Plastic Pollution Crisis In The Indian Ocean

Plastic pollution in the ocean is a pressing issue, with plastic debris being the most common and exponentially increasing human pollutant in the world's oceans. While the Pacific and Atlantic oceans have been the focus of many publications on this topic, the Indian Ocean, the second most polluted ocean in the world, has received less attention. The concentration, distribution, and impacts of plastics in the Indian Ocean are poorly understood due to insufficient measurements and under-sampling compared to other oceans. However, it is estimated that the Indian Ocean contains the second-largest plastic load, and some of the most plastic-polluted rivers empty into it, suggesting that it receives a significant amount of plastic debris annually. The mismanagement of plastic waste in countries bordering the Indian Ocean is a concern, and the unique atmospheric, oceanographic, and topographic features of the region further complicate the issue of plastic distribution.

Mismanagement of plastic waste in Indian Ocean rim countries

The Indian Ocean is one of the five main gyres contributing to the formation of massive patches of garbage around the planet. Despite this, the Indian Ocean has received less attention than the Pacific and Atlantic Oceans in terms of the distribution and impact of plastic pollution. This is partly due to the fact that the Indian Ocean region is under-sampled compared to other oceans.

Some of the Indian Ocean rim countries, including Indonesia, India, Thailand, Malaysia, Bangladesh, South Africa, India, Pakistan, and Myanmar, are among the top 20 countries ranked by mass in estimated mismanaged plastic waste (MMPW). Together, these countries produce around 15% of the world's total MMPW. The total amount of plastic waste produced by these countries in 2016 was estimated at 24 million tonnes, which is relatively low compared to the USA (34 million tonnes) and China (39 million tonnes). However, a large percentage of this waste ends up in the environment due to poor waste management practices in most Asian and African countries bordering the Indian Ocean. Jambeck et al. (2015) estimated that around 73% of plastic waste is inadequately managed along the Indian Ocean rim and released into the environment.

Plastic waste enters the Indian Ocean from various sources, including coastal sources transported by wind and tides, and rivers that carry waste from far inland. The rivers that contribute the most plastic waste to the Indian Ocean include those in Southeast Asia, which transport plastics through the Indonesian Throughflow, and those in Australia, which contribute negligible waste due to the lack of major rivers. In addition, a recent ship accident in May 2021 released 78,000 tonnes of nurdles (plastic pellets) into the Indian Ocean off the coast of Sri Lanka.

The distribution of plastic waste in the Indian Ocean is influenced by unique atmospheric, oceanographic, and topographic features. For example, reversing wind directions due to the monsoon, fronts, and upwelling regions can affect the transport of plastics. In the Northern Hemisphere Indian Ocean (NIO), the seasonally reversing monsoonal currents transport plastics back and forth between the Arabian Sea and the Bay of Bengal. Countries bordering the Bay of Bengal are particularly affected by plastics beaching on their coastlines due to both the high sources of plastic waste in the region and the ocean dynamics that concentrate plastics in the bay. In the Southern Hemisphere Indian Ocean (SIO), plastics accumulate in a garbage patch in the subtropical gyre, which is not well-defined, allowing plastics to leak into the Southern Atlantic or Pacific Oceans.

Plastic-polluted rivers flowing into the Indian Ocean

The Indian Ocean is the second-largest plastic load-bearing ocean after the North Pacific Ocean. Some of the most plastic-polluted rivers flow into the Indian Ocean, suggesting that it receives a significant amount of plastic debris each year. The Indus and the Ganges, which flow through India, carry the second and sixth-highest amounts of plastic debris to the ocean. The Meghna-Brahmaputra-Ganges river system is also responsible for carrying a substantial amount of plastic waste into the ocean. These rivers contribute to the accumulation of plastic in the Indian Ocean, with plastics ending up in garbage patches or on coastlines.

While the exact amount of plastic in the Indian Ocean is challenging to determine, it is clear that plastic pollution is a significant issue. India itself generates around 5.6 million tonnes of plastic waste annually, according to government figures. The country has taken steps to address this issue, with several states banning plastic carry bags and Prime Minister Modi pushing to limit the use of single-use plastics. However, enforcement has been lax, and plastic consumption is projected to increase.

The impact of plastic pollution in the Indian Ocean is not limited to India. Some of the countries bordering the Indian Ocean have the highest population densities globally, and mismanagement of plastic waste is a concern in many of these states. The distribution and impact of plastic in the Indian Ocean are complex due to unique atmospheric, oceanographic, and topographic features, such as reversing wind directions due to the monsoon, fronts, and upwelling regions.

Efforts to understand and address plastic pollution in the Indian Ocean are ongoing. Researchers have identified hotspots of possible plastic accumulation and are working to improve waste management and raise public awareness. Additionally, organisations like The Ocean Cleanup are developing focused mitigation strategies and technologies to reduce riverine plastic emissions.

The plastic pollution in the Indian Ocean is a pressing issue that requires collective global action. By targeting the most polluting rivers and implementing a range of mitigation measures, it may be possible to substantially reduce the amount of plastic waste entering the ocean.

The impact of the Indian Ocean's oceanographic features on plastic transport

The Indian Ocean is estimated to contain the second-largest plastic load in the ocean after the North Pacific Ocean. However, the specific amount of plastic in the Indian Ocean is unknown, as it is a relatively under-sampled region. Some of the most plastic-polluted rivers in the world empty into the Indian Ocean, suggesting that it receives a significant amount of plastic debris each year. The unique oceanographic features of the Indian Ocean, such as reversing wind directions due to the monsoon, fronts, and upwelling regions, also play a role in controlling the distribution of plastic within the ocean.

