"Phosphorus retention in a lowland Neotropical stream following an eig" by Gaston E. Small, Marcelo Ardón et al.

US Geological Survey

 

Document Type

Article

Date of this Version

2015

Citation

2016 by The Society for Freshwater Science

DOI: 10.1086/684491

Comments

Freshwater Science. 2016. 35(1):1–11

Abstract

Human alteration of the global P cycle has led to widespread P loading in freshwater ecosystems. Much research has been devoted to the capacity of wetlands and lakes to serve as long-term sinks for P inputs from the watershed, but we know much less about the potential of headwater streams to serve in this role. We assessed storage and retention of P in biotic and abiotic compartments after an 8-y experimental P addition to a 1st-order stream in a Neotropical wet forest. Sediment P extractions indicated that nearly all P storage was in the form of Fe- and Al-bound P (∼700 μg P/g dry sediment), similar to nearby naturally high-P streams. At the end of the enrichment, ∼25% of the total P added over the 8-y study was still present in sediments within 200 m of the injection site, consistent with water-column measurements showing sustained levels of high net P uptake throughout the experiment. Sediment P declined to baseline levels (∼100 μg P/g dry sediment) over 4 y after the enrichment ended. Leaf-litter P content increased nearly 2× over background levels during P enrichment and was associated with a 3× increase in microbial respiration rates, although these biotic responses were low compared to nearby naturally high- P streams. Biotic storage accounted for <0.03% of retention of the added P. Our results suggest that the high sorption capacity of these sediments dampened the biotic effects of P loading and altered the timing and quantity of P exported downstream.

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