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| "Plankton Munching on Microplastics" |
Our oceans and fresh lakes are contaminated with microplastic debris. Plastic Production is estimated to be at 225 million tons per year. (Browne 2007). Unfortunately, most of this plastic ends up in our marine and freshwater systems. There are two ways microplastics enter our water systems: either as primary or secondary microplastics. Primary microplastics enter marine and freshwater systems as “raw plastic material, such as virgin plastic pellets, scrubbers, and microbeads (Browne et al. 2007.) secondary plastics begin as large plastics but overtime, they begin to mechanical or biologically degrade, making them smaller and smaller. The degradation occurs through photodegradation, where the sunlight causes the plastic to oxidize and turn into smaller pieces (Browne et al. 2007.). Microplastics are defined as “plastic particles, smaller than 5 mm in diameter” ( K. Lee Lerner and Brenda Wilmoth Lerner 2014). The six different types of plastic are Polyethylene Terephthalate, high-density polyethylene, polyvinyl chloride, low-density polyethylene, polypropylene, and polystyrene. Microplastics are made out of these different plastics, and their densities, shape, and size all vary. Because of this, each type of plastic will be present in either the surface of the water (low density) or in sea sediments (High density). This is a determining factor of what species consume these plastic particles (Browne et al. 2007.)Organisms, both vertebrates, and invertebrates have been found to ingest microplastics. (Microplastics. 2014.) A study conducted on rodents determined that the microplastic Polystyrene can go from the digestive tract to the lymphatic system. The lymphatic system supplies molecules to the bloodstream, therefore, the potential of these microplastics ending up in different body tissues or the blood itself is not impossible.
There are three size levels of plastic, macroplastics (£5 mm), microplastics (<5mm), and microscopic plastic (<1 mm) (Browne et al. 2007.) Microplastics are becoming increasingly smaller, making them much more likely to be consumed by organisms. There has been research conducted to study the consumption of microplastics by marine life. One specific study, conducted by Marine ecologist and biochemist Andrew Watts and colleagues at the University of Exeter in England, fed microplastics to mussels, they then fed these mussels to crabs. It took 14 days for these crabs to excrete these microplastics, compared to the normal 2-day digestive process. Andrew and his colleagues also placed these crabs in tanks that released a high concentration of microplastics over the crabs’ gills for 16 hours, three weeks after the trial these crabs were still releasing microplastics from their system. ( Akpan 2014.) It is unclear whether these microplastics can travel up the food chain or why these microplastics take so long to be expelled from an organism’s system. The effects of microplastics on food chains and organisms remain an unresolved enigma in the science community. Thus, it is crucial to conduct more research on microplastics.
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