Modelling the distribution of fishing-related floating marine litter within the Bay of Biscay and its marine protected areas

Disentangling marine plastic impacts in Life Cycle Assessment: Spatially explicit Characterization Factors for ecosystem quality

Inputs of persistent plastic items to marine environments continue to pose a serious and long-term threat to marine fauna and ecosystem health, justifying further interventions on local and global scales. While Life Cycle Assessment (LCA) is frequently used for sustainability evaluations by industries and policymakers, plastic leakage to the environment and its subsequent impacts remains absent from the framework. Incorporating plastic pollution in the assessments requires development of both inventories and impact assessment methods. Here, we propose spatially explicit Characterization Factors (CF) for quantifying the impacts of plastic entanglement on marine megafauna (mammals, birds and reptiles) on a global scale. We utilize Lagrangian particle tracking and a Species Sensitivity Distribution (SSD) model along with species susceptibility records to estimate potential entanglement impacts stemming from lost plastic-based fishing gear. By simulating plastic losses from fishing hotspots within all Exclusive Economic Zones (EEZs) we provide country-specific impact estimates for use in LCA. The impacts were found to be similar across regions, although the median CF associated with Oceania was higher compared to Europe, Africa and Asia. Our findings underscore the presence of susceptible species across the world and the transboundary issue of plastic pollution. We discuss the application of the factors and identify areas of further refinement that can contribute towards a comprehensive assessment of macroplastic pollution in sustainability assessments. Degradation and beaching rates for different types of fishing gear remain a research gap, along with population-level effects on marine taxa beyond surface breathing megafauna. Increasing the coverage of impacts specific to the marine realm in LCA alongside other stressors can facilitate informed decision-making towards more sustainable marine resource management.

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.

Model-based estimation of seasonal transport of macro-plastics in a marine protected area

Management of plastic litter in Marine Protected Areas (MPAs) is expensive but crucial to avoid harms to critical environments. In the present work, an open-source numerical modelling chain is proposed to estimate the seasonal pathways and fates of macro-plastics, and hence support the effective planning and implementation of sea and beach cleaning operations. The proposed approach is applied to the nearshore region that includes the MPA of Capo Milazzo (Italy). A sensitivity analysis on the influence of tides, wind, waves and river floods over the year indicates that seasonality only slightly affects the location and extension of the macro-plastic accumulation zones, and that beach cleaning operations should be performed in autumn. Instead, the influence of rivers on plastic litter distribution is crucial for the optimal planning of cleaning interventions in the coastal area.

Lagrangian modelling of oil concentrations at sea: A sensitivity analysis to the grid resolution and number of Lagrangian elements

This paper presents a novel method to select the optimal combination of grid resolution and number of Lagrangian elements (LEs) required in numerical modelling of oil concentrations at sea. A sensitivity analysis in terms of grid resolution and the number of LEs, was carried out to understand the uncertainty that these user-dependent parameters introduce in the numerical results. A dataset of 211,200 simulations performed under 400 metocean patterns, 6 initial volumes, 11 grid resolutions, and different numbers of LEs (100 to 500,000), was used to analyze the sensitivity of the model along different Thresholds of Concern. Results show the importance of a correct selection of the number of LEs and the grid resolution in Lagrangian modelling of surface oil concentrations. The method proposed will allow selecting the optimal combination of these parameters to find an optimal balance between the accuracy and the computational cost of the simulation.

