hermit crabs related to the use of plastic or other anthropogenic materials as protective shells. We analysed images posted on social media to identify 386 individuals with artificial shells - mainly plastic caps (85 %). We report that 10 of the world's 16 terrestrial hermit crabs use artificial shells, a behaviour observed on all of the Earth's tropical coasts. Four non-exclusive mechanisms may drive individual choice for artificial shells: sexual signaling, lightness of artificial shells, odour cues, and camouflage in a polluted environment. Further research is needed to determine the impact of this behaviour on hermit crab evolutionary trajectories.

Litter traps: A comparison of four marine habitats as sinks for anthropogenic marine macro-litter in Singapore

The potential for marine litter being trapped in biodiverse marine habitats such as mangrove forests, seagrass meadows and coral reefs is poorly understood. This study presents the first comprehensive investigation on the status of macro-litter across four marine habitats in Singapore during the two monsoonal seasons. Overall, litter density did not vary considerably between the southwest and the northeast monsoon. The litter density in terms of count was generally lower in seagrass meadows and coral reefs compared to mangroves and beaches. Plastic was the major type of litter found across most habitat types. Notably, many fishing-related items were found on coral reefs, while drinking straws were abundant at the mangrove strandlines during the southwest monsoon. Foam fragments and cigarette butts were common at the beach strandlines. These results suggest that mangroves among other habitats examined here should be prioritised for clean-up efforts in order to restore these critical coastal habitats.

Cetaceans playing with single-use plastics (SUPs): A widespread interaction with likely severe impacts

Play is a common behaviour in wild cetaceans that includes the manipulation of natural, as well as artificial objects such as marine debris. Yet, very little is known about these interactions despite the potential impacts on cetacean health. We combined a detailed review of the scientific literature and social media with 12 years of observations to examine cetacean interactions with plastic litter. A total of 11 odontocete species (Tursiops truncatus, Stenella longirostris, Delphinus delphis, Grampus griseus, Steno bredanensis, Stenella frontalis, Sotalia guianensis, Pseudorca crassidens, Orcinus orca, Globicephala melas and Physeter macrocephalus) were documented in 59 events carrying or throwing plastic litter with their head and/or flippers suggesting a form of play. Interactions occurred in the Atlantic, Pacific, Indian Ocean, Mediterranean, and Red Sea, with single-use plastics composing the main typology registered. While these interactions appeared harmless to the observers, they can pose a significant risk through subsequent entanglement or ingestion.

Rocky reef incursions: challenges faced by reef fishes in a Brazilian Hope Spot region

Biodiversity conservation has been a critical challenge faced by environmental managers worldwide. From 2020 to 2022, a total of 576 underwater visual censuses focused on reef fishes, marine litter (ML), and non-native species were performed in the newest Brazilian Hope Spot, to understand the distribution, characteristics, and effects of ML and Tubastraea spp., on the reef fish community. Plastic was the main category recorded (34.54 %), followed by Metal and Line (mostly fishing gear within a Marine Protected Area). Tubastraea spp. was widely distributed, especially between 10-20 meters deep. The t-test analysis showed that fish abundance and richness were significantly higher at low Tubastraea cover areas. Our efforts present the baseline of ML (mean 1.92 ± 1.5 items/100 m2) and non-native species occurrence (15) and distribution (including three new records) showing their negative impacts on rocky reef ecosystems and provide managers support in the elaboration of marine conservation strategies.

Difference between invasive alien and native vegetation in trapping beach litter: A focus on a typical sandy beach of W-Mediterranean Basin

Beach litter is one of the most pervasive pollution issues in coastal environments worldwide. In this study, we aim to assess the amount and distribution of beach litter on Porto Paglia beach, its entrapment across psammophilous habitats, and whether the invasive Carpobrotus acinaciformis (L.) L.Bolus plays a different role in trapping litter than native vegetation. To this end, two seasonal samplings (in spring and autumn) were conducted using a paired sampling method that considers plots in all coastal habitats with and without C. acinaciformis. Our results confirm that the main beach litter category is plastic, and that its distribution varies across habitats: the white dune seems to play a greater role in trapping and filtering beach litter, reducing its amount in the backdune. A correlation was found between the Naturalness index (N) and the beach litter amount, supporting the finding that invaded habitats trap beach litter better than native ones.

Life on bottles: Colonisation of macroplastics by freshwater biota

While rivers are known to be the main vectors of plastics to the sea, it seems surprising that studies on interactions (e.g. colonisation/entrapment and drift) between macroplastics and biota continue to remain largely neglected, notwithstanding they represent unexpected threats to freshwater biota and riverine habitats. To fill these gaps, here we focused on the colonisation of plastic bottles by freshwater biota. To do so, we collected 100 plastic bottles from the River Tiber in summer 2021. Overall, 95 bottles were colonised externally and 23 internally. Specifically, biota mainly occurred within and outside the bottles rather than plastic pieces and organic debris. Moreover, while bottles were externally covered mainly by vegetal organisms (i.e. macrophytes), they internally entrapped more animal organisms (i.e. invertebrates). The taxa most occurring within and outside the bottles belonged to pool and low water quality-associated taxa (e.g. Lemna sp., Gastropoda, and Diptera). In addition to biota and organic debris, plastic particles also occurred on bottles reporting the first observation of 'metaplastics' (i.e. plastics encrusted on bottles). Furthermore, we observed a significant positive correlation between the colonising taxa abundance and the bottle degree degradation. In this regard, we discussed how bottle buoyancy may change due to the organic matter on the bottle, affecting bottle sinking and transport along rivers. Our findings might be crucial for understanding the underrepresented topic of riverine plastics and their colonisation by biota, given that these plastics may act as vectors and cause biogeographical, environmental, and conservation issues to freshwater habitats.

