Temporal variability of dissolved trace metals at the DYFAMED time-series station, Northwestern Mediterranean

• Published in: Marine Chemistry
• Main Authors: Migon, Christophe, Heimbürger-boavida, Lars-eric, Dufour, Aurélie, Chiffoleau, Jean-francois, Cossa, Daniel
• Format: Text
• Language: English
• Published: Elsevier BV 2020
• Subjects: envir; geo; North Atlantic
• Online Access: https://doi.org/10.1016/j.marchem.2020.103846; https://archimer.ifremer.fr/doc/00635/74691/74602.pdf; https://archimer.ifremer.fr/doc/00635/74691/

We present here results of an 18-month survey (July 2007–March 2009) of a suite of selected trace metals (TM: Co, Ni, Cu, Pb) in a 2350 m-deep offshore water column in the Ligurian Sea (Northwestern Mediterranean Sea). This low-nutrient low-chlorophyll region is characterised by a long stratification period (May–November) during which surface waters are depleted of macronutrients. Trace metals exhibit a range of biogeochemical behaviours from surface-enriched (scavenged-type) to surface-depleted (nutrient-like) with Co and Ni as representative cases. Cobalt (28–172 pM) distributions are governed by external inputs of aeolian dust deposition and removal by adsorption onto particles in surface, intermediate and deep waters as well. Nickel (3.57–5.52 nM) distributions are governed by internal biogeochemical cycles, together with physical mixing and circulation patterns. Nickel is primarily removed from surface waters with biogenic particles and then remineralised at depth. Copper (1.39–2.89 nM) distributions illustrate a mixture of the two typical behaviours mentioned above. Distributions of typically anthropogenic and particle-reactive Pb (82–235 pM) are in agreement with a Mediterranean flow source of Pb for the adjacent North Atlantic Ocean. The mechanisms controlling the biogeochemical cycling of TMs, such as atmospheric inputs, physical forcing, and interactions with primary production, are discussed according to the TM physico-chemical properties and biological importance.