Graduation Year


Document Type




Degree Name

Master of Science (M.S.)

Degree Granting Department

Marine Science

Major Professor

Dr. Norman J. Blake

Committee Member

Dr. Robert H. Byrne

Committee Member

Dr. Joseph J. Torres


A study was conducted to examine the influence of elevated inorganic phosphate and trace metal concentrations on the uptake and distribution of Zn65 and Mn54 into the body tissue and phosphoritic renal concretions of a subtropical estuarine bivalve, Mercenaria campechiensis. Chronological sampling of gills, mantle, adductor muscle, viscera, kidneys, and renal granules using gamma ray spectrometry allowed examination of both tissue distribution and accumulation patterns over time. The kidney was the principal site of Mn54 accumulation whereas Zn65 was concentrated in both the gill and the kidney. The gill initially accumulated zn65 three times faster than the kidney and reached a steady state concentration after about five days. The kidney exhibited a linear accumulation throughout the ten day study for both Zn65 and Mn54 without obtaining a steady state concentration.

Elevated total Zn and Mn concentrations caused increased accumulation levels to the kidney and stimulated general metal uptake and distribution rates. Elevated dissolved phosphate seemed to increase the metal excretion rate by increasing the excretion of metal containing phosphoritic renal granules. Large concretions (up to 400 microns) occur in the kidney lumen of this bivalve and are thought to result from the aggregation of smaller intracellular granules. Results from this study suggest that renal concretions function as both a long and short term detoxification response to elevations in the concentration of potentially toxic metals. Evidence also suggests that much of the metal metabolism involving the kidney, and consequently the general tissue distribution of metals, depends on the processes which control formation and excretion of these concretions.