Niemistö Juha P, Holmroos Heidi, Nurminen Leena, Horppila Jukka
Dep. of Biological and Environmental Sciences/Limnology, P.O. Box 65 (Viikinkaari 1), FIN 00014 Univ. of Helsinki, Finland.
J Environ Qual. 2009 Feb 6;38(2):560-6. doi: 10.2134/jeq2008.0075. Print 2009 Mar-Apr.
Sediment resuspension is an important factor for nutrient cycling in shallow lakes. Temporal variation in sediment resuspension and its influence on P concentrations and internal loading were studied in the shallow and eutrophic Kirkkojärvi basin. Gross sedimentation and sediment resuspension were estimated with sediment traps during three exposure periods in spring, midsummer, and autumn. The effects of resuspension on the concentrations of suspended solids, total phosphorus (TP), soluble reactive P, and chlorophyll a were followed. The level of sediment resuspension was greatest in midsummer (July-August 63.9 g dw m(-2) d(-1)), due to strong phytoplankton blooms modifying the surface film of the sediment more prone to resuspension. The dependence of high total P concentrations (226-385 microg L(-1)) on sediment resuspension and suspended solids was significant at the time. The concentrations of soluble reactive P were also high in midsummer (52-91 microg L(-1)), but had a negative dependence on suspended solids. This dependence was due to algal assimilation as was proved by a negative effect of chlorophyll a on soluble reactive P. Consequently, we suggest that the increase in the total P concentrations caused by sediment resuspension in midsummer was possibly intensified by strong algal blooms occurring at the time because strong assimilation resulting in high pH (pH 7.3 in May, 9.3-10.2 in July-August, 7.6 in October) may have increased the desorption of P from the suspended inorganic particles and intensified the P transfer into the phytoplankton biomass in midsummer.
沉积物再悬浮是浅水湖泊营养物质循环的一个重要因素。在浅水富营养化的基尔科耶尔维流域，研究了沉积物再悬浮的时间变化及其对磷浓度和内源负荷的影响。在春季、仲夏和秋季的三个暴露期，利用沉积物捕获器估算了总沉积量和沉积物再悬浮量。跟踪了再悬浮对悬浮固体、总磷（TP）、可溶性活性磷和叶绿素a浓度的影响。沉积物再悬浮水平在仲夏时最高（7 - 8月为63.9 g干重m(-2) d(-1)），这是由于强烈的浮游植物水华改变了沉积物的表面薄膜，使其更易于再悬浮。当时，高总磷浓度（226 - 385 μg L(-1)）对沉积物再悬浮和悬浮固体的依赖性显著。仲夏时可溶性活性磷浓度也很高（52 - 91 μg L(-1)），但与悬浮固体呈负相关。这种相关性是由于藻类同化作用，叶绿素a对可溶性活性磷的负面影响证明了这一点。因此，我们认为仲夏时沉积物再悬浮导致的总磷浓度增加可能因当时强烈的藻类水华而加剧，因为强烈的同化作用导致高pH值（5月pH值为7.3，7 - 8月为9.3 - 10.2，10月为7.6）可能增加了磷从悬浮无机颗粒中的解吸，并在仲夏时加剧了磷向浮游植物生物量中的转移。
