The green sea turtle (Chelonia mydas) owes its name not to the color of its outer shell, typically in shades of brown and yellow, but to a diet of chlorophyll-containing algae that imparts a faintly green color to the fat beneath its skin. Once commonly known as the edible turtle, this species of marine reptile is the traditional main ingredient in turtle soup, a culinary exploitation that contributed to their worldwide decline during the past century. While various international regulations now protect green sea turtles from the boiling pot, a new adversary has emerged – fibropapillomatosis. Producing numerous debilitating tumors on the skin and internal organs of the turtle, this disease is likely caused by the combined effects of viral infection and exposure to environmental toxins. One such toxin, lyngbyatoxin A, is a tumor-promoting substance produced by cyanobacteria that grow alongside the algae of the turtle's "green" diet.
Arthur, K. E.; Limpus, C. J.; Roelfsema, C. M.; Udy, J. W.; Shaw, G. R. A bloom of Lyngbya majuscula in Shoalwater Bay, Queensland, Australia: an important feeding ground for the green turtle (Chelonia mydas). Harmful Algae 2006, 5 (3), 251-265. Lyngbya majuscula, a toxic cyanobacterium, was obsd. blooming during June-July (winter) 2002 in Shoalwater Bay, Queensland, Australia, an important feeding area for a large population of green turtles (Chelonia mydas). The bloom was mapped and extensive mats of L. majuscula were obsd. overgrowing seagrass beds along at least 18 km of coast, and covering a surface area of more than 11 km2. Higher than av. rainfall preceded the bloom and high water temps. in the preceding summer may have contributed to the bloom. In bloom samples, lyngbyatoxin A (LA) was found to be present in low concn. (26 μg kg-1(dry weight)), but debromoaplysiatoxin (DAT) was not detected. The diet of 46 green turtles was assessed during the bloom and L. majuscula was found in 51% of the samples, however, overall it contributed only 2% of the animals' diets. L. majuscula contribution to turtle diet was found to increase as the availability of the cyanobacterium increased. The bloom appeared to have no immediate impact on turtle body condition, however, the presence of a greater proportion of damaged seagrass leaves in diet in conjunction with decreases in plasma concns. of sodium and glucose could suggest that the turtles may have been exposed to a substandard diet as a result of the bloom. This is the first confirmed report of L. majuscula blooming in winter in Shoalwater Bay, Queensland, Australia and demonstrates that turtles consume the toxic cyanobacterium in the wild, and that they are potentially exposed to tumor promoting compds. produced by this organism.
