The Scale of Ocean Plastic Pollution
The issue of ocean plastic pollution has reached a critical scale, posing a significant threat to marine life, ecosystems, and human health. Every year, approximately 8 million tons of plastic waste enter the oceans, contributing to a staggering accumulation of debris that affects even the most remote areas of the planet. This pollution is not just an eyesore; it breaks down into microplastics that infiltrate the food chain, leading to alarming levels of contamination in seafood consumed by humans.
According to recent studies, an estimated 100,000 marine mammals and 1 million seabirds die annually due to plastic ingestion or entanglement. The Great Pacific Garbage Patch, a collection of marine debris in the North Pacific Ocean, exemplifies the magnitude of the problem. Spanning an area twice the size of Texas, it contains around 1.8 trillion pieces of plastic, weighing approximately 80,000 metric tons. The sheer volume of plastic waste in our oceans necessitates immediate and innovative solutions.
To illustrate the widespread impact of plastic pollution, consider the following key statistics:
- 90% of seabirds have plastic in their stomachs.
- By 2050, it is estimated that there will be more plastic than fish in the oceans by weight.
- Plastic pollution impacts at least 267 species worldwide, including endangered species.
The economic cost of ocean plastic pollution is also significant, affecting industries such as tourism, fisheries, and shipping. Cleanup efforts and the loss of marine biodiversity add to the financial burden. Understanding the scale of the problem is crucial for developing effective strategies to mitigate plastic pollution and protect our oceans for future generations.
Current Methods of Plastic Cleanup
Current methods of plastic cleanup in the oceans are varied and multifaceted, employing both traditional and innovative technologies. One of the most widely recognized techniques is the use of mechanical skimmers. These devices are designed to float on the water’s surface, capturing plastic debris as it drifts by. Skimmers can vary in size from small, boat-mounted units to large, autonomous systems capable of operating in open seas. Despite their effectiveness, skimmers often face challenges related to weather conditions and the vastness of the ocean, which can limit their operational efficiency.
Another prevalent method involves barriers and booms. These are floating barriers that can be deployed in rivers and coastal areas to intercept plastic waste before it reaches the open ocean. Barriers are particularly effective in key locations where plastic waste funnels through, such as river mouths and estuaries. However, the effectiveness of barriers is contingent on regular maintenance and the proper disposal of the collected waste, which can be resource-intensive.
There is also a growing interest in the deployment of biodegradable and bio-based materials for ocean cleanup. These materials are designed to break down over time, reducing the long-term environmental impact. Some experimental projects are exploring the use of natural fibers and other biodegradable materials to create sustainable cleanup solutions. However, these methods are still in the early stages of development and require further research to determine their feasibility and effectiveness on a large scale.
In addition to mechanical and material-based methods, community-driven initiatives play a crucial role in plastic cleanup efforts. Programs that engage local communities in regular beach cleanups and waste management education have proven to be highly effective in reducing plastic pollution at the source. These initiatives often rely on volunteer efforts and public awareness campaigns to drive participation and success. Despite their potential, community-driven efforts can be limited by funding and the level of public engagement.
Introduction to AI in Environmental Science
Artificial Intelligence (AI) has rapidly become an integral tool in various fields, and environmental science is no exception. The deployment of AI technologies offers a promising avenue for addressing some of the most pressing environmental challenges of our time. From predicting climate patterns to managing natural resources, AI’s capabilities are being harnessed to foster a more sustainable future. Specifically, in the realm of ocean pollution, AI is poised to revolutionize how we detect, monitor, and mitigate the proliferation of plastic waste.
One significant advantage of AI in environmental applications is its ability to handle and analyze vast amounts of data. For instance, AI algorithms can process satellite images, oceanographic data, and other environmental datasets far more efficiently than traditional methods. This capability not only speeds up the data analysis process but also enhances the accuracy of pollution detection. By integrating AI with remote sensing technologies, scientists can now obtain real-time insights into the distribution and movement of plastic debris in the ocean.
Moreover, AI-powered systems are being developed to autonomously track and clean up plastic waste. These systems utilize machine learning to improve their efficiency over time. For example, AI-driven drones and underwater robots can be deployed to identify and collect plastic waste from various marine environments. These innovations are not just theoretical; real-world applications are already demonstrating the potential of AI to make a substantial impact. However, the journey is not without its challenges. Implementing AI solutions in environmental science requires overcoming technical, logistical, and financial hurdles.
