PBDEs Shift Marine Worm Dynamics

Sneaking into oceans via wastewater and the atmosphere, the flame retardants that coat our furniture and electronics can now be found in seafloor sediments worldwide. Researchers have now observed that these polybrominated diphenyl ethers (PBDEs) change how marine worms develop, possibly disrupting the balance of power in sea-bottom ecosystems (Environ. Sci. Technol., DOI: 10.1021/es1012615).

While scientists have studied how PBDEs interfere with fish development, they know little about their effects on invertebrates that live near the seafloor. Marine worms called polychaetes feature prominently in these environments and serve as an important food source for other organisms higher up the food web.

The worms start life as larvae floating in the ocean, but soon settle into the seafloor sediments, where they mature and spend most of their lives. So Rudolf Wu of the City University of Hong Kong and the University of Hong Kong, and his colleagues wanted to know how sediments contaminated with BDE 47, the most common PBDE, might affect the development of three polychaetes species common to the Hong Kong area.

In a laboratory experiment, the researchers presented the larvae of the three species— Pseudopolydora vexillosa, Capitella sp. I, and Polydora cornuta—with a choice of sediments to settle into. These soils included a PBDE-free option and one laced with a high concentration of BDE 47.

After 24 hours, the researchers counted how many larvae of each species had settled into each sediment type. While P. cornuta avoided the soil with high BDE 47 concentrations, Capitella sp. I and P. vexillosa preferred it, picking that option at three- and two-times the rate of P. cornuta, respectively.

Four weeks later, the researchers measured the body lengths of the adult worms as an indicator of their relative fitness. When the scientists examined the larvae that had developed in the high-dose sediment, P. cornuta was about three times smaller than the other two species.

So, Wu says, two worm species appear to benefit from PBDE contamination, while one appears to be at a competitive disadvantage. He adds that these species-dependent responses to the pollutants suggest that interspecies population dynamics could be altered by exposure.

The results are "unusual," says Heather Stapleton, assistant professor of environmental chemistry at Duke University in Durham, N.C., because studies of more complex organisms have mostly shown that PBDE exposure leads to less fit adults. She says that the contaminants may still harm P. vexillosa and Capitella sp. I, since the study did not examine long-term fitness or reproductive effects.

Currently Wu and his team are conducting experiments to determine how the three species behave in contaminated sediments in the ocean and whether P. vexillosa and Capitella sp. I actually outcompete P. cornuta.