Comparative Distributions of Alkalies, Alkaline Earths and Lead among Major Tissues of the Tuna Thunnus alalunga

Abstract

The occurrences of K, Rb, Cs, Ca, Sr, Ba and Pb have been determined in various tissues of the tuna fish Thunnus alalunga. K, Rb, and Cs are distributed uniformly throughout the organs of the fish; 95% of the ca and Sr, and 70% of the Ba and Pb are contained in the skeleton. It is found that there are smaller amouts of Cs, Ba and Pb associated with the nutrient metals K and Ca in a marine animal compared to a terrestrial animal. This difference is a result of the purity of K and Ca in sea-water and the smaller amounts of trace metals associated with them compared to the impurity of K and Ca in terrestrial rocks. Food-chain enhancement and depletion of metals can be evaluated by comparing rations of trace metals to abundant nutrient metals in seawater and tuna. Cs is enriched relative to K in going from seawater to tuna by a factor of 13. Sr and Ba are both depleted by factors of 5 relative to Ca in going from seawater to tuna, while Pb is enriched relative to Ca by a factor of 14. Special clean laboratory procedures were used to prepare samples for accurate analysis by stable isotope dilution mass spectrometric techniques.