Premium
Widespread Increases in Iron Concentration in European and North American Freshwaters
Author(s) -
Björnerås C.,
Weyhenmeyer G. A.,
Evans C. D.,
Gessner M. O.,
Grossart H.P.,
Kangur K.,
Kokorite I.,
Kortelainen P.,
Laudon H.,
Lehtoranta J.,
Lottig N.,
Monteith D. T.,
Nõges P.,
Nõges T.,
Oulehle F.,
Riise G.,
Rusak J. A.,
Räike A.,
Sire J.,
Sterling S.,
Kritzberg E. S.
Publication year - 2017
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1002/2017gb005749
Subject(s) - biogeochemical cycle , biogeochemistry , environmental science , total organic carbon , deposition (geology) , ecosystem , environmental chemistry , physical geography , ecology , earth science , geography , chemistry , geology , sediment , biology , paleontology
Recent reports of increasing iron (Fe) concentrations in freshwaters are of concern, given the fundamental role of Fe in biogeochemical processes. Still, little is known about the frequency and geographical distribution of Fe trends or about the underlying drivers. We analyzed temporal trends of Fe concentrations across 340 water bodies distributed over 10 countries in northern Europe and North America in order to gain a clearer understanding of where, to what extent, and why Fe concentrations are on the rise. We found that Fe concentrations have significantly increased in 28% of sites, and decreased in 4%, with most positive trends located in northern Europe. Regions with rising Fe concentrations tend to coincide with those with organic carbon (OC) increases. Fe and OC increases may not be directly mechanistically linked, but may nevertheless be responding to common regional‐scale drivers such as declining sulfur deposition or hydrological changes. A role of hydrological factors was supported by covarying trends in Fe and dissolved silica, as these elements tend to stem from similar soil depths. A positive relationship between Fe increases and conifer cover suggests that changing land use and expanded forestry could have contributed to enhanced Fe export, although increases were also observed in nonforested areas. We conclude that the phenomenon of increasing Fe concentrations is widespread, especially in northern Europe, with potentially significant implications for wider ecosystem biogeochemistry, and for the current browning of freshwaters.