Contaminant Baseline Data for Water, Sediments, and Fish of the Nowitna National Wildlife Refuge, 1985-1988
Published By US Fish and Wildlife Service, Department of the Interior
Issued oltre 9 anni ago
Summary
Description
Studies were conducted by the Fish and Wildlife Service between 1985 and 1988 to obtain baseline trace element and water quality data on water, sediments, and fish in rivers of the Nowitna National Wildlife Refuge and to assess the impacts of upstream placer mining activities. One river examined, the Sulatna River, had active placer mining on its tributaries. In addition, California Creek, a tributary to the Titna River, experienced upstream placer mining from 1979 1986. In the early 1900s, Our Creek, and the Susulatna River, tributaries to the upper Nowitna River, were mined, as was an unnamed tributary to the Sulukna River. The Sulatna River experienced significantly higher turbidity, iron, and manganese concentrations than sites on the upper, middle, or lower Nowitna River, the Sulukna River, or California Creek. The Tima River, only sampled in 1985, also had extremely high iron concentrations in the water. In other respects, the water quality of all sites was similar. Copper appears to be slightly elevated in water from all sites as a result of natural conditions, but meets water quality standards. However, concentrations were in the range of potential effects on young arctic grayling and other sensitive species. No significant differences were found between sites in sediment trace element concentrations, except for mercury. Mercury concentrations were higher in Sulama River sediments than at other sites, but occurred at elevated concentrations at all sample sites except California Creek. Fish tissue concentrations of mercury were highest in northern pike from the unmined Sulukna River. Concentrations in all five northern pike collected in 1987 exceeded the Food and Drug Administration FDA action level of 1 mgkg wet weight. Northern pike from the mouth of the Nowima River also contained elevated mercury concentrations, but concentrations did not exceed the FDA limit. Shellfish and arctic grayling were generally low in mercury concentration in comparison to the northern pike. The source of mercury in the Nowima Refuge fish is uncertain, but is most likely derived from natural sources, rather than placer mining activity. Mercury, used historically to amalgamate gold and discharged to waters, is another potential, but less likely, source. Mercury concentrations in northern pike were not correlated with fish length, weight, or condition index, suggesting that mercury concentrations did not affect fish health. The only negative statistical correlations found between northern pike measurements and metal concentrations were between liver copper, weight, and total length. Due to small sample sizes involved in this study, few conclusions should be drawn regarding the relationship of metal concentrations in fish and fish health at this time. The paucity of northern pike from the mined Sulama River also precludes conclusions regarding the effect of mining on fish tissue concentrations. Other species were collected in too few numbers to conduct betweensite comparisons. Additional studies are recommended to identify source areas of mercury, and to better define tissue concentrations in potentially affected biota.