Home > Research > Project Summary
link: GCRC homepage

Long-Term Water Quality Sampling
of the Skidaway River Estuary

PI: Peter Verity (Skidaway Inst. of Oceanography, Savannah, Georgia, USA)

Support: The National Science Foundation, Department of Energy, and Georgia Sea Grant College Program all provided general support during the project period, although the sampling program was not a grant-funded project.

Timeframe: 1986 - ongoing

Project Overview:
Starting in 1986, samples were taken at weekly intervals, at high and low tide on the same day at a single site from the waters adjacent to the docks at the Skidaway Institute of Oceanography.  Hydrography, nutrients, chlorophyll a, particulate matter, and microbial and plankton biomass and composition were measured.


  • Salinity varied inversely with river discharge and exhibited variability at all time scales, but with no long-term trend.
  • Water temperature ranged over 25 degrees C, and was without apparent long-term trend.
  • Seasonal cycles in concentrations of NO3, NH4, PO4, Si(OH)4 and DON were observed, with annual maxima generally occurring in late summer.
  • Superimposed on seasonal cycles, all five nutrients exhibited steady increases in minimum, mean, and maximum concentrations; mean concentrations increased c. 50-150% during the decade.
  • Nutrient concentrations were highly correlated with water temperature over the 10-year period, but weakly related to salinity and discharge.
  • Nutrients were strongly correlated with one another, and the relative ratios among inorganic nutrients showed little long-term trend.
  • Correlations among temperature and nutrient concentration exhibited considerable inter-annual variability.
  • Major spikes in organic and inorganic nutrient concentrations coincided with significant rainfall events.
  • All classes of particulate organic matter exhibited distinct seasonal patterns superimposed upon significant long-term increases during the study period.
  • Chl a increased 18-61% over ten years (depending on size fraction).
  • Particulate organic carbon and nitrogen increased 16% over the decade, and exhibited increases in annual amplitude.
  • The C:N ratio was typically 6.4-6.6 (wt:wt) and did not change significatntly, while the annual mean C:Chl a ratio decreased 19% from 165 to 140.
  • Temperature explained 45-50% of the variance in particulate organic matter.
  • Ambient concentrations of dissolved organic nitrogen or PO4 explained 60-75% of the variance in chl a, and particulate organic carbon and nitrogen.
  • These data strongly suggest that anthropogenic activities contributed to increased loading of dissolved nutrients, which became incorporated into living and nonliving particulate matter.


Verity, P.G. 2002. A decade of change in the Skidaway River Estuary. I. Hydrography and nutrients. Estuaries 25(5): 944-960.

Verity, P.G. 2002. A decade of change in the Skidaway River Estuary. II. Particulate organic carbon, nitrogen, and chlorophyll a. Estuaries 25(5): 961-975.

Please keep us current by submitting updates and new project summaries.

Contact us
This page was updated October 13, 2006