A global assessment of the relationship between anthropogenic debris on land and the seafloor

Beach litter deposition and turnover, effects of tides and weather, and implications for cleanup strategies: A case study in the Lofoten archipelago, Norway

Plastic pollution is ubiquitous in the marine environment. Beach cleanups are considered a cost-effective mitigative measure with generally few negative environmental impacts. Beached litter is not static, however, and may wash back out to sea or be buried, meaning it is only temporarily available for cleanup. We studied deposition and turnover of litter on three Arctic beaches in Lofoten, Norway, biweekly for 31 months. The mean estimated daily deposition rate was 10 items/100 m, with a median residence time of 99 days. Both processes were impacted by seasons and weather and varied both spatially and temporally. Strong winds during the fall increased litter influx and onshore winds contributed to its loss. Heavier objects and those higher on the beach persisted longer yet were still subject to turnover. Snow temporarily buries litter but protects it in the long run. Given the turnover of litter, frequent (albeit smaller) cleanups can readily remove 3-4 times more litter from circulation in the environment than larger, infrequent cleanups. With limited resources, it is recommended to prioritise late fall cleanups.

Boosting beach clean-up participation through community resilience hypothetical scenarios

Engaging coastal communities in beach clean-up initiatives is crucial for the sustainability of marine ecosystems and the support of the blue economy. This study aims to examine the influence of various resilience attributes on community willingness to participate in these activities. It uses choice experiment framework to test three distinct scenarios: (1) cultural recycling education, (2) social media task force, and (3) resilience debris recovery. The study surveyed 647 valid samples from metropolitan Bali, Indonesia to assess their preferences across these scenarios. Advanced econometric models, specifically the Random Parameter Logit (RPL) and Latent Class Model (LCM), were used to analyze the data. The results indicate that integrating cultural and digital engagement strategies can significantly enhance community participation in beach clean-ups, providing a model that can be applied in various coastal regions. Each scenario improves community engagement by aligning beach clean-up efforts with broader economic and cultural dynamics.

Synthetic polymers: A global threat to aquatic benthic environments

Finding time-efficient and cost-effective data collection methods is a challenge when addressing aquatic litter pollution on a global scale. In this study, we analysed data on aquatic benthic debris collected worldwide by volunteer scuba divers through the Dive Against Debris® citizen science initiative, examining its relationship with spatial and socio-economic factors. Plastic-dominated litter was found in both marine (64 %) and freshwater (48 %) environments, followed by metal and glass. Lower litter abundances have been recorded in high income countries such as in Europe, Central Asia and North America. Plastic fragments and fishing lines were the most abundant seafloor litter items, while takeaway containers (aluminium cans, glass bottles) were dominant in freshwater environments. Single-use plastics, including objects for food and beverage consumption, accounted for about 1/3 of the total benthic aquatic debris. Our findings highlight the need to prioritise the fishing industry and change our fast-paced modern lifestyle. Citizen science initiatives, once data cleanup is conducted to overcome any bias, can provide valuable tools for better understanding and quantifying marine litter pollution. The outcomes gained can be leveraged to improve consumer awareness and inform environmental policies aimed at addressing aquatic litter pollution more effectively.

What lies underneath: Comparison among beach litter in the underwater bathing area and exposed beach

The standard techniques for monitoring beach litter focus on the litter that is accumulated on beaches. Therefore, the underwater bathing area is usually overlooked. Our study aims to start the discussion about the litter in the bathing area, an important connection between the exposed beach and the ocean. We aimed to compare sampling methodologies between the underwater bathing area and the exposed beach. We highlighted litter's similarities and differences regarding the amount, material, possible sources, and interaction with the biota. We also performed a brand audit on the underwater bathing area litter. In the underwater region, 106 items were collected while 1706 items were collected from the exposed beach region. Plastic was the dominant type of material in both sites, exposed beach (89.92 %) and bathing area (83.96 %). The litter's possible source was different. In the underwater bathing area was more related to food packages (couscous, rice). On the other hand, litter on the exposed beach was associated with beach use (single-use plastic such as plastic cups). The brand audit identified 21 companies, whereby most brands were Brazilian and food-related. Regarding interactions with the biota, the litter in the bathing area had more bio-fouling (87.73 %) than the litter collected on the exposed beach (10.00 %). Information about bathing area litter can be useful to draw different management strategies. Due to the differences in litter types and behavior between the two sites, the same mitigation strategies might not be equally efficient.