Despite these challenges, the future of AI in environmental science looks promising. Collaboration between tech companies, environmental organizations, and governments is crucial to scale these solutions. As AI continues to evolve, its role in combating ocean plastic pollution will likely expand, offering new tools and methods to protect our oceans. The ongoing integration of AI in this field underscores a broader trend towards leveraging advanced technologies to promote environmental sustainability.
How AI Can Detect Ocean Plastic
Artificial intelligence has revolutionized the way we detect ocean plastic, employing sophisticated algorithms and machine learning techniques to identify plastic debris in vast oceanic environments. The deployment of AI in this field typically involves the use of satellite imagery, drone footage, and underwater sensors. By analyzing these data sources, AI systems can distinguish between plastic and other oceanic materials with remarkable accuracy. For instance, AI algorithms can process high-resolution satellite images to identify patterns and anomalies that indicate the presence of plastic waste.
One of the most effective methods involves the use of neural networks, which are trained on thousands of images of both plastic and non-plastic materials. These neural networks learn to recognize the unique spectral signatures of plastic, allowing them to detect even minuscule amounts of plastic debris. According to recent studies, AI models have achieved detection accuracies exceeding 90%, a significant improvement over traditional methods.
Additionally, AI-powered drones are increasingly being used for real-time plastic detection. These drones are equipped with high-definition cameras and AI software that can analyze video footage on-the-fly. This real-time analysis allows for immediate identification and mapping of plastic waste hotspots. The integration of AI with drone technology not only enhances detection capabilities but also enables more efficient deployment of cleanup operations.
The combination of AI and various data collection methods has been further enhanced by the use of underwater sensors. These sensors can gather data on the distribution and density of plastic particles below the ocean surface. When paired with AI, the collected data can provide a comprehensive understanding of plastic pollution patterns and trends. This multifaceted approach ensures that AI can detect ocean plastic with unprecedented precision and efficiency, paving the way for more effective intervention strategies.
AI-Driven Robotic Cleanup Solutions
Artificial intelligence has ushered in a new era of robotic cleanup solutions aimed at tackling the pervasive issue of ocean plastic pollution. Through the integration of AI, these robotic systems are becoming increasingly efficient and autonomous. One notable example is the development of AI-powered drones that can identify and collect plastic debris from the water surface with remarkable accuracy. These drones utilize advanced image recognition algorithms to distinguish between plastic waste and marine life, ensuring that the cleanup process does not harm the ecosystem.
A key advantage of AI-driven robotic solutions is their ability to operate continuously and in diverse environments. Unlike human-led initiatives which are often limited by time and weather conditions, these robotic systems can function tirelessly, adapting to different scenarios. For instance, some underwater robots are equipped with AI capabilities that allow them to navigate complex underwater terrains and gather plastic waste from difficult-to-reach areas on the ocean floor. This not only enhances the scope of cleanup operations but also significantly increases the volume of plastic waste collected.
One of the most promising applications of AI in robotic cleanup is the use of machine learning models to predict the movement and accumulation of plastic debris. By analyzing ocean currents, wind patterns, and other environmental factors, these models can forecast where plastic waste is likely to gather. This predictive capability enables robots to be deployed proactively to hotspots of plastic pollution, thereby maximizing the efficiency of cleanup efforts. In a recent study, AI-driven robots were able to reduce the amount of time spent locating plastic waste by 30%, highlighting the transformative potential of this technology.
However, the deployment of AI-driven robotic cleanup solutions is not without its challenges. High operational costs and the need for continuous technological advancements pose significant barriers. Moreover, the environmental impact of deploying large numbers of robotic systems in the ocean remains a concern. Despite these challenges, the ongoing advancements in AI are paving the way for more sustainable and effective strategies to combat ocean plastic pollution, offering hope for cleaner and healthier oceans in the future.
Case Studies of AI in Ocean Cleanup
Several case studies highlight the transformative impact of artificial intelligence in ocean cleanup efforts. One notable example is the collaboration between The Ocean Cleanup and various tech companies to deploy AI-driven systems for identifying and collecting ocean plastic. These systems utilize machine learning algorithms to analyze satellite images and drone footage, enabling the identification of plastic debris with remarkable accuracy. For instance, a study conducted in 2020 reported that AI technology was able to detect plastic debris with an accuracy rate of 92%, significantly higher than traditional methods.
