Research Methods

We are taking measurements of three different parameters; sediment accretion rates, litter decomposition rates, and soil respiration rates. Each of these require different methods.

Sediment Accretion Rates: For these we take sediment cores of the marsh and cut up the core into centimeter segments in order to get a depth profile. These segments will be analyzed for the amount of lead 210 (210Pb). Since 210Pb is known to be added to marshes at a constant rate from atmospheric deposition, which has particularly been found to be true on Long Island (Cochran et al), we can use this to determine how fast sediment has been accreting in a marsh.

(Jarvis Creek)

Litter Decomposition Rates: At the beginning of the summer, I attached multiple pre-weighed bags of dried plant matter to the marsh with garden staples. Every month, I have been going out to each of my sites and collecting some of the bags. Back in the lab I clean, dry, and weigh them to see what percentage of the plant matter has been lost and decomposed.

Respiration Rates: Each season I place metal rings into the marsh to isolate a certain area. Once the effect of the disturbance has decreased after around a week, I return and with a clear chamber. Creating a sealed environment, I take gas samples every five minutes over a half hour. I analyze these on a gas chromatograph, which tells me how much of three greenhouse gases (CO2, CH4, N2O) are in the sample. The change over time will tell me whether the marsh is releasing or taking up these gases.

Porewater Peepers: I made porewater peepers out of PVC pipes. I cut them, drilled holes, and beveled the ends of them. I fill little bottles with very pure water, attach a permeable membrane, put them in the holes in the PVC pipe, and tape mesh over them to keep them in place.  After taking a sediment core, I put the PVC pipe in the marsh and wait a week. Over that week, the porewater diffuses into the bottle and I come back to sample it. I measure the pH, salinity, and amounts of nitrogen, phosphorous, and silica.


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