Exploring the pathology of liver, kidney, muscle, and stomach of fledgling seabirds associated with plastic ingestion

There remain significant gaps in knowledge about 'sub-lethal' impacts of plastic ingestion, particularly chronic impacts on cells, tissues, or organs. Few studies have applied traditional animal health tools, such as histopathology, to assess physiological damage to wildlife, with fewer still providing information on the dosage or exposure to plastics needed to elicit negative effects. Our study seeks to investigate a common hypothesis in plastic pollution research; that an increasing plastics burden will have an impact on an animal's health, examining two wild species with high levels of environmental exposure to plastic through their diet. Here we assess the histopathology of the muscle, upper digestive tract, liver and kidney of two seabird species that are known to be commonly exposed to plastic, comparing exposed and non-exposed individuals. Fledgling seabirds showed histopathological evidence of cumulative pressures such as starvation, disease, and endoparasite burden. However, we observed no evidence of chronic harm that could be explicitly linked to the plastics. We found one case of haemorrhage, reaffirming that large/sharp plastic foreign bodies may cause acute physical damage. Given the numerous interacting pressures on the health of fledging seabirds, including exposure to plastic, this study highlights the need to scrutinise plastic-animal interactions and research though a One Health lens.

Polymer Characterization of Submerged Plastic Litter from Lake Tahoe, United States

Monitoring plastic litter in the environment is critical to understanding the amount, sources, transport, fate, and environmental impact of this pollutant. However, few studies have monitored plastic litter on lakebeds which are potentially important environments for determining the fate and transport of plastic litter in freshwater basins. In this study, a self-contained underwater breathing apparatus was used for litter collection at the lakebed along five transects in Lake Tahoe, United States. Litter was brought to the surface and characterized by litter type. Plastic litter was subsampled, and polymer composition was determined using attenuated total reflection Fourier transform infrared spectroscopy. The average plastic litter from the lakebed for the five dive transects was 83 ± 49 items per kilometer. The top plastic litter categories were other plastic litter (plastic litter that did not fall in another category), followed by food containers, bottles <2 L, plastic bags, and toys. These results are in line with prior studies on submerged litter, and intervention approaches or ongoing education are needed. The six polymers most frequently detected in the subsamples were polyvinyl chloride, polystyrene/expanded polystyrene, polyethylene terephthalate/polyester, polyethylene, polypropylene, and polyamide. These observations reflect global plastic production and microplastic studies from lake surface water and sediments. We found that some litter subcategories were primarily comprised of a single polymer type, therefore, in studies where the polymer type cannot be measured but litter is categorized, these results could provide an estimate of the total polymer composition for select litter categories.

Artisanal trawl fisheries as a sentinel of marine litter pollution

Systematic seafloor surveys are a highly desirable method of marine litter monitoring, but the high costs involved in seafloor sampling are not a trivial handicap. In the present work, we explore the opportunity provided by the artisanal trawling fisheries to obtain systematic data on marine litter in the Gulf of Cadiz between 2019 and 2021. We find that plastic was the most frequent material, with a prevalence of single-use and fishing-related items. Litter densities decreased with increasing distance to shore with a seasonal migration of the main litter hotspots. During pre-lockdown and post-lockdown stages derived from COVID-19, marine litter density decreased by 65 %, likely related to the decline in tourism and outdoor recreational activities. A continuous collaboration of 33 % of the local fleet would imply a removal of hundreds of thousands of items each year. The artisanal trawl fishing sector can play a unique role of monitoring marine litter on the seabed.

Open defaecation by proxy: Tackling the increase of disposable diapers in waste piles in informal settlements

Disposable diapers are becoming increasingly popular and present an emerging challenge for global waste management, particularly within LMICs. They offer a cheap and convenient way for caregivers to manage child excreta; however, insufficient understanding of safe disposal methods, combined with limited access to waste management services results in hazardous disposal. Used diapers are being increasingly found dumped in the open environment, including in water bodies and in open fields, leading to faecal contamination of the environment and an enhanced risk of transmission of faecal-oral diseases such as cholera and typhoid. United Nations SDG 6 aims to end open defaecation globally by 2030; however, improper disposal of used diapers will hamper progress towards reaching this goal. In this review, we identify current trends in use and subsequent disposal of single use disposable diapers in LMICs, and critically discuss the environmental and public health impacts of current practices, and potential solutions to address these challenges. Contemporary methods for managing the disposal of single use diapers for communities in LMICs tend to be cost prohibitive with few alternative options other than dumping in the environment. Modern cloth diapers offer a low waste alternative to disposable diapers but often carry an unaffordable high upfront cost. Here, in addition to advocating improved efforts by governments to upgrade access and quality of waste management services, we recommend the design and implementation of intervention schemes aimed to increase awareness of safe and hygienic disposal practices for disposable diapers.

