Institute of Marine Environment and Resources (IMER), Vietnam Academy of Science and Technology (VAST), Haiphong, Viet Nam.
Environ Monit Assess. 2014 Dec;186(12):8555-72. doi: 10.1007/s10661-014-4024-y. Epub 2014 Sep 10.
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.
浮游植物多样性和丰度在河口系统中受到许多因素的控制。盐度、浊度、无机养分浓度及其各自的比例都被认为是结构浮游植物多样性和影响潜在有毒物种出现的主要因素。虽然已经对温带河口进行了大量研究，但对于受水文季节性大变化和土地利用快速变化影响的热带季风系统中浮游植物多样性是如何控制的，人们了解较少。在这里，我们介绍了对热带季风河口（越南北部的 Bach Dang 河口）控制浮游植物物种组成和分布的因素的研究结果。共观察到 6 个藻类门的 245 个分类群和 89 个属。硅藻门是最多样化的群体，占微藻组合的 51.4%，其次是甲藻门（29.8%）、绿藻门（10.2%）、蓝藻门（3.7%）、裸藻门（3.7%）和黄藻门（1.2%）。浮游植物群落由无机养分比（DSi:DIP 和 DIN:DIP）以及盐度和浊度结构。还发现，浮游植物多样性的减少伴随着某些物种（如 Skeletonema costatum）的丰度和优势的增加以及一些潜在有毒物种的出现，这是过去二十年来的证据。浮游植物多样性的这些变化可能是由于土地利用变化导致养分比和浓度变化以及全球变化的综合作用，因为过去二十年来降雨量和温度都有所增加。因此，在未来，浮游植物多样性可能会继续发生变化，这可能有利于该系统中有毒物种的出现。
