摘要：The phytoplankton community composition, abundance and size-fractionated biomass (chlorophyll a) along with various physical and chemical parameters were assessed in Tajan estuary, in South Caspian Sea Basin. Monthly sampling was conducted at 6 stations. Based on results, the mouth or formed estuary could be categorized in three different classes. Category 1: station essentially related to river input and low net production (vary between 13.8 and 46.4 mg m-3 year-1. Category 2: consists of high net production (between 277.9 and 330.4 mg m-3 year-1) and mild consumption of (8.4 to 32.5 mg m-3 year-1). The 3rd category is considered to be in the middle of two above values from productivity point of view with (236.7 to 240.2 mg m-3 year-1) and relatively mild consumptions of (20.9 to 92.4 mg m-3 year-1). It seems that importance of such areas is much more in their nutrient inlet of the river from upper mouth. Net primary productions were high in the center of estuary with values near to 277 mg m-3 year-1. Selected station in lower mouth situated in the adjacent area inlet also showed high concentrations of 330 mg m-3 year-1, which suggests the existence of a nutrient front where fresh waters originated from rivers (rich in nutrient and phytoplankton decomposition materials) joint salt waters of the sea. In these stations phytoplankton has not enough time to be consumed because of soft sediments instability and inevitably is added to south Caspian basin production. Also primary production among months and seasons shows fluctuations, perhaps related to water inlet availability and residence time. There suggests a correlation between primary production and river discharge in different selected stations.
