Bioavailability of phosphorus of river sediments and its effect on
growth of Selenastrum capricornutum
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.