The Indian Ocean has distinct oceanographic characteristics that set it apart from other oceans. These unique features, including the presence of landmasses, influence how plastic is transported and distributed within the ocean. For instance, in the southern Indian Ocean, plastics accumulate in a garbage patch within the subtropical gyre. However, due to the absence of a subtropical gyre in the northern Indian Ocean, buoyant plastics are more likely to end up on coastlines rather than in a garbage patch. This disparity in plastic accumulation zones between the two hemispheres of the Indian Ocean highlights the impact of oceanographic features on plastic transport.

The Indian Ocean is bordered by countries with some of the highest population densities globally, and the mismanagement of plastic waste is a significant concern in these regions. The Indus River, for example, is among the top ten rivers contributing to continental plastic waste in the ocean. Additionally, the Gulf of Kachchh, located along the western coast of India, has been identified as a potential plastic accumulation zone due to its local oceanography and coastal geomorphology. The restricted water-mass exchange within the Gulf contributes to longer residence times for floating plastic particles.

The oceanographic features of the Indian Ocean, such as wind patterns and ocean currents, also influence the transport of plastic debris. For example, the Indonesian Throughflow is believed to be a source of plastic transport from Southeast Asia to the Indian Ocean. Furthermore, the reversing wind directions during the monsoon season can impact the movement and distribution of plastic within the ocean. While the specific mechanisms are not yet fully understood, it is clear that the oceanographic characteristics of the Indian Ocean play a crucial role in shaping the transport and accumulation of plastic pollution.

In conclusion, the Indian Ocean's oceanographic features significantly impact the transport and distribution of plastic pollution. The combination of riverine sources, coastal mismanagement of plastic waste, and unique oceanographic conditions contribute to the accumulation of plastic in the Indian Ocean. Further research and monitoring are necessary to fully understand the extent and impact of plastic pollution in this understudied region. Addressing the mismanagement of plastic waste in highly populated coastal countries bordering the Indian Ocean is also crucial to mitigating this environmental issue.

The Indian Ocean's plastic load compared to other oceans

The Indian Ocean covers about 20% of the Earth's surface and has unique physical characteristics that influence the circulation patterns and the fate of plastics. Some of the most plastic-polluted rivers in the world empty into the Indian Ocean, suggesting that it receives a tremendous amount of plastic debris each year. However, the concentration, distribution, and impacts of plastics in the Indian Ocean are poorly understood as the region is under-sampled compared to other oceans like the Pacific and Atlantic.

The Indian Ocean is bounded by the Indian subcontinent to the north, Africa and the Middle East to the west, Indonesia and Australia to the east, and the Southern Ocean to the south. These unique topographic, atmospheric, and oceanic features influence the transport of buoyant plastics. For example, the reversing wind directions due to the monsoon, fronts, and upwelling regions control plastic distribution in the Indian Ocean. In addition, the connection to the Pacific Ocean through Indonesia and the Atlantic Ocean through South Africa allows for debris exchange between the garbage patches in these oceans.

While the Indian Ocean is estimated to receive a significant amount of plastic waste, it does not seem to contain as much plastic as expected. This has led to the "mystery of the missing plastic". Researchers have found that the atmospheric and oceanic attributes of the Indian Ocean differ from other ocean basins, and there may not be a concentrated garbage patch. Instead, the Indian Ocean may have a "leak", with plastic seeping into the South Atlantic Ocean due to stronger southeast trade winds.

Compared to the Great Pacific Garbage Patch, which is believed to be around three times the size of France, the plastic accumulation in the Indian Ocean is less well-defined. The Indian Ocean's garbage patch is located in the subtropical gyre in the southern hemisphere, but plastics may leak into the southern Atlantic or Pacific Oceans. In contrast, the majority of buoyant plastics in the northern Indian Ocean likely end up on coastlines due to the presence of landmasses.

In summary, while the Indian Ocean is estimated to have the second-largest plastic load after the North Pacific Ocean, the distribution and impact of plastic in this ocean are not as well-studied as in other oceans. The unique characteristics of the Indian Ocean, including its connection to other oceans and stronger trade winds, may contribute to the "mystery of the missing plastic". More research and global tracking systems are needed to understand the fate of plastic in the Indian Ocean and address the overall problem of ocean plastic pollution.

The Indian Ocean's plastic accumulation zones

The Indian Ocean is estimated to contain the second-largest plastic load in the ocean after the North Pacific Ocean. However, the exact amount of plastic in the Indian Ocean is unknown due to insufficient measurements and the fact that the region is under-sampled compared to other oceans.

Some of the Indian Ocean rim countries have the highest population densities globally, and mismanagement of plastic waste is a significant concern in many of these states. Some of the most plastic-polluted rivers, such as those in Southeast Asia, empty into the Indian Ocean, suggesting that it receives a vast amount of plastic debris each year.

The Indian Ocean has unique oceanographic, topographic, and oceanic features that influence the transport of buoyant plastics. For example, reversing wind directions due to the monsoon, fronts, and upwelling regions can affect the distribution of plastic. The ocean's productivity during the southwest monsoon results in a high export flux of organic particles from the euphotic zone to the deep sea, which can cause the rapid biofouling of plastic debris and its subsequent sinking.

The Marine Protected Area of the Gulf of Mannar, a highly populated area with a range of human activities, is identified as a potential plastic accumulation zone along the Indian coast. The weak ocean currents during the Northeast Monsoon and Spring Intermonsoon (March-May) and the barrier effect of the Palk Strait contribute to the lack of strong mixing of the waters in this region, potentially trapping plastics.

The southern Indian Ocean also has a garbage patch in the subtropical gyre, but it is not well-defined, and plastics may leak into the southern Atlantic or Pacific Ocean. In contrast, the northern Indian Ocean does not have a subtropical gyre due to the presence of landmasses, so most buoyant plastics likely end up on coastlines.

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