The Role of Plastic Marine Debris in the Magnification of Methyl Mercury in Seafood
Plastics in some marine debris can adsorb significant amounts of methylmercuryThe presence of marine debris on beaches and in the ocean has caused concern about the interactions with and fate of toxic pollutants in the aquatic environment. Previous research indicates that plastic marine debris may bind to various contaminants in the marine environment; however, little is known about how methylmercury might bind to pieces of marine debris and how that could impact the food chain if the plastic is ingested by fish, marine mammals or shore birds. With funding provided by a N.H. Sea Grant development grant, researchers conducted analyses to quantify the adsorption of methylmercury to samples of different types of plastic in seawater. The data indicate that some types of plastics that may represent potential marine debris can adsorb significant fractions of aqueous methylmercury. This research will help scientists better understand the role that plastic marine debris might play in the fate of methylmercury in the marine environment and its potential to accumulate in seafood.
Description of the Work
Plastics in some marine debris can adsorb significant amounts of methylmercury
Description of the Work
Our hypothesis is that the levels of mercury in our fish will continue to rise, even as levels in ambient sea water drop, as the plastic marine debris concentrates methylated mercury in the food chain. This is consistent with work by Yukie Mato and Emma Teuten demonstrating that polyethylene, polypropylene, and polyvinyl chloride concentrate PCBs, DDE, and phenanthrene at up to one million times the levels found in the ambient seawater. This is, to our knowledge, the first study to examine mercury adsorption by plastic marine debris In our pilot study, laboratory technicians introduced styrene-butadiene and polychloroprene pellets (two common types of plastic resin) pellets into glass beakers of Puget Sound seawater. They added an environmentally relevant concentration (100 nanograms/liter) of methyl mercury to the beakers. Within 72 hours, the plastic pellets had adsorbed 72% and 17%, respectively, of the methyl mercury in the spiked sea water samples. These particular polymers are manufactured with thiolate (sulferhydrogen) molecules. Thiolates are also known as mercaptans, a name derived from the Latin mercurium captans (meaning “capturing mercury”). Lower levels of mercury adsorption by other types of plastics, particularly polyethylene, have been noted in the literature. Analytical chemists must compensate for this phenomenon, which they call “bottle wall loss,” when quantifying the levels of mercury in samples that are exposed to plastic containers. We would like to run a full test with a statistically defensible number of replicates that could make these findings publishable. We will test both pre-fabrication plastic resin pellets (sometimes called nurdles) and consumer products, including automobile tires and marine paints (which are made from styrene-butadiene block copolymer).
This research is intended to lead to a full N.H. Sea Grant Proposal in the priority area of ensuring a “safe and sustainable seafood supply” as well as a “healthy coastal ecosystem.” The proposal will relate directly to the objective described in the Strategic Plan 2011-2013: “Anthropogenic pollutants, naturally occurring pathogens and toxin producing algae in the region’s estuaries are detected, their sources and causes identified, and their impacts timely and effectively mitigated.” If the results from this project support our hypothesis, we will begin local field work, quantifying the abundance of and mercury levels in plastic marine debris off the New England coast. We will explore mercury desorption from ingested plastic marine debris in fish, and will aim to construct a quantitative model predicting the impact of plastic marine debris in the magnification of methyl mercury in fish.