Bajacalifornian dust deposition and atmospheric input of iron to the Gulf of California during the summer

Abstract

Iron (Fe) is an essential micronutrient for all living organisms and its atmospheric supply to the surface waters of marginal seas remains poorly understood. Here we report the seasonal and spatial variability of atmospheric mineral dust deposition and Fe fluxes along the west coast of the Gulf of California (GC). Meteorological data and dust samples were collected from June 2010 to October 2013 at three sites of the eastern side of Baja California Peninsula (BCP). Evidence of an across-BCP wind component (W-E) during the warm season (May–September) was found, suggesting that winds crossing the BCP from west to east were an important source of variability. Coincidently, dust deposition at the northern and center sites were significantly (p < .05) higher during the warm season, revealing that the BCP could be an important source of dust and Fe to the GC during the warm months. An analysis of the total Fe concentration and Fe/Al ratios also suggest that the BCP and the Mojave Desert are potential sources of the dust arriving to the northern and central region of the GC. Our total averages of dust and Fe fluxes were comparable to those reported for other marginal seas (e.g., Mediterranean, Aqaba) similarly influenced by inputs of mineral dust from the surrounding deserts. A comparison between fluxes show that atmospheric soluble Fe inputs are equivalent to between 6 ± 4% (cool season) and 71 ± 40% (warm season) of the dissolved Fe supplied by upwelling. Thereby, during the warm season, when the GC is warmer and strongly stratified, atmospheric deposition represents a significant source of soluble Fe. We estimate that this supply of Fe would be enough to meet the requirements of N2-fixing primary producers that reside in the oligotrophic surface waters of summer.