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Abstract
Phytoplankton plays a crucial role in aquatic ecosystems of estuaries where nutrient dynamics are often complex. This study evaluates the primary production and growth rate of phytoplankton in the estuarine area of Bà Rịa - Vũng Tàu, aiming to clarify the characteristics of the estuarine ecosystem for the better aquatic environmental management. The research was conducted through two surveys and experiments at 4 stations in June 2022 (rainy season) and December 2022 (dry season). Results indicated that primary production (GPP) of phytoplankton ranged from 387.0–2040.0 mgC m-3 day-1 in June and 355.5–1254.0 mgC m-3 day-1 in December. The GPP/CR ratio, ranging from 2.15 to 16.06, reflects the autotrophic status of the waters. The average growth rate of phytoplankton reached 0.975 ± 0.743 day-1 in June and 1.459 ± 0.494 day-1 in December. The growth rates were inversely proportional to the chlorophyll-a content, with higher growth rates observed in the December. Growth rates also showed a trend of decreasing with depth, due to light limitations at lower depths. These results demonstrated that estuarine waters in Ba Ria – Vung Tau is nutrient-rich environment that supports rapid phytoplankton growth. However, this also presents a potential risk for algal blooms under favorable light conditions. Understanding these dynamics is crucial for effective management and monitoring of aquatic environments, as well as for anticipating the potential ecological consequences of nutrient loading in the region.
Keywords: phytoplankton, growth rate of phytoplankton, estuaries, Bà Rịa – Vũng Tàu.