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>Long-term Monitoring and Analyses of Physical Factors Regulating Variability in Coastal Antarctic Phytoplankton Biomass, in situ Productivity and Taxonomic Composition Over Subseasonal, Seasonal and Interannual Time Scales
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Long-term Monitoring and Analyses of Physical Factors Regulating Variability in Coastal Antarctic Phytoplankton Biomass, in situ Productivity and Taxonomic Composition Over Subseasonal, Seasonal and Interannual Time Scales
A 3 yr high-resolution temporal data base related to phytoplankton dynamics was collected during the austral spring/summer periods of 1991 to 1994 in shelf waters adjacent to Palmer Station, Antarctica. Here, the data base is used (1) to quantify the variability in phytoplankton biomass, in situ productivity and taxonomic composition over subseasonal, seasonal and interannual time scales; (2) to elucidate environmental mechanisms controlling these temporal patterns; and (3) to ascertain which phytoplankton markers are most suitable for detecting longer-term (i.e. decadal) trends in phytoplankton dynamics in coastal waters of the Southern Ocean. The Long-Term Ecological Research (LTER) coastal study sites showed high interannual variability in peak phytoplankton biomass (75 to 494 mg chl a m-2) and integrated primary production (1.08 to 6.58 g C m-2 d-1). Seasonal and annual patterns in biomass and productivity were shown to be driven by shorter-time-scale physical forcing by local wind stress. Low daily wind speeds (s-1) were associated with water-column stabilization. However, extended periods (\u3e1 wk) of low wind stress were required for increased phytoplankton growth and biomass accumulation. Temperature data supports the view that water masses can be replaced on time scales of a less than a day to a few days in these coastal waters. Such disruptions are associated with abrupt changes in local primary production and may lead to sudden shifts in local phytoplankton community structure. Despite the high seasonal and interannual variability in biomass and associated in situ productivity in this coastal environment, the replacement sequence of one dominant phytoplankton group by another was very similar on subseasonal time scales for all 3 years. We suggest that changes in phytoplankton successional patterns may be a more sensitive marker for detecting long-term trends in Southern Ocean ecosystems than either biomass or productivity indices, where short-term variability of the latter is as great or greater than interannual variations documented to date.
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机译:在1991至1994年的南/南春季期间,在与南极洲帕尔默站相邻的陆架水域中收集了一个与浮游植物动力学有关的3年高分辨率时态数据库。在这里,数据库被用来(1)量化亚季节,季节和年际尺度上浮游植物生物量,原地生产力和生物分类组成的变化; (2)阐明控制这些时间模式的环境机制; (3)确定哪种浮游植物标志最适合检测南大洋沿海水域浮游植物动力学的长期趋势(即年代际变化)。长期生态研究(LTER)沿海研究地点显示,浮游植物峰值生物量(75至494 mg chl a m-2)和综合初级生产(1.08至6.58 g C m-2 d-1)的年际变化很大。研究表明,生物量和生产力的季节性和年度模式是由局部风应力引起的更短时间尺度的物理强迫驱动的。每天的低风速(s-1)与水柱稳定有关。然而,增加浮游植物的生长和生物量的积累需要长时间的低风压(\ u3e1wk)。温度数据支持以下观点:在这些沿海水域中,可以在不到一天到几天的时间范围内替换水团。这种破坏与当地初级生产的突然变化有关,并可能导致当地浮游植物群落结构的突然变化。尽管在这种沿海环境中生物量的季节性和年际变化较大,并且相关的原地生产力较高,但在整个三年内,一个主要的浮游植物群被另一个浮游植物群替换的顺序在亚季节尺度上非常相似。我们建议,与生物量或生产力指数相比,浮游植物演替模式的变化可能是检测南大洋生态系统长期趋势的更灵敏标记,后者的短期变异性大于或大于迄今为止记录的年际变化。
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