In addition to geochemical changes within my lake cores, I am attempting to analyze biological changes within my sediments in the form of diatoms. Diatoms are siliceous algae which can be identified and analyzed under a microscope. These tiny, single-celled organisms are abundant in these lake sediments and different species prefer different aquatic environments. Thus, by identifying different diatom species at different depths in my cores, I hope to develop an additional line of evidence for different depositional environments (freshwater, marine).

There have been a lot of ups and downs and frustrations in the process of figuring out how to best analyze these diatoms. With thousands of known species worldwide (many of which look so similar) and no expertise on the subject, it was hard to know where to start.

After contacting a colleague, my advisor Nick Balascio and I were given a procedure for mounting sediments for microscope diatom analysis. We digested samples using Hydrogen Peroxide and then used a lentil sized or smaller amount of sediment on each slide. Since neither of us are diatom experts, I decided on a survey method of analyzing each sample. For each slide, I surveyed in transects to look at about 300 individual diatoms. Other studies indicate this is an adequate sample size. I noted down different species by description and took a photo using the microscope camera. For each species, I tallied the number of individuals as I surveyed the slide.

From these tallies, I plan to identify the ten species that are most abundant in each sample. This will certainly be a tedious task, and we plan to verify my identifications with a diatom expert. I’ll admit that I have been procrastinating this, but I have to start sometime! I’ve checked out a huge stack of diatom books from Swem Library through interlibrary loan and found all of the best diatom websites, so wish me luck!

Diatoms in Farstad core FSD-01-17 at 85cm depth

Diatoms in Farstad core FSD-01-17 at 85cm depth