Another compelling case study involves the use of autonomous underwater robots by the non-profit organization SeaClear. These robots are equipped with AI software that allows them to differentiate between marine life and plastic waste. In a recent pilot project in the Mediterranean Sea, these robots successfully removed over 30 tons of plastic waste within a span of just six months. The AI algorithms not only guided the robots to the waste but also optimized the collection routes, thereby enhancing the efficiency of the cleanup process.
Additionally, consider the innovative approach taken by Project AWARE, which leverages AI-powered mobile applications to engage divers in ocean cleanup activities. The app allows divers to report plastic waste sightings and upload images, which are then analyzed using AI to map pollution hotspots. This crowdsourced data has been instrumental in directing large-scale cleanup operations. According to a report published in 2021, over 500,000 pieces of plastic debris were cataloged and removed from the ocean through this initiative, showcasing the power of community-driven, AI-enhanced environmental action.
Finally, a case study from the National Oceanic and Atmospheric Administration (NOAA) demonstrates the use of AI for predictive modeling. NOAA’s AI systems analyze ocean currents, weather patterns, and historical data to forecast areas where plastic waste is likely to accumulate. This predictive capability allows for preemptive action, making cleanup efforts more proactive rather than reactive. In one such initiative, predictive models helped reduce plastic waste in a targeted area by 40% within a year, proving the efficacy of AI in strategic planning for ocean cleanup.
Sustainable Impact of AI Technology
The sustainable impact of AI technology on ocean pollution is multifaceted and profound. One significant area is the ability of AI to enhance the efficiency and accuracy of waste collection processes. Traditional methods of tracking and collecting ocean plastic are often labor-intensive and imprecise. However, AI-powered systems, such as drones and autonomous underwater vehicles (AUVs), can survey large areas of the ocean, identify pollution hotspots, and execute targeted clean-up operations. These systems utilize advanced machine learning algorithms to distinguish between different types of debris, significantly increasing collection accuracy.
In addition to improving collection methods, AI technology also plays a critical role in recycling and waste management. AI-driven sorting systems in recycling plants can now identify and separate various types of plastics with a high degree of precision. This capability is crucial for ensuring that more plastic waste is recycled efficiently rather than ending up back in oceans. For instance, optical sorting technologies equipped with AI can differentiate between polyethylene terephthalate (PET), high-density polyethylene (HDPE), and other plastic types, optimizing the recycling process. These improvements lead to higher recycling rates and lower contamination levels in recycled materials.
Another sustainable impact of AI is in predictive analytics, which helps in understanding and mitigating future pollution scenarios. AI models can analyze vast amounts of environmental data to predict where plastic waste is likely to accumulate. This foresight allows for proactive measures to be taken, such as deploying clean-up crews before the waste reaches critical levels or implementing policies to reduce plastic use in vulnerable regions. Predictive analytics also aids in the development of smart materials and eco-friendly alternatives to traditional plastics.
Finally, AI fosters collaboration and innovation in the fight against ocean pollution through data sharing platforms and collaborative networks. By connecting researchers, environmental organizations, and policymakers with real-time data and insights, AI facilitates a unified approach to tackling plastic pollution. This collaborative effort is exemplified by initiatives like the Global Plastic Watch, which uses AI to provide comprehensive data on plastic waste globally. Such platforms enhance transparency, drive policy changes, and support the development of innovative solutions, amplifying the sustainable impact of AI technology.
Challenges and Ethical Concerns
Despite the promising advancements in using artificial intelligence to combat ocean pollution, several challenges and ethical concerns remain. One significant challenge is the accuracy and reliability of AI systems. While AI algorithms can process vast amounts of data to identify and target plastic waste, these systems are not infallible. False positives and negatives can occur, leading to either overlooked pollution or unnecessary interventions. For instance, an AI system might misidentify floating seaweed as plastic debris, resulting in wasted resources and efforts.
Another challenge pertains to the scalability of AI solutions. Deploying AI technologies on a global scale requires substantial investments in infrastructure, data collection, and maintenance. Many regions, particularly developing countries, may lack the resources to implement such advanced systems effectively. This disparity can lead to uneven progress in addressing ocean pollution worldwide, exacerbating existing environmental inequities.
