『Abstract
　The Anllons（oの頭に´） basin (NW Spain) has been included in the Natura 2000 Network and declared as Site of Community Importance. The main contamination problems of the basin come from a former gold mine and from agricultural activities, which influence the quality of the sediment-water system. Phosphorus P) enrichment in the bed sediments was evaluated by analyzing P in the pore waters, in the surface bed sediments, and in the vertical sediment profiles, including both total and bioavailable forms. Two granulometric fractions (＜2 mm and ＜63 μm) were evaluated. Pore waters, bed sediments, and vertical profiles showed high percentages of the bioavailable P fraction with respect to the total P content, which evidences the potential risk of pollution which suppose the bed sediments of the Anllons（oの頭に´） River. The vertical profiles showed P enrichment in the superficial layers, which could be the consequence of the increased use of fertilizers in the last decades. With regards to the granulometric distributions, the ＜63 μm showed, in general, higher P concentrations than the ＜2 mm fraction. However, at the sampling points most heavily contaminated, the concentration of both fractions becomes similar, thus indicating that, at these sites, the coatings formed over sands can retain important P concentrations in the bed sediments.

Keywords: Phosphorus; Bioavailability; Pore water; Sediments; Cores』

1. Introduction
2. Materials and methods
　2.1. Study area
　2.2. Methods
3. Results
　3.1. Pore waters
　3.2. Surface sediments
　3.3. Vertical profiles
　3.4. Statistical analysis
4. Discussion
5. Conclusions
Acknowledgements
References