Credit: Hans Peter Schaefer

The flux of dust from North Africa represents a major nutrient and contaminant source to the Atlantic Ocean. A new study shows that the majority of dust at one site comes from a single source region in Morocco.

Valérie Chavagnac at the National Oceanography Centre, Southampton, UK, and colleagues1 analysed a year-long time series of sediments collected near the ocean floor at the Madeira Abyssal Plain in the subtropical northeast Atlantic Ocean. The highest flux of dust particles to the seafloor occurred between January and March. Transient dust events also produced brief periods of high particle flux. As previously suggested, the types of clays found and the rare earth element composition of the grains suggests they were blown from North Africa. The strontium isotope ratio and the occurrence of palygorskite allow a more precise characterization of the dust and suggest a single source area in the Anti–Atlas Moroccan Chain.

This dust flux delivers, on average, 0.08 and 0.005 μmol m−2 per day of dissolved iron and phosphorus, respectively, to the surface ocean. Large dust events can raise these values by a factor of four. The addition of these nutrients, which are generally limiting factors in this setting, can fuel blooms of nitrogen-fixing bacteria and phytoplankton.