Understanding the interactions between cephalopods and marine litter: A research evaluation with identification of gaps and future perspectives

Litter is known to negatively affect numerous marine organisms, but the extent of such impacts is not well known for several groups, including cephalopods. Considering the ecological, behavioral and economic importance of these animals, we reviewed the types of interactions between cephalopods and litter in the scientific literature, to evaluate impacts and knowledge gaps. We found 30 papers, which included records of microplastic ingestion and the transfer of synthetic microfibers along the food web. The largest number of records involved litter use as shelter, and the common octopus was the most frequent species. At first sight, litter use as shelter could appear to be a potential positive effect, but it is necessary to clarify the implications of this choice and its long-term consequences. Regarding ingestion and trophic transfer, further research is needed to elucidate its occurrence and impacts on cephalopods and their predators, including humans.

Distribution and risk assessment of microplastics in typical ecosystems in the South China Sea

Microplastic pollution in the marine environment has attracted worldwide attention. The South China Sea is considered a hotspot for microplastic pollution due to the developed industries and high population density around the South China Sea. The accumulation of microplastics in ecosystems can adversely affect the health of the environment and organisms. This paper reviews the recent microplastic studies conducted in the South China Sea, which novelty summarizes the abundance, types, and potential hazards of microplastics in coral reef ecosystems, mangrove ecosystems, seagrass bed ecosystems, and macroalgal ecosystems. A summary of the microplastic pollution status of four ecosystems and a risk assessment provides a more comprehensive understanding of the impact of microplastic pollution on marine ecosystems in the South China Sea. Microplastic abundances of up to 45,200 items/m³ were reported in coral reef surface waters, 5738.3 items/kg in mangrove sediments, and 927.3 items/kg in seagrass bed sediments. There are few studies of microplastics in the South China Sea macroalgae ecosystems. However, studies from other areas indicate that macroalgae can accumulate microplastics and are more likely to enter the food chain or be consumed by humans. Finally, this paper compared the current risk levels of microplastics in the coral reef, mangrove, and seagrass bed ecosystems based on available studies. Pollution load index (PLI) ranges from 3 to 31 in mangrove ecosystems, 5.7 to 11.9 in seagrass bed ecosystems, and 6.1 to 10.2 in coral reef ecosystems, respectively. The PLI index varies considerably between mangroves depending on the intensity of anthropogenic activity around the mangrove. Further studies on seagrass beds and macroalgal ecosystems are required to extend our understanding of microplastic pollution in marine environments. Recent microplastic detection in fish muscle tissue in mangroves requires more research to further the biological impact of microplastic ingestion and the potential food safety risks.

Impacts of marine debris on coral reef ecosystem: A review for conservation and ecological monitoring of the coral reef ecosystem

Coral reefs are the most spectacular underwater creation of nature. It enhances ecosystem functioning and marine biodiversity while also ensuring the livelihood of millions of coastal communities worldwide. Unfortunately, marine debris poses a serious threat to ecologically sensitive reef habitats and their associated organisms. Over the past decade, marine debris has been regarded as a major anthropogenic threat to marine ecosystems and gained scientific attention around the globe. However, the sources, types, abundance, distribution, and potential consequences of marine debris on reef ecosystems are hardly known. The goal of this review is to provide an overview of the current status of marine debris in various reef ecosystems across the world, with special emphasis on its sources, abundance, distribution, species impacted, major categories, potential impacts and management strategies. Furthermore, the adhesion mechanisms of microplastics to coral polyps, diseases caused by microplastics and are also highlighted.

Macro- and microplastics as complex threats to coral reef ecosystems

The impacts of macroplastics (macro-), microplastics (MPs, <5mm), and nanoplastics (NPs, <100 nm) on corals and their complex reef ecosystems are receiving increased attention and visibility. MPs represent a major, contemporary, sustainability challenge with known and unknown effects on the ocean, and coral reef ecosystems worldwide. However, the fate and transport processes of macro-, MPs, and NPs and their direct and indirect impacts on coral reef ecosystems remains poorly understood. In this study, we verify and briefly summarize MPs distribution and pollution patterns in coral reefs from various geographical regions and discuss potential risks. The main interaction mechanisms show that MPs may substantially affect coral feeding performance, proper skeletal formation, and overall nutrition and, thus, there is an urgent need to address this rapidly growing environmental problem. From a management perspective, macro-, MPs, and NPs should, ideally, all be included in environmental monitoring frameworks, as possible, to aid in identifying those geographical areas that are most heavily impacted and to support future prioritization of conservation efforts. The potential solutions to the macro-, MP, and NP pollution problem include raising public awareness of plastic pollution, developing robust, environmental, conservation efforts, promoting a circular economy, and propelling industry-supported technological innovations to reduce plastic use and consumption. Global actions to curb plastic inputs, and releases of macro-, MP, and NP particles, and their associated chemicals, to the environment are desperately needed to secure the overall health of coral reef ecosystems and their inhabitants. Global scale horizon scans, gap analyses, and other future actions are necessary to gain and increase momentum to properly address this massive environmental problem and are in good accordance with several relevant UN sustainable development goals to sustain planetary health.

Anthropogenic marine litter: An approach to environmental quality for India's southeastern Arabian Sea coast

Anthropogenic marine litter (AML), mainly plastic, is a global concern that is persistent and widespread. To prevent and mitigate this threat, we need to understand the magnitude and source of AML. There is limited knowledge about AML pollution on the Indian Coast. In this context, the present study examined the distribution, abundance, typology, and beach quality based on AML along 22 beaches on the southeastern coast of the Arabian Sea. A total of 4911 AML items were classified into 9 categories, weighing 16.79 kg, and retrieved from a total area of 8000 m². The mean abundance and weight of AML in the current study were 0.45 ± 0.34 items/m² and 1.53 ± 0.92 g/m², respectively. Thottapally showed the most abundant AML among the studied beaches with 0.96 items/m², followed by Azheekkal with 0.73 items/m². Plastic, being the most common item, accounts for 77.6 % of all items and has a mean density of 0.35 items/m² comprising hard plastic (22 %), thermocol (13 %), food wrappers (7 %), cigarette butts (7 %), plastic rope (6 %), and plastic cutlery (6 %). Hazardous anthropogenic litter (HAL) was maximum at Thottapally (17.71 %; 85 out of 480 items collected). Based on the cleanliness of beaches, they are graded "moderately clean" (63 %) by the General Index (GI), "clean" (54 %), and "moderately clean" (40 %) as calculated by the Clean Coast Index (CCI). Hazardous Anthropogenic Beach Litter Index (HABLI) classifies 72 % of beaches as "moderately safe", while the Environmental Status Index (ESI) rates 68 % of beaches as "mediocre". Besides, model simulations demonstrated the pathways of AML propagation, which correlate to the littoral and coastal current flow patterns over the region. Land-based activities were the crucial factors influencing AML distribution. The study highlighted the need for effective regional litter management strategies, policy instruments for the litter impact pathways, economic, regulatory, and behavioural management tools, which were also discussed.

