Sediment Phosphorus Chemistry and Microbial Biomass along a Lowland New Zealand Stream

Author: McDowell R.W.

Source: Aquatic Geochemistry, Volume 9, Number 1, 200303 , pp. 19-40(22)

Publisher: Springer

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Abstract:

An evaluation of the distribution of P concentrations in streamflow, P fractions and the microbial biomass P pool was made of bed and bank sediments along a lowland stream in New Zealand. Agricultural intensification increased downstream. However, most P fractions decreased downstream (total P decreased from c. 400 to 250 mg kg^-1) in bed sediments, while P in streamflow remained relatively constant (generally < 0.005 mg l^-1) and sediment microbial P increased from 2 to 8 mg kg^-1. An investigation of P release from dried and rewetted sediments showed that solution P (CaCl2-P) increased, on average > 300%, and proportional to the size of the microbial biomass P pool before drying, except in sediments with much organic carbon (OC). When supplied with a P source (1 mg l^-1) and then simultaneously with a C source (glucose, 100 mg l^-1), all sediment behaved similarly and biotic sorption accounted for, on average, 27 and 34% of the total sediment uptake, respectively (maximum of 58%). The quantity of P taken up was related to the initial size of the microbial biomass P pool, and the availability of P as influenced by organic P complexes and OC. The sediment microbial biomass represents a transient, but small store of P could be useful to indicate bioavailable P inputs.

Keywords: Stream; fluvial; sediment; phosphorus; microbial biomass P

Document Type: Research article

Affiliations: 1: AgResearch Ltd, Invermay Agricultural Centre, Private Bag 50034, Mosgiel, New Zealand, Email: richard.mcdowell@agresearch.co.nz

Publication date: 2003-01-01