NUTRIENT CYCLING IN THE PIERMONT MARSH BASED ON TIDAL TIME SERIES

Marsh ecosystems are important modifiers of nutrients from sewage and agricultural runoff. Piermont Marsh, a brackish tidal marsh in the lower Hudson River Estuary, is an irregularly inundated wetland system with two tidal creeks and one freshwater creek. We hypothesized that Piermont Marsh is an active metabolizer of water nutrients in the Hudson River. Our specific aim was to estimate the fluxes of nutrients in the marsh during tidal flow. The marsh nutrient cycle was measured with three time-series collections in two of the creeks at locations with greatest fluxes between marsh and estuary from high to low tides. Water samples and sensor data were collected for nutrients (nitrate, nitrite, phosphate, and ammonium) at 45-minute intervals for two outgoing and one in-going tides. The samples were frozen for later spectrophotometric analysis with absorbance to calculate nutrient concentrations. Data was collected summer of 2015. The marsh appears to be a significant consumer of nitrate during the summer and a source of phosphate to the adjacent river water. The marsh is dominated by the invasive species Phragmites australis (Common Reed) which we hypothesize is the major nutrient absorber in the marsh. Our sensor data consists of dissolved oxygen content, water salinity, conductivity, and temperature, which will be applied to our findings in order to verify and refine our nutrient concentration analysis.

All samples were collected and processed by public high school students, teachers, and scientists from the Secondary School Field Research Program at Lamont Doherty Earth Observatory.