First baseline assessment of seafloor litter on Italian coralligenous assemblages (Mediterranean Sea) in accordance with the European Marine Strategy Framework Directive

A monitoring programme for coralligenous assemblages was carried out in Italy for implementation of the Marine Strategy Framework Directive (MSFD), aiming to characterise the coralligenous' environmental status and litter distribution. A standardised monitoring protocol, based on ROV-imaging, has been applied; this paper analyses the data obtained during the first MSFD cycle (2015-2019). Ninety-five areas were monitored at depths ranging between 14 and 199 m in the three subregions bordering Italy. Overall, 4316 macrolitter items were recorded. The median litter density was 2 items 100 m^-2 (range: 0-120 items 100 m^-2), but significant subregional differences emerged in litter quantities and composition. Fishery-related litter (mainly lines and ropes) was the most common type (86 %), affecting vulnerable coralligenous reefs. A first baseline is proposed for assessing achievement toward Good Environmental Status and evaluation of the efficacy of the Italian MSFD measures aiming to eliminate the negative effects of marine litter on vulnerable reefs.

Plastic pollution of four understudied marine ecosystems: a review of mangroves, seagrass meadows, the Arctic Ocean and the deep seafloor

Plastic pollution is now a worldwide phenomenon affecting all marine ecosystems, but some ecosystems and regions remain understudied. Here, we review the presence and impacts of macroplastics and microplastics for four such ecosystems: mangroves, seagrass meadows, the Arctic Ocean and the deep seafloor. Plastic production has grown steadily, and thus the impact on species and ecosystems has increased, too. The accumulated evidence also indicates that plastic pollution is an additional and increasing stressor to these already ecosystems and many of the species living in them. However, laboratory or field studies, which provide strong correlational or experimental evidence of ecological harm due to plastic pollution remain scarce or absent for these ecosystems. Based on these findings, we give some research recommendations for the future.

Limited effects of environmentally-relevant concentrations in seawater of dibutyl phthalate, dimethyl phthalate, bisphenol A, and 4-nonylphenol on the reproductive products of coral-reef organisms

Plastic additives (PAs) are chemical compounds incorporated into the plastic during the manufacturing process. Phthalate acid esters, bisphenols, and nonylphenols are all PAs found in marine environments and associated with endocrine-disrupting processes. However, our knowledge regarding the impact of endocrine-disrupting PAs on coral-reef organisms is limited. As reef population structure is directly linked to reproduction and larval settlement processes, interference with hormonal systems can impact coral-reef community structure, particularly if the effects of PAs differ among species. In the current study we exposed the reproductive products of four tropical coral-reef invertebrates to environmentally-relevant concentrations of four prevalent PAs in seawater: dibutyl phthalate (DBP), dimethyl phthalate, (DMP), 4-nonylphenol (4-NP), and bisphenol A (BPA), as well as to 10³ higher laboratory concentrations of these PAs. Our results revealed that apart from the significant negative effect of the 1 μg/L of 4-NP on the settlement of the soft coral Rhytisma fulvum, none of the other tested materials demonstrated a significant effect on the exposed organisms at environmentally-relevant concentrations in seawater. The 4-NP high laboratory concentration (1000 μg/L), however, had significant negative effects on all the examined species. The high laboratory BPA concentration (1000 μg/L) significantly reduced fertilization success in the solitary ascidian Herdmaniamomus, up to its complete failure to reproduce. Moreover, the high laboratory DMP concentration (100 μg/L) had a significant negative effect on planulae settlement of the stony coral Stylophora pistillata. Our findings demonstrate the negative and selective effects of PAs on the development and reproduction of coral-reef organisms; and, specifically, the significant effect found following exposure to 4-NP. Consequently, if we aim to fully understand the impact of these contaminants on this endangered ecosystem, we suggest that the actual concentrations within the living organism tissues should be tested in order to produce relevant risk assessments for brooding-coral species.

Benthic litter in the continental slope of the Gulf of Naples (central-western Mediterranean Sea) hosts limited fouling communities but facilitates molluscan spawning

Seafloor pollution by benthic litter is an emerging phenomenon, although debris colonization by biota remains largely unexplored. We characterized the litter of the continental slope (~400-600 m) of the Gulf of Naples (Mediterranean) and investigated its fouling biota through integrative taxonomic approaches. Plastic pieces (82 %) with land-based origin (96 %) and limited sizes (10-20 cm) were the items most commonly encountered, suggesting a transfer to deep waters through floating and sinking. The majority of the items were not fouled, and the debris hosted an impoverished biota, leading to hypothesize that benthic litter supports wide communities only in shallow waters. Higher colonization rates were observed for gastropod and cephalopod eggs with no preference for materials and sizes, suggesting that even small pieces of soft plastic provide a spawning habitat for molluscs and affect species' connectivity in the deep-sea ecosystem. Holistic approaches are necessary to evaluate interactions between litter and biota.

