Sefid-Rood River Estuary is the most important riverine ecosystem in the south Caspian Sea. The aim of this study was to examine spatial and temporal variability of physical and Chemical factors, Chl-a and pelagic primary production during a year (November 2004 to October 2005) in five sampling stations in the Sefid-Rood River Estuary. Annual means (±SD) Physical and Chemical factors were: temperature 17.2±8.6oC, Surface salinity 1.77±1.32 ppt, bottom salinity 2.79±3.27ppt, turbidity 311.86±345.18FTU, water tranprancy 36.5±25.33cm, DO 8.69±2.88mgL-1, NH+ 4 0.512±0.66mgL-1 , SiO2 5.68±1.91, TP 0.136±0.103mgL-1, T. O. C. 10.3±9.9 mgL-1 and Chl. a 4.44±7.45mgL-1. Minimum was zero in October and maximom in September was 22.85±2.5mgL-1.
There was a spatial variability along the estuary and high level Chl. a determined in the river mouth (Station 4) with 7.5±10.65mgL-1. Primary production determined in this estuary by dark and light bottle method and GPP 38.27±34.12 mgcm-2 h-1 and NPP 201.6±289.9 mgcm-2 d-1. Everywhere in this estuary nutrients appeared to be in excess to algal requirement and did not influence Chl. a and primary production. The most important factor that influenced Chl. a was water temperature.