Seabirds as biovectors in the transport of plastic debris across ecosystem borders: A case study from the Humboldt Current Upwelling System.

Seabirds have become biovectors of plastic pollutants between marine and terrestrial ecosystems, and transport of plastics to their nesting sites becomes relevant due to increasing levels of pollution. To determine the pathways by which plastic reaches their colonies, we analysed the abundance of plastics at the nesting sites of five seabird species (Humboldt penguin Spheniscus humboldti, Peruvian booby Sula variegata, kelp gull Larus dominicanus, grey gull Leucophaeus modestus, Markham's storm-petrel Hydrobates markhami) nesting in northern Chile. Seabirds were primarily grouped according to their nesting behaviour, but two species foraging in contrasting habitats (kelp gull and Markham's storm-petrel) were also compared directly. The abundance, type, and polymer of macro-, meso- and microplastics were analysed in the soil of colonies and control sites, and microplastic ingestion was evaluated for selected species. Densities of plastics in colonies of surface-nesting seabirds ranged from 0 to 21.4 items m-2 (mainly plastic bags and thin films), and 0.002 to 19.7 items m-2 (mainly hard fragments) in colonies of burrow-nesting seabirds. Mean microplastic loads in the stomachs of seabirds were between 3.7 ± 4.2 plastic items individual-1. Overall, the abundances of plastic items in all seabird colonies were low, suggesting a limited transfer of plastics from sea to land. For kelp gulls, the results indicate transfer of macroplastic items to colonies, reaching the colony via regurgitates, with landfills considered as the main plastic source. Our results suggest that contrasting nesting behaviour and foraging habitats among species can explain differential plastic accumulation in seabird colonies, but also other factors, such as wind, contribute to the accumulation of plastic debris in colonies. Proper management of sanitary landfills are key to reduce plastic contamination of coastal seabirds and their colonies.

What potential does the EU Single-Use Plastics Directive have for reducing plastic pollution at coastlines and riversides? An evaluation based on citizen science data.

To address environmental pollution by plastic litter, the European Union adopted EU Directive 2019/904, the so called "Single-Use Plastics Directive" (SUPD), which bans several single-use plastic products and addresses additional items with measures such as extended producer responsibility and obligatory requirements for product redesign. This study assessed the potential of the SUPD to reduce litter pollution in the environment with three scenarios. The "best case" scenario assumed that all measures of the SUPD completely prevent targeted items from getting into the environment. Another scenario assumed that no measures besides bans were effective. An intermediate scenario assumed partial effectiveness of measures. Data of almost 5,000 sampling events from citizen science protocols (Plastic Pirates, International Coastal Cleanup, Marine Litter Watch) and the OSPAR protocol were used to analyse litter at riversides and coastlines in Germany and the European Union. 44 to 68% of litter items in citizen science protocols consisted of single-use plastics (cigarette butts were the most prominent items). At coastlines sampled by the OSPAR protocol, fishing gear and undefined plastics prevailed. The scenario analysis revealed that substantial litter reductions could be achieved in the "best case" scenario (upwards of 40%), while the intermediate scenario resulted in litter reductions of 13 to 25%. The marginal effect of the "only bans" scenario achieved a reduction of 2-6% in Germany and the European Union, respectively. Thus, depending on implementation and enforcement, the current SUPD can be an important first step, yet further legislative actions are needed to effectively prevent plastic waste pollution.

Mountain streams flushing litter to the sea - Andean rivers as conduits for plastic pollution.

Rivers polluted by anthropogenic litter are major transport routes of litter from inland to the coastal zone and the ocean. However, litter studies have primarily focused on marine environments, and the litter dynamics in rivers are still poorly understood. Herein, we explored the abundances, composition and sources of litter at the riversides and in surface waters of mountain rivers from continental Chile in two different years. Additionally, we evaluated whether different temporal, geographic, topographic, hydrologic or anthropogenic factors influence the abundances of litter. Anthropogenic litter was prevalent in Chilean rivers, both at the riversides and in surface waters. Average abundances of riverside litter, floating macrolitter, and small floating plastics were 1.8 items m-2, 10.1 items h-1 and 5.8 items h-1, respectively, and abundances were generally higher in northern Chile. Plastics dominated in all compartments, comprising 29% of riverside litter and more than 70% of small floating litter, but other litter categories were also present at riversides. Sources of litter in Chilean rivers were mostly local, such as recreational visitors, residents, and illegal dumping, and there were no clear effects of the different tested factors on the abundances of litter. Litter densities in surface waters were low compared to those in lowland slow-flowing rivers in other countries, suggesting that retention of litter is limited in the highly dynamic and rapidly flushing mountain rivers, and thus most litter (primarily plastics) is transported directly to the sea. The results suggest that to adequately address this problem in Chile, prevention measures should be aimed at the identified local sources, by means of education, public policies, legislation, and enforcement.

A desert in the ocean - Depauperate fouling communities on marine litter in the hyper-oligotrophic South Pacific Subtropical Gyre.

