Effects of ocean acidification on trace metal cycling and bioavailability – clarifying the dust chain
In cooperation with SOPRAN Themes 1 and 2 this sub-project elucidates the interrelations of atmospheric dust deposition, organic matter in seawater, and trace metal cycling on metal bioavailability in context of ocean acidification (OA). We synthesize previous contributions of the trace metal group to SOPRAN on dust deposition (SOPRAN Phase I) and photochemical processes on trace metals (SOPRAN II) at Cape Verde into future projections of trace metal biogeochemistry. The effects of OA on trace metal biogeochemistry have not been assessed in SOPRAN yet, but OA and trace metal biogeochemistry are manifested in the overarching questions of Theme 3 and therefore are addressed here.
We will participate in a mesocosm CO2 enrichment experiment near the Canary Islands in early 2014. In communication with atmospheric chemists and modeling partners within SOPRAN, the actual trace metal and macronutrient solubility from dust in natural seawater was identified as a further key question that needs to be answered in order to achieve the goals set in the overarching key questions of SOPRAN. Thus, controlled laboratory dust solubility experiments using natural seawater and dust collected by atmospheric samplers from Sao Vicente (Cape Verde) are planned. Moreover, we aim to expand the scope of concept from a single metal’s role (Fe) as a limiting nutrient towards a more holistic concept involving the broader composition of biorelevant trace metals (e.g. Mn, Cu, Zn, Cd) and their speciation in seawater. This work is carried out in close cooperation with other SOPRAN sub projects and aims to provide improved parameterizations for ocean biogeochemical modeling. This project directly contributes to the goal of “clarifying the dust chain: how do oceanic physical and biological responses to dust relate to: [trace metal] deposition and solubility, seawater optical properties and photochemistry, macronutrient import, and trace nutrient bioavailability.
PI: K. Wuttig