Abstract:
Primary production (PP) of phytoplankton plays an essential role in food web
dynamics, biogeochemical cycles and marine fisheries. It is used as one of the basic information
for evaluating marine ecosystems. In this paper, monthly composite PP data on a 4 km x 4 km
grid for the period 2003-2020 was used to evaluate the distributional characteristics of PP in the
coastal marine area of Vietnam South Centre. The statistical results show that the climatological
average of PP in 18 years reached 449.2 mgC/m2
/day, ranged from 272.1 to 14,205.4
mgC/m2
/day. The PP has seasonal and spatial variations. In time, the lowest value of PP was in
spring, and the highest was in winter; in space, PP tended to decrease from shore to offshore, PP
was higher in coastal areas than in the open sea areas. During the northeast monsoon season, PP
increased by more than 1000 mgC/m2
/day in the coastal area. Meanwhile, in the southwest
monsoon season, due to the ecological influence of the upwelling phenomenon, PP increased
with a value greater than 1500 mgC/m2
/day, distributed along the coastline of Ninh Thuan - Binh
Thuan. Primary productivity positively correlated with chlorophyll content but negatively
correlated with sea surface temperature with correlation coefficients of 0.9 and -0.6, respectively. There was a weak correlation between PP and ONI with correlation coefficients of -0.23. The temporal-spatial variation of PP was affected by the ENSO (El Niño-Southern Oscillation) phenomenon, the positive phase of ENSO (El Niño conditions) corresponded to lower PP, and the negative phase of ENSO (La Niña conditions) corresponded to higher PP. The research results from this paper can be used as a reference in marine ecosystem management.