The hyper-oligotrophic waters of the South Pacific Subtropical Gyre (SPSG) and the productive coastal Humboldt Current System (HCS) constitute an extreme nutrient gradient in the eastern South Pacific Ocean. Rich and dense fouling communities are known from floating objects in the HCS, but they have not been studied in the SPSG and it is not known which factors are influencing their richness and abundance. Here we present the first extensive study of rafting by marine invertebrates on floating anthropogenic debris in the eastern SPSG. We compared the effect of 9 raft-related categorical predictors on epibiont richness and fouling cover. Raft complexity was the most important predictor of richness. Fouling was dominated by thin crusts and biofilms, with more advanced communities only observed on few items. Fouling cover could not be predicted by any of the categorical factors tested. However, when tested as continuous predictors, raft volume and surface area were significantly correlated with both cover and richness. The most frequently encountered epibionts were common pelagic rafters, particularly Lepas spp., Planes spp., and Jellyella spp. Low fouling cover suggests that the SPSG's hyper-oligotrophic conditions strongly limit fouling growth, while the low frequency of coastal taxa points to the HCS/SPSG nutrient gradient acting as a filter for such organisms.

Schoolchildren discover hotspots of floating plastic litter in rivers using a large-scale collaborative approach.

Rivers are an important transport route of anthropogenic litter from inland sources toward the sea. A collaborative (i.e. citizen science) approach was used to evaluate the litter pollution of rivers in Germany: schoolchildren within the project "Plastic Pirates" investigated rivers across the entire country during the years 2016 and 2017 by surveying floating macrolitter at 282 sites and taking 164 meso-/microplastic samples (i.e. particles 24.99-5 mm, and 4.99-1 mm, respectively). Floating macrolitter was sighted at 54% of sampling sites and floating macrolitter quantities ranged from 0 to 8.25 items m-1 h-1 (average of 0.34 ± 0.89 litter items m-1 h-1). Floating meso-/microplastics were present at 57% of the sampling sites, and floating meso-/microplastic quantities ranged from 0 to 220 particles h-1 (average of 6.86 ± 24.11 items h-1). As only particles >1 mm were sampled and analyzed, the pollution of rivers in Germany by microplastics could be a much more prevalent problem, regardless of the size of the river. We identified six plastic pollution hotspots where 60% of all meso-/microplastics collected in the present study were found. These hotspots were located close to a plastic-producing industry site, a wastewater treatment plant, at and below weirs, or in residential areas. The composition of the particles at these hotspots indicates plastic producers and possibly the construction industry and wastewater treatment plants as point sources. An identification of litter hotspots would enable specific mitigation measures, adjusted to the respective source, and thereby could prevent the release of large quantities of small plastic particles in rivers. The adopted large-scale citizen science approach was especially suitable to detect pollution hotspots by sampling a variety of rivers, large and small, and enabled a national overview of litter pollution in German rivers.

Plastic Pirates sample litter at rivers in Germany - Riverside litter and litter sources estimated by schoolchildren.

Rivers are an important source of marine anthropogenic litter, but the particular origins of riverine litter itself have not been well established. Here we used a citizen science approach where schoolchildren examined litter at riversides and identified possible sources at over 250 sampling spots along large and small rivers in Germany, during autumn 2016 and spring 2017. Litter densities have an overall median of 0.14, interquartile range 0-0.57 items m-2 and an overall average (±standard deviation) of 0.54 ±â€¯1.20 litter items m-2. Litter quantities differed only little by sampling year. The principal litter types found were plastics and cigarette butts (31% and 20%, respectively), followed by glass, paper, and metal items, indicating recreational visitors as the principal litter source. At many sites (85%), accumulations of litter, consisting principally of cigarettes and food packaging, have been found. At almost all sampling sites (89%), litter potentially hazardous to human health has been observed, including broken glass, sharp metal objects, used personal hygiene articles and items containing chemicals. In the search for litter sources, the schoolchildren identified mainly people who use the rivers as recreational areas (in contrast to residents living in the vicinity, illegal dumping, or the river itself depositing litter from upstream sources). These results indicate the urgent need for better education and policy measures in order to protect riparian environments and reduce input of riverine litter to the marine environment.

Microplastic sampling with the AVANI trawl compared to two neuston trawls in the Bay of Bengal and South Pacific.

Many typical neuston trawls can only be used during relatively calm sea states and slow tow speeds. During two expeditions to the Bay of Bengal and the eastern South Pacific we investigated whether the new, high-speed AVANI trawl (All-purpose Velocity Accelerated Net Instrument) collects similar amounts and types of microplastics as two established scientific trawl designs, the manta trawl and the DiSalvo neuston net. Using a 335 µm net, the AVANI trawl can collect microplastics from the sea surface at speeds up to 8 knots as it "skis" across the surface, whereas the manta and DiSalvo neuston trawls must be towed slowly in a less turbulent sea state and often represent shorter tow lengths. Generally, the AVANI trawl collected a greater numerical abundance and weight of plastic particles in most size classes and debris types than the manta trawl and DiSalvo neuston net, likely because these trawls only skim the surface layer while the AVANI trawl, moving vertically in a random fashion, collects a "deeper" sample, capturing the few plastics that float slightly lower in the water column. However, the samples did not differ enough that results were significantly affected, suggesting that studies done with these different trawls are comparable. The advantage of the AVANI trawl over traditional research trawls is that it allows for collection on vessels underway at high speeds and during long transits, allowing for a nearly continuous sampling effort over long distances. As local surface currents make sea surface abundance widely heterogeneous, widely spaced short-tow trawls, such as the manta and DiSalvo trawls, can catch or miss hotspots or meso-scale variability of microplastic accumulations, whereas the AVANI trawl, if utilized for back-to-back tows of intermediate distances (5-10 km), can bridge variable wind conditions and debris concentrations potentially reducing variance and provide a greater resolution of spatial distribution.