Continuous Salinity, Temperature and Water Level Monitoring Network

Committee Members:  Daniela Di Iorio (chair), Steve Pennings, Jacob Shalack and Wade Sheldon

The long-term objective of this network is to document spatial and temporal variability of salinity and its relationship to water level and river discharge.

Long-term measurements of conductivity, temperature and sub-surface pressure are collected at 30 minute intervals at 8 sites in the GCE-LTER domain, as described below. These monitoring sites were chosen to span the salinity gradient as well as to take advantage of existing physical structures (e.g. docks or pilings) for mounting instruments. The long-term moorings are located in transect regions used for quarterly oceanographic surveys and near to GCE-LTER marsh study sites.

Sea-Bird Electronics^®, Inc. MicroCAT data loggers were selected for their ability to reliably record temperature and conductivity (from which salinity is calculated) for extended periods of up to 3 or 4 months. Sub-surface pressure (depth) is added to each MicroCAT as a physical monitoring parameter that provides valuable information about tidal forcing at the seaward sites and an indication of tidal distortion upstream. MicroCATs also have the advantage of anti-foulant protection of the conductivity cell, which is a necessity in areas of extreme biological fouling, such as the GCE-LTER domain.

As of July 2003 instruments have been deployed at 8 locations throughout the GCE study area (view map, view coordinates, view data), including:

Sapelo River Transect
GCE1_Hydro (Sapelo River near Eulonia, within site GCE1)
GCE2_Hydro (Sapelo River near Four Mile Island, within site GCE2)
GCE3_Hydro (Sapelo Sound near North Sapelo, within site GCE3)

Doboy Sound Transect
GCE6_Hydro (Doboy Sound near Commodore Island, near site GCE6)

Altamaha River Transect
GCE7_Hydro (Altamaha River near Carrs Island, within site GCE7)
GCE8_Hydro (Altamaha River near Alligator Creek, within site GCE8)
GCE9_Hydro (Altamaha River near Rockdedundy Island, near site GCE9)
GCE11_Hydro (Altamaha River near Lewis Creek, within site GCE11)

Duplin River Transect
GCE10_Hydro (Duplin River at Flume Dock, within site GCE10)

These stations were established where extreme ranges in salinity were expected, and to complement other continuous hydrographic monitoring stations operated by USGS, the Sapelo Island National Estuarine Research Reserve, and UGAMI monitoring programs (see map). Values at the interior sites are expected to fall in between those measured at the edges. Waterways within or adjacent to all ten primary GCE sampling sites will eventually be instrumented.

MicroCATs are typically inspected and cleaned every 1-2 weeks and swapped about every 2 months, but the maintenance schedule is adjusted throughout the year in response to the degree of fouling at each deployment to maximize the quality/accuracy of the salinity record. Salinity is calibrated to a standard immediately after each deployment.

After each retrieval the data is downloaded and transmitted to the GCE Information Management Office for processing. Provisional data and plots are posted on the private GCE web site within 1-2 days of retrieval, and quality-controlled and reviewed data for each site are added to the GCE Data Catalog and GCE Data Portal on an annual basis to provide public access.