How does the ocean deal with garbage?

The Short Answer: I guess the really short answer is that it doesn’t. But a more complete answer would be that it depends on the type of garbage. Things like food waste and sewage probably get broken down and enter the food chain. Plastic, however, is another story. The ocean is having a serious problem with plastic.

More Information: There’s a lot of documentation in recent years of giant floating garbage dumps of plastic in both the Pacific and the Atlantic oceans. The facts are disturbing. Plastic in ocean water is degraded by a combination of ultraviolet sunlight, oxidation, and seawater. This makes the plastic brittle, so that it keeps breaking into smaller and smaller pieces. This seems like a good thing, but unfortunately, the smaller the pieces get, the more likely they are to be eaten by everything from albatrosses to small organisms that filter food particles out of seawater. Prior to the introduction of huge amounts of plastic into the oceans, any tiny floating object was likely to be edible, so all the animals in the ocean are adapted to feed with that assumption. The damage goes all the way from the bottom of the food chain with microorganism up to birds, and fish and whales. A while back, I posted some unsettling photos of what happens when albatrosses mistake plastic for food and feed it to their chicks (click here to go to that post). Even if ingested plastic doesn’t kill animals outright, it tends to leach out chemicals that disrupt biochemical systems.

In addition, ocean creatures like barnacles affix themselves to floating plastic. This creates two problems. One is that it allows animals to travel across the oceans and colonize new regions, resulting in the usual invasive species issues and loss of biodiversity. The second is that plastic loaded down with growing barnacles eventually sinks. Since the plastic takes so long to break down, we may eventually end up with large parts of the sea floor covered with a thin layer of plastic, sealing off the normal processes of nutrient recycling.

And the problem is probably going to get worse. As the economies of China, India, Brazil and other countries develop the kind of disposable consumer product markets prominent in Europe and North America, the amount of plastic released into the ocean will continue to grow. Charles J. Moore, author of a report on ocean plastic (Moore 2008), pointed out that “Since the ocean is downhill and downstream from virtually everywhere humans live, and about half of the world’s population lives within 50 miles of the ocean, lightweight plastic trash, lacking significant recovery infrastructure, blows and runs off into the sea.” Moore cites a White Paper by the California Integrated Waste Management Board in 2003 as showing that if you add up the weight of all the plastic material made in the U.S. and then subtract what is made into durable goods, what ends up in landfills, and what is recycled, you still come up short by about 25%. The conclusion is that 25% of all the plastic made in the U.S. ends up in the environment. Most of that will eventually wash into the ocean. And that’s in a country with a modern recycling and landfill system.

So really, the picture of plastic and the ocean is not good.

Back to food waste and sewage. Given that these other types of garbage serve as legitimate food sources for marine life, the picture is probably a little better there than with plastic garbage. Generally, bacteria and microorganisms will eat the organic material in the sewage or garbage. Those organisms will be eaten by slightly larger organisms, and in that way, our garbage and sewage gets broken down and entered into the marine food chain.

However, there are problems with this process. First, our food waste and sewage are rarely without contaminants including household cleaning products, medications, and other biologically active chemicals. Also, introducing large piles of nutrients into one place tends to overwhelm the ability of the food chain to consume and convert the waste. And when the bacteria and other organisms growing on the waste use up the oxygen in the water, this can create low- or no-oxygen (anoxic) conditions that can kill all animal life nearby. Over-abundance of nitrogen and phosphorus from organic waste can fertilize toxic algae blooms that kill fish and shellfish – and people who eat them. These toxic algae blooms have become a problem all over the globe.

So while I think the oceans have a greater ability to deal with food and waste garbage than with plastic, still, it would probably be best if we kept our garbage on land.

Sources:

Synthetic polymers in the marine environment: A rapidly increasing, long-term threat. Moore, C.J. Environmental Research, 108 (2008) 131-139.

California Integrated Waste Management Board White Paper on Optimizing Plastics Use, Recycling, and Disposal in California, May 2003.