Major and trace elements in zooplankton from the Northern Gulf of California during summer

Abstract

We report of the distribution of major and trace element concentrations in epipelagic zooplankton collected in the Northern Gulf of California in August 2003. The Bray–Curtis index defined three element assemblages in zooplankton: (1) major metals, which included only two elements, Na (3.6– 17.0%) and Ca (1.0–4.8%). Na had its highest concentrations in the shallow tidally mixed Upper Gulf, where high salinity, temperature, and zooplancton biomass (dominated by copepods) prevailed. Ca showed its highest concentrations south of Ballenas Channel, characterized by tidal mixing and convergence-induced upwelling, indicated by low sea-surface temperature, salinity, and zooplankton biomass; (2) Six biological essential elements, like Fe (80–9,100 mg kg−1) and Zn (20–2,570 mg kg−1), were detected in high concentrations in zooplankton collected near Guaymas Basin, which had high surface temperature and chlorophyll a concentrations. (3) Metals of terrigenous origin, such as Sc (0.01–1.4 mg kg−1) and Th (0.03–2.3 mg kg−1), and redoxsensitive metals, like Co (3–23.8 mg kg−1); this was the assemblage with the largest number of elements (15). Both types of elements had maximum concentrations in the cyclonic eddy that dominates the summer circulation in the Northern region. We concluded that sediment resuspension by tidal mixing in the Upper Gulf, upwelling south of Ballenas Channel, and the cyclonic eddy were key oceanographic features that affected the element concentrations of epipelagic zooplankton in the Gulf of California. Oceanographic mechanisms such as these may contribute to element incorporation in marine organisms in other seas.