To verify weather mangroves act as sinks for marine litter, we surveyed through visual census 20 forests along the Red Sea and the Arabian Gulf, both in inhabited and remote locations. Anthropogenic debris items were counted and classified along transects, and the influence of main drivers of distribution were considered (i.e. land-based and ocean-based sources, density of the forest and properties of the object). We confirmed that distance to major maritime traffic routes significantly affects the density of anthropogenic debris in Red Sea mangrove forests, while this was independent of land-based activities. This suggests ocean-based activities combined with surface currents as major drivers of litter in this basin. Additionally, litter was more abundant where the mangrove density was higher, and object distribution through the mangrove stand often depended on their shape and dimension. We particularly show that pneumatophores act as a sieve retaining large plastic objects, leading to higher plastic mass estimates in mangroves compared to those of beaches previously surveyed in the Red Sea.

It has become apparent that the coastal zones of aquatic environments are significantly affected by plastics pollution. The accumulation of marine plastic litter on beaches is an important problem due to their significant environmental impacts. In this study, 13 coastal areas in Iskenderun Bay (NE Levantine coast of Turkey) were sampled in May 2018 to investigate meso and macroplastic (0.5–123.4 cm) pollution. A total of 1424 meso and macroplastic items in five categories (filament, film, foam, fragments, and pellets) were collected. The average meso and macroplastic concentration was 12.2 ± 3.5 pcs m−2 (12.3 ± 3.5 g m−2) and the mean size for all stations was 3.7 ± 0.16 cm. The highest meso and macroplastic concentration was found in the Dörtyol location (46.2 ± 7.6 pcs m−2) and the lowest concentration was found in the Y. Lagün location (2.3 ± 0.2 pcs m−2). Plastics were separated into 14 different groups based on their origins. The most dominant type was hard plastics (broken, fragmented, and deformed) with 59.8% and greenhouse coverage films with 11%. Our results shows that regardless their source plastics fluxes at beaches from various pathways. Results of this study provide useful information for designing monitoring strategies and setting management goals.

Plastic pollution is prevalent worldwide and affects marine wildlife from urbanized beaches to pristine oceanic islands. However, the ecological basis and mechanisms that result in marine animal ingestion of plastic debris are still relatively unknown, despite recent advances. We investigated the relationship between scavenging behavior and plastic ingestion using green turtles, Chelonia mydas, as a model. Diet analysis of C. mydas showed that sea turtles engaging in scavenging behavior ingested significantly more plastic debris than individuals that did not engage in this foraging strategy. We argue that opportunistic scavenging behavior, an adaptive behavior in most marine ecosystems, may now pose a threat to a variety of marine animals due to the current widespread plastic pollution found in oceans.

Three-quarters of all marine debris (MD) consists of plastic, a reflection of their worldwide use, production and waste mismanagement. Data on MD distributions can improve our ability to effectively reduce debris that escapes onto shorelines and the ocean. In this study, the Matrix Scoring Technique (Marine Strategy Framework Directive Technical Group on Marine Litter) was applied as an approach to calculate the likelihood of single debris items originating from a series of potential sources. Factors considered were: identity and function of debris, beach location, influential activities, “mix” of debris found, presence of indicator items, and quantity of MD. The standing-stock (abundance and composition) of MD was investigated in two sandy beaches (Conceição and Porto Pim) of the Azores Archipelago (NE Atlantic) for the period 2012–2018. The results of this study show promise towards the implementation of a new classification method to determine beach debris sources in remote open-ocean areas.

Microplastics (MPs), are tiny plastic fragments from 1 μm to 5 mm generally found in the aquatic environment which can be easily ingested by organisms and may cause chronic physical but also toxicological effects. Toxicological assays on fish cell lines are commonly used as an alternative tool to provide fast and reliable assessment of the toxic and ecotoxic properties of chemicals or mixtures. Rainbow trout liver cell line (RTLW-1) was used to evaluate the toxicity of pollutants sorbed to MPs sampled in sandy beaches from different islands around the world during the first Race for Water Odyssey in 2015. The collected MPs were analyzed for polymer composition and associated persistent organic pollutants: polycyclic aromatic hydrocarbons (PAHs), polychlorobiphenyls (PCBs) and dichlorodiphenyltrichloroethane (DDT). In addition, DMSO-extracts from virgin MPs, MPs artificially coated with B[a]P and environmental MPs were analyzed with different bioassays: MTT reduction assay (MTT), ethoxyresorufin-O-deethylase (EROD) assay and comet assay. Microplastics from sand beaches were dominated by polyethylene, followed by polypropylene fragments with variable proportions. Organic pollutants found on plastic from beach sampling was PAHs (2–71 ng g⁻¹). Samples from Bermuda (Somerset Long Bay) and Hawaii (Makapu'u) showed the highest concentration of PAHs and DDT respectively. No toxicity was observed for virgin microplastics. No cytotoxicity was observed on cells exposed to MP extract. However, EROD activity was induced and differently modulated depending on the MPs locations suggesting presence of different pollutants or additives in extract. DNA damage was observed after exposure to four microplastics samples on the six tested. Modification of EROD activity level and DNA damage rate highlight MPs extract toxicity on fish cell line.

