How Available are Toxic Chemicals in Lake Ontario Sediments?
Ann Arbor, MI — Dioxins and furans are toxic chemicals found in Lake Ontario sediments. They may be less available and thus less harmful to the lake's food chain than previously assumed.
Just how much of the dioxins/furans in lake bottom sediments are readily available to the resident aquatic community has been an unanswered question for decades. It has been generally assumed that aquatic organisms are exposed to all of these chemicals found in the sediments. However, lab experiments on Lake Ontario sediments show that a portion of these chemicals are not available to organisms which live directly in the lake sediment where most of the contamination lies.
"Most people think that all of the chemicals which end up in bottom sediments are harmful to organisms that live in the lake, including the fish," says Scott Pickard, an Ecologist at the U.S. Army Corps of Engineers in Buffalo, New York.
"This study was able to measure how much of the dioxins/furans in Lake Ontario sediments are actually available for uptake and might therefore be potentially toxic to bottom-dwelling organisms," said Pickard. "Because sediments act as a storehouse for lake contaminants and bottom-dwelling organisms are often the basis of a food chain, this study offers a first line and conservative estimate as to how much of the dioxins/furans might potentially pose a risk," he added.
Dioxins/furans are a group of toxic organic chemicals found in the environment as a result of human activities, and are major contaminants of concern in Lake Ontario. The compound 2,3,7,8-tetrachlorodibenzo-p-dioxin, widely known as "TCDD," is the most toxic dioxin.
Pickard and Joan Clarke (a Statistician at the U.S. Army Engineer Research and Development Center) found the overall availability of TCDD in Lake Ontario sediments to be a bit lower than expected. Knowing the levels to which aquatic organisms are exposed is particularly important for dioxins/furans because they tend to be toxic at very low levels. Also, the actual effects of dioxins/furans can differ dramatically between species, or even among life stages of a single species.
Original Publication Information
Results of this study, "Benthic Bioaccumulation and Bioavailability of Polychlorinated Dibenzo-p-Dioxins/Dibenzofurans from Surficial Lake Ontario Sediments," are reported by Scott W. Pickard and Joan U. Clarke in the latest issue (Volume 34, No. 3, pp. 418-433) of the Journal of Great Lakes Research, published by the International Association for Great Lakes Research, 2008.
Contacts
For more information about the study, contact Scott Pickard, U.S. Army Corps of Engineers, 1776 Niagara Street, Buffalo, NY 14207; , (514) 283-6499.
For information about the Journal of Great Lakes Research, contact Marlene Evans, Editor, National Water Research Institute, 11 Innovation Boulevard, Saskatoon, SK, S7N 3H5, Canada; editor@iaglr.org; (608) 692-1076.
Links
Since 1967, IAGLR has served as the focal point for compiling and disseminating multidisciplinary knowledge on North America's Laurentian Great Lakes and other large lakes of the world and their watersheds. In part, IAGLR communicates this knowledge through publication of the Journal of Great Lakes Research, available to members in print and electronic form. A searchable archive of the journal is available online and includes the abstracts of articles from the journal's inception in 1975 through the most recent issue. In addition, complete articles are available to members who have signed up for an electronic subscription.