humans were here -- 11/24/21
Today's selection -- from The Brilliant Abyss by Helen Scales. Plastic in the ocean:
"The immense size of the deep ocean swallows debris from human lives. Two studies published in 2014 estimated the total amount of microplastics floating on the surface of the world's oceans to be around 39,000 tons. That was far less than expected, given the amount thought to have been manufactured, thrown away, washed out to sea, and crumbled into pieces. These two surveys point toward there being tens of thousands of tons of missing plastic.
"It has become a miserable truth that plastics are everywhere now: littering beaches on remote islands, trapped in Arctic sea ice, in soils, rivers, and lakes, and blowing in the wind. And a large portion of the oceans' missing plastic is ending up in the deep sea -- how could it not?
"Big pieces are easy enough to spot. In 2019, American multimillionaire adventurer Victor Vescovo descended almost seven miles into the Challenger Deep in the Mariana Trench. When he looked out the window of his submersible at the oceans' very deepest point, Vescovo saw a plastic bag and a bunch of candy wrappers.
"Deep-sea sediments are also filled with microplastics. Until recently, the most heavily contaminated parts of the deep were thought to be submarine canyons, which act as garbage chutes, funneling plastics off the edges of continental shelves and into the abyss. Masses of microplastics also end up falling into oceanic trenches. Then, a 2020 study announced the highest concentrations of microplastics yet found in the deep -- double previous estimates. The worst affected area researchers tested was in the Mediterranean, off the coast of Italy, where swirling currents blow like sandstorms across the deep seabed, collecting and concentrating microplastics. If the two open pages of this book were contaminated to the same extent, they would be covered in more than one hundred thousand plastic fragments.
|Microplastic fibers identified in the marine environment|
"A dusting of microplastics covers the abyssal seabed, and all sorts of bottom-dwelling animals have been found to eat or get tangled in plastic fibers, including sea cucumbers, sea pens, and hermit crabs. Amphipods living at the bottom of the deepest hadal trenches have been found with microplastics in their guts, including a newfound species, which was named, accordingly, Eurythenes plasticus. For decades already, deep-sea animals have been swallowing plastic fragments. Starfish and brittle stars from the Rockall Trough, 6,600 feet down off the northwestern coast of Ireland, which were collected in the 1970s, preserved and kept in storage, then recently brought out and examined -- and microplastics were picked out from their insides.
"Plastics have also been found in the open midwater of the deep. Anela Choy and colleagues have been tracking microplastics in Monterey Bay using a submersible to collect seawater and catch marine snow at intervals down into the twilight zone. They've found a hidden garbage patch between 650 and 1,000 feet composed of flurries of plastic-contaminated marine snow. Plankton, sea butterflies, vampire squid, and other snow eaters are getting mouthfuls of this indigestible grit. Giant larvaceans have been found to filter microplastic particles from the water with their mucous bubble houses; either the plastic gets eaten by the larvacean and then excreted in its feces, or the larvacean abandons its plastic-flecked house -- in either case adding to the fall of plasticized marine snow into the deep.
"Impacts of microplastics have been traced throughout the bodies of individual organisms: a bellyful of plastic suppresses an animal's appetite so it stops feeding, and eventually it can starve and die; microplastics cause internal wounds and lesions; they pass into the bloodstream, even into cells, where they interfere with enzymes and gene expression. Among the animals affected, growth rates fall, and reproduction is interrupted. Harm comes not just from the plastics but also the toxic chemicals and coatings added during manufacturing, such as fire retardants and PCBs; ocean-borne microplastics get contaminated with other pollutants, pathogenic viruses, and bacteria picked up from seawater. Most challenging is untangling the effects of the ubiquitous microplastics on entire populations and ecosystems, including cryptic, sublethal impacts that are difficult to track but doubtless reach into the severely polluted deep.
"Plastics have made a permanent mark on the planet. In 2019, scientists at Scripps Institution of Oceanography in San Diego analyzed a core of sediment taken from the seabed off Santa Barbara from 1,900 feet underwater. The thirty-inch cylindrical core consisted of neat sediment layers, each one presenting a year's worth of particles settling onto the seabed, stretching from 2010 back to the 1830s; these layers were so neat because there are no strong currents sweeping over this part of the seabed, and the sediments hold little oxygen, so not much lives there to burrow, trample, or otherwise stir things up. The team cut the muddy column into thin slices, then picked out and characterized every plastic scrap in each slice, be it fiber, film fragment, or misshapen globule. This time capsule revealed the arrival of plastics in the modern era, and it precisely tracked the growth of the plastics industry. Between 1945 and 2009, the number of plastic particles falling to the seabed increased exponentially, doubling every fifteen years, in direct proportion to the amount of plastics being manufactured worldwide. The plastic age has written an indelible message on the deep seafloor. The message reads: HUMANS WERE HERE."