Accumulation of phosphorus in coastal marine sediments: relationship to benthic and diffusive fluxes

Rocio Ponce,Jesús M Forja,Abelardo Gómez-Parra,Teodora Ortega

doi:10.3989/scimar.2010.74s1115

Abstract

Sedimentary phosphorus was characterized in sediment cores from 3 coastal ecosystems of the Gulf of Cadiz. High spatial variability was observed in total phosphorus (from 445 to 20291 μg g.sed -1 ) and in the other phosphorus phases studied. This variability correlates with the proximity of the 10 sampling stations to sources of urban and/or industrial effluent in the zone. The benthic and diffusive fluxes were measured concurrently with sediment collection at these stations. The measured values of benthic fluxes range between –14 and 6 mmol m -2 d -1 . Generally, stations that showed increased interstitial phosphate concentrations with increasing depth were characterized by positive values in phosphate benthic fluxes and by high percentages of reactive forms of sedimentary phosphorus. Negative benthic fluxes were associated with stations receiving more anthropogenic matter, which showed progressively decreasing phosphate concentrations in the interstitial water with depth. In these anthropogenic areas, the non-reactive forms of phosphorus (those associated with ferric oxyhydroxide and authigenic carbonate fluorapatite) are abundant, and reach values exceeding 75% of total phosphorus in sediment.

Highlights

IntroductionPhosphorus is a key element in biogeochemical cycles, and is believed to act as a limit to marine productivity (Berner et al, 1993; Ruttenberg, 1993)
Being an essential nutrient, phosphorus is a key element in biogeochemical cycles, and is believed to act as a limit to marine productivity (Berner et al, 1993; Ruttenberg, 1993)
These profiles can be seen to be very irregular at some stations, as a consequence of organic matter remineralization and subsequent phosphate removal from interstitial water due to authigenic mineral formation

Summary

Introduction

Phosphorus is a key element in biogeochemical cycles, and is believed to act as a limit to marine productivity (Berner et al, 1993; Ruttenberg, 1993). An important characteristic of phosphorus is that it can be transferred from seawater to the sediment. Sedimentary phosphorus has been the subject of a number of studies, mainly because of its role in the eutrophication of marine and freshwaters. Phosphorus is deposited in sediments in several ways: through incorporation in organic matter, through inclusion in apatite and calcium carbonate minerals, and through association with hydrous ferric oxides Once incorporated into the sediment, phosphorus undergoes transformations itself, determined by the physicochemical characteristics of the sediment (Sundy et al, 1992; Lucotte et al, 1994; Louchouarn et al, 1997)

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