Things that should not be in the ocean, Part I

Technical difficulties and life in general have not been cooperative in this week's rigid posting schedule. Fear not, we're getting a double post today.

 This past weekend, I was involved in a semi-serious conversation about using genetically engineered algae to turn plastic garbage into biodiesel. It’s an elegant solution, in a way - using the ever-growing avalanche of humanity’s own waste to power further growth. The idea raises two points - one, the science (and feasibility) of that kind of biodiesel production, and two, the availability of the medium (plastic waste). We’ll take a look at the microbiology part of the equation in a few weeks, but today, let’s look at plastic waste. And not just any plastic waste, but what I consider to be its most dramatic manifestation. Because really, there’s no way to start the week off right like the Pacific Garbage Patch.

 Wait, that’s it? I bet you were hoping for something more impressive. After all, isn’t the garbage patch a Texas-sized agglomeration of debris that can be seen from space? Shouldn’t it look something like this?

 

Not quite. The Pacific garbage patch is real, and a real threat, but it doesn’t quite look like that. It isn’t a solid island, and it can’t be seen from space. It doesn’t have a proper fixed location, either. Let’s look at this one term at a time, starting with “Pacific”. 

 

Ocean currents are fun. They arise from a combination of tides, differences in the density of water, and wind patterns (which, in turn, ultimately derive from the uneven heating of Earth’s atmosphere). In this case, we’re mostly concerned with the wind-driven currents. Global winds create what are called gyres within oceans - massive spirals of circulating water, with areas of relative calm in the middle. 

There are five main gyres out there - the North Pacific, South Pacific, North Atlantic, South Atlantic and Indian Ocean gyres. Way back in 1988, the National Oceanic and Atmospheric Administration predicted that there was a high likelihood of plastic debris accumulating in the calm area at the center of the North Pacific gyre. These predictions were confirmed by the discovery of high concentrations of plastic debris exactly where expected. It’s entirely possible (and highly likely) that debris are accumulating within the other gyres, however, the massive amount of “ground” to cover somewhat hinders the amount of sampling possible.

Ok, let’s move onto the “garbage” part of the phrase. The garbage is all plastic or plastic-derived - nothing else would float in water. The sources vary - about 80% comes from land, and of that, 65% comes from garbage. Garbage might be accidentally or intentionally dropped into a stream, washed off of a landfill (plastic has a regrettable tendency to float), or spilled in the process of being transferred from the home to the landfill. Other plastics make their way from the land to the sea when the plastic pellets used in manufacturing plastic goods are spilled into waterways. Finally, the remaining 20% or so is dropped, washed or dumped from ships directly into the ocean - this could be anything from a coffee cup washing off a fishing boat to a container being washed off a cargo vessel.

Once in the ocean, the plastics quickly degrade. Well, sort of. I’m going to swerve over into earth science here, and present a relevant (I think) concept. Weathering, in this context, describes the breakdown of rocks into smaller and smaller pieces (and eventually soils and mineral-rich water). There are two types of weathering, physical and chemical. Physical weathering is the physical breakdown of rocks - imagine a hammer smashing a rock into bits. The bits get smaller and smaller, but the chemical structure remains unchanged - quartz beach sand has the same chemical formula (SiO2) as a gigantic quartz crystal. Chemical weathering acts at the chemical level - the rock is dissolved or leached, and the resulting pieces have a chemical composition different from the rock pre-weathering. Plastic debris in the ocean can be understood to undergo physical weathering - the particle size is reduced, reduced, and reduced again, but the chemical structure remains the same. Even those compostable plastics that are coming into greater use don’t really dissolve in the oceans - compostable plastics are designed to dissolve under land conditions, not in oceans. You’re starting to see why “proper disposal” is so important with any kind of waste, right?

One more word about the garbage bit. The tendency of plastic waste in the ocean to become floating “microplastics” explains why you can’t see the patch from space. Much of the patch consists of a high concentration of microplastics in the upper portion of the water column.

 

Ok, so these are a little bigger than micro, but you get the point.

Now, a little more about the patch part of the phrase. We already know that the garbage patch is not actually a floating island of waste. Instead, it is an area with a high concentration of plastics relative to things that would normally be in the water column (plankton, for example) - typically within the patch, the concentration of plastic is greater than the concentration of plankton. The high concentration is a consequence of water movement being relatively restricted within the center of an oceanic gyre - plastic that finds its way in does not readily find its way out. The location and size of a given patch depend on the gyres. Now, is it possible for the location and size to shift?

Of course it is! Both the size and extent of the garbage patch change throughout the year, in combination with the shifting weather patterns. Given that the patch we’re focusing on is in the Pacific Ocean, there is also the (so-far uninvestigated) effect of the El Nino - La Nina cycle on the whole mess.

The patch is also, well, patchy. While concentrations of microplastics might be relatively constant throughout the entire estimated garbage patch, larger plastic debris are going to congregate in certain areas, as a result of more local tidal action. Reports of sailors in the North Pacific encountering floating piles of visible plastics are tied to these “sub-patches”. All of this makes it hard to pin down the exact location or extent of the garbage patch, and subsequently, hampers clean-up of the patch.

And do we ever need clean-up. All of this plastic in the ocean is not doing marine life any favors. There are the obvious problems, like suffocation or entanglement in larger pieces of ropy plastic - anyone who has ever cut up the plastic rings on a six-pack holder has been trying to avoid this outcome. There is also a more insidious threat, from the smaller plastics. A number of marine organisms feed on plankton, fish eggs, small fish, or other bits of tasty marine life floating on or near the surface. Now, what happens when the concentration of small pieces of plastic rises above the concentration of that upper-water column marine life?
 

Rather than insert a disturbing image, I suggest that the strong-stomached among you image search “albatross plastics autopsy”

Birds are particularly threatened. Take the increasingly unhappy case of the Laysan albatross, a truly remarkable bird. Like all albatross, these birds spend much of their lives flying over the open ocean - albatross are capable of both weathering harsh weather, and sleeping on the wing. Laysan albatross are particularly large representatives of the albatross family, with a wingspan that often reaches (or exceeds) 2 m. They only come ashore to breed, and that’s where the trouble starts. Laysan albatross prefer to feed their young on the fish eggs and small squid found in the upper water column. Much of the feeding range of Laysan parents happens to overlap with the North Pacific garbage patch. I won’t get into the (depressing) mechanics, but up to forty percent of Laysan albatross chicks born each year die from ingestion of plastics which their parents mistake for fish eggs. 

I shot the albatross

Clean-up of the garbage patch is difficult, maybe impossible. However, it’s very possible, even easy, to prevent the patch from getting any bigger. The damage is done, but we can prevent it from getting worse. Reducing, reusing and recycling plastics (in that order), along with taking pains to properly dispose of plastics (remember the biodegradable plastics problem) that can’t be reused or recycled can cut off the source for much of the plastic in the patch. Sure, there’s only so much we can do about containers being lost from cargo vessels, but that’s only 20% of the problem. The other 80% is up to you.