Ethical concerns also play a critical role in the deployment of AI for ocean conservation. The use of AI-driven surveillance to monitor marine environments raises privacy issues, particularly for communities that rely on these waters for their livelihoods. Balancing the need for environmental protection with the rights and privacy of individuals is a complex task. Additionally, there is the question of data ownership and management. The vast amounts of data collected by AI systems are valuable, and there must be clear guidelines on who owns this data and how it can be used.
Furthermore, the environmental impact of AI itself cannot be ignored. Training AI models, especially deep learning algorithms, requires significant computational power, which in turn consumes large amounts of energy. This energy consumption contributes to carbon emissions, potentially offsetting some of the environmental benefits gained from using AI to reduce ocean plastic pollution. Hence, developing more energy-efficient AI technologies is crucial for ensuring that the overall impact on the environment remains positive.
Challenge | Details |
---|---|
Accuracy and Reliability | AI systems can have false positives/negatives, leading to inefficient resource use. |
Scalability | Global deployment requires significant infrastructure and resources, which may not be available in all regions. |
Ethical Concerns | Issues include privacy, data ownership, and the environmental impact of AI technologies. |
Future Prospects of AI in Ocean Conservation
The future prospects of artificial intelligence (AI) in ocean conservation are promising and multifaceted. One of the most exciting areas of development is the integration of AI with autonomous underwater vehicles (AUVs). These advanced machines, equipped with AI algorithms, can perform real-time monitoring and data collection in harsh and inaccessible oceanic environments. By processing vast amounts of data, they can identify pollution hotspots, track the spread of plastic waste, and even predict future pollution patterns.
Moreover, AI-driven predictive modeling can play a crucial role in preemptive conservation efforts. By analyzing historical data and current trends, AI models can forecast potential pollution scenarios and enable timely interventions. For instance, AI can help in identifying the most effective locations for deploying barriers or cleanup operations before the plastic waste reaches critical levels. This proactive approach can significantly enhance the efficiency and effectiveness of ocean cleanup initiatives.
Another promising application of AI is in the realm of citizen science and public engagement. AI-powered apps and platforms can enable individuals to contribute to ocean conservation efforts by reporting plastic waste sightings and participating in cleanup activities. These platforms can aggregate data from thousands of users, providing valuable insights and fostering a sense of community involvement. Additionally, AI can facilitate the development of educational tools that raise awareness about the impact of plastic pollution and promote sustainable practices.
Despite these advancements, several challenges remain. The complexity of marine ecosystems, the vastness of the oceans, and the ever-evolving nature of plastic pollution require continuous innovation and collaboration. Future research should focus on enhancing the accuracy and efficiency of AI algorithms, improving the interoperability of different AI systems, and ensuring the ethical use of AI in conservation efforts. By addressing these challenges, the potential of AI in safeguarding our oceans can be fully realized.
Community and Policy Support
Community and policy support are crucial in the fight against ocean pollution. Local communities play a significant role in waste management and can greatly benefit from AI technologies that help in efficient sorting and recycling processes. AI-powered applications can educate citizens on proper waste disposal and recycling practices through interactive platforms and real-time feedback. This grassroots involvement not only enhances public awareness but also fosters a sense of responsibility and partnership in environmental conservation efforts.
On the policy front, governments and international bodies are increasingly recognizing the potential of AI in environmental protection. Policies that encourage innovation and provide funding for AI-driven environmental projects are essential. For instance, the European Union’s Horizon 2020 program has allocated substantial funds towards AI research aimed at environmental sustainability. Furthermore, integrating AI into national waste management policies can lead to more robust and adaptive systems that are better equipped to handle the complexities of ocean pollution.
Several case studies underscore the importance of community and policy support in the successful implementation of AI initiatives. For example, in Singapore, the government has partnered with local organizations to deploy AI-powered drones for monitoring and cleaning coastal areas. This collaboration has resulted in significant reductions in plastic waste and has served as a model for other countries. Similarly, in the United States, the National Oceanic and Atmospheric Administration (NOAA) has utilized AI to enhance its marine debris monitoring programs, demonstrating how policy-backed AI initiatives can lead to tangible environmental benefits.
