Tracing the impact of coastal water geochemistry on the Re-Os systematics of macroalgae: Insights from the basaltic terrain of Iceland

Sproson, Adam D.; Selby, David; Gannoun, Abdelmouchine; Burton, Kevin W.; Dellinger, Mathieu; Lloyd, Jeremy M.

Abstract

This study presents rhenium (Re) and osmium (Os) elemental and isotope data for macroalgae, dissolved load and bed load from Icelandic coastal and/or river waters, an environment adjacent to predominantly basaltic terrains, ranging in age from historic to ca. 12 Ma. Both the Re (0.1 to 88.4 ppb) and Os (3.3 to 254.5 ppt) abundance in macroalgae are shown to be primarily controlled by uptake from the dissolved load of local seawater and are largely dependent on the relative influence of local freshwater inputs. Incorporation of Re and Os into macroalgae appears to be complicated by additional Re and Os uptake from the bed load. The 187Os/188Os (0.16 to 0.99) composition of macroalgae is highly variable and is explained in terms of an unradiogenic187Os/188Os contribution from rivers draining younger basaltic catchments that have undergone congruent weathering (and/or hydrothermal input), and a radiogenic 187Os/188Os contribution from two distinct sources: rivers draining older catchments that have undergone incongruent weathering of radiogenic primary basaltic minerals; and, North Atlantic seawater. The 187Re/188Os composition (~65 to 40,320) of macroalgae traces that of water, with higher values associated with higher salinity waters, but far exceeds the 187Re/188Os of water due to the preferential uptake of Re over Os by macroalgae in areas of high dissolved and/or bed load Re abundances. This study substantiates the utility of macroalgae as a proxy for the long‐term (months to years) average 187Os/188Os composition of seawater, which holds the potential to elucidate a range of Earth system and anthropogenic processes.

Citation

Sproson, A. D., Selby, D., Gannoun, A., Burton, K. W., Dellinger, M., & Lloyd, J. M. (2018). Tracing the impact of coastal water geochemistry on the Re-Os systematics of macroalgae: Insights from the basaltic terrain of Iceland. Journal of Geophysical Research: Biogeosciences, 123(9), 2791-2806. https://doi.org/10.1029/2018jg004492

• Journal Article Type: Article
• Acceptance Date: Aug 2, 2018
• Online Publication Date: Sep 13, 2018
• Publication Date: Sep 13, 2018
• Deposit Date: Aug 20, 2018
• Publicly Available Date: Mar 13, 2019
• Journal: Journal of Geophysical Research: Biogeosciences
• Print ISSN: 2169-8953
• Electronic ISSN: 2169-8961
• Publisher: American Geophysical Union
• Peer Reviewed: Peer Reviewed
• Volume: 123
• Issue: 9
• Pages: 2791-2806
• DOI: https://doi.org/10.1029/2018jg004492
• Public URL: https://durham-repository.worktribe.com/output/1316874