The term for a community of algae, bacteria and other natural material is “periphyton.” Periphyton is a complex mixture of algae, bacteria, and detritus that is attached to submerged surfaces in most aquatic ecosystems.
Researchers have been looking into a Superfund site along the Androscoggin River (in Berlin, New Hampshire, U.S.) The results of the examination have found that expected levels of methylmercury in marine animals like crayfish, mayflies and small fish downstream from a former chemical plant along the river were higher than expected.
Methylmercury is a variant of mercury, but one far more toxic. Methylmercury is formed from inorganic mercury by the action of anaerobic bacteria found in lakes, rivers, wetlands, sediments, soils and the open ocean. In humans and animals ingested methylmercury is readily and completely absorbed by the gastrointestinal tract and it can cause poisoning.
The factory, a paper mill, was closed during the 1960s, however levels of mercury in the river remain high. Mercury concentrations in the water next to the site remain over five times higher compared with further downstream.
Researchers speculate that mercury is transformed into methylmercury via a complex biogeochemical process mediated by bacteria. Due to the high concentration of bacteria in the periphyton, the toxic chemical builds up in this region. This build-up is described as bioaccumulation. The periphyton is a prime food source for fish, which leads to the toxic mercurial compound entering the food chain.
The issue is of concern because methylmercury is a highly toxic form of mercury and one that can readily enter the food chain.
The findings have been reported to the journal Environmental Toxicology and Chemistry. The paper is headed “Influence of a chlor-alkali Superfund site on mercury bioaccumulation in periphyton and Low-trophic level fauna.”
