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This article in JEQ

  1. Vol. 38 No. 2, p. 560-566
     
    Received: Feb 11, 2008
    Published: Mar, 2009


    * Corresponding author(s): juha.niemisto@helsinki.fi
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doi:10.2134/jeq2008.0075

Resuspension-Mediated Temporal Variation in Phosphorus Concentrations and Internal Loading

  1. Juha P. Niemistö *,
  2. Heidi Holmroos,
  3. Leena Nurminen and
  4. Jukka Horppila
  1. Dep. of Biological and Environmental Sciences/Limnology, P.O. Box 65 (Viikinkaari 1), FIN 00014 Univ. of Helsinki, Finland

Abstract

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 μg 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 μg 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.

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Copyright © 2009. American Society of Agronomy, Crop Science Society of America, Soil Science SocietyAmerican Society of Agronomy, Crop Science Society of America, and Soil Science Society of America