Too tiny to see or touch, manmade nanoparticles are increasingly becoming a by-product of industry and chemical and pharmaceutical technology. But once these super small materials enter the water supply, do they reach coastal areas and enter salt marshes and tidal zones, where shellfish and finfish grow?
Researchers at the University of South Carolina's Nanocenter, working with scientists at the National Oceanic and Atmospheric Administration in Charleston, examined whether gold nanorods could readily pass from water to the marine food web.
Their findings, published in this week's edition of Nature Nanotechnology, suggest that nanoparticles move easily into the marine food web and are absorbed in marsh grasses, trapped in biofilms and consumed by filter feeders, such as clams. "This is the first study to report on the fate of gold nanoparticles in a complex ecosystem containing sediments, biofilms, grasses, microscopic organisms, filter feeders and omnivores," said environmental chemist Dr. John L. Ferry of the University of South Carolina.
The gold nanorods - rod-shaped nanomaterials that have applications for medicine and even adding color to stained glass - were used for this study because of their ability to be traced, he said.
For the study, scientists at the Coastal Center for Environmental Health and Biomolecular Research (CCEHBR), one of NOAA's National Centers for Coastal Ocean Science, created three estuarine mesocosms, which are experimental enclosures replicating a coastal estuarine ecosystem. NOAA scientists constructed a tidal marsh creek, containing natural, unfiltered water from Wadmalaw Island; planted Spartina grass in sediments; and added clams, mud snails and grass shrimp. The gold nanorods were synthesized by researchers at the University of South Carolina and introduced into the ecosystems. At the end of the experiment, the university team developed the techniques necessary to measure the transport of the nanoparticles and found that clams and biofilms accumulated the most.
"As the first study to examine the fate and effects of nanoparticles in marine ecosystems, we really didn't know what to expect," said Dr. Geoff Scott, the CCEHBR director, who collaborated with Drs. Michael Fulton and Paul Pennington, environmental toxicologists at the CCEHBR.
"This study enabled us to understand how these nanomaterials were transported and distributed through the ecosystem," he said. "One significant finding is that bivalve shellfish, such as clams, accumulated a significant amount of the nanomaterial." The research has implications for all coastal environments and will provide a baseline for future studies on the environmental impact of nanomaterials, Scott said.
The study is significant because it shows that manmade nanoparticles can enter the estuarine food and ultimately could find their way into the shellfish and fish that humans eat, said Ferry.
"This study is a road map for where we go next," he said. "We did not look at what happens 'up the food chain.'" Dr. Thomas Vogt, director of the university's Nanocenter, said, "This landmark study points toward things to come in the near future when we enlarge our national and international R&D footprint even more by developing the recently endowed Center of Economic Excellence for Nanoenvironmental Research and Risk Assessment."