Trace metal concentration in blood of the Kemp's ridley sea turtle (Lepidochelys kempii)

Abstract

Trace metal concentration was analyzed from the blood of 106 critically endangered Kemp's ridley sea turtles (Lepidochelys kempii), captured off the coast of Texas and Louisiana during June-October 1994 and May-August 1995. These analyses characterized the level of five trace metals in Kemp's ridleys and compared these levels in headstart and wild cohorts as well as between the sexes. Overall, copper, lead, mercury, silver and zinc levels in the blood of Kemp's ridleys were: copper (range = 215-1,300 ng/g, mean = 524 ng/g), lead (range = 0.00-34.3 ng/g, mean = 1 1.0 ng/g), mercury (range = 0.50-67.3 ng/g, mean = 18.0 ng/g), silver (range = 0.042-2.74 ng/g, mean = 0.94 ng/g) and zinc (range = 3,280-18,900 ng/g, mean = 7,500 ng/g). Metal concentration appeared to reflect dietary uptake. There were no significant differences between mean trace metal concentration in whole blood of headstart, wild, female and male ridleys. Copper, mercury and zinc concentration exhibited significant positive relationships with size of turtle. Female ridleys displayed a stronger positive correlation between mercury and zinc concentration and turtle size than did male counterparts. Trace metal blood levels in ridleys were lower than tissue levels reported in the literature for marine and freshwater turtles, other reptiles, invertebrates, fish, marine birds and mammals. The present study indicates that analysis of blood for trace metals is an effective method to detect and monitor trace metal levels in living sea turtles. Future research needs include a synoptic analysis of trace metals in blood and selected tissues and comparison of resulting concentrations.