Discarded bottles entrap endemic small mammals species in a large Mediterranean island

We examined the entrapment effect of discarded bottles on small mammals, along a road network located in North-Western Sardinia (Italy). On 162 bottles, 49 (> 30%) contained at least one animal specimen (invertebrate or vertebrate) and 26 (16%) entrapped 151 small mammals: insectivorous shrews (Soricomorpha) were more frequently recorded. Larger bottles (66 cl.) showed a higher number of entrapped mammals, but difference was not significant when compared to smaller bottles (33 cl.). Our data highlighted as abandoned bottles represent a threatening factor for small mammals on a large Mediterranean island with over-represented endemic shrews (predators of high trophic level) attracted by insects entrapped in bottles. Correspondence analysis suggest a weak segregation between bottles of different size, related to the abundance of the most entrapped species, the Mediterranean shrew (Crocidura pachyura). This still neglected type of litter, reducing number and biomass of insectivorous mammals of high trophic level and high ecological value may affect the food web in terrestrial insular communities, yet impoverished for biogeographical reasons. However, discarded bottles may represent as low-cost surrogate pitfall traps useful to improve knowledge in poor studied areas. Following the DPSIR (Driving force, Pressure, State, Impact, Response) approach as a framework to select indicator, we suggest as the effectiveness of removal clean-ups could be monitored using both the density of discarded bottles (as indicator of threat pressure) and the abundance of entrapped animals (as indicator of impact on small mammals).

Piers are hotspots for benthic marine debris in an urbanised estuary

Records of anthropogenic marine debris and the threats it poses are increasing worldwide, yet we know relatively little about the distribution of benthic debris. The seafloor is the final destination for a large proportion of debris due to the degradation and sinking of items. A more detailed understanding of debris distributions in hotspots such as urbanised estuaries can help decision makers target management and remediation activities. We selected sites frequented by fishers and boaters in Sydney Harbour, an urbanised estuary, to investigate the impacts of recreational activities on debris abundance. The aim of this study was to examine variation in macro debris (>5mm in diameter) type and abundance at two habitat types (piers and non-piers). We chose five locations at various distances from the estuary mouth. In each location SCUBA teams performed fixed transects at two sites, one under a pier and one over nearby soft-sediment habitat. Debris was recovered by the divers and brought to the surface for classification and disposal. Surveys were repeated multiple times at each location between November 2019 and February 2020, recording a total of 2803 debris items over 36 survey events. Overall, piers had more than ten times the debris abundance of soft-sediment sites, and much higher proportion of debris types related to recreational fishing. Over half of the debris items in this study were plastic (65%), and approximately 70% of the total debris was classified as related to recreational fishing. This trait was most prominent in debris at sites closest to the estuary mouth, likely reflecting increased fishing activity in this area. This study indicates that policy makers and community groups in urbanised estuaries should focus monitoring, reduction, and remediation efforts near artificial structures such as piers, and that public awareness campaigns should target the behaviour of recreational users of these structures.

A systematic review and risk matrix of plastic litter impacts on aquatic wildlife: A case study of the Mekong and Ganges River Basins

Plastic litter is a pollutant of aquatic environments worldwide, with some of the world's highest litter densities occurring in freshwater ecosystems. Little information about the risk that plastic litter poses to aquatic wildlife is available across the world's most polluted waterways. To help assess the risk to aquatic species where empirical data is lacking, our review presents i) a risk assessment methodology for predicting plastic litter impacts on aquatic wildlife in data poor environments, ii) a case study demonstrating this risk assessment methodology for wildlife across two heavily polluted river basins in Asia, the Mekong and Ganges River Basins; and iii) a broad review summarising common trends in litter interactions and risk to freshwater fish, aquatic birds, cetaceans and raptors. This risk analysis unites a systematic review approach with risk matrices following International Standards Organization's risk assessment criteria, evaluating the risk of plastic entanglement and ingestion and the potential for harm to the animal. In the Mekong and Ganges River Basins, we found that the risk of litter entanglement is higher than litter ingestion. Four species were forecast to be at high risk of entanglement: Ganges River dolphin, Gharial, Mekong giant catfish and Irrawaddy dolphin. The eastern imperial eagle and greater spotted eagle were noted to be at moderate risk of entanglement. Both the Ganges River dolphin and Irrawaddy dolphin were predicted to have a moderate risk of plastic ingestion. Interestingly, cranes, waterfowl and wading birds were deemed at low or negligible risk from plastic litter. This risk matrix methodology can be applied to other waterways and taxa to assess the risk posed by plastic. It can also be readily updated as more information becomes available. This review enables decision makers to bridge a data gap by providing a tool for conservation and management before comprehensive empirical data is available.

