The Indian Ocean: A Plastic Crisis

Plastic is the most common human pollutant in the world's oceans, and the Indian Ocean is no exception. While the exact amount of plastic in the Indian Ocean is unknown, it is estimated that there are 358 trillion microplastic particles floating on the surface of the oceans, with many more found on the ocean bed. The Cocos Keeling Islands, an archipelago in the Indian Ocean, are covered with an estimated 414 million pieces of plastic weighing 238 tons. The Indian Ocean is surrounded by some of the most densely populated countries in the world, and some of the most plastic-polluted rivers empty into it, suggesting that it receives a significant amount of plastic debris each year.

The Cocos Keeling Islands are covered in plastic

The Cocos Keeling Islands, a remote archipelago in the Indian Ocean, are home to fewer than 600 people and sit 1,300 miles off the northwest coast of Australia. The islands are covered with an estimated 414 million pieces of plastic pollution, weighing 238 tons. This plastic pollution was mostly made up of single-use items, such as bottles, plastic cutlery, bags, and straws. In addition, 977,000 shoes and 373,000 toothbrushes were found on the beaches of the islands.

The plastic buildup on the Cocos Keeling Islands is emblematic of the vast amount of plastic waste circulating in the world's oceans. The islands act as a "canary in the coal mine", warning about the sheer amount of plastic waste in the oceans. The plastic found on the islands is not unique, with significant quantities of plastic documented on islands and coastal areas worldwide, from the Arctic to the Cocos Keeling Islands.

The plastic pollution on the Cocos Keeling Islands was measured by researchers through a comprehensive beach debris sampling method. They surveyed debris on the beach surface, buried, and in beach-back vegetation. They marked off transects and counted all the plastic pollution inside each one, digging down 4 inches (10 cm) into the sand to measure any waste buried under the surface. They then multiplied their findings by the island chain's total beach area.

The results of the study highlight the problematic nature of plastics, especially single-use items, on remote islands. It also underscores the utility of beach survey data in understanding the state of the world's oceans. The Cocos Keeling Islands provide a unique insight into debris accumulation trends due to their isolation and lack of human occupation.

The lead researcher, Lavers, emphasized the urgency of acting on the warnings provided by the plastic pollution on the Cocos Keeling Islands. She stated that plastic pollution is now ubiquitous in our oceans, and remote islands offer an objective view of the volume of plastic debris circling the globe. The study's findings underscore the need to reduce plastic production and consumption while improving waste management practices to prevent plastic from entering our oceans.

Mismanagement of plastic waste in IO rim countries

The Indian Ocean (IO) is one of the most polluted oceans, with plastic debris being the most common and exponentially increasing human pollutant. Some of the IO rim countries have the highest population densities globally, and mismanagement of plastic waste is a significant concern in many of these states. The Cocos Keeling Islands, a remote archipelago in the Indian Ocean, are covered with an estimated 414 million pieces of plastic pollution, weighing 238 tons. This plastic pollution is a result of the mismanagement of plastic waste in the IO rim countries.

Some of the most plastic-polluted rivers empty into the IO, suggesting that the IO receives an enormous amount of plastic debris each year. The concentration, distribution, and impacts of plastics in the IO are poorly understood due to a lack of data and undersampling compared to other oceans. This lack of knowledge about the IO makes it difficult to fully grasp the extent of the plastic pollution crisis in the region.

The mismanagement of plastic waste in IO rim countries is a significant contributor to the plastic pollution in the ocean. Jambeck et al. estimated that around 73% of plastic waste is inadequately managed along the IO rim and released into the environment. Nine out of the top 20 countries ranked by mass in estimated mismanaged plastic waste are located along the IO rim, including Indonesia, India, Thailand, Malaysia, Bangladesh, South Africa, India, Pakistan, and Myanmar.

The high population densities in some IO rim countries contribute to the large amount of plastic waste generated in these regions. Additionally, the lack of proper collection systems, limited workers for collection, and mismanagement after collection (open burning, unwise dumping, poorly managed dumping sites) exacerbate the problem. The plastic waste generation rate is also influenced by income level, with lower-income countries often lacking the infrastructure and resources for effective waste management.

The impact of plastic pollution in the IO is evident in the ecosystem and the wildlife that inhabits it. For example, studies have shown that approximately 50% of wandering albatross chicks on the Kerguelen and Crozet Islands in the IO had ingested plastic fragments. While the plastic content was relatively low, it still highlights the presence of plastic pollution in the food chain.

Plastic-polluted rivers that empty into the IO

The Indian Ocean (IO) is one of the most plastic-polluted oceans in the world. While the Pacific and Atlantic oceans have been the subject of many publications on plastic pollution, the same cannot be said for the Indian Ocean. The concentration, distribution, and impacts of plastics in the IO are poorly understood as the region is under-sampled compared to other oceans.

Some of the most plastic-polluted rivers in the world empty into the IO. The Ganges and Indus rivers, which flow through India, carry the second and sixth-highest amounts of plastic debris into the ocean. The Brahmaputra river, which flows through India, Bangladesh, and China, is also one of the top 10 plastic waste-carrying rivers in the world. These three rivers are responsible for a large amount of the plastic pollution in the IO. The highest river discharges occur during the wet season, with plastic waste input from rivers in the IO peaking in August.

