Abstract
Coastal eutrophication is expected to increase due to expanding and intensifying agriculture which causes a large amount of soil-associated P to be transported into aquatic systems. We performed anaerobic long-term incubations on field soil to mimic the conditions that eroded soil encounters in brackish sediments. The release of P from soil increased with the amount of labile organic C (acetate) addition and decreased with the soil/solution ratio. We deduce that in less-productive brackish systems, microbial Fe reduction allows for the maintenance of the coupled cycling of Fe and P and restricts the amount of P entering the oxic water. In more eutrophic systems, the formation of Fe sulfides as a result of SO4 reduction inactivates Fe, and leads to a higher release of P, thus generating an adverse feedback effect. The dependence of the fate of soil-bound Fe and P on the trophic status of the receiving water should be recognized in eutrophication management.
Highlights
Agricultural phosphorus (P) losses cause eutrophication and hypoxia in coastal waters (Conley et al 2011)
The release of P correlated inversely with SO4 concentration (Fig. 5a), i.e., positively with SO4 consumption. This pattern can be explained by the collapse of the P binding ability of Fe by sulfides formed as a result of SO4 reduction
The redox-states, pH, and the concentrations of Mn, Fe, SO4, and H2S prevailing at the end of incubations were typical of those found in the sediments of brackish systems, such as the open and coastal Baltic Sea
Summary
Agricultural phosphorus (P) losses cause eutrophication and hypoxia in coastal waters (Conley et al 2011). Phosphorus is transported from arable land to waters in two major forms: (1) dissolved, readily bioavailable P and (2) soil-bound P that has to be released into a dissolved form before incorporation by biota. To design efficient agri-environmental measures, the eutrophying effect of soil-bound P should be known. This knowledge is important as agricultural production is expected to expand and intensify (Tilman et al 2002), and the changing climate may further increase erosion (Puustinen et al 2007)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
