Temporal and spatial variations of chlorophyll a concentration and primary production in Jiulongjiang Estuary waters

A comprehensive survey of hydrological,chemical and biological resources was conducted in Jiulongjiang Estuary waters in spring,summer and autumn of 2009,for the ecological management of the estuarine safety.This paper studied the seasonal and spatial variation of chlorophyll a concentration and primary production,with their relation to environmental factors.The results showed that the chlorophyll a concentration varied from 0.77 to 15.89 mg /m3 with a mean of 3.11 mg/m3.The primary production varied from 19.05 to 332.91 mg/(m2·d) with a mean of 103.51 mg/(m2·d).Chlorophyll a concentration was the highest in summer and the lowest in autumn.Primary production was the highest in spring and the lowest in autumn.Compared with literature data chlorophyll a concentration in surface water increased 1.3 to 1.6 times higher than that in 1990.While the primary production in surface water dropped 32% less than that in 1990.Pearson correlate analysis of chlorophyll a concentration with the primary production and environmental factors indicated that the chlorophyll a concentration correlated positively to the primary production,SiO3-Si concentration and temperature,while correlated insignificantly to phytoplankton density.When the concentrations of DIN and SiO3-Si were high,the water temperature and PO4-P concentration became important in controlling the chlorophyll a concentration and primary production in Jiulongjiang Estuary waters.