2015 Al and Fe concentrations. Dissolved Al (A) and Fe (D) concentrations in the sea surface microlayer (SML) and underlying water column (UWC) in the Summerland Key Bay (SB; solid red circles = SML; open red triangles = UWC) and Looe Key National Marine Sanctuary (LK; solid black circles = SML; open black triangles = UWC). Total particulate Al (B) and Fe (E) concentrations in the SML and UWC in the SB and LK. Total Al (C) and Fe (F) concentrations in 24-hour integrated aerosol samples. Solid red lines show the average microlayer concentrations and the dashed red lines show the average water column concentrations. DOI: https://doi.org/10.1525/elementa.237.f8