The Occurrence and Distribution of Ca, Sr, Ba, and Pb in Marine Ecosystems

Citation

Burnett, Michael Welch (1980) The Occurrence and Distribution of Ca, Sr, Ba, and Pb in Marine Ecosystems. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/6b1e-bw74. https://resolver.caltech.edu/CaltechTHESIS:03112024-200920705

Abstract

Processes of enrichment and depletion of Pb, Ba, and Sr relative to Ca in transfers between trophic levels of selected marine ecosystems were studied using ultra-clean laboratory techniques and stable isotope dilution mass spectrometry. Metal relationships between cellular subfractions of marine algae and major Ca reservoirs of consumer animals show that at the primary producer level large bioenrichments in the Pb/Ca ratio occur on algal surfaces as a result of selective chelation of soluble Pb by extra­ cellular algal polysaccharides. This is followed by biopurification of Ca with respect to Pb during active transport of Ca from surfaces to interiors of algal cells and during subsequent transfers to consumer animals at successively higher trophic levels of marine food chains.

Ca, Sr, Ba, and Pb share covariant and coincident distributions in marine organisms, residing chiefly in cell wall mucilages of algae and skeletons of animals. Pb/Ca ratios of major Ca reservoirs in marine biota correlate with variations in the Pb/Ca ratio of source reservoirs which result from different ambient concentrations of industrial Pb in seawater. Pb/Ca ratios of gastropod shell layers correlate directly with Pb/Ca ratios of food but inversely with organism size. The partitioning of Pb between shell layers generally favors calcite relative to aragonite but is influenced by species, size, and ambient environmental Pb concentrations.

A linear model of the pelagic food web based on data of this and another recent study indicates that recycling of organic matter in food chains does not act as a continuous extraction process by which Pb becomes most concen­trated at the highest trophic levels.

A model of biological fluxes of Pb through the surface mixed layer of the NE Pacific indicates that sinking of zooplankton fecal pellets containing Pb-rich phytoplankton debris satisfies geochemical constraints requiring a short residence time of Pb in these waters and is an important mode of vertical mass transport of Pb.

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