It is a common sight today to see plastic bags and bottles floating in our seas and oceans. Plastic particles of varying sizes have become the dominant form of marine litter. Scientists have estimated that we have discarded around 5.25 trillion plastic particles weighing over 268,000 tons in our oceans. According to the United Nations Environment Assembly, we introduce an average of 4.8 to 12.7 metric tons of plastic annually to the sea.
Today, plastic comes in virtually everything we buy. Their durability, low cost, strength, and durability make them suitable for manufacture in a wide range of daily use products. However, their high demand and inappropriate use and disposal have led to their accumulation in the environment. During the COVID-19 pandemic, worldwide production of face masks and other laboratory and medical materials drastically increased. This poses a new challenge for the marine plastic litter problem.
When we look to the future, the number of microplastics increasing in the environment seems inevitable. Microplastics are plastic particles ranging in size from a few microns to several millimeters in diameter. Even if, by some miracle, we could stop plastics from entering the ocean, the fragmentation of plastics already presents in the sea would continue for decades to come.
Scientists have reported microplastic pollution in the marine environment from the poles to the equator. Scientists have even reported microplastics in significant concentrations in Arctic sea ice.
Sources and Types of Marine Microplastics
Plastics are chemically stable. They can exist in environments for hundreds to thousands of years.
The most significant sources of plastic pollution in marine environments are coastal cities, ports, and shipping activities. Once plastic enters the ocean, it breaks down into microplastics. Studies have shown that microplastics continuously occur in the ocean. Their small size poses a risk to filter-feeding animals like clams and some fish. Filter feeders confuse the microplastics for phytoplankton and end up consuming them. Thus, microplastics enter our food chain. Microplastics pose a severe threat to marine animals and the health of our oceans. Ingesting microplastics causes harmful toxicological and physical effects on the bodies of marine organisms.
The primary sources of microplastics in the marine environment are:
1. Land flow
Rain and wind wash away plastic wastes like plastic bags and fibers into rivers. Rivers carry these wastes into marine environments. Even cosmetics contain microplastics. These microplastics can enter marine environments through sewers and pollute oceans.
2. Coastal tourism
Seaside tourist attractions cause the accumulation of plastic bags, water bottles, and other plastic waste discarded by tourists on beaches.
People traveling and working on ships throw plastic waste into the ocean. Additionally, shipping accidents also cause plastics to enter the marine environment.
The abrasion of fishing nets introduces microplastics into the seas and oceans. When fisherfolk can no longer use their nets, ropes, and other fishing gear, they abandon them in the sea. These nets are a source of plastics and microplastics in the ocean.
We can also classify microplastics into primary and secondary based on their mode of occurrence. Primary microplastics are those that occur in the microstate itself. Secondary microplastics result from the breakdown or fragmentation of larger plastic bodies.
Effect of Microplastics on Marine Animals
Microplastic pollution in the marine environment has a toxic effect on fish and other aquatic life. They reduce food intake, delay growth, and cause abnormal behavior. Additionally, nano-scale microplastics can penetrate biological barriers and accumulate in tissues. The accumulation of microplastics at the molecular level can affect an organism’s metabolism. Because of their small particle size, marine life can easily consume them. Their consumption can produce a series of toxic effects that include:
1. Growth and development inhibition
When eaten by marine life, microplastics accumulate in their digestive tracts and block them. The blocking of the tract causes them to consume less food, therefore reducing energy in their bodies. Low energy affects their growth and development. Their energy decreases as the concentration of microplastics in their bodies increases.
2. Toxicological effects
Microplastics negatively affect reproductive processes in marine life. Because of microplastic consumption, scientists have recorded decreased ovulated eggs and sperm levels in many marine species. When microplastics enter their biological tissues and organs, they trigger immune responses. Their bodily responses can damage white blood cells, further causing immunotoxicity.
3. Genetic damage
Many studies have indicated that microplastics absorb hydrocarbons. When marine life consumes these microplastics, it causes a range of neurotoxicity, immunotoxicity, and genotoxicity responses in their bodies. It causes genetic damage, particularly in mussels. However, currently, there are very few studies highlighting the effects of microplastics on genetics.
Microplastics pollute marine environments all around the world. It is choking life in our oceans. Several marine species ingest microplastics. In some species, a vast majority of the population contains microplastics in their bodies. Ingesting microplastics causes physical and toxicological harm to these animals. Every marine species is vital to the systematic functioning of marine ecosystems. For example, filter feeders help reduce pollution in ocean waters. The destruction of marine ecosystems can result in the decreased capacity of our oceans to absorb carbon dioxide. Therefore, for our own survival, it is vital that we address and overcome the issue of microplastic pollution in the marine environment.
We have limited knowledge about the future trend of microplastics in the ocean. However, we know it is inevitable that microplastic pollution in the marine environment will increase. Larger plastic items will continue fragmenting and creating more microplastics in the seas. Even after 10 years since the term ‘microplastics’ first came into existence, we have more questions than answers about the consequences of microplastic pollution in the marine environment. However, the world collectively recognizes that microplastics simply do not belong in oceans.
We need to urgently change how we produce, consume, and dispose of plastic items and products. We need to find innovative ways of using end-of-life plastics as raw materials to manufacture new products. Principles like these are essential in the development of a circular economy. Rethinking the way we use plastic material will increase our resource efficiency.
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