Stakeholder Analysis as a strategic tool in framing collaborative governance arenas for marine litter monitoring

Monitoring and assessment of marine litter requires multi-stakeholder involvement at national and subnational levels. Collaborative governance approaches are important, but often fail without adequate effort towards identifying and engaging stakeholders with appropriate profiles for the issue at stake. Stakeholder Analysis (SA) is increasingly used to ensure efficient governance arrangements. Our hypothesis is that SA contributes to collaborative governance processes for marine litter policies. We explored a pioneer participatory process in Brazil, where SA was applied to identify, categorize, and prioritize stakeholders, and analyze their power and interest, for the Strategic Plan for Monitoring and Assessing Marine Litter in the state of São Paulo. A top-down/bottom-up approach revealed that snowball sampling complemented the stakeholder assemblage identified by the consultation of experts. Prioritization of data-related stakeholders streamlined the participatory process. The interest-power matrix evaluated stakeholders' influences, guiding specific engagement strategies. We highlight the significance of SA in collaborative governance and mobilizing key stakeholders for effective marine litter monitoring initiatives, contributing to the global agenda to combat marine pollution.

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.

Sources, sinks and transformations of plastics in our oceans: Review, management strategies and modelling

Currently, 60-80 % of litter is plastic, and almost 10 % ends up in the ocean directly or indirectly. Plastics often suffer from photooxidation producing microplastics and these microplastics derived from the breakdown of larger plastics are called secondary microplastics. These compounds simply cannot be extracted from the oceans, and once mixed, they enter the food chain and may have toxic effects. This work reviews the current existing information on the topic in the scientific literature. Then, the current plastic management strategies in the marine environment are analysed, with the objective of identifying possible needs and improvements from a sustainable point of view, and to define new approaches. Simultaneously, a material flows analysis in different media of the marine environment is carried out using system dynamics. A preliminary model of plastics mobilization into the ocean to other media of the marine environment (like sediments and biota) is developed and validated with the existing data from the previous steps of the work. This work expands the current knowledge on the plastics management, their transformations and accumulation in the marine environment and the harmful effects on it. Likewise, preliminary dynamic model of mobilization of plastics in the ocean is implemented, run, and validated. The developed model can be used to predict trends in the distribution of the plastics in the ocean with time. In addition, the most important reservoirs of plastics in the ocean can be observed. Although plastics undergo transformations in the marine environment, it is not a means of disposal since most of them are non-biodegradable. Most plastics accumulate on the seabed. The proportion of microplastics found in sediments is higher than that of macroplastics.

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.

The coastal waters of the south-east Bay of Biscay a dead-end for neustonic plastics

Numerical models point to the south-east Bay of Biscay as a convergence area for floating particles, including plastics. The few existing studies on plastic abundance in the area mainly focus on open waters and yet information on the coastal area is limited. To fill this gap, neustonic samples were taken along the coastal waters of the south-east Bay of Biscay (2017-2020) to define the spatial distribution of plastic abundances and composition. Results show an average plastic abundance of 739,395 ± 2,625,271 items/km² (998 ± 4338 g/km²). French waters were more affected, with five times higher plastic abundances than Spanish coasts. Microplastics represented 93 % of the total abundance of plastic items (28 % in weight), mesoplastics 7 % (26 %) and macroplastics 1 % (46 %). This study demonstrates that this area is a hotspot for plastic with levels in coastal waters similar to those in the Mediterranean Sea or other litter aggregation areas.

First assessment of floating marine litter abundance and distribution in the Bay of Biscay from an integrated ecosystem survey

In the Bay of Biscay, regional monitoring programmes and data on abundance and distribution of floating marine litter are scarce, contrary to many other European marine regions. Here, a joint analysis of multiyear observations (2017-2019) of floating micro and macrolitter and oceanographic conditions was conducted for the Bay of Biscay by combining microlitter samplings with neuston nets and vessel-based macrolitter observations. Results show spatiotemporal abundance and distribution patterns. The density of floating microlitter increased from 26,056 items/km² in 2017 to 1,802,4611 items/km² in 2019; floating macrolitter densities barely varied amongst year (2.52 items/km² in 2017 and 3.70 items/km² in 2019). No significant correlation was found between densities of micro and macrolitter, neither for the oceanographic variables. We conclude that longer micro and macrolitter monitoring periods and standardized datasets based on the cross-border cooperation are needed to collect more comparable information, evaluate trends, and support decision making in the area.