CHOOSE YOUR OWN RADIATION ADVENTURE – Nuke Crabs

Since I used the word earlier today, “extended, unplanned deployment to an uninhabited island” is an excellent euphemismspeak for being marooned.

Luckily, you aren’t marooned. You’ve just been sent in on a zodiac raft to get samples while boss-type sips coffee back on the boat.

[The third in an ongoing series of my compiled explainers for my CHOOSE YOUR OWN RADIATION ADVENTURE quizzes. There’s never really a right answer but some might work out better under the constraints of the scenario. It’s like poetry, really.]

In an ideal world with infinite funding & space, you grab all these samples and more. Why limit yourself to mere coconuts when you can take an entire tree? Yes, I have seen a crate labeled “ONE [1] PALM TREE, ENIWETOK” before. Oh, how the money must have flowed in those days. But, no, you’re working as an afterthought in the Twilight of Big Science to do the monitoring of the sins of the past. You’re overhead, likely as part of a regulatory requirement or lawsuit settlement. Congratulations! You are the bare minimum good faith effort. 

Which is why you were sent to go grab a samples really quick. Because every minute you spend on the island is one that the boat is in the water and a crew has to be paid. As discussed earlier in the Navy base decon adventure, any work that is done on water adds a serious cost multiplier. If you’re of the frame of mind “The sooner I do this, the sooner I get to have beers”, then you don’t even need to hit the beach. Break off a piece of coral from the reef like a Kit Kat bar, put it in your cooler, and head back to the boat. MISSION ACCOMPLISHED! 

Except you’re gonna want to be careful about that. Coral close enough to smash & grab from your zodiac is water shallow enough for the coral to sink it. So, you might be doing some snorkling to get to the boat-safe coral. Of course, you aren’t alone on the reef.

via GIPHY

As a sample, coral is pretty great for sampling and sequestering material as the reef slowly grows if there is persistent material in the lagoon for the polyps. But the reef is also continuously washed by the rest of the ocean, diluting that signal. If there isn’t a persistent, perceptible presence of material in the lagoon, there will be one season (The Event) in the coral skeleton you can detect and then nothing. This makes it look like the island is now clean when really it’s just that the reef is continuously flushed. Corals grow just like trees, marking the seasons with layers, but they’re really, incredibly slow by comparison. Which is one reason a lot of you winced at the idea of doing a smash & grab on the reef. You have good impulses. :) 

So, instead you make it past the reef without sinking or stealing any of it and hit the lovely white coral sand beach. For the next minimum effort sample, you can grab the sand right there by just reaching over the side of the zodiac, right? No, you’re a professional. You want a composite sample from the low to high tide line and above. The littoral zone of sand is constantly washed, just like the reef. You’ll want a sample from somewhat deeper in the sand. But sand sort of isn’t good at holding on to things. Or you might get very unlucky and sample way too thoroughly and get a chunk of the material that started the incident. When my parents had a pet store, we had to be careful about crushed coral/sand for saltwater aquariums lest you get some fish-killing WWII plane parts. SURPRISE! The composite will help average things out, but coral sand isn’t like clay for binding materials up.

So you look further up the beach and see the coconut palms, the dropped coconuts at the high tide line, and some very large shell-less hermit crabs between you and them. As a reminder, coconut crabs are these. They are the largest land arthropod in the world and have claws that *tear coconuts apart*. You can totally outrun one, but can you avoid the minefield of all of them? Do you dare steal their precious coconuts? 

Some of you remembered the bioaccumulation rule that each higher step of trophic layer = 10x concentration of materials of interest. So, while coconuts will be representative of the nutrients the palm is sucking up like a straw, the coconut crabs show the coconuts in aggregate. Most of the longer lived nuclides that would constitute the contamination you’re sampling for chemically behave like nutrients the palms would like and that the sand is very poor in. Palms absolutely soak Cs-137 out the sand to the point it’s almost bioremediation. This will show up in the coconuts and the crabs that eat them. Ideally, you’d get some coconuts directly from the palms as fresh samples, but unless you’re practiced at nutting a tree just grab the ones on the sand for least effort. 

If you are PARTICULARLY BRAVE, grab a smaller crab and hope you can get back to the boat before it destroys the box you put it in. To me, the efficiency of a crab as a environmental sample does not offset the terror of being trapped on a zodiac with an angry coconut crab. 

The events that inspired this scenario involves the Navy of a nation that rhymes with Beknighted Spates deciding that the best way to deal with radioactive waste on their vessels was to throw it overboard when they weren’t near any inhabited islands or fishing grounds. Of course, this didn’t stop things from floating so they did their very best to prevent that by having warrant officer with shotguns shoot at them until they sank. Sometimes that didn’t happen fast enough. It also made sure contamination spread. 

And so, a barrel of something ended up floating into a lagoon before sinking and coming to it’s final rest. The ocean doing as the ocean does, swiftly encased the barrel in marine concrete. But the release had happened, the beach contaminated, and the palms went to work. The sampling in this case was to assess impacts to nesting birds here. Do you know what nesting birds don’t like? People messing with their nests. After a bunch of razor sharp, leather glove destroying beak cuts and surprisingly painful wing slaps, the crabs were deemed safer. 

And this is how the nine-fingered researcher introduced me to the coconut crab that lived in his lab freezer. It cost a finger and a fair bit of blood to get those samples and he was proud of it even 20 years later. I would like you to know that the crab took up more than half of his full size freezer.

His advice, “Coconuts only hurt if they fall on you.”

~fin~