General:
This data set is part of an on-going LTER project at the Plum Island Ecosystem (PIE) site. The sampling location is in a Spartina patens-dominated marsh at Law's Point between the Rowley River and West Creek in Rowley MA.
Sampling Description:
Triplicate porewater diffusion samplers were permanently installed in control plots on the marsh platform in a Spartina patens-dominated salt marsh. Each sampler collects porewater from depths of 10, 25, 50, 75, and 100 cm. Samples are retrieved approximately monthly from May through October. Porewater samples are either filtered (0.2 uM) and preserved with H2SO4 (for PO4 and NH4) or preserved unfiltered with ZnAc (for sulfides) either in the field or immediately upon return from the field. The samples are then shipped to a lab in SC. Porewater collection began in August 2000. In May 2006 the Control porewater plots were relocated due to potential contamination from fertilized plots.
Lab Methods:
Filtered porewater samples are analyzed for PO4 and NH4 according to standard laboratory protocols (Strickland and Parsons 1972) and for chloride concentrations by coulometric titration using a Haake-Buchler chloridometer. Unfiltered, preserved porewater samples are analyzed for sulfide concentrations colorimetrically (Cline 1969). Salinity was calculated from chloride concentrations of filtered porewater samples (by coulometric titration using a Haake-Buchler chloridometer) before August 2020. Beginning in August 2020, salinity was measured using an EXTECH EC600 conductivity meter.
Numerical Processing:
Data are reported as geometric means of sample concentrations from 3 depths within the root zone (10, 25, and 50 cm), and the 95% confidence interval, for 3 replicate samplers (n=9 per time). Statistics were computed using SAS (SAS System for Windows; release 8.02; SAS Institute, Inc; Cary, NC).
Elevation: LTE-MP-LPP, ~ 1.45 meters NAVD88