SILICA, DIATOMS AND A FRESH-WATER PRODUCTIVITY MAXIMUM IN ATLANTIC COASTAL-PLAIN ESTUARIES, CHESAPEAKE BAY
SILICA, DIATOMS AND A FRESH-WATER PRODUCTIVITY MAXIMUM IN ATLANTIC COASTAL-PLAIN ESTUARIES, CHESAPEAKE BAY
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DOI：
10.1016/0272-7714(86)90112-5
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发表时间：
1986-02-01
影响因子：
2.8
通讯作者：
ANDERSON, GF
中科院分区：
文献类型：
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作者：
ANDERSON, GF
1981年从詹姆斯河、约克河和拉帕汉诺克河收集的月度数据表明，溶解硅（=硅酸）在这些河口全年呈现两种不同类型的纵向分布。保守的行为，观察在冬季或当河流流量高。第二种分布发生在浮游硅藻的吸收将浓度降低到海水稀释的水平以下时。在所有这三个系统中，非保守行为的特点是快速吸收的潮淡水部分，盐入侵的限制上游，并对应于叶绿素最大值显示含有水华密度的硅藻。在硅藻最大值附近，硅酸被消耗到低于可检测浓度，代表超过98%的河流源去除。非保守分布的总硅（=硅酸+生物硅）在同一地区表明沉积物的生物硅。同时，淡水河段的硅藻耗尽了河流水源，硅酸被重新供应到河口寡盐部分的水柱中。这种再补给被证明是显着的，几乎等于进入河口的河流输入的草酸的量，这表明在淡水区生产的生物硅的完全矿化。上述的空间分布定期在所有三个系统中观察到，表明增强浮游植物生产和营养盐再生的过渡区附近是这些部分混合河口河流的自然特征。浮游植物生物量的积累和硅的循环增强可能的机制进行了讨论。
Monthly data collected in 1981 from the James, York and Rappahannock rivers show that dissolved silica (= silicic acid) exhibits two distinct types of longitudinal distributions in these estuaries during the year. Conservative behavior was observed during winter or when river discharge was high. The second distribution occurs when uptake by planktonic diatoms reduces concentrations below the levels attributable to dilution by seawater. In all three systems, the non-conservative behavior is characterized by rapid uptake of silicic acid in the tidal freshwater portion, just upstream of the limit of salt intrusion, and corresponds to a chlorophyll maximum shown to contain bloom densities of diatoms. Silicic acid is exhausted below detectable concentrations in the vicinity of the diatom maxmum, representing more than 98% removal of the riverine source. Non-conservative distributions of total silicia (= silicic acid + biogenic silica) in this same region indicate deposition of biogenic silica to the sediments. At the same time the riverine source is depleted by the diatoms in the freshwater reaches, silicci acid is resupplied to the water column in the oligohaline portion of the estuaries. This resupply is shown to be significant, nearly equal to the amount of silicic acid entering the estuary in river input, suggesting complete mineralization of biogenic silica produced in the freshwater zone. The spatial distributions described above were observed regularly in all three systems, indicating that enhanced phytoplankton production and nutrient regeneration in the vicinity of the transition zone is a natural feature of these partially-mixed estuarine rivers. Possible mechanisms contributing to the accumulation of phytoplankton biomass and the enhanced cycling of silicon are discussed.