Plastics are a new threat to Palau’s coral reefs

Plastic pollution of the oceans has long been an ongoing and growing problem. Single-use plastic (plastic bags and microbeads) is responsible for most of this pollution. In recent years, studies have highlighted the importance of the size of plastic particles, and the impact of this pollution source on the environment. We determined the concentration of small marine plastics in seawater, sediments and beach sand around a pristine reef area (Republic of Palau) using very simple tools (plankton net, sieves, organic matter degradation, density separation, Nile red fluorochrome). In this study, we succeeded in detecting microplastic (MPs) particles and microplastic fibers, but also nanoplastic (NPs). These three types of particles were found in all samples with a large heterogeneity, from 0.01 to 0.09 particles L-1 and 0.17 to 32.13 particles g-1 DW for MPs in seawater, sediments and sand, respectively. Even when NPs were identified, the amounts of NPs were underestimated and varied from 0.09 to 0.43 particles L^-1 in seawater and from 1.08 to 71.02 particles g^-1 DW in sediment and sand, respectively. These variations could be attributed to the environmental characteristics of the different sites. This study shows that plastic pollution must be considered in environmental studies even in the most pristine locations. It also shows that NPs pollution is related to the amount of MPs found at the sites. To understand the effects of this plastic pollution, it is necessary that the next toxicological studies take into account the effects of this fraction that makes up the NPs.

What Teachers Should Know for Effective Marine Litter Education: A Scoping Review

Marine litter has had a huge impact on the marine environment and the socio-economic activities that depend on healthy oceans. All members of the community must play their part to address marine litter. Teachers are agents of change that are capable of encouraging pro-environmental practices among the community that will reduce environmental issues, including marine litter. However, teachers were found to have limited knowledge regarding ocean literacy and marine pollution. A scoping review was conducted to identify various aspects of content knowledge related to marine litter education that has been recently conducted for school teachers and students. Web of Science, Scopus and ERIC databases were searched for articles published in English between 2015 and 8 July 2021. Fourteen peer-reviewed articles were selected for this study and were subjected to content analysis. Topics related to marine litter were frequently addressed. Meanwhile, topics related to teaching Environmental Education/Education for Sustainable Development (EE/ESD) were the least addressed. Benthic marine litter, solutions to marine litter and the introduction of new types of marine litter were identified as topics that need to be addressed in future marine litter education. This study lists content knowledge based on previous literature and identified the gaps, which will be useful for teachers to improve their knowledge and implement effective marine litter education in school.

In an octopus's garden in the shade: Underwater image analysis of litter use by benthic octopuses

Benthic octopuses have been widely documented in artificial shelters for decades, and this use is apparently increasing. Despite any possible positive effects, the use of litter as shelter could have negative implications. In this work, we aimed to elucidate the interactions of octopuses with marine litter, identifying types of interactions and affected species and regions. To achieve this, we obtained 261 underwater images from 'citizen science' records, and identified 8 genera and 24 species of benthic octopuses interacting with litter. Glass objects were present in 41.6% of interactions, and plastic in 24.7%. Asia presented the highest number of images, and most records were from 2018 to 2021. Citizen science provided important evidence on octopus/marine litter interactions, highlighting its value and the need for more investigations on the subject. This information is fundamental to help prevent and mitigate the impacts of litter on octopuses, and identify knowledge gaps that require attention.

A comprehensive approach to assess marine macro litter pollution and its impacts on corals in the Bangka Strait, North Sulawesi, Indonesia

This is a comprehensive study showing the marine anthropogenic litter pollution within North Sulawesi, Indonesia. From an area of 2972 m² that encompassed five sparsely populated locations, a total of 9421 litter items weighing 137 kg were collected. One location (Talisei North) contributed 50% of all collected litter items. Plastic litter always dominated with 96-99%. Litter was unevenly distributed across investigated areas reaching from the upper beach (3.6-30.1 items/m²) to the reef slope (0-0.03 items/m²). Litter composition and daily accumulation showed spatial-temporal dynamics, with upper beach areas displaying the overall highest accumulation rates. Reef micro-habitats were differently affected, with the reef moat and reef flat showing the highest litter concentrations, although litter amounts were much lower compared to the corresponding beaches. Branching corals, especially Porites cylindrica, were most affected by litter entanglement. Field experiments with P. cylindrica showed that attached plastic induced bleaching, necrosis, and algal overgrowth within five months.

The waste collector: information from a pilot study on the interaction between the common octopus (Octopus vulgaris, Cuvier, 1797) and marine litter in bottom traps fishing and first evidence of plastic ingestion

Few studies focused on behaviour adaptations of organisms to marine litter (ML) pollution in Mediterranean Sea. This research, investigates on some behavior traits of Octopus vulgaris, focusing on the interaction with ML during the artisanal fishing activities by the bottom traps in a small coastal area of the southern Tyrrhenian Sea. For the first time, this pilot study uses an integrated approach based on the Fishermen Ecological Knowledge as well as the analysis of ML found in the traps. First assessment of plastic ingestion in this species are also reported. Plastic and metal were the predominant ML categories observed into the bottom traps. A total of 62 plastics, mainly small microplastics and fibres shaped, were ingested. The ML finding in the bottom traps suggests an interesting behavior of the common octopus regarding its interaction with ML, in fact, it seems to bring ML inside its dens, as a collector.

Low quantities of marine debris at the northern Ningaloo Marine Park, Western Australia, influenced by visitation and accessibility

Marine debris (MD) is a serious environmental concern globally. Yet, few studies have reported on MD in sanctuary zones of the Indian Ocean. Consequently, coastal transects were conducted to determine MD quantity, composition and distribution at northern Ningaloo Marine Park, Western Australia. Debris density ranged between 0.004 and 0.02 items m^-2 with the greatest density near Exmouth township. Composition was predominantly plastic (61%) with fishing-related items (25.5%) and plastic fragments/remnants (16%) the most numerous overall. Land-based and general sourced MD accounted for 88% of all debris. Debris levels were significantly lower at sites with higher visitation and increased distance from access points. There was no significant difference between sanctuary and non-sanctuary zones. Although not immune to MD, this study suggests its remote location, environmental awareness and management strategies implemented at Ningaloo Marine Park may be key to its low MD levels.