Towards a North Pacific long-term monitoring program for ocean plastic pollution: A systematic review and recommendations for shorelines

Increased organized monitoring is key to improving our understanding of marine debris on shorelines. Shorelines are demonstrated sinks for marine debris but efforts to quantify debris often fail to capture and report core variables and survey design techniques necessary to ensure study repeatability, comparability and to provide meaningful results. Here, we systematically review the available literature regarding marine debris distribution and abundance on shorelines of countries bordering the North Pacific Ocean (NPO), which are demonstrated to have unusually high marine debris abundance and diversity both at the ocean surface and stranded on shorelines. The majority of the 81 papers documenting shoreline debris in the NPO were studies that took place for less than one year (76.5%). Additionally, most sampling sites were visited only once (57.3%). Precise site locations (GPS coordinates) were provided in only 44.4% of the evaluated studies. Debris quantities were reported using nine different measurement units, with item counts per area and item counts per mass being most commonly reported for macro- and microplastics, respectively. Taken together, most of the reviewed studies could not be repeated by others given the information provided. We propose a series of guidelines with regard to marine debris shoreline sampling metrics, indicators, methods, and target goals in the NPO in order to improve comparability and repeatability. These follow the basic tenets of environmental survey design, which when not accounted for, can limit the applicability and value of large-scale shoreline monitoring efforts.

Industrialised fishing nations largely contribute to floating plastic pollution in the North Pacific subtropical gyre

The subtropical oceanic gyre in the North Pacific Ocean is currently covered with tens of thousands of tonnes of floating plastic debris, dispersed over millions of square kilometres. A large fraction is composed of fishing nets and ropes while the rest is mostly composed of hard plastic objects and fragments, sometimes carrying evidence on their origin. In 2019, an oceanographic mission conducted in the area, retrieved over 6000 hard plastic debris items > 5 cm. The debris was later sorted, counted, weighed, and analysed for evidence of origin and age. Our results, complemented with numerical model simulations and findings from a previous oceanographic mission, revealed that a majority of the floating material stems from fishing activities. While recent assessments for plastic inputs into the ocean point to coastal developing economies and rivers as major contributors into oceanic plastic pollution, here we show that most floating plastics in the North Pacific subtropical gyre can be traced back to five industrialised fishing nations, highlighting the important role the fishing industry plays in the solution to this global issue.

Bottled & canned - Anthropogenic debris as an understudied ecological trap for small animals

Nowadays, littering is one of the biggest challenges that environmental conservation is facing. Although beverage containers, such as bottles and cans, belong to the most common threats in this context, their effect on animals has been poorly studied. The aim of this study was to assess the diversity and mortality level of the animal taxa entering discarded containers and to investigate which container features influence the number and functional composition of the trapped animals. The study was conducted in 10 urban woodlands in the city of Wrocław, Poland. In total, 939 open containers were collected. In 56% of them, a total number of 10,162 dead individuals (10,139 invertebrates and 23 vertebrates) was found. The most common amongst them were insects (orders: Coleoptera, Diptera, Hymenoptera), malacostracans (Isopoda), arachnids (Opiliones, Sarcoptiformes) and gastropods (Stylommatophora). The number of dead animals was affected positively by the container capacity and was significantly higher in glass and plastic bottles when compared to aluminium cans. At the same time, the presence of a neck negatively affected the number of dead animals. Container capacity was also positively correlated with the abundance of the most common functional groups: predators, phytophages and saprophages. Moreover, colourless and green, but not brown, containers were a significant predictor for the abundance of the latter two groups. Our study revealed that discarded containers constitute an ecological trap for many groups of animals. There is an urgent need to reduce the amount of rubbish in the environment by, for example, the implementation of regional and international regulations addressing the problem of littering, or organising repeated clean-up and educational activities.

