Song of the Diatom
WHEN I WAS LITTLE I collected things, dreaming of other futures. I wasn’t picky about collecting. Rocks with black lines down the middle, tiny white shells, perfectly round pebbles—all these made it into my personal museum. Each item was sorted and then grouped, exhibited by size, shape, color, and ornamentation. I had no idea that this is exactly what I would be doing fifty years later as a diatomist, sorting and identifying small objects, that this odd talent was an ideal skill for deciphering the stories hidden inside miniscule, single-celled plants whose skeletons are found in polar marine sediments and whose stories are written in a language I am still working to translate.
Diatoms live within a shell, or frustule, constructed of two valves that fit together like the top and bottom of a pillbox, one valve a little smaller than the other. The valves are attached to one another with the help of often intricate girdle bands that look much like belts. Taxa are identified by the symmetry, shape, and overall ornamentation of their valves. They can be radially or bilaterally symmetric, centric, and pennate accordingly. Their shapes range from circular to triangular to fanlike or needlelike. Small holes, or areolae, provide the finishing touches, bundled together in a seemingly endless variety of arrangements, zebra stripes, zigzags, and sunflowers.
My research is in the seas surrounding Antarctica, the Southern Ocean, where diatoms, the base of the food web, are eaten by krill (small crustaceans) that then become the primary food source for baleen whales—many orders of magnitude greater in size. Diatoms can live almost anywhere, but each species is sensitive to its immediate environment, preferring