Collaborative Efforts with NGOs
Non-Governmental Organizations (NGOs) play a crucial role in the fight against ocean plastic pollution, and their collaboration with artificial intelligence (AI) initiatives has been instrumental in advancing this cause. NGOs like Ocean Conservancy and The Ocean Cleanup have been at the forefront, leveraging AI to enhance their operations and outreach. These organizations collect vast amounts of data on ocean health, which AI systems analyze to identify patterns and predict future pollution hotspots. This synergy allows for more efficient allocation of resources and targeted cleanup efforts.
AI-powered drones and underwater robots, developed in partnership with tech companies and NGOs, have revolutionized the way plastic waste is detected and collected. These autonomous systems can cover large oceanic expanses, capturing high-resolution images and videos that AI algorithms then process to distinguish between marine life and plastic debris. For example, The Ocean Cleanup’s Interceptor uses AI to optimize its waste collection routes, significantly increasing the amount of plastic gathered from polluted rivers before it reaches the ocean.
Furthermore, NGOs often spearhead educational campaigns to raise public awareness about ocean pollution. AI-driven platforms have been utilized to analyze social media trends and public sentiment, helping NGOs tailor their messages for maximum impact. By understanding the demographics and interests of their audience, these organizations can create more engaging and informative content, thus fostering a more informed and active community.
In addition to these technological advancements, collaborative efforts also focus on policy advocacy. NGOs, equipped with AI-analyzed data, can present compelling evidence to policymakers, pushing for stricter regulations on plastic production and waste management. The ability to demonstrate the effectiveness of AI interventions through data visualizations and statistical models holds significant sway in legislative discussions. These collective efforts underline the importance of AI-NGO collaborations in creating a sustainable future for our oceans.
AI Innovations in Recycling
The advent of artificial intelligence has introduced revolutionary changes in the way we approach recycling, particularly in dealing with ocean plastic pollution. AI-powered systems are now capable of identifying, sorting, and processing various types of plastics more efficiently than traditional methods. By utilizing machine learning algorithms, these systems can be trained to recognize the subtle differences between recyclable and non-recyclable materials. This not only increases the accuracy of recycling processes but also significantly reduces the amount of plastic waste that ends up in the ocean.
One of the key innovations in this area is the development of smart sorting robots. These robots use a combination of computer vision and deep learning to scan and sort plastics on conveyor belts at high speeds. For instance, companies like AMP Robotics have created AI-driven robotic systems that can sort up to 80 items per minute, far surpassing the capabilities of human workers. This level of efficiency is crucial for handling the massive amounts of plastic waste generated daily.
Another groundbreaking application of AI in recycling is predictive maintenance for recycling machinery. By deploying AI algorithms that monitor the performance and condition of recycling equipment, operators can predict when a machine is likely to fail and perform maintenance proactively. This minimizes downtime and ensures that recycling operations run smoothly, further enhancing efficiency. Additionally, AI can optimize the logistics of waste collection and transportation, ensuring that recycling centers operate at maximum capacity.
Beyond these practical applications, AI is also playing a significant role in advancing research and development in the field of recycling. Machine learning models are being used to develop new materials that are easier to recycle and to find innovative ways to break down existing plastics into reusable components. This focus on material science driven by AI has the potential to create a more sustainable future by reducing the reliance on virgin plastics and encouraging the use of recycled materials.
Public Awareness and Education
Public awareness and education are crucial components in the fight against ocean plastic pollution. Leveraging artificial intelligence (AI), numerous initiatives have been launched to educate the public about the severity of ocean pollution and the steps they can take to mitigate it. AI-driven platforms analyze vast amounts of data from social media, news outlets, and other sources to identify trends and craft targeted educational campaigns. These campaigns often include interactive elements such as quizzes, games, and virtual reality experiences that engage users and make the learning process more impactful.
AI Innovations in Education: One of the innovative uses of AI in public education is through personalized learning experiences. AI algorithms can tailor educational content to individual users based on their knowledge level, interests, and learning pace. For instance, an AI-driven app might recommend articles, videos, or interactive modules that align with a user’s previous interactions and preferences. This personalized approach ensures that the information is not only accessible but also engaging, making it more likely that individuals will retain and act on what they learn.
