Nutrient ratios and the complex structure of phytoplankton communities in a highly turbid estuary of Southeast Asia

• Published in: Environmental monitoring and assessment Vol. 186; no. 12; pp. 8555 - 8572
• Main Authors: Chu, Thuoc Van, Torréton, Jean-Pascal, Mari, Xavier, Nguyen, Huyen Minh Thi, Pham, Kha Thi, Pham, Thu The, Bouvier, Thierry, Bettarel, Yvan, Pringault, Olivier, Bouvier, Corinne, Rochelle-Newall, Emma
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.12.2014; Springer Nature B.V; Springer
• Subjects: Atmospheric Protection/Air Quality Control/Air Pollution; Bacillariophyceae; Biodiversity; Brackish; Chlorophyceae; Cyanobacteria; Cyanophyceae; Diatoms - classification; Diatoms - growth & development; Dictyochophyceae; Dinoflagellida - classification; Dinoflagellida - growth & development; Dinophyceae; Earth and Environmental Science; Ecology; Ecology, environment; Ecosystems; Ecotoxicology; Environment; Environmental economics; Environmental Management; Environmental Monitoring; Estuaries; Euglenophyceae; Eutrophication; global change; Hydrology; Land use; land use change; Life Sciences; microalgae; Monitoring/Environmental Analysis; Nitrogen - analysis; Nutrient concentrations; Phosphorus - analysis; Phytoplankton; Phytoplankton - classification; Phytoplankton - growth & development; Plankton; rain; Ratios; Salinity; Seasons; Seawater - chemistry; Skeletonema costatum; Species composition; species diversity; Studies; Temperature; toxicity; Turbidity; Vietnam; Water Pollutants - analysis; Water quality; Wind; Vietnam; Southeast Asia; ISEW, Southeast Asia; ISEW, Vietnam; Phytoplankton diversity; HAB; Vietnam; Southeast Asia
• ISSN: 0167-6369; 1573-2959; 1573-2959
• DOI: 10.1007/s10661-014-4024-y

Phytoplankton diversity and abundance in estuarine systems are controlled by many factors. Salinity, turbidity, and inorganic nutrient concentrations and their respective ratios have all been proposed as principal factors that structure phytoplankton diversity and influence the emergence of potentially toxic species. Although much work has been conducted on temperate estuaries, less is known about how phytoplankton diversity is controlled in tropical, monsoonal systems that are subject to large, seasonal shifts in hydrology and to rapidly changing land use. Here, we present the results of an investigation into the factors controlling phytoplankton species composition and distribution in a tropical, monsoonal estuary (Bach Dang estuary, North Vietnam). A total of 245 taxa, 89 genera from six algal divisions were observed. Bacillariophyceae were the most diverse group contributing to 51.4 % of the microalgal assemblage, followed by Dinophyceae (29.8 %), Chlorophyceae (10.2 %), Cyanophyceae (3.7 %), Euglenophyceae (3.7 %) and Dictyochophyceae (1.2 %). The phytoplankton community was structured by inorganic nutrient ratios (DSi:DIP and DIN:DIP) as well as by salinity and turbidity. Evidence of a decrease in phytoplankton diversity concomitant with an increase in abundance and dominance of certain species (e.g., Skeletonema costatum ) and the appearance of some potentially toxic species over the last two decades was also found. These changes in phytoplankton diversity are probably due to a combination of land use change resulting in changes in nutrient ratios and concentrations and global change as both rainfall and temperature have increased over the last two decades. It is therefore probable in the future that phytoplankton diversity will continue to change, potentially favoring the emergence of toxic species in this system.