Lake cores provide an amazingly detailed record of the past which can be precisely dated with radiocarbon isotopes. Sediment and organic matter simply accumulate on the bottom of the lake layer upon layer. These deposits may contain clues about the past in the form of fossilized pollen (which can tell how warm it was based on species identification), fossilized plant and insect matter (for carbon dating, or identification), nutrients (which can be analyzed to determine how much photosynthesis was occurring on land or in the pond and well as how rich the environment was for growth) and sedimentation rates (which can tell a lot about how the surrounding landscape looked). IGERT tagged along this past winter when Meredith Kelly cored Post Pond, just up the road from Dartmouth in Lyme, NH. That effort pulled thousands of years of history from the bottom of the lake, and so we were excited to see more.
Unfortunately for the coring efforts the lake we chose was having an incredible bloom of an unidentified thing which looked like a tomato. The bottom of the lake was literally covered with tens of thousands of 2-5” rubbery, nearly spherical, peach colored objects which felt a lot like a tomato, but were significantly more durable. They weren’t anchored anywhere, none of us had ever seen anything like it, and cutting them open revealed little. They were uniformly rubbery, with a small lighter colored and different textured center. As interesting as the discovery of these sea tomatoes was, they significantly hampered our coring efforts and three serious coring attempts (which take about 3-4 hrs each) resulted in no core. The sea tomatoes clogged the corer and let the cores slip right back out of the tube as we tried to extract them. In our frustration, we nearly forgot our interdisciplinary goals, but soon realized we were treating a potentially exciting new discovery as an obstacle to accomplishing some other science. Weary of coring attempts, we sampled some of the sea tomatoes for analysis and returned to town for further investigation and an effort to query the local knowledge about the amazing productivity of this lake. The locals informed us that these things were actually locally known as sea tomatoes, occurred only in this lake, and that there were some interesting games which involved extracting one from the lake using a road reflector as a giant straw. Our intrigue sharpened, and Lauren and Matt did some further sluthing to determine that each of these balls was actually an immensely productive patch of colony forming, nitrogen fixing cyanobacteria of the genus Nostoc. Why this lake is so productive is anybody’s guess, but hopefully the water samples will tell us more.