2004—2016年夏季长江口网采浮游植物及其影响因素

DISTRIBUTION OF SUMMER COMMUNITY OF NET-COLLECTED PHYTOPLANKTON FROM 2004 TO 2016 AND THE FACTORS IN THE CHANGJIANG RIVER ESTUARY

基于2004—2016年夏季长江口生态监控区13年的生态环境调查数据,开展网采浮游植物年际变化及其与环境因子关系研究。结果表明:(1)共鉴定出浮游植物7门263种,以硅藻占绝对优势,甲藻次之,物种数呈增加趋势,其中硅藻种类数占有比下降,而甲藻的种类数占有比呈上升趋势;(2)总细胞丰度、硅藻细胞丰度和甲藻细胞丰度都呈上升趋势,除2014年外,其余年份硅藻细胞丰度都占绝对优势并与总细胞丰度的分布曲线和变化趋势基本一致;(3)水平分布模式及其年际变化受环流变化和水团消长的影响,总体趋势是河口区细胞丰度较低,由河口到外海呈逐渐增大趋势,部分年份呈现先增大后减小的趋势;(4)生物多样性多年呈下降趋势,物种组成随空间和时间变化较大,只有较少的种类能够保持稳定,多数物种只是偶尔被检出;(5)中肋骨条藻有10年为区域第一优势种,41种常见种中有31种细胞丰度呈增加趋势,10种细胞丰度呈下降趋势。(6)浮游植物细胞丰度与活性磷酸盐和无机氮具有相关性,种类数、多样性指数除了与溶解氧、氨氮、叶绿素a无相关性外与其他10种环境因子都相关。本研究能够较好反映研究区域浮游植物的本底情况及演变趋势。

Based on ecological environment survey data collected in the Changjiang （Yangtze） River estuary ecological monitoring area in summer from 2004 to 2016, the interannual variation of net-collected phytoplankton and its relationship to environmental factors were studied. Seven phyla including 263 species of phytoplankton were identified and dominated by diatoms, followed by dinoflagellates. In the past 13 years, the number of species tended to increase; the contribution of diatom diversity to total phytoplankton diversity declined, and the proportion of dinoflagellates diversity increased correspondingly. The cell abundance of the total species, including diatom and dinoflagellates displayed an increasing trend. The diatom cell abundance dominated except for 2014, and the distribution and variation patterns were consistent with the total cell abundance in the rest of the year. The horizontal distribution pattern of cell abundance and its interannual variation were affected by circulation change and water consumption. The cell abundance was relatively low in the estuary and increased toward the open sea; the overall cell abundance increased gradually but fluctuated in some years. The biodiversity slightly decreased, and the community composition changed greatly in temporal and spatial scopes. Only a few species remained stable during the period, and most could be detected occasionally. Skeletonema costatum was dominant species in at least 10 years. Of 41 common species, 31 showed an increasing trend and 10 decreased in cell abundance. In addition, phytoplankton cell abundance was correlated with phosphate and inorganic nitrogen. The species number and diversity index were related to 10 out of 13 studied environmental factors, exclusive of dissolved oxygen, ammonia nitrogen, and chlorophyll a. This study would be of great significance to understand the current situation and evolution trend of phytoplankton.