my latest paper, which is published in the open-access journal PeerJ. So first of all HAI EVERYONE! Second of all – here’s how I accidentally discovered that gooseneck barnacles are eating plastic, and why it’s so difficult to figure out what effect that is having on the ocean.I’ve been temporarily released from my social media silence to talk about
On my 2009 expedition
to the North Pacific Subtropical Gyre, otherwise known as the “Great
Pacific Garbage Patch,” I collected a bunch of barnacles, along with
samples of a lot of other organisms that were growing on the debris,
because I was interested in seeing what species were there. Gooseneck
barnacles look kind of freaky. Like acorn barnacles (the ones that more
commonly grow on docks),
they’re essentially a little shrimp living upside down in a shell and
eating with their feet. Unlike acorn barnacles, gooseneck barnacles have
a long, muscular stalk.
It took me a couple years to get around to processing those samples,
but eventually I found myself in the lab dissecting barnacles in order
to identify them. As I sat there, I thought “Well, I’m working on these
barnacles anyway – wonder what they’re eating?” So I pulled out the
intestine of the barnacle I was working on, cut it open, and a bright
blue piece of plastic popped out. I reached into my jar o’ dead
barnacles and dissected a few more, and found plastic in their guts as
Thinking about it logically, it makes a lot of sense that gooseneck
barnacles are eating plastic. They are really hardy, able to live on
nearly any floating surface from buoys to turtles, so they’re very
common in the high-plastic areas of the gyre. They live right at the
surface, where tiny pieces of buoyant plastic float. And they’re extremely non-picky eaters that will shove anything they can grab into their mouth.
But, since I didn’t really collect barnacles with this study in mind,
I didn’t have enough samples to figure out how widespread this
phenomena might be. Fortunately, I’d been lucky enough to collaborate
with the wonderful Sea Education Association and one of their chief scientists, Deb Goodwin,
for several years. SEA kindly took samples for us, and Deb, once a
perfectly respectable remote sensing expert, got deep into some pretty
smelly barnacle guts.
After dissecting 385 barnacles, Deb and I found that 33.5% –
one-third – had plastic in their guts. Most barnacles had eaten just a
few particles, but we found a few that were absolutely filled with
plastic, to a maximum of 30 particles, which is a lot of plastic in an
animal that is just a couple inches long. We also analyzed the type of
plastic in the barnacle guts, and found that it was approximately
representative of plastic on the ocean surface – the barnacles are
probably just grabbing whatever they come across and shoving it into
their mouths. Barnacles are perfectly capable of pooping out plastic – I
observed plastic packaged up in fecal pellets, ready to be excreted the
next time the barnacle had access to a couple minutes and a magazine –
so it is very likely that more barnacles are eating plastic than we were
able to measure.
So, this is disturbing. As I’ve discussed many times, there is a ton of plastic in the North Pacific Subtropical Gyres (but no island!) and it is being eaten by birds, turtles, and fish.
And now we’ve documented plastic ingestion in a very common
invertebrate – probably the numerous animal living attached to the
plastic – as well. But just finding plastic in barnacle guts does not
really tell us much about how plastic is impacting the oceanic
ecosystem. This is because we don’t really understand how barnacles are
interacting with the rest of the ocean.
Gooseneck barnacles aren’t necessarily incredibly central to the
North Pacific Gyre ecosystem. The barnacles are voracious predators, but
since plastic is so patchy, it’s not clear that they eat enough
zooplankton to really affect the ecosystem – and a lot of the food I
found in the barnacle guts were their own cyprid babies.
nasty cannibals, apparently.) They’re eaten by a few predators – a pretty little sea slug and some crabs
– but fish don’t seem that interested in barnacles, maybe because those
fish didn’t evolve with a ton of floating debris. If barnacles are an
important prey item, it is possible that their ingestion of plastic
particles could transfer plastic or pollutants through the food web, but
it is far from clear this is the case.
However, the most dire effects could be the most subtle. The
subtropical gyres are 40% of the entire earth’s surface, and so they are
very important to controlling the way that nutrients and carbon move
around in the ocean. The microbes and animals that live on plastic
debris are not the same
as the microbes and animals that float around in the ocean, and may not
act in the same way. It’s such a cliché for a scientist to call for
more research, but we just don’t understand enough about the way that
the ocean works, and enough about the way that plastic affects the
ocean, to really say what the effects of barnacles eating plastic might
Of course, none of this uncertainty changes the fact that plastic
trash does not belong in the ocean, and we need to be a lot better about
preventing it from getting in there in the first place. However, I am
skeptical of plastic cleanup schemes, so please read these Open Ocean Cleanup Guidelines (which I co-authored) and Dr. Martini’s post before
you suggest that we just clean it up. I think we are probably stuck
with the plastic pollution that we have, so understanding what it is
doing to the ocean is important.
I’ll be back in a couple weeks to do another behind-the-scenes post
on a second debris-related paper! In the meantime, I’m happy to answer
your questions about the barnacles.