Methods and Results for Organic Carbon and Pollen Analyses
Organic Carbon
The organic content of the sediment core was analyzed using loss-on-ignition (LOI). In this process, samples of sediment approximately one cubic centimeter in size were dried in an oven at 60 C for 24 hours . The dried samples were weighed and combusted in a furnace at 550 C for five hours to remove all organic content. After the samples have cooled a final weight was taken. To determine what percent of the sample consisted of organic content the following equation was used: (dry weight/weight after ignition)* 100.
Pollen Analysis
For the pollen analysis, Lycopodium spores were used as tracers to more accurately determine species abundance. Tablets containing a known amount of Lycopodium spores were be dissolved in 10% potassium hydroxide (KOH) and added to a beaker containing a small sample (1 cubic cm) of sediment. From there, the samples underwent several chemical treatments to remove organic matter, carbonates, and silicates leaving spores and pollen grains in a clear solution to be observed under a microscope.
After adding the Lycopodium and KOH the mixture was sieved over a 200-250 µm screen and the samples were centrifuged. From there, the liquid in the sample was decanted and washed with deionized water twice. After this, carbonates are removed. The samples were vortexed with ethanol and water, then 96% acetic acid was added and the samples were left overnight and washed with water twice the following day. Then the samples were washed with acetic acid, treated with an Acetolysis mixture and heated before being centrifuged and decanted again.
The final step is heavy liquid separation to remove silicates. For this, sodium polytungstate (SPT0 was added, followed by water. The samples were centrifuged, leaving silicates and other heavy materials at the bottom of the test tube and a layer of pollen floating between the SPT and water. The suspended samples were carefully removed and placed in a new test tube and washed. Finally, silicone oil was added to the samples and they were mounted on microscope slides for counting.
​
The site I used for this method is here
Preliminary Results
The organic content of the core has two primary areas of transition that are followed by a stable period. The second stable period begins around 5,000 years ago, and is probably the formation of the wetland that the core was collected from. This stable period ranges between 80% and 90% organic content which would be expected in a wetland.
The pollen analysis is currently ongoing but the top half of the core (0-160cm, up to 5,000 yrs) has been processed and samples have been mounted on microscope slides. So far, jack pine (Pinus banksiana) appears to be one of the more abundant species present, which was expected based on the current plant community at the Flat Rock. Pictured below are some of the species that have been identified and observed in several samples so far.
Pinus banksiana
Populus tremuloides
Kalmia sp.
Nuphar sp.
