The Ocean Cleanup

Rivers are key pathways for transporting plastic pollution to the ocean, yet global estimates of riverine plastic export remain highly uncertain due to catchment diversity and the complexity of transport processes. To better understand dynamics at the river–ocean interface, we analyzed a comparative dataset from three rivers in the Caribbean, Southern Africa, and Southeast Asia, each characterized by distinct hydrometeorological and tidal regimes. We tracked 196 GPS drifters and monitored surface transport using forty-one cameras deployed across six river locations over multiple seasons. These observations informed simulations of three years of plastic transport (2020–2022). We find that rivers flush 50% of their floating plastics downstream within only 7–12% of the time. Annual average mass fluxes for the three rivers were 34–98% lower than previously reported by global models. Our results highlight that rivers act as long-term sinks for plastic pollution, and that estuarine transport is more limited than often assumed. This study provides critical observational and modelling insights to refine river‑to‑ocean plastic flux estimates and emphasizes the heterogeneity of emission dynamics across diverse river systems.

The case studies in this book and the interventions from the International Seabed Authority (ISA) (see Appendix) meetings showcase the types of Ocean Heritage, natural and cultural, tangible and intangible, that may be lost if deep sea mining (DSM) goes ahead. The chapters also provide some suggestions to protect heritage in the deep sea for future generations. For example, exclusion zones, as seen with dredging regulations (Chap. 5 , this vol.). What is needed most, is surveys of the Ocean Heritage in the deep, especially in zones proposed for mining. We cannot protect heritage we do not know about. These surveys must be done to standards that archaeologists can work with, and the results should be publicly available. Underwater cultural heritage (UCH) must be included in these surveys along with natural heritage and environmental impact assessments. This is because UCH can support ecological marine biodiversity and help boost sea connectivity. Understanding UCH, including intangible UCH, is also key to respecting international commitments to human rights (including intergenerational rights, the right of public participation, the right to culture, and Indigenous peoples’ rights).

Elasmobranchs, one of the most endangered animal groups, have been affected by different anthropogenic stressors, including marine litter. To better understand the interactions of elasmobranchs with litter we analyzed the gastrointestinal tract of sharks and examined skate nest composition in southern Brazil. Among 47 sharks caught in longline fisheries, three had ingested mesoplastic items (FO=6.4%); a subsample of 18 of these sharks was assessed for microplastic ingestion, revealing 34 microplastics in 12 individuals (FO=66%). Gillnet-captured sharks (n=7) only ingested three microplastics (FO=42.85%). Sixteen skate nests examined for litter interaction presented a total of 269 egg capsules and 1676 litter items. The FO of litter in nests was 100%, with plastic being the predominant material (96.71%), mainly fishing lines (85.98%). While litter ingestion by sharks was less frequent than other groups, litter prevalence in skate nests was high and primarily linked to fishing activities.

This perspective article invites readers to (re)imagine research as a means of practicing right relations with the places we inhabit and descend from. We anchor our work in a Kanaka Hawaiʻi, a Native Hawaiian cosmogeny and epistemology, one that recognizes all life as kin. We begin with the central question, “Where have the sand turtles gone?” to explore how a Kanaka Hawaiʻi-informed perspective, grounded in the genealogical creation chant, ke Kumulipo, can guide plastics research in Hawaiʻi. We elaborate this perspective through a moʻolelo, a story of a collaboration between a Kanaka Hawaiʻi cultural practitioner and a French and Swedish plastics researcher along the shores of Kapua, Waimānalo. By tracing the transformation of a conventional scientific study, we aim to grow entry points for research that is accountable to the place and the genealogical descendants of those specific lands, who have inherited the privilege and responsibility to steward them. We conclude by discussing how this perspective might offer critical insights for global environmental policy, such as the UN Plastic Treaty, urging a shift from treating Indigenous Peoples as stakeholders to honoring them as rights-holders. Ultimately, this work is a call to research in ways that honor the original peoples of the places where we are blessed to live, work, and research, particularly in ways that amplify the knowledge traditions and lifeways birthed from those specific lands. We write this piece for and with Waimānalo as a living, reciprocal co-author. We hope the experiences shared here return to and strengthen those places and people.

To understand the full scope of plastic pollution in aquatic environments, continuous and large-scale monitoring techniques are essential, especially for tracking mass balance and long-term trends. Over recent years, advancements in automated monitoring of floating marine debris have gained momentum. Satellite-based mapping of coastal regions has progressed significantly with the development of multispectral, hyperspectral, thermal infrared, polarimetry, and synthetic aperture radar (SAR) methods, among others. However, tracking debris in the open ocean presents unique challenges. In this environment, floating debris is widely dispersed, making satellite detection difficult. Large floating macroplastics (>50 cm) represent a significant portion of the ocean plastic mass budget, yet remain under-quantified by traditional methods, such as surface trawls and visual surveys that are costly and labor intensive. This presentation highlights recent advancements in the Automated Debris Imaging System (ADIS), a technology developed to tackle these limitations. Designed to be deployed onboard existing vessels of opportunity, ADIS uses optical imaging combined with deep learning algorithms to detect and capture geo-tagged snippets of floating macroplastics (>50 cm) along sailing routes. Recently endorsed as an official UN Decade of Ocean Science action, ADIS offers promising potential for global-scale debris tracking. Since the initial proof of concept, we have built a comprehensive global dataset comprising over 10 million images, identifying thousands of floating macroplastics. By comparing ADIS detections with concurrent surface net samples and visual observations from selected transects, we can now rigorously evaluate the system's accuracy and precision, underscoring its value for global marine debris monitoring.

