Abstract
Abstract. Heavy metal pollution originating from anthropogenic sources, e.g. mining, industry and extensive land use, is increasing in many parts of the world and influences coastal marine environments even after the source has ceased to pollute. The elevated input of heavy metals into the marine system potentially affects the biota because of their toxicity, persistence and bioaccumulation. An emerging tool for environmental applications is the heavy metal incorporation into foraminiferal calcite tests, which facilitates monitoring of anthropogenic footprints on recent and past environmental systems. The aim of this study was to investigate whether the incorporation of heavy metals into foraminifera is a direct function of their concentration in seawater. Culturing experiments with a mixture of dissolved chromium (Cr), manganese (Mn), nickel (Ni), copper (Cu), zinc (Zn), silver (Ag), cadmium (Cd), tin (Sn), mercury (Hg) and lead (Pb) in artificial seawater were carried out over a wide concentration range to assess the uptake of heavy metals by the nearshore foraminiferal species Ammonia aomoriensis, Ammonia batava and Elphidium excavatum. Seawater analyses revealed increasing concentrations for most metals between culturing phases and high metal concentrations in the beginning of the culturing phases due to sudden metal addition. Furthermore, a loss of metals during the culturing process was discovered by an offset between the added and the actual concentrations of the metals in seawater. Laser ablation ICP-MS (inductively coupled plasma mass spectrometry) analysis of the newly formed calcite revealed species-specific differences in the incorporation of heavy metals. The foraminiferal calcite of all three species exhibited Pb and Ag concentrations strongly correlated with concentrations in the seawater culturing medium (partition coefficients and standard deviation for Ag – Ammonia aomoriensis, 0.50 ± 0.02; Ammonia batava, 0.17 ± 0.01; Elphidium excavatum, 0.47 ± 0.04; for Pb – Ammonia aomoriensis, 0.39 ± 0.01; Ammonia batava, 0.52 ± 0.01; Elphidium excavatum, 0.91 ± 0.01). Ammonia aomoriensis further showed a correlation with Mn and Cu, A. batava with Mn and Hg, and E. excavatum with Cr and Ni and partially also with Hg. However, Zn, Sn and Cd showed no clear trend for the species studied, which in the case of Sn was maybe caused by the lack of variation in the seawater Sn concentration. The calibrations and the calculated partition coefficients render A. aomoriensis, A. batava and E. excavatum as natural archives that enable the determination of variations in some heavy metal concentrations in seawater in polluted and pristine environments.
Highlights
Particular heavy metals, for example, zinc (Zn), iron (Fe), molybdenum (Mo), cobalt (Co) and copper (Cu), serve as micronutrients (e.g. Hänsch and Mendel, 2009) for eukaryotic life and play an important role in the metabolism, growth, reproduction and enzymatic activity of organisms (e.g. MartínGonzález et al, 2005; Gallego et al, 2007)
Culturing experiments with a mixture of dissolved chromium (Cr), manganese (Mn), nickel (Ni), copper (Cu), zinc (Zn), silver (Ag), cadmium (Cd), tin (Sn), mercury (Hg) and lead (Pb) in artificial seawater were carried out over a wide concentration range to assess the uptake of heavy metals by the nearshore foraminiferal species Ammonia aomoriensis, Ammonia batava and Elphidium excavatum
We present results from culturing studies with Ammonia aomoriensis, Elphidium excavatum and Ammonia batava assessing the relationship between heavy metal concentrations in seawater and foraminiferal tests
Summary
Particular heavy metals, for example, zinc (Zn), iron (Fe), molybdenum (Mo), cobalt (Co) and copper (Cu), serve as micronutrients (e.g. Hänsch and Mendel, 2009) for eukaryotic life and play an important role in the metabolism, growth, reproduction and enzymatic activity of organisms (e.g. MartínGonzález et al, 2005; Gallego et al, 2007). Other metals like mercury (Hg), on the other hand, are not known to have any positive effect on the body and are believed to have higher toxic potential (Jan et al, 2015) All these metals occur naturally in the environment as geogenic traces in soils, water and rocks and, in plants and animals. Schmidt et al.: Heavy metal uptake of benthic foraminifera during culturing experiments as elements with a density > 7 g cm−3 (Venugopal and Luckey, 1975) and an atomic number beyond calcium (Bjerrum, 1936; Thornton, 1995) They are highly persistent in the marine environment and are not excreted by organisms after the uptake of these metals into their system and cells (Flora et al, 2012; Kennish, 2019). Coastal environments act as natural catchments for anthropogenic pollutants because these areas are directly affected by industry, agriculture and urban runoff (e.g. Alloway, 2013; Julian, 2015; Tansel and Rafiuddin, 2016)
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