Columbia River: Contaminants in the Food Chain

The Columbia River is an important resource for fish and wildlife, and a number of National Wildlife Refuges (NWRs) were established along the river to protect migratory birds, species listed under the Endangered Species Act, and habitat necessary for the survival of these species. Fish and wildlife are exposed to environmental contaminants entering the Columbia River from point and nonpoint sources. Even when released in small concentrations, some contaminants can biomagnify and harm top level predators, and can impact species using NWR lands.

In 1990 and 1991, we collected sediment, invertebrates, fish, and eggs of piscivorous and non-piscivorous birds within various river segments to determine contaminant concentrations, compare concentrations within river segments, identify concentrations in biota that exceed guidance or reference levels, and derive biomagnification factors (BMFs) for persistent, bioaccumulative compounds. BMFs were used to develop target fish concentrations (TFCs), or the concentrations in fish that would protect upper trophic level species such as bald eagles. We collected samples in the lower Columbia River below Bonneville Dam (four river segments including three NWRs), at Umatilla NWR and above McNary Dam, and in the lower Willamette River near Portland.

We found most organochlorine (OC) pesticides were below detection in sediment and biota. However, similar to previous and concurrent studies, DDE and DDD (transformation products of the pesticide DDT) were the most commonly detected and most elevated compounds in biota from the river. DDE was detected in all fish samples during both years of the study, and in nearly all samples of clams and bird eggs. Polychlorinated biphenyls (PCBs) were commonly found in fish and bird egg samples, but were rarely detected in sediment or invertebrates. PCBs and DDE in most fish samples exceeded mean concentrations reported in nationwide comparison studies, and exceeded estimated guidance values for the protection of avian predators. Concentrations of DDE and total PCBs exceeded estimated no-observable adverse effect levels (NOAELs) in some eggs of double-crested cormorants and Caspian terns in the lower river segment.

Mercury was detected in all invertebrates and birds eggs, and in most fish sampled. In invertebrates, mercury was below estimated guidance values for the protection of avian invertebrate predators, but some fish samples exceeded these guidance values. Mercury in eggs of some piscivorous birds in the lower river segments exceeded values associated with impaired reproduction in sensitive individuals.

Most dioxin and furan congeners were near or below detection in sediment and invertebrates, but were commonly detected in fish and bird eggs. Nearly all fish sampled contained 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and 2,3,7,8-tetrachlorodibenzofuran (TCDF) in excess of guideline values derived in this study or other studies for the protection of bald eagles or other avian predators. TCDD and TCDF exceeded estimated NOAELsin eggs of some piscivorous birds, particularly double-crested cormorants.

BMFs derived based on data from Columbia River fish and bald eagle eggs were fairly consistent among river Segments 1 to 3 in the lower river, and the combined BMFs for the three segments were 113 for total PCBs, 75 for DDE, 2.8 for mercury, 16 for TCDD, and 2 for TCDF. The TFC values derived from the BMFs were 0.06 ug/g for total PCBs, 0.04 ug/g for DDE, 0.20 ug/g for mercury, 0.9 pg/g for TCDD, and 7.5 pg/g for TCDF.

Although bioaccumulative contaminants were near or below detection limits in sediment and invertebrates, our results document biomagnification of some OC compounds to concentrations likely resulting in adverse impacts to piscivorous bird individuals. Although sample size was limited, our results did not indicate that individual river segments differed in there contribution to the contaminant concentrations observed in biota. This trend indicates that the river receives contaminants from numerous widespread sources, and that contaminants were evenly distributed in biota. Currently, it is unknown if bed sediment in the Columbia River plays an important role in transfer of contaminants to biota, and additional information is needed to characterize this role and to develop better management strategies for bed sediment disturbance. We recommend a basin-wide strategy to better control release of bioaccumulative contaminants in the river and minimize impacts to fish-eating birds, to monitor changes in OC contaminants over time, and to better address contaminant uptake from sediment sources.

Final Report: Environmental Contaminants in Aquatic Resources from the Columbia River

Environmental Contaminants in Aquatic Resources from the Columbia River, a scientific poster presenting summary of results of the food chain study. For a printable version, click on one of the following:
11 X 17 printable poster
8.5 X 11 printable poster

Bald Eagle Hazard Assessment Poster