Dr. Carr suggested that of all the inhabitants of driftlines, little sea turtles appear to be the most vulnerable to the pollution found there. His observations from the Atlantic coincided with work undertaken half way around the world by researcher George Balazs on the impact of plastic on larger sea turtles in the Pacific. Balazs documented plastic entanglement and ingestion in 79 turtles, including consumption of fishing line, net, plastic bags, beads, and vinyl film. One dead turtle had swallowed a sheet of heavy plastic that measured 10 by 12 feet. Taken together, this early work provided compelling evidence of the effect of plastic pollution on sea turtles throughout their lives.
Today, marine plastic pollution has assumed catastrophic proportions and is a pervasive problem in even the most remote and pristine seas. In the last 25 years, billions of tons of plastic have been purposefully dumped or accidently swept into the oceans from rivers and coasts. And, despite prohibitions on the ocean disposal of plastics by Annex V of MARPOL, the international Marine Pollution Treaty, this practice continues. In the vast Central Pacific gyre (rotating ocean currents), unfathomable quantities of plastic circulate on and below the surface and to a depth of at least 100 feet. Researchers with the Algalita Marine Research Foundation found recently that each square nautical mile in this region had over 1.1 million plastic bits, which outweighed plankton in the area six to one. Similar vast “garbage patches” lie near the centers of gyres in each hemisphere of all three major oceans.
Plastic marine debris affects sea turtles in numerous ways. Turtles caught in lost or abandoned plastic fishing gear may be injured or drowned. Those that mistake floating debris for food are at risk from intestinal compaction or tearing, digestive suppression, and exposure to chemical toxicants adsorbed by (accumulated on the surface of) the plastics. Leatherbacks, for example, are believed to mistakenly eat floating plastic bags instead of jellyfish, a primary food. Miscellaneous debris, such as plastic rings, can cut, maim or amputate limbs and cause severe and sometimes lethal infections. At least 100,000 marine animals are estimated to die as a result of plastic marine debris each year, a number that may increase dramatically with better estimates of mortality from marine debris affecting difficult-to-observe neonate sea turtles.
Several decades ago, Dr. Carr was dismayed to encounter significant quantities of marine debris in the Gulf Stream as he searched for little pelagic (open ocean) turtles. In recent years, Dr. Blair Witherington of the Florida Fish and Wildlife Conservation Commission has documented this increasing threat while studying neonate loggerheads, green turtles, hawksbills, and Kemp’s ridleys in their early, open-sea developmental habitat off Florida. In samples of ingested material collected from the mouths of these small turtles, he has found balloons, fishing line, plastic film, and a wide variety of rigid plastic shards that had undergone partial degradation in sunlight. In a separate group of post-hatchling turtles that were swept ashore following severe hurricanes, Dr. Witherington found that 71 of 87 green turtles had plastics in their gut contents, and that all of 94 loggerheads had ingested plastics. Although these turtles had been feeding out in the open sea for less than two months, this synthetic material made up more than a third of their diet by weight.
Perhaps the most insidious characteristic of plastic is its inability to biodegrade. As plastic photo-degrades in sunlight, it breaks into smaller and smaller pieces, becoming suspended over time in the water column as tiny particulate matter which remain plastic polymers. Unfortunately, this plastic attracts and accumulates non-soluble toxins such DDT and PCB in high concentrations. Plastic polymers have been implicated as hormone disruptors in a number of species and are believed to contribute to other health problems.
Our society has become dependent upon lightweight, versatile, and inexpensive plastics and these products are likely to remain a part of our world for decades to come. But all of us should aspire to consciously using less plastic and carefully recycling that which we need. For example, each year Americans throw away 100 billion plastic grocery bags, only 0.6 percent of plastic bags are recycled, which are produced by nearly 2,500 barrels of oil. Replacing plastic grocery bags with reusable bags not only reduces the plastic stream but also conserves oil.
Like many other environmental issues, making a difference means making a personal commitment to address the issue on land and at sea. For many years, maritime tradition worldwide has been to discard galley waste, fishing gear, and other garbage in open waters away from port. Although this practice clearly violates international agreements, it is one that takes place far from any watchful authority, save one’s own conscience.