Phytoplankton community in a tropical estuarine gradient after an exceptional harmful bloom of Akashiwo sanguinea (Dinophyceae) in the Todos os Santos Bay
H. M. Affe, Lorena Pedreira Conceição, D. S. Rocha, L. Proença, J. M. Nunes
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引用次数: 5
Abstract
The objective of this study was to evaluate variations in the composition and abundance of the phytoplankton community after an exceptional harmful bloom of Akashiwo sanguinea that occurred in Todos os Santos Bay (BTS) in early March, 2007. Samples were collected every ten days, between April, 2007 and March, 2008, from the estuarine gradient of the Paraguacu River to BTS. The physical and chemical variables were measured in situ using a multiparameter sensor. Water samples were collected for analysis of the dissolved inorganic nutrient concentrations and for the study of composition and abundance of the microphytoplankton. Overall, 135 taxa were identified, with a higher richness of diatoms. The total cell density ranged from 2.92 × 103 to 1.16 × 107 (5.47 × 105 ± 1.69 × 106) cells L−1, with higher values in the freshwater zone than in the marine area. Five species showed peaks of abundance throughout the study, forming small blooms. Four of these blooms occurred in the rainy season, formed by the species Guinardia striata (April, 2007), Scrippsiella cf. acuminata (August, 2007), Euglena gracilis (August, 2007), and Skeletonema cf. costatum (September, 2007), while a new bloom of the species Akashiwo sanguinea occurred during the dry season (December, 2007). The environment was typically oligotrophic, with low spatiotemporal variation in the concentrations of dissolved nutrients. Even so, we observed short-term variations in the structure and composition of the phytoplankton community, demonstrated by rapid bloom events, followed by an increase in the total abundance of microphytoplankton, especially during the rainy season. The blooms did not cause any notable changes in the water column and did not present any harmful effects on the system.
本研究的目的是评估2007年3月初在Todos os Santos湾(BTS)发生的Akashiwo血藻异常有害水华后浮游植物群落组成和丰度的变化。从2007年4月到2008年3月,每十天从巴拉圭河河口梯度到BTS采集一次样本。物理和化学变量使用多参数传感器进行现场测量。采集水样用于分析溶解的无机营养物浓度,并用于研究微小浮游生物的组成和丰度。总共鉴定了135个分类群,硅藻的丰富度较高。总细胞密度范围为2.92×103至1.16×107(5.47×105±1.69×106)个细胞L−1,淡水区的值高于海洋区。在整个研究过程中,有五个物种表现出丰富的峰值,形成了小花。其中四次开花发生在雨季,由条纹Guinardia striata(2007年4月)、尖尖斯克里普菌(2007年8月)、细眼虫(2007年八月)和中肋骨Skeletonema cf.costatum(2007年9月)形成,而赤血赤藻的一次新开花发生在旱季(2007年12月)。环境通常是贫营养的,溶解营养物质浓度的时空变化很低。即便如此,我们观察到浮游植物群落结构和组成的短期变化,表现为快速水华事件,随后微小浮游植物的总丰度增加,尤其是在雨季。水华没有引起水柱的任何显著变化,也没有对系统产生任何有害影响。