Photo-Bio Part 6: Incubation, Sampling, and Analysis
Toolik Field Station, North Slope, AK
June 24, 2019
Video of the Day:
During our lunch break yesterday at Imnavait Creek, we had a very close encounter with a red fox (Vulpes vulpes).
As a preface to this post, you’ll benefit from reading my overview of the photo-bio project. It’s important to pay attention to the key independent variables:
- Soil Type - Surface layer (organic mat) soil vs. permafrost
- Sunlight Exposure - Dark control vs. sunlight-exposed.
We have now finished Photo-Bio Parts 1-5 for both permafrost and surface mat soil samples. To review the steps:
- Collect soil samples from permafrost and surface mat layers (Part 1).
- Prepare crude soil leachate by adding water to the soil samples and incubating for 72 hours (Part 2).
- Filter crude soil leachate to remove particulates and microbes (Part 3).
- Exposed filtered soil leachate samples to sunlight for 24 hours (with corresponding dark controls) (Part 4).
- Inoculate soil leachate samples with bacteria from the corresponding soil type (Part 5).
Currently, we are incubating inoculated samples and sampling at critical time points for analysis. I’ve starred (yellow) our current location on the below flow chart of the photo-bio experimentation process.
The two major time points for sampling are at 4 hours and 5 days (post-inoculation). Samples are subjected to a wide array of analyses, both biological and chemical. Here’s the list of data that is taken at multiple time points:
Many of these assays are completed on-site at Toolik Field Station. Others are completed back in the home labs of the principal investigators (University of Michigan and Oregon State University), the Pacific Northwest National Laboratory, and the U.S. Department of Energy Joint Genome Institute.
Yesterday, I worked in the Toolik woodshop to prepare a modified rack for solid phase extraction. It definitely took awhile to figure out the locations of things in a new shop, but I was pleased with the final product.
Dr. Rose Cory uses this technique to concentrate DOC samples from the leachate, prior to further analysis. The below video and photos provide more information:
I’m still very amazed at the amount of high-level chemistry and biology conducted on-site up here in the Arctic. This is truly a world-class facility.