Using long-term citizen science data to distinguish zones of debris accumulation

Studies show that a driver of coastal debris is the rate between debris deposition and resuspension; however, the influence of beach zone topography on the distribution of debris remains poorly understood. Using five years of marine debris data collected by the COASST citizen science program, we explored the spatiotemporal trends in debris abundance within two regions of the United States Pacific Northwest and investigated whether higher debris loads are associated with beach zones that have a higher propensity to trap debris. We found that beaches with larger wood zones had higher debris loads, adding to the growing evidence that backshore areas of beaches act as sinks for debris. Higher debris loads were also associated with beaches that had larger wrack zones suggesting that onshore transport from the marine reservoir is a dominant source of debris. This study provides a long-term baseline of marine debris which managers could use to inform source reduction interventions.

Landward zones of mangroves are sinks for both land and water borne anthropogenic debris

The hotspots for mangrove diversity and plastic emissions from rivers overlap in Asia, however very few studies have investigated anthropogenic marine debris (AMD) pollution in these threatened coastal ecosystems. Despite Hong Kong's position at the mouth of the Pearl River, a major source of mismanaged waste in Asia, the mangroves in Hong Kong have never been extensively surveyed for AMD. Here we assessed the patterns of AMD abundance within 18 mangrove forests across Hong Kong surveying both their landward and seaward zones. We recorded and categorised, according to their material and potential uses, both the amount of debris items and area they covered, to better quantify its potential impact on the mangroves. Across Hong Kong mangroves, the average abundance of debris was 1.45 ± 0.38 (SE) items m^-2, with an average coverage of 6.05 ± 1.59%. Plastic formed a high proportion of AMD accounting for 70.31% by number of items and 49.71% by area covered, followed by glass/ceramics and wood/bamboo. Disposable food packaging, fishing gear and industrial and construction related waste were the major sources of AMD we documented. On average, we recorded about six times more debris items m^-2 at the landward sites than at the seaward one, but these abundances varied between the East and the West coastlines of Hong Kong. Our data confirms the hypothesis that landward areas of mangrove forests act as traps and retain marine borne debris, but they also suggest that direct dumping of waste from the land could represent a serious impact for these forests placed in between the land and the sea. More research is needed to ascertain the impact of land disposed debris on mangrove degradation, and this study strongly advocates for a cultural shift about the perception of these forests by the public.

Where does marine litter hide? The Providencia and Santa Catalina Island problem, SEAFLOWER Reserve (Colombia)

The SEAFLOWER Biosphere Reserve (SBR) is the largest Marine Protected Area in the Caribbean Sea and the second largest in Latin America. Marine protected areas are under pressure from various stressors, one of the most important issues being pollution by marine litter, especially plastic. In this study our aim is to establish the distribution pattern and potential sources of solid waste in the different marine/coastal ecosystems of the islands of Providencia and Santa Catalina (SBR), as well as assess any interconnections between these ecosystems. At the same time, the distribution characteristics of marine litter in the different compartments facilitated a more dynamic understanding of the load of marine litter supplied by the islands, both locally and externally. We observed that certain ecosystems, principally back-beach vegetation and mangroves, act as crucial marine litter accumulation zones. Mangroves are important hotspots for plastic accumulation, with densities above eight items/m² (minimum 8.38 and maximum 10.38 items/m²), while back-beach vegetation (minimum 1.43 and maximum 7.03 items/m²) also removes and stores a portion of the marine litter that arrives on the beaches. Tourist beaches for recreational activities have a low density of marine litter (minimum 0.01 and maximum 0.72 items/m²) due to regular clean-ups, whereas around non-tourist beaches, there is a greater variety of sources and accumulation (minimum 0.31 and maximum 5.41 items/m²). The low density of marine litter found on corals around the island (0-0.02 items/m²) indicates that there is still no significant marine litter stream to the coral reefs. Identifying contamination levels in terms of marine litter and possible flows between ecosystems is critical for adopting management and reduction strategies for such residues.

