The progression through grad school is measured in milestones; some are official (like qualifying exams), others less so, but no less important. This week, I passed such a milestone: I counted the very last pollen grain of my dissertation.
For those of you less familiar with the details of paleoecological proxies, let me explain. Pollen analysis, or palynology, is the study of ancient pollen grains in order to reconstruct past plant assemblages. Pollen, that copious evidence of plant sex that causes so much misery to allergy sufferers, doesn’t always end up fulfilling its procreative duty– oh, no! Much of it falls onto lakes (or bogs, etc.), settles to the bottom, and becomes incorporated into layers and layers of mud that accumulate through time, until one day, an enterprising graduate student comes along on a floating picnic table (unless you’re one of those winter coring people who stand on the ice) and pulls it all up in a long tube of mud: the core.
We bring the core back to the lab, take many samples, do all kinds of nasty things to them with fun chemicals like acetic anhydride and hydrofluoric acid to remove sands, clays, humic acids, carbonates, and organic material, until all that’s left at the end is a mostly-pollen sludge. This pollen-rich residue then gets smeared on a slide for viewing with a microscope (400x), and painstakingly identified to the genus or family level (rarely species). Changes in the types and abundances of different types of pollen tell us about plant communities in the past– like how forests respond to climate change, for example. In my case, I use spores from a dung fungus to tell us about how plant communities changed following the extinction of ice-age herbivores.
But back to the pollen. A couple of days in the field translate into about a year in the lab, starting with the time it takes to put samples through the chemical digestions necessary to extract the pollen (as much as 40 hours for every 16 samples). Then, you count. And count. And count some more. For every sample through time, you need to make sure you count enough pollen grains to make sure you’re really getting a sense of the rare types (not all plants produce the same amount of pollen, which complicates things). I counted, on average, over 400 pollen and spores for each sample. “Counting” is an oversimplification– sometimes, the pollen are easy to identify (like grass). Other times, I’d spend quite a bit of time going through various keys and reference slides to determine a new or unknown type. Early on, there were times I realized I’d been mis-identifying a particular grain, and had to go back and re-check. Sometimes, my count sheet in Excel would crash. Other times, uncooperative sediments meant that I’d have to re-process an entire batch of samples in order to count them.
But now, I’m done! I figure I’ve counted more than 140,000 pollen grains for my thesis and dissertation. Figuring a pollen grain a minute, that’s 2300 hours in front of a microscope– more than a full year: that’s 1/30th of my entire life.
I’ve always said that all research involves tedium of some kind; you just have to find the tedium that bothers you the least. I generally enjoyed counting pollen, though I can’t say I’ll be sad if I never count another grain (in theory, I’ll have grad students, or even someday a computer, to do that). Pollen analysis wasn’t always tedium; I once caused an explosion in the fume hood by forgetting in a crucial moment that concentrated sulfuric acid is highly reactive with water (it really, really is). Another time, a house centipede crawled into my lab’s $60,000 Zeiss microscope and died, leaving a multi-legged spoke in my optics that had to be fixed by an out-of-state technician.
I am indebted to the many hundreds of hours of podcasts and audiobooks that got me through those 2300 hours, to the undergraduates that helped me in the field and with processing, and to coffee shop across the street for keeping me caffeinated through ten-hour counting binges.
And now, I get to analyze all that data.
P.S. The Donors Choose Science Bloggers for Students Challenge ends tomorrow (Saturday, October 22nd!). Through tomorrow, any contribution you make through my blog’s giving page will be doubled by the Donors Choose board (you’ll get a gift card to make a second donation to a project of your choice). We’re so close to funding the last three projects on my page, so if you’ve considered making a contribution, please don’t delay! And don’t forget, each $5 contributed gets you an entry to win a set of custom science magnets in the theme of your choice (made by me)!
Categories: Grad School