Program     Biogeochemical processes in land-ocean interfaces, surface estuaries, subterranean estuaries and sediment-water interface       1010 Trace element cycling in coastal systems (GEOTRACES): riverine and benthic supplies and control by oxygen Monday 7th @ 1010-1030, Conference Room 1 Eric Achterberg* , GEOMAR Insa Rapp, GEOMAR Lucia Vieira, GEOMAR Mark Hopwood, GEOMAR Stephan Krisch, GEOMAR Tom Browning, GEOMAR Martha Gledhill, GEOMAR Jan Scholten, University of Kiel Presenter Email: eachterberg@geomar.de The distinctive physical-biogeochemical environment of shelf seas results in these regions being 3-4 times more productive than typical oceanic systems, supporting 90% of global fish catches. Deoxygenation is globally affecting many shelf seas, and glacier and sea-ice melt is influencing Arctic systems. However, our understanding of sources and controls on trace elements (incl Fe) in these systems is limited. Shelf sediments, rivers and glacier melt are major contributors of iron (Fe) and other bioessential trace metals to shelf seas and also adjacent ocean systems. Resolving the processes that determine trace metal supply, and also their stabilisation preventing loss by scavenging and precipitation, and facilitating off shelf transport is essential for our understanding of current and future ocean productivity. To this end, we will present a range of GEOTRACES studies in contrasting shelf systems (Peru, Namibia, Arctic) where we diagnose the supply and biogeochemical processes using oxygen levels and tracers including Ra isotopes, Al, Mn, and assess implications for off shelf transport.

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