Microplastic Pollution in the Ocean Is More Prevalent Than Previously Believed

How Microplastics Threaten Ocean Life Cycle - The Green Optimistic

Photo collage: The Green Optimistic

We already know that microplastics (bits that are less than 5 mm) are omnipresent in the ocean, but now scientists believe that previous estimates about how much plastic is in the ocean are actually way too low.  Using very fine mesh nets, researchers surveyed the coasts of the U.S. and U.K. and were able to estimate that there could be at least twice as many microplastic particles in the ocean as previously thought.  When the smaller particles they picked up in these survey trawls are added to global estimates of surface microplastics, it increases the range from between 5tn and 50tn particles to between 12tn-125tn particles, the scientists say.

Why This Matters:  Microplastic is more abundant than the tiniest and one of the most abundant life forms in the ocean — zooplankton — if these estimates are correct.   The smaller particles mean that they are similar in size to the food eaten by zooplankton, which are a key part of the marine food chain and important in regulating climate.  As the authors say, “Microplastics are a prolific, persistent and pernicious contaminant, posing an environmental and economic risk to marine ecosystems across the globe.”  We need to reduce our plastics load on the marine environment and soon.

 Microplastics Found In Greater Abundance on the Seafloor Too

Recently, another group of scientists found that microplastics are also more abundant on the seafloor than had been believed. The plastic floating on the surface in the large ocean garbage patches is actually only 1% of the total plastic in the ocean.  Where does the rest end up?  On the seafloor.  The research shows that “powerful currents sweep these microplastics along the seafloor into large ‘drifts,’ which concentrate them in astounding quantities.”  They found the highest levels of microplastics ever on the seafloor — they counted “1.9 million pieces of microplastic in a 5 cm-thick layer covering just one square meter.”  Scientists believe that deep-sea currents push microplastics to the seabed like giant deepsea waves and deposit it in vast sediment drifts, thereby creating plastic “hotspots” on the seafloor and accumulating in the very same locations as biodiversity hotspots, where deep-sea life is abundant.

Microplastics Carried To The Ocean In Rivers

Other research has shown that rivers transport microplastics to the ocean.  Researchers found that microplastic contamination was pervasive on all river channel beds, and after extreme flooding events in 2015-16, flooding transported approximately 70% of the microplastic load stored on these river beds and flushed it into the ocean.  And now a new study shows that microplastics also enter the food chain via rivers because birds consume hundreds of particles of microplastics a day when they feed on aquatic insects.  The latest study, published in the journal Global Change Biology, found that a certain bird species in Wales that feeds on river insects was consuming about 200 pieces of plastic a day.   These same birds were also feeding thousands of plastic fibers to their nest-bound babies.

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