Dangerous traps: Macroplastic encounters affecting freshwater and terrestrial wildlife

Encounters (or interactions) between plastic debris and wildlife can cause great harm to individuals and populations. The most common encounters are ingestion, entanglement and plastic usage (plastic as nesting material, vector for biota transport and refuge/shelter). Hundreds of plastic-encounters have been reported for marine species. However, there is a lack of studies reporting encounters in other ecosystems, such as freshwater and terrestrial ones. Based on a citizen science approach, we documented and analyzed 90 different cases of macroplastic-fauna encounters for 44 freshwater and terrestrial species. Herein, we provided evidence (photographically documented) of the negative consequences of macroplastic debris discarded in freshwater and terrestrial environments. Birds were by far the taxon most frequently reported in encounters (72.2% of the encounters, 30 different species). The dominant type of plastic-fauna encounter was the use of plastic as nesting material (42% of the total cases) and the second one was entanglement (33%). Most of the entanglements had lethal consequences for the organisms involved (almost 60%). Entanglement in ghost fishing gear and bottle (security) rings were particularly dangerous and comparatively frequent in this study. Some invasive species could benefit from the encounters to the detriment of the environment's health, using plastics as settlement substrata. Finally, we lay the foundation for creating worldwide lists of non-marine species impacted by encounters with plastic debris.

Distribution of seafloor litter and its interaction with benthic organisms in deep waters of the Ligurian Sea (Northwestern Mediterranean)

The Mediterranean Sea is one of the most polluted marine basins and currently serves as a hotspot for marine litter. The seafloor represents the ultimate sink for most litter worldwide. Nevertheless, the knowledge about litter distribution and its interactions with benthic organisms in deep water is poorly understood. In 2018, we investigated spatial patterns of macro- and micro-litter distribution, and their effects on benthic communities in the Ligurian Sea. An oceanographic survey was carried out with a remotely operated vehicle and a multibeam echosounder on seven seamounts and canyons, at depths ranging from 350 to 2200 m. High litter accumulations were discovered at the mouth of the Monaco canyon, where estimated densities of up to 3.8 × 10⁴ items km^-2 were found at 2200 m depth. The highest abundance of urban litter items was found on the soft substrate, at the bottom of the deeper parts of the submarine canyons, which seem to act as conduits carrying litter from the shelf towards deeper areas. In contrast, fishing-related items were most abundant in the upper layer of the seamounts (300-600 m depths). Furthermore, more than 10% of the observed deep gorgonian colonies were entangled by lost longlines, indicating the detrimental effects of this fishing gear on benthic habitats. The discovery of new litter hotspots and the evaluation of how deep-sea species interact with litter contribute to increasing the knowledge about litter distribution and its effects on the deep ecosystem of the Mediterranean basin. All the observations recorded in this study showed substantial and irreversible changes in the deep and remote areas of marine environments, and these changes were found to be caused by humans. Our findings further stress the need for urgent and specific measures for the management of deep-sea pollution and the reduction of litter inputs in the environment.

Spatiotemporal variations in anthropogenic marine litter pollution along the northeast beaches of India

Marine litter is widely distributed in marine environments and has been a severe concern worldwide, due to the disposal of waste from diverse sources. The severity of this threat has garnered increasing attention in India over the last decade, but the full consequences of this pollution are yet to be quantified. To estimate the spatiotemporal distribution, composition and beach quality of marine litter pollution, 17 beaches along the Hooghly estuary, a part of the Gangetic delta was studied. Marine litter was collected from 100 m long transects during two seasons (monsoon and post-monsoon). The OSPAR monitoring standard was applied to the 16,597 litter items collected, then grouped under 6 types and 44 categories. In terms of number, litter abundance was higher during monsoon (1.10 ± 0.39 items/m²) than that of post-monsoon (0.86 ± 0.32 items/m²). Most of the beaches were categorized as low cleanliness as computed by the general index and clean coast index and the good for the pellet pollution index. Hazardous litter constituted 6.5% of the total collected litter items. The model prediction revealed that the influence of high discharge from Hooghly, Rasulpur and Subarnarekha River carried enormous anthropogenic litter to the northeast beaches. The litter flux decreases with an increase in distance from the shore, and act as a sink to the sea-floor. The results denote that the distribution and typology of marine litter were representatives of household, tourism and fishing, which in turn highlights the need for better regional litter management measures. Suggested management practices include source reduction, mitigation, management of beach environment and change in littering behaviour through environmental education.

Are microplastics destabilizing the global network of terrestrial and aquatic ecosystem services?

Plastic has created a new man-made ecosystem called plastisphere. The plastic pieces including microplastics (MPs) and nanoplastics (NPs) have emerged as a global concern due to their omnipresence in ecosystems and their ability to interact with the biological systems. Nevertheless, the long-term impacts of MPs on biotic and abiotic resources are not completely understood, and existing evidence suggests that MPs are hazardous to various keystones species of the global biomes. MP-contaminated ecosystems show reduced floral and faunal biomass, productivity, nitrogen cycling, oxygen-generation and carbon sequestration, suggesting that MPs have already started affecting ecological biomes. However, not much is known about the influence of MPs towards the ecosystem services (ESs) cascade and its correlation with the biodiversity loss. MPs are perceived as a menace to the global ecosystems, but their possible impacts on the provisional, regulatory, and socio-economic ESs have not been extensively studied. This review investigates not only the potentiality of MPs to perturb the functioning of terrestrial and aquatic biomes, but also the associated social, ecological and economic repercussions. The possible long-term fluxes in the ES network of terrestrial and aquatic niches are also discussed.

Microplastic and artificial cellulose microfibers ingestion by reef fishes in the Guarapari Islands, southwestern Atlantic

This study investigated the ingestion of microplastics and artificial cellulose particles by 103 specimens belonging to 21 reef fish species from the southwestern Atlantic. Specimens of six species had ingested microplastics and artificial cellulose particles, while those of another three species had ingested only one type of material. In our samples, man-made cellulose fibers were more common than microplastics. The tomtate grunt, Haemulon aurolineatum, ingested more particles than any of the other species. Overall, transparent particles were predominant, and polyamide was the most common plastic material. Household sewage, fishery activity, and navigation appear to be the principal sources of the artificial particles ingested by the reef fishes. Our results provide an important database on oceanic contamination by microplastics and artificial cellulose particles. Understanding this impact on tropical reef fish will contribute to the development of strategies to mitigate pollution by anthropogenic debris in reef systems.

