HIERARCHICAL CONTROL OF PHYTOPLANKTON SUCCESSION BY PHYSICAL FACTORS
HIERARCHICAL CONTROL OF PHYTOPLANKTON SUCCESSION BY PHYSICAL FACTORS
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DOI：
10.3354/meps019211
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发表时间：
1984-01-01
影响因子：
2.5
通讯作者：
LEGENDRE, L
中科院分区：
文献类型：
--
作者：
LEVASSEUR, M;THERRIAULT, JC;LEGENDRE, L
在圣劳伦斯河口（加拿大）的年度循环中评估了物理因素对浮游植物演替的影响，该河口全年营养物质仍然丰富。通常，浮游植物生产期较短（6 月至 9 月），并以出现 3 个不同的高峰为特征。 7月的水华以Thalassiosira Nordenskioldii和Chaetoceros debilis这2种硅藻为主，9月初和9月底分别以细柱藻和菱形藻为主。 3个开花期的出现与混合层中平均光强度的增加有关，这是由于强烈的密度分层导致混合层的深度减小而引起的。在这些花期期间，硅藻物种的演替主要受温度变化的控制。鞭毛虫全年都可观察到，但在硅藻开花期更为丰富。它们的丰度与表面温度的变化有关。在营养物质通常不受限制的河口，观察到的类群演替仅限于 Margalef (1958) 演替模型的第一阶段（具有高增长率的小细胞，是经常不稳定环境的典型物种）。结果表明，水柱不稳定的频率通过营养条件选择细胞的生长速率。混合层中的平均光强度决定了硅藻等非运动形式的出现，而温度则决定了最佳代谢活动的条件（鞭毛数量和硅藻物种的连续性）。这产生了一个概念模型，其中稳定性条件、混合层中的平均光和温度分层控制浮游植物的演替。
The influence of physical factors on phytoplankton succession was assessed during an annual cycle in the St. Lawrence Estuary (Canada), where nutrients remain abundant throughout the whole year. Typically, the phytoplankton production period is short (June-Sept.) and characterized by the occurrence of 3 distinct peaks. The July bloom was dominated by the 2 diatoms Thalassiosira nordenskioldii and Chaetoceros debilis, while Leptocylindrus minimus and Nitzschia seriata were dominant at the beginning and end of Sept. respectively. The occurrence of the 3 bloom periods is related to an increase in mean light intensity in the mixed layer, caused by strong density stratification which decreases the depth of the mixed layer. During these bloom periods, the succession of diatom species is mainly controlled by variations in temperature. Flagellates were observed all year round, although they were more abundant during the diatom bloom periods. Their abundance is related to variations in surface temperature. In the estuary where nutrients are usually non-limiting, the observed succession of taxa is restricted to the 1st stage of the Margalef (1958) succession model (small cells with high growth rates, which are typical species for frequently destabilized environment). Results demonstrate that the frequency of destabilization of the water column selects the growth rates of the cells, through nutrient conditions. Mean light intensity in the mixed layer determines the occurrence of non-motile forms such as diatoms and temperature sets the conditions for optimal metabolic activity (flagellate numbers and succession of diatom species). This results in a conceptual model where stability conditions, mean light in the mixed layer and temperature hierarchically control phytoplankton succession.