Publication Date:
2024-02-07
Description:
Some heavy metals e.g., zinc, copper or manganese serve as micronutrients for eukaryotic life and play an important role for the cellular metabolism, growth of organisms, reproduction and enzymatic activity. However, other metals like mercury or lead are not known to have any
beneficial effects for organisms and are believed to have a higher toxic potential. Heavy metals occur naturally in the environment. However, in higher concentrations, they become toxic and have hazardous effects on marine biota. Furthermore, they are highly persistent in the marine environment as they are not readily degraded by organisms. Pollution originating from anthropogenic sources, e.g., mining, industry and extensive land use, increased the heavy metal concentration in certain areas above a critical level. Especially temperate and tropical coastal environments act as natural catchment for anthropogenic pollutants because these areas are densely populated and highly affected by industry, agriculture and urban runoff. Therefore, it
is vitally important to assess past heavy metal distributions, spatially and temporally and to
compare those with recent pollution in order to evaluate contemporary emission reduction
measures.
The chemistry of the tests of benthic foraminifera and the skeletons of scleractinian corals are widely used for the reconstruction of changes in past environmental conditions including temperature, salinity and carbonate system parameters. Recent studies further demonstrated that the trace metal concentration in the aragonite of corals and the calcite of foraminifera is linked to that in seawater. Therefore, the geochemical analysis of coral skeletons and foraminiferal tests offers the opportunity to gain insights into past heavy metal concentrations in seawater, which can in turn help to improve coastal management. However, it is important to understand distribution patterns, ecological and environmental factors influencing the organism itself and associated species in order to evaluate which species is suitable and representative for a certain area. Therefore, the living and dead foraminiferal assemblage along a transect in the German North Sea was investigated. The results of this study indicate that transport via tidal currents is the dominant environmental factor shaping the foraminiferal assemblages. Haynesina germanica, Ammonia batava and different Elphidium species from the living foraminiferal fauna depict a close linkage between open North Sea areas like Helgoland and the mainland. These species share an opportunistic behaviour and are able to occupy a variety of environments rendering them as possible proxy-carriers for heavy metal contamination in seawater. Nevertheless, an application of the heavy metal concentration in the calcium carbonate of both of the organism groups will only be possible after a calibration of this proxy. Therefore, benthic foraminifera from temperate environments (Ammonia aomoriensis, Ammonia batava and Elphidium excavatum) and tropical corals (Porites lichen and Porites lobata) were exposed to 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) over a wide concentration range. High frequency water monitoring in combination with laser ablation ICP-MS measurements of the calcium carbonate, which was precipitated during the culturing period, revealed the uptake of some of these metals mainly depends on its concentration in seawater, which is indicated by strong positive correlations between the metal concentration in seawater and in the calcium carbonate. All three foraminiferal species showed a strong positive correlation between Pb and Ag in the water and their calcite. Ammonia aomoriensis further revealed a correlation with Mn and Cu, Ammonia batava with Mn and Hg and Elphidium excavatum with Cr and Ni, and partially also with Hg. Zinc, Sn and Cd showed no clear trends in all three foraminiferal species studied, which in case of Cd may be due to the exposure to more than one metal at a time. The investigated coral species revealed a positive correlation between the trace metal concentration in seawater and in the coral skeleton for Cr, Mn, Ni, Zn, Ag, Cd and Pb. No correlation was found for Cu, Sn and Hg. The calculated partitioning coefficients (DTE) allow a determination of the heavy metal concentrations in seawater. Therefore, the trace element concentration in benthic foraminifera and in scleractinian corals provides a promising tool for ecosystem status assessments in the future, which can serve as a deciding support for governments and environmental agencies.
Type:
Thesis
,
NonPeerReviewed
Format:
text
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