Impact on Public Behavior: The integration of AI in public education efforts has shown promising results. According to a study by the Environmental Protection Agency (EPA), communities that participated in AI-driven educational programs showed a 20% increase in recycling rates and a 15% decrease in single-use plastic consumption. These statistics underscore the potential of AI to not only inform but also transform public behavior. By continually refining these educational strategies based on real-time data and feedback, AI can drive significant progress in the global effort to combat ocean pollution.
In addition to these direct educational efforts, AI also plays a role in amplifying the voices of environmental activists and organizations. AI tools can analyze social media trends to identify key influencers and popular hashtags, allowing campaigns to reach a broader audience. This amplification effect helps to create a more informed and engaged public, ultimately leading to greater collective action against ocean plastic pollution.
Economic Implications of AI in Cleanup
The economic implications of leveraging artificial intelligence in the cleanup of ocean plastic pollution are multifaceted and significant. On one hand, AI technologies can make cleanup efforts more efficient and cost-effective. Automated drones and robots can continuously monitor and clean vast ocean areas without the need for human intervention, reducing labor costs. The use of AI for predictive analytics can also help in optimizing the allocation of resources, ensuring that efforts are concentrated in the most polluted areas. A McKinsey & Company report suggests that AI-driven solutions could reduce cleanup costs by up to 30% when compared to traditional methods.
However, the initial investment required for deploying AI technologies can be substantial. Developing, testing, and maintaining AI systems, including hardware and software, demands significant financial resources. For developing nations or organizations with limited budgets, this can pose a barrier to adoption. Moreover, there is a need for skilled personnel to manage and operate these advanced systems, which can further increase operational costs. To illustrate the potential economic impact, consider the following cost comparison table:
Cleanup Method | Initial Investment | Operational Costs (per year) | Efficiency |
---|---|---|---|
Traditional Methods | $1 million | $500,000 | Moderate |
AI-Driven Solutions | $5 million | $300,000 | High |
Despite the high initial costs, the long-term economic benefits of AI in ocean cleanup are promising. AI systems can operate 24/7 and cover larger areas more quickly than human teams, providing a higher return on investment over time. Additionally, the data collected by AI systems can be invaluable for research and policy-making, potentially leading to more informed and effective environmental regulations. Governments and private stakeholders are increasingly recognizing these benefits, leading to growing investments in AI technologies for environmental applications.
In summary, while the economic implications of AI in ocean plastic cleanup present both challenges and opportunities, the potential for cost savings and increased efficiency makes it a compelling option. Stakeholders must weigh the initial investment against the long-term benefits to make informed decisions. As AI technology continues to advance, it is likely that the costs will decrease and the efficiency will improve, making it an even more attractive solution for combating ocean plastic pollution.
Global Initiatives and Partnerships
Global initiatives involving artificial intelligence (AI) and environmental sustainability are rapidly gaining momentum. International organizations, governments, and private enterprises are collaborating to leverage AI technologies to combat ocean plastic pollution. One notable example is the partnership between the United Nations Environment Programme (UNEP) and various tech companies to deploy AI-driven monitoring systems in coastal areas. These systems use machine learning algorithms to identify and track plastic waste, providing real-time data to policymakers and environmental organizations.
Several countries have also launched national programs aimed at utilizing AI for ocean health. For instance, the European Union’s Horizon 2020 project has funded multiple initiatives that integrate AI with satellite imagery to monitor marine litter. Additionally, the Ocean Cleanup project has partnered with AI firms to enhance their plastic interception devices, making them more efficient in identifying and capturing debris. These partnerships are essential for pooling resources and expertise, thereby accelerating the development and deployment of effective solutions.
Private sector involvement is equally crucial. Tech giants like IBM and Microsoft have been at the forefront of AI research and development aimed at environmental sustainability. IBM’s “Plastic Waste Reduction Initiative” employs AI to optimize recycling processes and reduce plastic waste, while Microsoft’s “AI for Earth” program funds projects that use AI to address environmental challenges, including ocean pollution. These collaborations between tech companies and environmental organizations highlight the potential of AI to drive meaningful change.
Data visualization tools are also playing a critical role in these global initiatives. Interactive maps and dashboards powered by AI provide stakeholders with accessible and actionable insights. For example, a table summarizing the impact of various AI-driven projects can help illustrate progress and identify areas needing further attention. Similarly, ul and ol lists can be used to outline key partnerships and their respective contributions, offering a clear and concise overview of the global effort against ocean plastic pollution.