Marine litter pollution on coral reefs of Darvel Bay (East Sabah, Malaysia)

Marine litter is recognized as an increasing component of marine ecosystem pollution. In this baseline study, we document the magnitude, types, sources, and potential impacts of litter on six coral reefs in East Sabah. We applied a simplified classification of litter to extract abundance data from video transects. The average density was 10.7 items per 100 m². Plastics represent 91% and the remaining 9% were metal, glass, and wood. Most (~70%) plastics are single-use items derived from dumping. Discarded fishing gear accounts for ~25%. Litter pollution increases closer to urban developments, with Sakar reef having higher densities (51 items per 100 m²), and higher Clean Coast Index (CCI = 10.2, dirty) and higher Plastic Abundance Index (PAI = 4.68) scores. This method could and should be readily integrated into ongoing monitoring programs to support assessments of the extent and magnitude of marine litter pollution on reefs worldwide.

Scientific knowledge on marine beach litter: A bibliometric analysis

Litter reduction in the coastal and marine environment represents a major challenge but must be prioritized to preserve biodiversity and ecosystems, as well as the goods and services that humans derive from seas and oceans. This paper reviews the available global scientific literature focusing on marine beach litter and tracks its evolution and trends by combining social network analysis and bibliometrics. The relationships and co-occurrences among authors, countries and keywords retrieved from the Scopus abstract and citation database are presented. A total of 1765 publications are analysed: the majority being journal articles. Results reveal the notable worldwide increase in scientific interest in beach litter in the last decade, as well as its multidisciplinary perspectives. This information could be beneficial for the processes that support the improvement of international efforts for beach litter monitoring, removal, and management activities.

Comparing marine anthropogenic debris on inhabited mainland beaches, coastal islands, and uninhabited offshore islands: A case study from Queensland and the Coral Sea, Australia

Anthropogenic debris (AD) including plastics, foams and fishing debris, are an undesirable accompaniment to beaches worldwide, arriving through direct deposition (littering) and oceanic transport. We investigated the standing stocks of 12 types of AD on inhabited islands, uninhabited islands and mainland locations, and the potential factors relating to AD deposition. We undertook beach-transects and sea-surface trawl surveys; comparing 13 uninhabited offshore islands, four inhabited/touristed coastal islands and 81 mainland beaches in Queensland, Australia. The abundance and type of AD differed between sites. Geographic factors had stronger relationships with AD density on islands than mainland beaches. Hard plastic density was linked with forcing from wind and sea surface currents. Beach width and onshore/side-shore forcing were the most important factors affecting AD loads (predominantly hard plastics) on islands. We found an inverse relationship between the density of beached plastic and plastic floating at the sea surface nearby and suggest that islands may act as a local sink for buoyant plastic.

On the path to minimize plastic pollution: The perceived importance of education and knowledge dissemination strategies

Environmental awareness and education have been recognized as tools to help mitigate environmental issues. This study, performed in Portugal, aimed to describe perceived factors building environmental awareness on plastic pollution, study how perceptions are influenced by sociodemographic characteristics, and identify perceived priority targets for intervention. Results showed that participants recognize society's important role to raise awareness and to develop mitigation strategies. Higher perception was reported by women and participants with a higher level of school education. The more educated participants consider individuals possessing expert knowledge as a more reliable information source, whereas older and less schooled participants trust more in media messaging. Participants acknowledge that environmental education should be included in school plans, particularly in the first nine years of education (students with ages between 6 and 14, approximately). Data support the idea that target specific dissemination strategies should be planned according to variables like age, gender and education level.

Climate Change and Anthropogenic Impact on Coastal Environments

Coastal-transitional areas, including delta plains, strandplains, lagoons, embayments, salt marshes, and mangroves, are some of the most valuable global resources in terms of both socioeconomic interest and cultural–natural heritage [...]

Effects of cigarette butts on marine keystone species (Ulva lactuca L. and Mytilus edulis L.) and sediment microphytobenthos

Outdoor mesocosms with constantly flowing natural seawater were used to test the effects of littered cigarette butts on the filter feeder Mytilus edulis (blue mussel), the macroalga, Ulva lactuca (sea lettuce) and sediment microphytobenthos in a semi-natural marine setting. Either conventional, cellulose acetate, or biodegradable, cellulose, smoked cigarette butts were added at densities of 0.25 or 1 butt L^-1. The clearance rates of mussels exposed to 1 butt L^-1 of cellulose acetate butts were three times less than the controls. The growth of U. lactuca was not measurably affected by cigarette butts, however the sediment chlorophyll content was significantly less in mesocosms exposed to 0.25 and 1 butt L^-1 of cellulose acetate butts. These effects occurred despite constant replacement of seawater indicating how hazardous conventional cigarette butts are to marine life. Biodegradable cellulose cigarette butts had minimal effects on the measured variables but should still not be discarded as litter.

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.