Soluble reactive phosphorus SRP transport and re

Authors: Frank Triska Catherine M Pringle John H Duff Ronald J Avanzino Gary Zellweger

Publish Date: 2006/10/03

Volume: 81, Issue: 2, Pages: 145-157

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Abstract

Soluble reactive phosphorus SRP transport/retention was determined in two rain forest streams Salto Pantano draining La Selva Biological Station Costa Rica There SRP levels can be naturally high due to groundwater enriched by geothermal activity within the surfically dormant volcanic landscape and subsequently discharged at ambient temperature Combined field and laboratory approaches simulated high but natural geothermal SRP input with the objective of estimating the magnitude of amended SRP retention within high and low SRP settings and determining the underlying mechanisms of SRP retention First we examined shortterm SRP retention/transport using combined SRPconservative tracer additions at high natural in situ concentrations Second we attempted to observe a DIN response during SRP amendment as an indicator of biological uptake Third we determined SRP release/retention using laboratory sediment assays under control and biologically inhibited conditions Shortterm in situ tracerSRP additions indicated retention in both naturally high and low SRP reaches Retention of added SRP mass in Upper Salto low SRP was 17 75 mgP m−2 h−1 and 20 109 mgP m−2 h−1 in Lower Salto high SRP No DIN response in either nitrate or ammonium was observed Laboratory assays using fresh Lower Salto sediments indicated SRP release 154 ± 59 μgP g dry wt−1 h−1 when incubated in filter sterilized Salto water at ambient P concentration but retention when incubated in filter sterilized river water amended to 20 mg SRP l−1 2332 ± 58 μgP g dry wt−1 h−1 SRP uptake/release was similar in both control and biocidetreated sediments indicating predominantly abiotic retention High SRP retention even under biologically saturated conditions absence of a DIN response to amendment patterns of desorption following amendment and similar patterns of retention and release under control and biologically inhibited conditions all indicated predominantly abiotic P fluxThe authors gratefully acknowledge support from National Science Foundation grants DEB 9528434 and DEB 0075349 and from the National Research Program Water Resources US Geological Survey We also acknowledge the field assistance of Minor Hildago La Selva Biological Station

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