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Bioavailability of phosphorus of river sediments and its effect on growth of Selenastrum capricornutum
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  • Hamed Arfania,
  • Abbas Samadi,
  • Farrokh Asadzadeh,
  • Ebrahim Sepehr,
  • S. E. A. T. M. van der Zee
Hamed Arfania
Agricultural Research Education and Extension Organization
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Abbas Samadi
Urmia University
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Farrokh Asadzadeh
Urmia University
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Ebrahim Sepehr
Urmia University
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S. E. A. T. M. van der Zee
Wageningen University and Research
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Abstract

Increasing anthropogenic loading of phosphorus (P) threatens aquatic ecosystems. The bioavailability of P in sediments for algal growth depends on several physiochemical properties such as particle size distribution, mineralogy, pH, electrical conductivity (EC), and carbonate-content. This study was aimed on selecting the best chemical extraction method to characterize P-availability for the algae Selenastrum capricornutum. Principal component analysis (PCA) of the data identified two components that cover 79.3% of the total variation, and these components were dominated by particle size distribution, active calcium carbonate equivalence (ACCE), and EC. Many of the considered extractions were positively correlated with each other, with the exception being Bray-II. The sediments of some rivers had a higher Olsen-extractable P than 20 mg kg-1, that is considered a threshold value above which the aquatic environment may become negatively affected. The average rank order of P extraction by single extractants was: Colwell > Mehlich III > NaOH 0.1 M > Olsen > Morgan > AB-DTPA > Bray II. The Colwell-extractable P concentrations of sediments varied from 1.44 to 88.0 mg kg-1. This extractant significantly correlated with algal growth (r2=0.92, P<0.001) and was the best single extraction method to characterize sediment P-bioavailability. Algae (S. capricornutum) growth was also well correlated with Mehlich III, NaOH 0.1 M, Olsen, and Morgan extractable-P concentrations. Algae growth was highly significantly correlated with EC.