As nanomaterials begin to be manufactured in larger quantities in the coming years, scientists are concerned about ecosystems becoming unintentionally contaminated. Nanoparticles behave very differently to macromaterials when it comes to interacting with the environment because of their unique physical, chemical and electronic properties.

John Ferry at the Department of Chemistry at the University of South Carolina and colleagues looked at how gold nanoparticles pass from a water column into the marine food web in three artificially made chambers that mimic an estuarine environment. The mesocosms studied contained seawater, sediment, sea grass, microbes, biofilms, snails, clams, shrimp and fish. The researchers added a single dose of gold nanorods measuring 65 nm long and 15 nm across into each chamber and monitored how the nanomaterials spread through the systems over a period of 12 days.

Using inductively coupled plasma mass spectrometry, Ferry and co-workers observed that the nanoparticles dispersed throughout the three chambers, with clams and biofilms accumulating the most nanoparticles by mass. This could be a serious problem if the same thing happened in the natural environment because biofilms are used as food sources for several different kinds of detritivores, some of which are prey for larger arthropods and small fish. We routinely eat clams, normally after a depuration process because these animals readily take up toxic materials from water. Depuration involves holding the animals in clean water for some time so that they can metabolise or excrete the contaminants they have absorbed.

"Currently, we have no idea what the depuration time would be for shellfish that have taken up synthetic nanoparticles," Ferry told nanotechweb.org.

The researchers say that they are not sure how nanomaterials might transmit through the food web, but that they can be taken up by marine ecosystems, something that certainly highlights the need to study the problem further, says Ferry. "The environmental impact of nanomaterials is likely to track their economic impact, which suggests that funding in this research area should be a high priority."

The team is continuing to study nanoparticle uptake in marine food webs and is now beginning to look at different nanomaterials and additional species. "We have a very friendly and cooperative group of people at South Carolina and will certainly be working in this area for quite a while longer," said Ferry.

The results were published in Nature Nanotechnology.