It’s mighty easy to throw away a plastic bag or plastic cup-lid, and then think nothing of it. Into the wastebasket it goes — out of sight, out of mind — and then into the trash bin, and then into the waste truck, then to the landfill. Plastic indefinitely clogging our terrestrial landfills constitutes its own problem, but an alarming amount of this detritus ends up in our drainage systems. It may take years, but these scraps may eventually find themselves adrift in the ocean — ultimate receiver of the continents’ freshwater output — thousands of miles from their factory origin, let alone the site of their discarding.
In recent years, firsthand observation has borne out the predictions of oceanographers: Much of this marine litter, as it’s called, ultimately turns up contained in and by the loops of rotating currents called gyres that mark each ocean basin. The spin of the earth and the heat-driven coasting of winds help create these prevailing current configurations. Ocean-borne debris is drawn into the encircling “highways” of the gyre, then edged into the calm waters of its center — where they remain.
First to be empirically documented was the Great Pacific Garbage Patch, associated with the North Pacific Gyre between the west coast of North America and the east coast of Asia. We now know that several other major gyres, including the North Atlantic and Indian Ocean examples, support their own massive garbage accumulations. Estimates of the size of these gyre trash reservoirs vary, and information is still scanty, but some may cover thousands of square miles of the water column.
The high-pressure systems affiliated with the subtropical gyres make for calm waters between the rotating currents, and the lack of large-scale mixing translates to a general paucity of nutrients. Larger consumers, like sharks, tuna, and marine mammals, are usually scarce in these so-called “oceanic deserts.” So are human seafarers, partly because of the scant fishing opportunities and partly because of the often-dead winds. The gyres tend to be in exceedingly remote parts of the ocean, which explains both the recentness of the garbage-patch discoveries and the sobering shock those marine waste reservoirs deliver: It seems nearly unfathomable to some that so much human trash could accumulate in such far-flung, hard-core wilderness.
The main issue is that plastic in its standard form doesn’t biodegrade: Designed for extreme durability, it won’t be broken down by microorganisms over time. Instead, it photodegrades: Sunlight renders it into increasingly smaller particles that nonetheless stubbornly embody the plastic-polymer form of the original product. Indeed, most of the documented tracts of the oceanic garbage patches aren’t crammed with easily identifiable plastic objects — water bottles, jugs, packages, and the like — but with a soupy or stewy miasma of plastic chunks, bits, and minute fragments. (That’s not to suggest, of course, that large, intact plastic creations aren’t rife in the oceans — they are — but that the popular conception of the garbage patch as a continuous raft of solid trash isn’t quite accurate.) Some of the junk is in the special form of nurdles, the little beads from which plastic products are synthesized, accidentally discharged into rivers and oceans through spills and other accidents.
Even while big marine predators are usually hard to find in the garbage patches, phytoplankton — which use solar energy to conduct photosynthesis in the upper layers of the water column — and the zooplankton that consume it form the foundation of the local food web. Filter-feeding zooplankton like small jellyfish may readily suck up plastic bits, introducing them into the food-energy cycle. The plastic — which can actually absorb toxic chemicals in the water — can poison or physically obstruct these creatures. Seabirds and fish can take in the harmful debris by eating the filter-feeders or the plastic itself. This has been documented in wide-ranging albatrosses, which in places like Midway Island in the Hawaiian Archipelago may haul the unsatisfying and dangerous meal home to feed to their chicks.
The problem of plastics entering the marine food web isn’t, of course, restricted to the gyre garbage patches — because plastic refuse isn’t restricted to gyres. Sea turtles are known to chomp on plastic bags, probably mistaking them for jellyfish. And human beings all over are potentially affected, too: We may be eating toxic plastic compounds along with our tuna or mackerel.
Another issue is that the very existence of hard materials like plastic in the middle of the open ocean — where such surfaces are scarce — significantly changes the ecological dynamics of the place. Organisms that cling to hard surfaces, like barnacles, may be migrating into these pelagic wildernesses on plastic debris and fundamentally shifting the food web — the effects of which we can’t yet fully comprehend.
We’re only beginning to understand the dynamics of the giant oceanic garbage patches, but the fact of their existence alone suggests the enormous responsibility we all share: striving for more sustainable, biodegradable, and recyclable products in our lifestyles, using only what we need, and — crucially — disposing of our goods in environmentally friendly manners. No matter where you live in the world — even thousands of miles from the nearest seacoast — you could be unwittingly contributing to a faraway mid-ocean trash island.
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Guest post contributed by Jordan Rogers, on behalf of Fugrogeoconsulting.com. Jordan is an expert in geology and geophysics. He provides geohazard assessment and analysis for companies. In his spare time, he enjoys writing about green technology.