Why is this interesting? - The Plastic Ocean Edition

Colin here. Some of the most powerful emotional appeals that raised plastic pollution into public consciousness were rescue videos. We’ve all seen the animals being freed from plastic waste, with a particularly horrifying example of a team of scientists removing a plastic straw from the nose of a sea turtle. These videos, often jarring, move the idea of plastic in the oceans from abstraction to reality. 

They’re mistaking the plastic for something edible. But the reason why is more complicated. As the Economist explains: 

Turtles have an unfortunate habit of devouring plastic objects floating in the sea. These then get snared in their alimentary canals, cannot be broken down by the animals’ digestive enzymes and may ultimately kill them. It is widely assumed that this penchant for plastics is a matter of mistaken identity. Drifting plastic bags, for instance, look similar to jellyfish, which many types of turtles love to eat. Yet lots of plastic objects that end up inside turtles have no resemblance to jellyfish.

Why is this interesting? 

But some scientists have a theory that something in the actual plastic compound is inducing turtles and other sea life to feed. In addition to reducing waste in the oceans, a near-term solution could be to try and understand the chemical compounds in the plastics being eaten and the scents they give off. The Economist continues: 

Since turtles are known to break the surface periodically and sniff the air when navigating towards their feeding areas, Dr Pfaller theorised that they are following these same chemicals, and are likewise fooled into thinking that floating plastic objects are edible.

To test that idea, he and his colleagues set up an experiment involving loggerhead turtles, a species frequently killed by plastic. They arranged for 15 of the animals, each around five months old, to be exposed, in random order, to four odours delivered through a pipe to the air above an experimental arena. The odours were: the vapour from deionised water; the smell of turtle-feeding pellets made of shrimp and fish meal; the smell of a clean plastic bottle chopped up into ten pieces; and the smell of a similarly chopped bottle that had been kept in the ocean for five weeks to allow algae and bacteria to grow on it.

Two of the smells proved far more attractive to the animals than the others. When sniffing both the odour of food pellets and that of five-week-old bottles turtles kept their nostrils out of the water more than three times as long, and took twice as many breaths as they did when what was on offer was the smell of fresh bottle-plastic or deionised-water vapour. On the face of it, then, the turtles were responding to the smell of old bottles as if it were the smell of food.

Their hypothesis: they think dimethyl sulfide is the culprit. According to Science Direct, “Dimethyl sulfide is a volatile organic sulfur compound that is produced and emitted by terrestrial vegetation and marine phytoplankton at rates that can have a significant impact on the chemistry of remote atmospheres.” 

The scientists believe that in a clear, unpolluted ocean, “pretty much anything that had this smell would be edible, or at least, harmless.” When I was poking around and falling down the rabbit hole, I noticed a fragrance site that described the scent as: 

Cabbage, sulphurous, onion, creamy. Very powerful and diffusive. Can be used in perfumes only in the most extreme dilution to add realism to gourmand (particularly coffee, chocolate and similar), fruity and certain flower perfumes, particularly rose. Can also be used as part of an authentic sea-breeze accord as this material has been shown to be the actual source of the smell of the sea, commonly described as ozone.

The compound in the plastic trash could be confusing sea-born creatures. They aren’t actively looking to munch on trash but rather, it’s a double threat: a floating visual representation that approximates what they want to eat, and also the chemicals in the waste have similar signatures to things they naturally—and safely—consume. (CJN)

Mix of the day:

We’re super fans of the Scottish DJ duo Optimo, and this is one from the archives. It is a mix of psych music, drones, and gorgeous, out there cuts. According to Pitchfork when it came out in 2005, “Psyche Out is less manic, more roiling, brooding, cosmic. If anything unites the 40 years of music here, it's the compulsive, hypnotic power of repetition. From psyche rock to krautrock to disco to acid house…” 

Quick Links:

• What your Zoom background says about you (CJN) 

• Startups and the Great Unwinding (CJN) 

• Reinventing the DTC business model (CJN) 

Thanks for reading,

Noah (NRB) & Colin (CJN)

Why is this interesting? is a daily email from Noah Brier & Colin Nagy (and friends!) about interesting things. If you’ve enjoyed this edition, please consider forwarding it to a friend. If you’re reading it for the first time, consider subscribing (it’s free!).