General sampling protocol
Semi-annual samplings for nutrients and water quality are conducted in Spring - pre growing season and typically characterized by high river discharge (spring freshet) and Fall - post growing season and generally lower discharge. Sampling times are coordinated with separate surveys done along the same transect measuing oxygen. Grab samples and sonde measurements are taken at 11 stations along a 24Km transect from the mouth of Plum Island Sound up the main stem of the Parker River to as near the dam at the head of the estuary as possible, depending on tide stage at time of sampling. Sampling times are coordinated with separate surveys done along the same transect measuing oxygen using a flow-through sampling technique. (see EST-PR-O2: PIE LTER transects of the Parker River Plum Island Sound Estuary, Massachusetts conducted at dawn and dusk, containing dissolved oxygen, conductivity, temperature, percent saturation, pH, DIC and pCO2 data)
Conductivity (and salinity) and temperature are measured using appropriate probes on a water quality sonde (Hydrolab H20 for 1994-2003; YSI Sonde for 2004-2019). Water quality sondes are backed up by field thermometers and refractometers.
Secchi depth is considered to be the shallowest depth at which the black and white sections of a Secchi disk become indistinguishable.
Water samples for nutrients are collected in acid-washed, 1-liter polycarbonate bottles. Samples are transported to the field lab and filtered within three hours of collection through GF/F filters. Filtered samples are immediately preserved for later analysis of dissolved materials, and filters are preserved for later analysis of particulates.
Sampling locations
From 1994 through 2005, samples were taken at designated stations along the transect; latitude and longitude and state plane variables assigned to these stations were fixed. Beginning with the April 2006 transect, samples have been collected in salinity space rather than at fixed station locations (because they are sampled in salinity space, this location will vary depending on the salinity gradient and depending on the tide at which the samples were taken) Beginning in 2008, GPS allowed more precise location of sampling points to be taken at the time of sampling, and state coordinates were no longer included in the dataset. For more details on sampling protocols, contact Nat Weston (nathaniel.weston@villanova.edu).
