Sampling, Sequencing, and Statistics

Post date: Jul 30, 2012 7:38:09 PM

On July 17, my supervisor Jessica and I headed to the USGS office in Menlo Park to meet up with two marine biologists and one USGS scientist. From there, the five of us drove to Rio Vista – a tiny town in the North Bay – to board the R/V Polaris, one of USGS’s research vessels. It was such an amazing experience! I’ve never been on a yacht before, so it was cool to see everything on the ship and to get to sleep on it while hanging out with all the scientists. After eating pizza then getting a good night’s sleep, we woke up early in the morning on July 18 to begin what we had actually set out to do – collect sediment samples. Throughout the day we traveled on the San Francisco Bay and stopped at five designated spots; we used a pulley and grab system to get the sediment from the bay and some seawater. Once we got the samples and seawater, we used a YSI to measure the salinity, temperature, pH, dissolved oxygen content, and other qualities of the water. We then filtered some of the seawater to get rid of large bacteria, and froze all seawater and sediment samples in a cooler with dry ice. In addition, at the first two stops we got to help the marine biologists pick out clams from all the sediment we had gotten. It was cool to be able to not only help my supervisor with her sampling, but also to help other scientists as well. I’m really thankful that my supervisor let me join her for this once-in-a-lifetime experience!

In addition to doing some sampling, I have been working on some new DNA sequences that the sequencing company sent us. After aligning and comparing all the new sequences, I compared these to sequences from previous months, and am now looking at the different trends between seasons and regions where the samples the sequences came from were collected. I am going to create a couple phylogenetic trees and graphs comparing all the different communities soon, and draw some conclusions about the diversity of denitrifying bacteria in the San Francisco Bay based on the similarities of the nirK gene in the bacteria.