By Kelly

Scientific writing doesn’t have to be dry. When done properly it reads like a well written story, like your favourite bedtime story. Other times it is written in a way that makes you fall asleep, which is also like a bedtime story. Hmm not such a good analogy. Nevertheless, for years my favourite article was on a study that looked at the radiocarbon signature of DNA from deep ocean microbes. The authors were able to show that the carbon that made up the backbone of that most fundamental of biological molecules didn’t come from surface waters but was incorporated by in situ production, at 700 m beneath the ocean surface!

What is the significance? This study has implications for what we understand about carbon cycling in the ocean, for what we understand about biology on earth and more importantly it really got me thinking about my work and what implications this may have for my own findings. It also got me thinking how I could design an experiment that required me to hang out on a beach in Hawaii for a few months under the guise of research…

Hansman and authors filtered around 50,000 litres of seawater pumped directly from depth, and through some seriously sophisticated techniques separated the nucleic acids for analysis on a radiocarbon accelerator. How do we use radiocarbon in this way? Well the surface ocean has a VERY different radiocarbon signature from that at depth for a number of reasons, the most obvious being that deep water is largely cutoff from exchange with the atmosphere and therefore it ‘ages’. The fact that the DNA had an ‘old’ signature meant that the organisms were not assimilating carbon from food that was produced in the surface waters above, i.e the biological pump. These considerations are very important when trying to close the carbon budget: where it is produced, where it goes, and how it is recycled.

And while you will have to wait until my own research is in press before I’m willing to discuss the implications for my own work…you can try and guess by reading the full article. If you have access to the PNAS journal then the article can be found through the reference below*, if not, take my word for it, it’s a really great story! To hear more from one of the researchers involved you can hear a talk at the Scripps Oceanographic Institute seminar series here. Or look for the Scripps seminars on  iTunes.

*Roberta L. Hansman,  Sheila Griffin, Jordan T. Watson, Ellen R. M. Druffel, Anitra E. Ingalls, Ann Pearson, and Lihini I. Aluwihare

The radiocarbon signature of microorganisms in the mesopelagic ocean

PNAS 2009 106 (16) 6513-6518; published ahead of print April 6, 2009,doi:10.1073/pnas.0810871106