PCBs in eggs linked to lower survival of young turtles.

Sep 03, 2009

Eisenreich, KM, SM Kelly and CL Rowe. Latent mortality of juvenile snapping turtles from the upper Hudson River, New York, exposed maternally and via the diet to polychlorinated biphenyls (PCBs). Environmental Science and Technology doi:10.1021/es9008344.

Environmental Science and Technology
DOI: 10.1021/es9008344
 

Synopsis by Karen Kidd

A mother's contribution of pollutants to her offspring is more important to the survival of a young turtle than its exposure through food, according to this wildlife study that compared the long-term effects of PCBs from both sources.

A mother turtle's lifetime exposure to PCBs is more influential to the health and well being of her progeny than the exposure they get through their post-hatch diet, report researchers in a recent edition of Environmental Science and Technology.

The snapping turtles that were exposed to higher – yet environmentally relevant – levels of PCBs during development in their eggs started dying at eight months of age and almost half did not survive to 14 months when the study ended. In contrast, almost all (90 percent) of the turtles of the same age that were exposed to lower egg PCB levels survived, regardless of the PCB levels in their diet after hatching.

The results show for the first time that it is exposure from the mother, and not diet, that has more serious consequences for survival of these turtles. Additionally, the most severe effect – death – was only seen after an 8-month delay.

Female turtles deposit the pollutants into their eggs where the developing young are exposed to them. Based on the results from this recent study, it is very likely that the numbers of wild snapping turtles living in PCB “hotspots” are reduced.

PCBs are a group of chlorinated contaminants that were used in transformers, capacitors, oils, paints, and electronics in North America until the late 1970s. They were heavily used in industrial applications because of their non-flammability, resistance to heat, insulating properties and chemical stability.

The chemicals' widespread contamination of the environment occurred because of their heavy use, improper disposal, resistance to breakdown and ability to move long distances in air and water currents. They congregate in fat and can concentrate through food chains to levels that can cause health effects for wildlife and humans exposed to the pollutants through their diets.

PCBs have been linked to cancers in animals, and they are considered to be probable carcinogens in humans. Effects on the immune, nervous and reproductive systems have been documented in wildlife and humans. 

Birds, fish and turtles deposit the pollutants into their eggs, but the effects of these chemicals on the offspring are still under study.

In this recent study, eggs of common snapping turtles were collected from 16 nests in clean or contaminated sites (PCB “hotspots”) in New York state. The eggs were either incubated in the lab at a temperature that produces only males or frozen for later PCB analysis.

Hatchlings from the clean and contaminated sites were then raised either on food – containing 83 parts per billion PCBs – collected from the clean site or food – containing 5,955 parts per billion PCBs – collected from the contaminated site. The researchers compared survival and growth rates of both groups to understand whether PCBs from their mothers, their diets or a combination of the two most affected the health of the young turtles.

The results were surprising because of the delay in symptoms and severity in effects of the PCBs. After 8 to 9 months, the young turtles that were exposed to the higher PCB levels from their mothers started to die; no effects on survival were seen before this time. This delayed mortality has not been observed before, most likely because these types of studies typically end earlier.

In addition, PCBs in the diet of the turtles did not cause greater mortality than the maternal exposure alone. At 14 months when the study ended, only 40 percent of the turtles from the contaminated sites survived compared to 90 percent of the turtles from the clean area.

Snapping turtles are the largest of the freshwater turtles and can live more than 40 years. They mature between 5 and 7 years old and feed on a wide variety of aquatic life including plants, fish, insects and amphibians. The turtles range is throughout the middle and eastern United States as well as in parts of Canada.