Fuente: REALscience
Expuesto el: miércoles, 16 de mayo de 2012 19:05
Autor: Michael Bradbury
Asunto: Pacific Garbage Patch Changes Ocean Ecology
| For several years conservationists, big-hearted celebrities and oceanographers have been talking about the Great Pacific Garbage Patch (and other garbage patches around the world.) Now scientists are showing that the Texas-sized piece of water real estate is growing bigger every year, fed by plastic pollution from developing countries like China. The diffused mass of micro-plastic gets stuck in an area between Hawaii and California called the North Pacific Subtropical Gyre.
Tiny Plastic Confetti Dots Open Ocean for Thousands of Miles, Making Garbage Patch Almost Invisible from Above, courtesy of Scripps Think of it like a vortex where ocean currents and wind patterns converge to create a circular motion that traps anything that floats into a large but contained area. New research by a graduate student at Scripps Oceanographic Institute at the University of California San Diego shows the patch has experienced a 100-fold increase in the number & mass of plastic per unit seawater in the last 40 years. The study appears in the journal Biology Letters. Miriam Goldstein, the lead author of the study says, “Plastic only became widespread in late ’40s and early ’50s, but now everyone uses it and, over a 40-year range, we’ve seen a dramatic increase in ocean plastic.”
Water Strider Finds Mid-Ocean Plastic Ideal Spot to Lay Eggs, courtesty of Scripps, photo by Anthony Smith So dramatic in fact that her research shows the beginning of a significant shift in marine ecology as a result. A water-loving insect known as the water strider has begun laying eggs in the middle of the ocean by landing on fingernail-sized pieces of plastic that dot the ocean surface for thousands of miles. The flotsam in the gyre has created a suitable hard surface home for these bugs, which are generally found on lakes and ponds not in the open ocean. Goldstein says the water striders “have exploited the influx of plastic garbage as new surfaces for their eggs [which] has led to a rise in the insect’s egg densities.” That’s good news for the predators that eat the insect, including crabs. And this ecological shift is very bad news for the critters that the bugs eat. The study found that the explosion of the insects’ population could lead to a dwindling supply in zooplankton and fish larvae, the water strider’s favorite foods. That can have devastating impacts up the food chain. The research noted a significant increase in egg-laying but didn’t comment on any resulting increase in adult water striders in the garbage patch.
Microplastics Cleaned and Dried, courtesy of NOAA Of all the plastic discarded into the ocean about 80 percent originates on land. And the floating pieces that don’t sink will eventually break down thanks to the sun’s energy and the pounding of waves. While those natural forces shred the material over time into smaller and smaller pieces, this micro-material gets ingested by marine birds and fish. A similar study resulting from the same Scripps research expedition in 2009 found that nine percent of fish in the gyre had some plastic in their stomachs. That study published in Marine Ecology Progress Series, estimated the fish at intermediate ocean depths in the North Pacific Ocean could be ingesting plastic at a rate of roughly 13,000 to 26,000 tons per year. And many of us have seen pictures of young dead albatrosses near Midway island who have starved to death because their stomachs are full of plastic which their mothers mistakenly feed to them thinking they are some other source of food. Most scientists worry about the toxic plastic bioaccumulating in marine animals and because of that Goldstein expected to see fewer water striders perched on mid-ocean plastic not more. But she was surprised to find that the insects seemed to be thriving in their new artificial environment. She says, “The study raises an important issue, which is the addition of hard surfaces to the open ocean.”
Gooseneck Barnacles and Anemones on a Piece of Rope Found during 2009 SEAPLEX Expedition, courtesy of Scripps There is no seaweed floating on the surface between Hawaii and California. Occasional pumice (floating volcanic rock), seashells and other natural buoyant surfaces provide homes for barnacles, crabs, sea anemones and other creatures. The animals, the plants and the microbes that live on hard surfaces are different than the ones that live floating around in the water. And the addition of plastic is adding a whole new layer of surfaces in the middle of the ocean. The water strider is already taking advantage of this new micro-plastic habitat. Goldstein says, “So, what plastic has done is add hundreds of millions of hard surfaces to the Pacific Ocean. That’s quite a profound change.”
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