Nutrients and Primary Production in the Estuary of the Razdol’naya River (Amur Bay, Sea of Japan)

The behavior of the basic nutrients (NO sub(3), PO sub(4), SiO sub(2)) was studied in the estuary of the Razdol'naya River in low and high water, the flow was 4.3 x 10 super(6) m super(3)/day and 10.8 x 10 super(6) m super(3)/day, respectively. It was shown that within the limits of the euphotic zone the nutrients were characterized by a pronounced nonconservative behavior caused by their removal by phytoplankton in primary production. It was determined that phytoplankton removal of nutrients occurred with ratios Delta C : Delta NO sub(3) : Delta P : Delta Si = 105 : 18 : 1 : 37 and Delta C : Delta NO sub(3) : Delta P : Delta Si = 93 : 11 : 1 : 29 at a respective ratio P : NO sub(3) : Si = 1 : 22 : 140 in low water and P : NO sub(3) : Si = 1 : 17 : 120 in high water. It was also determined that the maximum rate of nutrient removal was 4 times higher in the high water than in the low water. The maximum value of primary production of phytoplankton was 2.5-4.0 gC/m super(2) day. The estuary area of the Razdol'naya River was specified by rather high production. Such a rate of estuarine primary production, caused by nutrients carried out by the river, being no less than 250 t of dry weight of phytoplankton a day, can provide daily production up to 800 t of biomass in the secondary chain of the ecosystem.