Diatoms and Mayhem

I just started watching the campy murder mystery series Castle, which centers around a sexy NYPD officer and Nathan Fillion being approximately Nathan Fillion.  Together, they fight crime!

One of the first episodes I watched after thesis week was “Double Down”, in which diatoms featured prominently.  I was stunned when they mentioned them.  Fingers crossed they would show some appealing microscopy photos to get people engaged, but alas they merely described them as a type of algae.

I wondered how people reacted to diatoms in pop culture, so I checked some message boards.  Here is one sample response.  I can see how the viewer got confused.  A single diatom would not help you zero in on a body of water, although it could indicate the general region.   But they were not referring to a single diatom – they meant a diatom profile.  Meaning they found multiple diatoms on the victim, and extrapolated relative proportions from that.  Every body of water has a unique set of proportions – i.e. Hudson River water might be 23% Coscinodiscus, 10% Cymbella, 7% Pennate while the fountain at Washington Square might be 40% Cosccinodiscus, 1% Cymbella, 1% Pennate.  This is a gross oversimplification, but so is most tv forensic science.

Now, moving water is more difficult to profile.  But the Hudson for example is unique for being brackish water – a mix of fresh water from contributing rivers and the salt water of the ocean.  Different diatoms adapt to different conditions – that makes its profile quite distinct from neighboring bodies of water.  And there are records of New York lakes and rivers going back quite a long time.  Here is a river profile from 1853.  So I think diatoms were a surprisingly useful plot point in this episode.  I was entertained!

I could use this as a jumping off point to discuss various perversions of science in crime shows, but I think we all know they are skipping steps and jumping to conclusions all over the place in tv.  It is fiction and nothing will change that.  But it is FUN fiction, and it can certainly get people looking up things they would never hear about otherwise!

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