The plastic pollution in these rivers is attributed to a variety of factors, including an increase in tourism, shipping, and fishing activities. However, a considerable portion of plastic garbage afloat in the open waters originates on land and is drained into the seas by rivers. The plastic waste found in these rivers includes gutka packets, sachets of everyday consumables, and discarded plastic from community events.

The Indian government has recognized the problem of plastic pollution in its rivers and has launched projects such as the Namami Gange to clean up the Ganges. In addition, India signed a resolution to reduce marine plastic waste at the United Nations Environment Assembly in 2017. Despite these efforts, the plastic pollution in these rivers continues to be a significant problem, with the National Green Tribunal stating that "not a single drop of the Ganga has been cleaned so far".

The impact of seasonal winds and currents

The Indian Ocean's hydrological characteristics are shaped by the interaction of atmospheric conditions (rain, wind, and solar energy) with the surface, the sources of its water, and the deep (thermohaline) circulation. The Indian Ocean experiences strong monsoonal winds, which reverse seasonally. The North Indian Ocean (NIO) is divided into the Arabian Sea and the Bay of Bengal (BoB) basin by the Indian peninsula. The NIO experiences the strongest monsoonal winds due to its distinct geographic position, which is landlocked to the north by the Asian landmass.

During the northeast monsoon, a weak counterclockwise gyre develops in the Arabian Sea, and a strong clockwise gyre forms in the Bay of Bengal. The current reverses during the southwest monsoon, with warm and cold-core eddies forming in the Arabian Sea. The coastal currents, such as the East Indian Coastal Current (EICC) and the West Indian Coastal Current (WICC), also reverse seasonally. These seasonal reversals of ocean currents, such as the Somalia Current and the Southwest/Northeast Monsoon Current south of India and Sri Lanka, are caused by monsoonal winds.

The impact of these seasonal winds and currents on plastic distribution in the Indian Ocean is significant. The concentration of microplastics in the Northern Indian Ocean varies with the seasons, with higher concentrations during the monsoon and post-monsoon periods. The abundance of microplastics is highest in the convergence zones of five subtropical gyres in the open ocean. Positively buoyant plastics can be transported by wind and water currents, eventually becoming trapped in different coastal habitats. The microplastics concentration in the Bay of Bengal during the pre-monsoon and post-monsoon periods remains the same, except in the northern Bay of Bengal, where weak winds cause a change in concentration.

The Indian Ocean does not have a subtropical gyre and an associated garbage patch like the Pacific and Atlantic Oceans due to the presence of landmasses. Instead, buoyant plastics are likely to end up on coastlines. However, there is evidence of a garbage patch forming in the Bay of Bengal. The impact of seasonal winds and currents on plastic distribution in the Indian Ocean is a critical area of study, as the region is under-sampled compared to other oceans, and the concentration, distribution, and impacts of plastics in the Indian Ocean are not yet fully understood.

The lack of data on plastic in the IO

The Indian Ocean (IO) is a major recipient of plastic waste, with some of the most plastic-polluted rivers in the world emptying into it. Despite this, the concentration, distribution, and impacts of plastics in the IO are poorly understood. This is due to a scarcity of data in both the surface and deeper ocean, with only a few data points available for the whole IO, including along coastlines and the deeper ocean. This lack of data is a significant constraint that needs to be addressed.

While research on marine plastic pollution has grown exponentially in the last decade, there is limited information on the holistic effects of marine plastic and its impact on ecosystems, human well-being, society, and the economy. This is particularly true in the Indian context, where marine plastic research is still in its early stages. India is considered one of the major plastic polluters of the ocean, so understanding the source, distribution, and dynamics of plastics in the IO is crucial for implementing effective mitigation policies.

The distribution and impact of plastic in the Pacific and Atlantic oceans have been the subject of many publications, but the same cannot be said for the IO. This is despite the fact that some of the IO rim countries have the highest population densities globally, and mismanagement of plastic waste is a significant concern in these states. The unique atmospheric, oceanographic, and topographic features of the IO, such as reversing wind directions due to the monsoon, fronts, and upwelling regions, also play a role in the distribution of plastic in the IO.

To address the lack of data in the IO, numerical models and simulations have been used to simulate the transport of plastics. However, confirmation of these results is crucial, and further investigations are needed to pinpoint regions that require attention. For example, it is unclear which type of simulated garbage patch best represents the behavior of plastic waste in the subtropical southern IO. The scarcity of data in the IO highlights the need for more comprehensive research and monitoring efforts to fully understand the extent and impact of plastic pollution in this region.

The plastic problem is of particular concern to Indian Ocean nations as Asia currently contributes the highest share of mismanaged plastic waste. Eight of the top ten rivers that transport the highest plastic loads to the ocean are in Asia. The Indian Ocean has likely been polluted with plastic litter since the late 1950s when the first plastic industry was established in the country. Today, India has one of the fastest-developing plastic industries, with a large number of polymer manufacturers, plastic processing units, and recycling units.

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