Abstract. A major challenge for cleanup operations in the Great Pacific Garbage Patch is the daily prediction of plastic concentrations that allows identifying hotspots of marine debris. Lagrangian simulations of large particle ensembles are the method in use and effectively reproduce observed particle distributions at synoptic scales 𝒪(1000 km). However, they lose accuracy at operational scales 𝒪(1–10 km), and operators regularly experience differences between predicted and encountered debris accumulations within the garbage patch. In Lagrangian methods, it would be common to ask this question: where do objects go as they follow the current? Here, we take a different approach and instead ask this question: which locations attract material? The recently developed concept of Transient Attracting Profiles (TRAPs) provides answers because TRAPs uncover the most attracting regions of the flow. TRAPs are the attracting form of hyperbolic Objective Eulerian Coherent Structures and are computable from the instantaneous strain field on the ocean surface. They describe flow features which attract drifting objects and could facilitate offshore cleanups that are currently taking place in the Great Pacific Garbage Patch. However, the concept remains unapplied since little is known about the persistence and attraction of these features, specifically within the Pacific. Therefore, we compute a 20-year dataset of daily TRAP detections from satellite-derived mesoscale velocities within the North Pacific subtropical gyre. We are the first to track these instantaneous flow features as they propagate through space and time. It allows us to study the life cycle of TRAPs, which can range from days to seasons and lasts an average of 6 d. We show how long-living TRAPs with lifetimes beyond 30 d intensify and weaken over their life cycle, and we demonstrate that the evolution stage of TRAPs affects the motion of nearby surface drifters. Our findings indicate that, at the mesoscale, operators in the Great Pacific Garbage Patch should search for long-living TRAPs that are at an advanced stage of their life cycle. These TRAPs are the most likely to induce a large-scale confluence of drifting objects and their streamlining into hyperbolic pathways. Such a streamlined bypass takes, on average, 5 d and creates an opportunity to filter the flow around TRAPs. But we also find TRAPs that retain material over multiple weeks where we suspect material clustering at the submesoscale. Prospective research could investigate this further by applying our algorithms to soon-available high-resolution observations of the flow. Our analysis contributes to a better understanding of TRAPs, which can even benefit other offshore operations besides ocean cleanups, such as optimal drifter deployment, oil spill containment, and humanitarian search and rescue.

The original version of this Article contained an error in Fig. 5 , in which the colour coded precipitation range legend contained wrong values. This has been corrected in both the PDF and HTML versions of the Article.

Understanding the transport behaviour of mismanaged plastic waste in riverine and estuarine environments is growing. However, many studies to date focus on the surface layer transport while a limited number look to measure the vertical distribution of plastic waste within these systems. Factors such as density, shape, the influence of wind and flow velocity can determine the vertical distribution of the plastic waste in a river, but many knowledge gaps remain. With this, and as technology developers move to create innovative river surface focused interception solutions to extract plastic waste, a greater understanding of the transport behaviour of sub-surface plastic debris is required. Here, we present a comprehensive overview of the development stages required to build and deploy a low-cost depth trawl tool designed to sample plastic waste at a depth of up to 5m in a heavily polluted river in Malaysia. Topics covered include tool design concepts, manufacturing methods, onsite testing, river deployment learnings and sampling results. Field data is compiled from over 60 sampling surveys conducted over 14 days in several locations along the Klang River, Malaysia. The depth trawl is mounted to a locally available fishing boat (sampan) and consists of two steel horizontal arms, a steel frame, two winches, cables, weights, five nets, and is operated manually with the assistance of a solar-powered motor. The dimensions of each net are 30cm (W) x 50cm (H) x 100cm (L) with a mesh size of 30mm x 30mm. To ensure that the nets remain aligned vertically during deployment, a weight of 15kg is tied to the bottom of the net system on both sides. Samples were collected every 1 metre to a depth of 5 metres. Each sampling was conducted for 15 minutes, six times per day with an interval of 1 hour between samples to allow for changes in the tide and river flow direction. An ADCP was deployed in parallel to the depth trawl to provide measurements of flow velocity variation at the river surface and with depth. In addition, this paper reviews the depth trawl system’s capabilities and recommendations for further studies and applications in the field.