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首页> 外文期刊>Hydrobiologia >Longitudinal trends and discontinuities in nutrients, chlorophyll, and suspended solids in the Upper Mississippi River: implications for transport, processing, and export by large rivers
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Longitudinal trends and discontinuities in nutrients, chlorophyll, and suspended solids in the Upper Mississippi River: implications for transport, processing, and export by large rivers

机译：密西西比河上游养分，叶绿素和悬浮固体的纵向趋势和不连续性：对大型河流的运输，加工和出口的影响

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摘要

Across the distances spanned by large rivers, there are important differences in catchment characteristics, tributary inputs, and river morphology that may cause longitudinal changes in nutrient, chlorophyll, and suspended solids concentrations. We investigated longitudinal and seasonal patterns in the Upper Mississippi River (UMR) using long-term data (1994–2005) from five study reaches that spanned 1300 km of the UMR. Lake Pepin, a natural lake in the most upstream study reach, had a clear effect on suspended material in the river. Suspended solids and total phosphorus (TP) concentrations were substantially lower downstream of the lake and percent organic material (OM%) in suspension was higher. Below L. Pepin, mean total and organic suspended solids (TSS, OSS) and TP increased downriver and exhibited approximately log-linear relationships with catchment area, whereas OM% declined substantially downriver. Despite the downriver increase in TSS and OSS, concentrations similar to those above L. Pepin do not occur until ~370 km downriver indicating the extent of the influence of L. Pepin on the UMR. Chlorophyll concentrations were lower in the most downstream study reach, likely reflecting the shorter residence time and poor light climate, but there was not a consistent longitudinal decline in chlorophyll across the study reaches. Dissolved silica (DSi), DSi:TN, and DSi:TP declined downriver suggesting that DSi uptake and sedimentation by river phytoplankton may be reducing DSi transport in the river, and indicating that the eutrophication of the river may contribute to a reduction of DSi export to the Gulf of Mexico.
机译：在大河流域的整个距离上，流域特征，支流输入和河流形态存在重要差异，可能导致养分，叶绿素和悬浮固体浓度的纵向变化。我们使用来自五个研究河段（横跨UMR 1300公里）的长期数据（1994-2005年）调查了密西西比河上游（UMR）的纵向和季节性模式。佩平湖是研究最上游的天然湖泊，对河流中的悬浮物具有明显的影响。湖泊下游的悬浮固体和总磷（TP）浓度明显较低，悬浮物中的有机物百分比（OM％）较高。在L. Pepin以下，平均总悬浮固体和有机悬浮物（TSS，OSS）和TP增加了下游，并显示出与流域面积的近似对数线性关系，而OM％显着下降了下游。尽管TSS和OSS的下游增加，但直到L. Pepin向下约370 km才出现类似于L. Pepin之上的浓度，这表明L. Pepin对UMR的影响程度。在最下游的研究范围内，叶绿素浓度较低，这可能反映了更短的停留时间和恶劣的气候条件，但整个研究范围内叶绿素的浓度并没有持续下降。溶解二氧化硅（DSi），DSi：TN和DSi：TP下降到下游​​，表明河流浮游植物对DSi的吸收和沉积可能会减少河流中DSi的运输，并表明河流富营养化可能有助于减少DSi的出口到墨西哥湾。

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