Coastal litter abundance and its effects have increased for years. Waste reduction is the most effective countermeasure to fight against this problem. Littering attitudes may have an effect on people's involvement in coastal cleanups. In this study, coastal litter perception, awareness about its impact and likely sources were investigated in local population from south Bay of Biscay, Spain. People of different age groups and commitment levels regarding litter were interviewed and their answers compared with data from the area. Results showed differences in perception between volunteers and non-volunteers, but not between children and adults. Interaction effect of age was found for awareness. Volunteers and children tended to erroneously attribute the main litter origin to beachgoers, more than non-volunteers or adults. Our results suggest that encouraging local population to clean beaches would contribute to improve their perception of the problem and their attitudes toward taking action.

The objective of this study was to evaluate relationships between local factors (beach geomorphology and management) and regional factors (infrastructure improvements and temperature changes) against levels of fecal indicator bacteria (FIB) at recreational beaches. Data were evaluated for 17 beaches located in Monroe County, Florida (Florida Keys), USA, including an assessment of sanitary infrastructure improvements using equivalent dwelling unit (EDU) connections. Results show that elevated FIB levels were associated with beach geomorphologies characterized by impeded flow and by beaches with lax management policies. The decrease in EDUs not connected coincided with a decrease in the fraction of days when bacteria levels were out of compliance. Multivariate factor analysis also identified beach management practices (presence of homeless and concession stands) as being associated with elevated FIB. Overall, results suggest that communities can utilize beach management strategies and infrastructure improvements to overcome the negative water quality impacts anticipated with climate change.

Estimates of marine debris are often based on beach surveys. Few studies have documented the veracity of these observations and the factors that may affect accuracy. Our laboratory-scale experiment identified potential sources of error associated with visual identification of marine debris (1–2 cm long) during shoreline surveys of sand beaches. Characteristics of the survey site (beach characteristics), observer (personal characteristics), and debris (color and size) may be important factors to consider when analyzing data from shoreline surveys. The results of this study show that the ability of individuals to accurately identify plastic fragments depends on the plastic and sand color, and density of shell fragments. Most suggestively, the high accuracy of blue plastic counts (95%) and the under-counting of white (50%) and clear plastic counts (55%) confirmed the hypothesis that a significant amount of clear and white plastic fragments may be missed during shoreline surveys. These results highlight the need for further research and possible modifications of visual shoreline survey methodologies in order to optimize this cost-effective method of marine debris monitoring.

With the recovery of whale populations, carcass strandings on beaches are growing. Beach burial is a common management option for stranded carcasses. However, communities fear shark attraction following leachate transport to the ocean via submarine groundwater discharge. Here, a sediment column mesocosm experiment indicated that carcasses can be a localised source of dissolved organic carbon (DOC), phosphate and ammonium to groundwater. The spatial reach of the leachate plume was <2.5 m, while the temporal stabilisation occurred over 100–300 days. No significant chemical signals were observed under a beach-buried carcass, implying effective attenuation of decomposition plumes. For beaches with conditions similar to our one-directional, fast-flowing sediment experiment generating extreme groundwater contamination, it is unlikely that any leachate from a whale carcass would reach the ocean if buried >25 m onshore. Therefore, carcass leachate plumes would only potentially attract sharks to the surf under specific conditions not experienced during our experiments.

Since 2011, tropical beaches from Africa to Brazil, Central America, and the Caribbean have been inundated by tons of sargassum seaweed from a new equatorial source of pelagic sargassum in the Atlantic. In recent years the extraordinary accumulations of sargassum make this a nuisance algal bloom for tropical coasts. In 2018 satellite data indicated floating mats of sargassum that extended throughout the Caribbean to the northeast coast of Brazil with the highest percent coverage over the water yet recorded. A literature review suggests that Atlantic equatorial recirculation of seaweed mats combined with nutrients from several possible sources may be stimulating the growth and accumulations of sargassum. In the western equatorial recirculation area, new nutrient sources may include Amazon River floods and hurricanes; in the eastern equatorial recirculation area, nutrient sources that could sustain the sargassum blooms include coastal upwelling and Congo River freshwater and nutrients.