An ecotoxicological approach to microplastics on terrestrial and aquatic organisms: A systematic review in assessment, monitoring and biological impact

Marine and land plastic debris biodegrades at micro- and nanoscales through progressive fragmentation. Oceanographic model studies confirm the presence of up to ∼2.41 million tons of microplastics across the Atlantic, Pacific, and Indian subtropical gyres. Microplastics distribute from primary (e.g., exfoliating cleansers) and secondary (e.g., chemical deterioration) sources in the environment. This anthropogenic phenomenon poses a threat to the flora and fauna of terrestrial and aquatic ecosystems as ingestion and entanglement cases increase over time. This review focuses on the impact of microplastics across taxa at suggested environmentally relevant concentrations, and advances the groundwork for future ecotoxicological-based research on microplastics including the main points: (i) adhesion of chemical pollutants (e.g., PCBs); (ii) biological effects (e.g., bioaccumulation, biomagnification, biotransportation) in terrestrial and aquatic organisms; (iii) physico-chemical properties (e.g., polybrominated diphenyl ethers) and biodegradation pathways in the environment (e.g., chemical stress, heat stress); and (iv) an ecotoxicological prospect for optimized impact assessments.

Seafloor litter along the Italian coastal zone: An integrated approach to identify sources of marine litter

A heterogeneous amount of waste of different origins is continuously generated along Italian coasts in the Mediterranean Sea. In this paper, using information regarding the quantities and the different types of marine litter based on Project AWARE's "Dive Against Debris" data, we try to identify the main sources of this waste. In particular, the methodological approach used associates the origin of marine litter sources with the dataset of geo-localised state-owned maritime concessions, which are loaded by the granting bodies (regions, municipalities, port authorities) on the State Property Information System (Sid). The sources of marine litter were evaluated using the matrix scoring technique (MST). Then, to assess the weight of each source in each station, the community-level weighted mean (CWM) was calculated. Single-use plastic accounted for the highest percentage (19.13%), followed by glass beverage bottles (10.90%), shopping bags (9.03%), aluminium beverage cans (4.91%), and cigarette butts (4.61%). Tourism and beach users contributed to 42.3% of the litter found, followed by fishing (15.7%) and yachting (11.3%). The overlapping of the data collected by scuba divers with the state concessions of activities from offshore and mainland areas was used to distinguish the anthropic pressures that impact the coast. Policy makers and the local administrator may use these results to define new methods of collection and reuse of anthropic waste through a more harmonised approach in the management of marine waste.

Microplastics in the coral reefs and their potential impacts on corals: A mini-review

Plastic debris exists worldwide and research on microplastic pollution has gradually spread from the oceans to freshwater and terrestrial systems. Coral reefs not only serve as one of the most charismatic and biodiverse ecosystems on our planet, but also maintain the human harvesting of natural resources and livelihoods of hundreds of millions of people. However, the abundance and distribution characteristics of microplastics in coral reef systems receive little scientific attention. Meanwhile, the impacts of microplastics and nanoplastics on coral health and its potential mechanisms remain further studied. Herein, this review first summarized the current status of microplastics pollution in global coral reefs, especially included (i) abundance and distribution characteristics of microplastics in different media (e.g., seawater, sediment, corals), and (ii) possible sources of microplastics in reef regions. Furthermore, the main interaction mechanisms between microplastics and corals are highlighted. Following this, the direct or indirect impacts of microplastics on coral species are discussed. With the rapid increase of plastic consumption and background of pervasive global coral bleaching, research on marine microplastics must focus on the critical coral reef regions and include a comprehensive knowledge about the distribution, fate, and potential risks from an ecosystem perspective.

Natural and anthropogenic-induced stressors affecting the composition of fish communities on the rocky reefs of Ecuador

Natural and human-induced stressors have threatened the sustainability of the fish communities of coral-rocky reefs worldwide in the last decades. The composition of the fish communities on the reefs of Ecuador and the factors affecting spatiotemporal changes are unknown. We studied the influence of the descriptors of structural complexity, the current status of coral and human-induced variables over fish communities. A video transect method was used to assess fish communities in three zones (slope, crest, and bottom) of two reefs during two seasons (rainy and dry). The structure of fish communities was highly influenced by the zones and season; rugosity and live coral affected the fish composition on the crest and slope zones. The fractured coral and derelict fishing gear on coral produced an adverse effect on fish composition over the crest. A multifactorial process causing loss of structural complexity and affecting fish composition was identified, however, periodical assessment is required for a greater understanding of this process.

Shading by marine litter impairs the health of the two Indo-Pacific scleractinian corals Porites rus and Pavona cactus

Marine litter is recognized as one factor affecting coral health. It causes shading, bleaching, physical damage, necrosis, and mortality. This study provides the first evidence that direct contact by plastic and cotton affects coral health within 60 days. In a controlled aquarium experiment, two common Indo-Pacific scleractinian corals, Porites rus and Pavona cactus, were shaded for 60 days by transparent plastic (polypropylene, PP), dark plastic (PP) and cotton. Cotton disintegrated completely after 30 to 42 days, allowing the corals to recover. Transparent plastic became opaque over time due to microfouling, resulting in bleaching of the affected coral parts. Dark plastic had the strongest effect, including bleaching, necrosis and reduced growth within 60 days. Moreover, the two coral species responded differently to the treatments. This is the first report demonstrating that plastic and cotton litter can affect coral health and even cause partial mortality within 60 days.

