Lake Erie Chemophobia: A Tale of Two Anatoxins

At first, I thought it might be an April Fools' prank in poor taste, but then I read the latest PNAS -

Looks like Lake Erie wants to hurt you.

OK, not the lake itself, but the potentially toxic concentrations of cyanobacteria formed in recent record algal blooms. Yesterday, a multi-institution group of ecologists and environmental engineers reported a 'perfect storm' of runoff fertilizer, warm weather, and quiet waters in the lake that led to a marked increase in 2011 cyanobacteria populations. In fact, there appear to have been two blooms - the first Microcystia, and the second Anabena, two bacterial baddies* associated with liver and neurotoxicity. Scary stuff!

Well, the press coverage stemming from the study hasn't calmed fears. Here's a sampling from NSF, Huffington Post, and Discover. The HuffPo title really runs the chemophobia angle:
"Lake Erie Blooms Expected to Continue, Threatening Ecosystem, People." (!!!)
They dress the presser up for the occasion, with words like noxious, toxic, ugly, hazard, and problem. Discover writes 'toxic' three times, without pointing out what the toxins are! Even the normally staid NSF jumps on the bandwagon, referring to a mysterious 'liver toxin.'

What types of toxins are we talking about? Actually, that's a bone of contention here: the researchers only mention two, microcystin and anatoxin. Those turn out to be confusing terms, since the generic names cover >80 types of different microcystins, and at least two anatoxins [A(s) and A, right]. One assumes that the scariest anatoxin (Anatoxin-A, or 'Very Fast Death Factor'), operates here, which certainly warrants concern.

But, sans information, there's a panicked sense to the releases not grounded in the published text. Both Discover and HuffPo indicate "~200x concentration" of "toxic stuff" in the cyanobacteria-enriched water. Do the researchers actually say this? Let's go to the PNAS (emphasis mine):

"Surface toxin concentrations could have reached over 4,500 μg/L in early August assuming all Microcystis and microcystin formed a surface scum 10 cm in thickness. The World Health Organization guideline for microcystin in recreational waters is 20 μg/L..."

This statement relies on multiple qualifiers and conditionals. Where's your skepticism, science writers? Yes, things were bad in Lake Erie in 2011, but to spit this couched statement back as fact does a real disservice.

Worst part? Of the three media, only Discover actually links back to the actual study. Sigh.

*Boy, I love science: the Purdue blue-green algae fact sheet I linked to for Anabena indicates that ecologists nickname the major detected species (Anabena, Aphanizomenon, Microcystia) Annie, Fannie, and Mike!

Calimari Calligraphy: Same Ink, 160 Million Years Later

Old news: Geologists, digging up ancient British sea bed, unearth a fossilized cephalopod.


Big news: Its pigment sacs contain the same ink squid still use today!

Fossilized Ink Sac
Source: British Geological Soc. | Nat Geo

This archaeology, with a dash of chemistry for good measure, went to press in PNAS earlier today. As Nat Geo, Discovery News, and msnbc tell it, a stroke of luck brought the multi-national (Japan, India, USA, UK) team a fully intact ink sac, which still contained eumelanin, the ubiquitous black pigment found in skin, hair, and feathers throughout the biological world (for more on the structure and function of melanins, click here).  


Quoth the lead author, John D. Simon (UVA-Charlottesville), to Discovery: 

"Out of all of the organic pigments in living systems, melanin has the highest odds of being found in the fossil record" 

In other words, this collection of highly-oxidized tyrosine and indoleacetic acid residues, chained into polymeric pigments, stays preserved - and structurally sound - for 160 Million Years. Could we say that about most of the materials we make today? Moreover, by comparison of various spectral techniques, the authors wager that the ancient melanin composition looks nearly identical to what squid use today to scare off predators.

IR Data, "flipped"
Source: PNAS Supp Info

Well, I'd like to see some data, wouldn't you? Digging through the Supporting Info, I see loads of evidence: degradation studies, EPR, IR, Mass Spec, CHN analysis, Carbon-13 NMR, UV, pyrrolysis TIC, and X-Ray photoelectron spectroscopy (Whew!). 


Let's examine two of these a little closer. For the IR data, I've switched the view around 180 degrees, to present the peaks the way you'd normally see 'em in the lab. Note the top 2, calcium carbonate and hydroxyapatite, with their nice, sharp C=O and P=O stretching bands. When the researchers looked in the partially-fossilized sediment, they found mostly these two...but look at the dye! Even after all those millennia, the absorbances for the fossil dye line up almost perfectly with the modern-day sample.

Total Ion Chromatogram, Current (top) vs. Fossil (bottom)
Source: PNAS Supp Info

How about a little heat? If you cook the ink at 600 Celsius, then pass it quickly through a mass spec, plotting ion current vs. time, you get the next spectrum, the TIC. It shows the same breakdown products, a variety of small heterocycles and fatty acids, and something I wasn't familiar with: diagenetic products. These products, formed from reactions that occur during fossilization, show up here as sulfur heteorcycles. Since the samples have had quite a bit of time underground, they show much more diagenetic decomposition.