University of Southern California

Growing Ice on a Sponge

Dennis Evangelista, January 25, afternoon — When setting about to write this post, I recalled a nuclear engineer who once told me to explain complicated things as though I were relaying them to my grandmother (or “lola,” as Filipinos say); in doing so, one is forced to make the material understandable. Of course, I always wish for the work to sound interesting and cool, especially because these days my grandmother is rather hard of hearing and falls asleep if the talk is not entertaining.

Lola, I have been filling drink trays with seawater and amputated bits of sponges and anemones, and watching ice grow. We find that the ice tends to grow better on some organisms than others; notably, it grows well on sponges.

spongeice.jpegI do some of this work in a freezer set at -4F. Remember, here it is summer — it’s 32F outside right now — quite warm. The extreme cold weather clothing they issued us works wonderfully in my freezer. It’s a bit odd to come to Antarctica and spend some time in a freezer trying to get even colder (I try to think of it as being “macho”). Why do we do this?

dennisexperiment2.jpegA major source of disturbance in the McMurdo Sound area is a type of ice called anchor ice, which forms below the surface. The mechanisms of anchor ice formation have to do with a mix of salinity, temperature, pressure, mixing and heat transfer. A physicist could have years of fun with microscopes with cryogenically cooled stages and fancy chilling rigs funded by ice cream companies and manufacturers of aircraft de-icing equipment.

For us biologists, what’s interesting is that anchor ice sticks to organisms, “disturbing” them by either ripping them off the bottom or killing them outright. Imagine instead of a forest fire or a hurricane, thin wafers of ice reaching off into a sea-bottom horizon... a translucent shimmer like crystal.
It would be wonderful to come back in winter — life in the cold, dark winter is really an unknown here, as most of the science is done in the summers, when scientists can get here. The logistics of doing many counts under ice or slicing up large chunks of ice to do some sort of stratigraphy on it are so difficult that for this first pass we really are focusing on the ice formation on organisms and its effect on their immediate survival and behavior. So we go to an ice hole, send a diver down, get some organisms, and play with ice.

Dennis Evangelista is a Ph.D. student at the University of California, Berkeley.