Microplastic pollution around remote uninhabited coral reefs of Nansha Islands, South China Sea

Microplastic (MP) pollution is a growing environmental problem in the global oceans. However, there is relatively little evidence of the extent of MP pollution around remote islands, such as coral reefs, in the open ocean. In this study, we conducted a large-scale investigation of MP pollution in the surface waters around the remote uninhabited coral reefs of Nansha Islands in South China Sea. Microplastics were widespread in the surface waters with an average abundance of 0.0556 ± 0.0355 items/m³, although this varied among the coral reefs. The MPs were predominantly composed of polypropylene (PP) and polyethylene (PE), and > 70% of them were <3 mm in size. Fragments and fibers comprised the most common MP types. The similarity between macro plastic and MP compositions provided evidence for the tracing of MP sources in the study area. The main pollutants (transparent PP fibers and PE fibers) around these remote coral reefs may originate from fishing gear abrasions. The plastic waste released from nearby residential islands and high-intensity fishing activities around Nansha Islands likely represented important local sources. Overall, the abundance of MPs found in the surface waters surrounding these remote coral reefs in the South China Sea was relatively low; however, these levels of MP pollution should not be disregarded given the importance of coral reef ecosystems.

Incidence of anthropogenic material in Sula leucogaster nests in a distant archipelago of Brazil

Anthropogenic debris has been affecting fauna in different ways. We investigate the frequency of anthropogenic material in nests of a brown booby (Sula leucogaster) colony in the Saint Peter and Saint Paul Archipelago (SPSPA), Rio Grande do Norte, Brazil in February 2015 and November 2016. The items were classified according to type (threadlike plastic, sheet plastics, hard fragments, foamed synthetics and miscellaneous) and color. In 2015, a total of 30 anthropogenic items were found in 20.4% of the nests. In nests containing debris, miscellaneous items were found in 73.6% of nests. White/clear was the most common color, 52.6% of nests containing debris had items of this color. In 2016, 45 anthropogenic items were observed in 13.3% of the nests. Threadlike plastic was found in 59.2% of nests. Blue/purple was the most common color (55.5%). Even far from the Brazilian coast, the S. leucogaster colony has been affected by marine pollution.

Quantitative overview of marine debris ingested by marine megafauna

This review quantifies plastic interaction in marine biota. Firstly, entanglement and ingestion records for all marine birds, mammals, turtles, fish, and invertebrate species, are summarized from 747 studies. Marine debris affected 914 species through entanglement and/or ingestion. Ingestion was recorded for 701 species, entanglement was documented for 354 species. Secondly, the frequency of occurrence of ingestion per species (Sp-%FO) was extracted for marine birds, mammals and turtles. Thirdly, for seabird species, average numbers of plastics ingested per individual were determined. Highest Sp-%FO and average number of plastics were found in tubenosed seabirds with 41% of all birds analysed having plastics, on average 9.9 particles per bird. The Sp-%FO and average number of ingested particles is lower for most other species. However, for certain species, ingestion rates of litter are reason for serious concern. Standardized methods are crucial for future studies, to generate datasets that allow higher level ecosystem analyses.

The spatial distribution of microplastic in the sands of a coral reef island in the South China Sea: Comparisons of the fringing reef and atoll

Microplastic pollution of coral reef ecosystems has received increasing attention since the discovery that several typical coral types have the ability to ingest (micro-) plastics. However, data on the distribution of microplastics in coral reef ecosystems are still very limited. The study reported here selected sands/sediments from coral reef islands located in the South China Sea as a representative study site. The abundance of microplastics was found to reach 90 ± 5 items/kg and 530 ± 7 items/kg at the Weizhou Island and Sanya Lu Hui Tou (LHT) sites (fringing reef), respectively. Each of these qualities are lower than the quantity of microplastics collected from the Xisha Islands (atoll) (60 ± 3 to 610 ± 11 items/kg), which experiences less human activity and pollution. Moreover, further investigation demonstrated that the differences in the microplastics in the sands of these atolls and fringing reefs were determined not only by their sources, but were also dependent on their water exchange rates. The primary type and color of the microplastics found in these four sampling zones was red polypropylene and there was a greater proportion of smaller size particles (<1 mm) in the remote atolls of the Nansha and Xisha islands than in the other fringing reef sites. Additionally, there were no obvious differences found in the abundance of microplastics and the compositions/structures of coral sand in the Weizhou Island and Sanya LHT sites.

Predicting the exposure of coastal species to plastic pollution in a complex island archipelago

Plastic pollution in the marine environment is a pervasive and increasing threat to global biodiversity. Prioritising management actions that target marine plastic pollution require spatial information on the dispersal and settlement of plastics from both local and external sources. However, there is a mismatch between the scale of most plastic dispersal studies (regional, national and global) and the scale relevant to management action (local). We use a fine-resolution hydrodynamic model to predict the potential exposure of coastal habitats and species (mangroves, coral reefs and marine turtles) to plastic pollution at the local scale of a management region (the 1,700 km² Whitsunday Islands, Queensland, Australia). We assessed the potential exposure of mangroves, coral reefs and marine turtles to plastics during the two dominant wind conditions of the region; the trade wind and monsoon wind seasons. We found that in the trade wind season (April to September) all habitats and species had lower exposure than during the monsoon wind season (October to March). In both wind seasons we found a small proportion of coral reef habitat and large area of turtle habitat were in high potential exposure categories. Unlike coral reefs or marine turtles, mangroves had consistent hotspots of high exposure across wind seasons. Local scale management requires data at fine resolution to capture the variability that occurs at this scale. The outputs of our study can inform the development of conservation resources and local scale management action.

