Evaluating the impact of atmospheric deposition on dissolved trace-metals in the Gulf of Aqaba, Red Sea

• Published in: Marine Chemistry
• Main Authors: Chase, Z, Paytan, A, Beck, A, Biller, D, Bruland, K, Measures, C, Sanudo-Wilhelmy, S
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier Science Bv 2011
• Subjects: Earth Sciences; Oceanography; Chemical Oceanography; North Atlantic
• Online Access: https://doi.org/10.1016/j.marchem.2011.06.005; http://ecite.utas.edu.au/75117

Trace metals in the ocean act as both essential micro-nutrients and as toxins. There are relatively few multielementstudies of dissolved trace metals in the ocean, and none from the Gulf of Aqaba, Red Sea. This semienclosedbasin surrounded by desert is a natural laboratory for studying the impact of atmospheric drydeposition of trace metals on the ocean surface. We have combined measurement of dissolved metals inseawater with measurements of the flux of metals associated with dry deposition. The total dissolved tracemetal concentrations in Gulf of Aqaba water are generally higher (Fe, Cu, Zn, Co, Mn, Pb) or similar (Ni, Al, Cd,Mo) to those measured in the open North Atlantic Ocean. The concentrations of elements that are highlyenriched in aerosols relative to Al (e.g. Cd, Pb, Zn and Cu) are not necessarily proportionally enriched insurface seawater when compared to Al, indicative of the high reactivity of these elements in seawater. Ironconcentrations in the Gulf of Aqaba are high relative to Al, despite the fact that the aerosols are not moreenriched in Fe relative to Al. There may be additional sources of dissolved iron to the Gulf of Aqaba, notassociated with Al. Alternatively, intense photochemically-driven redox cycling may act to enhance Fedissolution from aerosols, or may otherwise increase the lifetime of Fe in the water column, relative to Al.Copper concentrations in the Gulf of Aqaba are close to the value found to be a threshold for Cu toxicity in thisregion. A surface maximum in Cd:P is found in the Gulf of Aqaba, in contrast to the more typical surfaceminimum in this ratio observed in other locations. The surface maximum appears to be driven by atypicallylow uptake of Cd relative to P. A low Cd:P uptake ratio for this region is consistent with known environmentaldeterminants of low Cd:P uptake, such as high concentrations of dissolved Zn and Fe, and a predominance ofsmall phytoplankton including cyanobacteria.