Clementz, Fox-Dobbs, Wheatly, Koch, and Doak, 2009, Revisiting old bones: coupled carbon isotope analysis of bioapatite and collagen as an ecological and palaeoecological tool: Geological Journal, v. 44, p. 605-620.
What’s it about?
“Trophic level” is a term scientists use to describe where an organism lies in the food chain (or food web). Animals of high trophic level are the carnivores, and organisms low in tropic level are the primary producers, like algae, or other plants. In the middle are the herbivores (primary consumers) that eat the primary producers. This paper is a discussion of another means by which one can interpret trophic level of animals, particularly those for which we only have fossil evidence.
Why does it matter?
Isotopes of nitrogen are typically used to interpret trophic level. One can measure the ratios of nitrogen for all organisms in a single ecosystem. Those organisms of low trophic level have lower quantities of the heavy isotope of nitrogen (15-N) than do those at high trophic levels. This is a relatively simple means of establishing what organisms are being eaten and what organisms are doing the eating.
However, nitrogen is often lost from fossils, making this method unusuable in the fossil record. The authors here describe a means of establishing trophic level through the measurement of carbon from fossil and modern bones. Carbon is far easier to analyze.
Why did I read this?
I am working on a research project in which I will be interpreting trophic interactions. I should be able to measure nitrogen from my specimens, but I will also measure carbon as a secondary method for approaching questions about trophic level for the organisms that I am studying.