Marine litter from fishery activities in the Western Mediterranean sea: The impact of entanglement on marine animal forests

The anthropogenic marine debris, especially abandoned, lost or otherwise discarded Fishing Gear (ALDFG), represents a rising concern, because of its potential harmful impact on the marine animal forests. We carried out 13 km of video recordings, by means of a remotely operated vehicle, from 10 to 210 m depth, in an anthropised area of the Tyrrhenian Sea (Mediterranean Sea). This site, for its high ecological importance and biodiversity value, has been identified for the establishment of a new marine protected area (MPA). The aim of this paper was to assess marine litter abundance and its effects on the benthic fauna. The debris density, in the study area, ranged from 0.24 to 8.01 items/100 m², with an average of 3.49 (±0.59) items/100 m². The derelict fishing gear, mainly fishing lines, were the main source of marine debris, contributing 77.9% to the overall litter. The impacts of debris on the benthic fauna were frequently recorded, with 28.5% of the litter entangling corals and impacting habitats of conservation concern. These impacts were exclusively caused by the derelict fishing gear (91.2% by longlines), and the highest percentage (49.1%) of ALDFG causing impacts was observed from 41 to 80 m depth, in the coralligenous biocenosis. The results of the present study will help the fulfilment of "harm" monitoring, as recommended by the Marine Strategy Framework Directive (MSFD) and the UN Environment/MAP Regional Plan on the marine litter management in the Mediterranean Sea. Regarding the actions to reduce the derelict fishing gear, preventive measures are usually preferred instead of the extensive removals based on cost-effectiveness and sustainability. The establishment of a new MPA in the area could be a good solution to reduce ALDFG, resulting in the improvement of the ecological status of this coastal area.

Evaluation of microplastic ingestion by tropical fish from Moorea Island, French Polynesia

Microplastics are ubiquitous throughout the oceans, yet few studies have documented their occurrence in marine organisms associated with coral reefs. Four genera of adult fish were sampled (Myripristis spp., Siganus spp., Epinephelus merra and Cheilopogon simus) from different trophic guilds around the tropical island of Moorea, French Polynesia. Digestive tracts from 133 adult fish were surveyed and microplastics were found in 28 tracts (21%). Abundance of ingested microplastic pieces per individual fish varied from 1 to 3 pieces, with an average of 1.25 ± 0.13 ingested microplastic pieces. Microplastics size ranged from 0.031 to 2.44 mm and 70% of microplastics did not exceed 0.3 mm in size. Overall, this study shows that the number and size of microplastic ingested per trophic groups are independent of trophic guild. Additional studies are needed to sample in other tropical regions in order to have a better assessment of microplastic occurrence in coral reefs.

Abundance and distribution of beach litter along the Atlantico Department, Caribbean coast of Colombia

A total of 5993 litter items divided into 13 categories were found at 25 beaches located along the Atlantico Department coastline, Caribbean of Colombia, with an average litter abundance of 7 items/m. Agglomerative Hierarchical Clustering (AHC), Multidimensional Scaling (MDS) and Principal Components Analysis (PCA) were applied with the objective of highlighting similarities and contrasts between litter categories and abundances. Results indicated two specific groups of beaches in terms of amounts of litter. The first group is composed of 17 "dirty beaches" (urban, resort and village) while the second group includes 8 "clean beaches" (village and resort). This division was confirmed by means of the EA/NALG (2000) grading system, which highlighted that 68% of beaches belonging to the Atlantico Department coastline are in an unacceptable condition of cleanness. Current patterns of litter abundance and accumulation are related to sources as well as beach characteristics such as degree of exposition and morphodynamic state.

Urban coral reefs: Degradation and resilience of hard coral assemblages in coastal cities of East and Southeast Asia

Given predicted increases in urbanization in tropical and subtropical regions, understanding the processes shaping urban coral reefs may be essential for anticipating future conservation challenges. We used a case study approach to identify unifying patterns of urban coral reefs and clarify the effects of urbanization on hard coral assemblages. Data were compiled from 11 cities throughout East and Southeast Asia, with particular focus on Singapore, Jakarta, Hong Kong, and Naha (Okinawa). Our review highlights several key characteristics of urban coral reefs, including "reef compression" (a decline in bathymetric range with increasing turbidity and decreasing water clarity over time and relative to shore), dominance by domed coral growth forms and low reef complexity, variable city-specific inshore-offshore gradients, early declines in coral cover with recent fluctuating periods of acute impacts and rapid recovery, and colonization of urban infrastructure by hard corals. We present hypotheses for urban reef community dynamics and discuss potential of ecological engineering for corals in urban areas.

Pollution and coral damage caused by derelict fishing gear on coral reefs around Koh Tao, Gulf of Thailand

Most lost fishing gear is made of non-biodegradable plastics that may sink to the sea floor or drift around in currents. It may remain unnoticed until it shows up on coral reefs, beaches and in other coastal habitats. Stony corals have fragile skeletons and soft tissues that can easily become damaged when they get in contact with lost fishing gear. During a dive survey around Koh Tao, a small island in the Gulf of Thailand, the impact of lost fishing gear (nets, ropes, cages, lines) was studied on corals representing six different growth forms: branching, encrusting, foliaceous, free-living, laminar, and massive. Most gear (>95%) contained plastic. Besides absence of damage (ND), three categories of coral damage were assessed: fresh tissue loss (FTL), tissue loss with algal growth (TLAG), and fragmentation (FR). The position of the corals in relation to the fishing gear was recorded as either growing underneath (Un) or on top (On), whereas corals adjacent to the gear (Ad) were used as controls. Nets formed the dominant type of lost gear, followed by ropes, lines and cages, respectively. Branching corals were most commonly found in contact with the gear and also around it. Tubastraea micranthus was the most commonly encountered coral species, either Un, On, or Ad. Corals underneath gear showed most damage, which predominantly consisted of tissue loss. Fragmentation was less common than expected, which may be related to the low fragility of T. micranthus as dominant branching species. Even if nets serve as substrate for corals, it is recommended to remove them from reefs, where they form a major component of the plastic pollution and cause damage to corals and other reef organisms.

Marine animal forests as useful indicators of entanglement by marine litter

Entanglement of marine fauna is one of the principal impacts of marine litter, with an incidence that can vary strongly according to regions, the type and the quantity of marine litter. On the seafloor, areas dominated by sessile suspension feeders, such as tropical coral reefs or deep-sea coral and sponge aggregations, have been termed "animal forests" and have a strong potential to monitor the temporal and spatial trends of entanglement by marine litter, especially fishing gears. Several characteristics of these organisms represent advantages while avoiding constraints and bias. Biological constraints and logistical aspects, including tools, are discussed to better define a strategy for supporting long-term evaluation of accumulation and entanglement of marine litter.