INTRODUCTION
Tanana Chiefs Conference, Inc. (TCC) is a regional non-profit organization representing
forty-three (43) tribal governments in interior Alaska. TCC works toward meeting
the health and social service needs of more than 13,000 Alaskan natives spread
across a region of approximately 235,000 square miles. Among the many challenges
faced by TCC is the need to maintain active involvement in issues that affect
subsistence use of natural resources. Within the Wildlife and Parks Program,
priority is given to protecting the natural resources on which member villages
depend.
Results from two United States Fish and Wildlife Service (USFWS) studies (Snyder-Conn
et al. 1992a,b) addressing contaminants within three National Wildlife Refuges
in west central Alaska, prompted TCC to initiate a project to determine the
concentrations of total mercury in fish tissue within the Northern Unit of the
Innoko National Wildlife Refuge. Results summarized in Snyder-Conn et al. (1992b)
indicated potentially high mercury concentrations in northern pike.
However, due to poor quality control/quality assurance (QA/QC), water samples
collected for mercury analysis were not analyzed within the required 28-day
holding time. For sediment and tissue samples, spike recoveries and/or standard
reference material recoveries were too high in 1987 and too low in 1988. Snyder-Conn
et al. (1992b) note that although QA/QC was not met, mercury concentrations
in fish tissue were possibly greater than 1.0 ppm wet weight; the Food and Drug
Administration (FDA) action level for consumption of fish tissue. It was also
recommended that mercury be a target analyte in future studies. Therefore, generating
data that would assist in determining potential health risks posed to individuals
consuming fish from the study area became the goal of this project.
Study Area
This report summarizes the results of investigations of heavy metals concentrations
in fish and surface waters, and general water quality within the 351,000-acre
Northern Unit of the Innoko National Wildlife Refuge located in west central
Alaska. The refuge is bordered on the southwest and southeast by the Kaiyuh
Mountains. The Yukon River forms the northern and western boundary of the refuge.
The refuge is known locally as the "Kaiyuh Flats" or "the Kaiyuh." The Kaiyuh
Flats is an interconnected lake and river complex that is important for various
subsistence uses by members of the four villages in the region. The villages
are Kaltag, Nulato, Koyukuk, and Galena, and have a year-round, cumulative population
of approximately 1200-1300.
Background on Mercury, Methylmercury, and Selenium
Elemental (inorganic) mercury (Hg) is a naturally occurring metal that is neurotoxic
to humans, fish, and other biotic systems when in the methylated (organic) form
(CH3Hg+). The methylation process is the result of microbial
activity that may occur in soil, sediments, fish intestines, and the water column
as a whole (Rudd et al. 1980).
Researchers have shown that methylmercury is the predominant form of mercury found in fish, often comprising greater than 95% of the total mercury body burden (Huckabee et al 1979; Eisler 1987). Although water and tissue samples collected during this project were analyzed for total mercury, we can assume that the majority of the mercury was in the methyl form.
Consumption of fish is the normal pathway of methylmercury exposure to humans. Methylmercury has the ability to diffuse through cell membranes where it is rapidly bound by sulthydryl groups. Once this occurs, a concentration gradient results that allows for rapid accumulation of methylmercury in the organism.
Clarkson (1990) and the Health & Environment Digest (1990) report several adverse human health effects due to methylmercury poisoning. These adverse health effects include, but are not limited to, paresthesia (abnormal sensations) of extremities, blurred vision, loss of teeth, loss of vision, equilibrium disruption, and developmental damage to the fetus. The threshold for prenatal effects occurs at a lower dose level than that for adult male exposure.
Mercury recycles between land, water, air, and plants and enters fish tissue from their food source and by water passing over their gills. There is no method of cooking or cleaning fish that will reduce the amount of mercury that is present in the tissue. Generally the larger predator fish, or longer living fish of the species, accumulate the greater percentage of mercury (MDH 1992).
Mercury may enter the aquatic ecosystem in numerous ways. The potential sources
of mercury to the Kaiyuh Flats area include:
1. Inefficient.use of mercury as a gold amalgamate in placer mining operations.
2. Airborne deposition of mercury from fossil fuel burning, industrialized areas
in northern latitudes. Mercury has a long residence time in the atmosphere and
may settle out far from its source.
3. Weathering of natural deposits of mercury that occur in the form of cinnabar
(HgS).
The micro-nutrient selenium (Se) is present in the environment in varying quantities and is required by the human body in limited quantities. While selenium is toxic to fish at elevated concentrations, limited quantities do provide benefits to the organism. The ability of selenium to bind with methylmercury, making it unavailable to biotic systems, is poorly understood. However, Japanese researchers have shown that the selenohydryl group has the ability to bind methylmercury up to 100 times more tightly than the sulfhydryl group (Sugiura et al 1976).
Turner and Alison (1983) have demonstrated that when selenium was elevated in food, the proportion of methylmercury in muscle tissue of northern pike decreased. In some marine environments, it has been documented that healthy sea mammal populations that have high mercury concentrations also have correspondingly high selenium concentrations of roughly a 1:1 ratio. High mercury concentrations have affected fecundity in California sea lions, where a mercury to selenium imbalance was associated with the tendency to produce pups prematurely (Koeman et al 1973; and Martin et al 1975).
It may be inferred that when in sufficient quantities, and incorporated in the food web, selenium may limit the toxic effects of methylmercury poisoning. Regardless of the mechanism that reduces the effect, it would be of benefit to determine the selenium levels in the water and fish of the Kaiyuh Flats area.
PROJECT OBJECTIVES
1. Determine the total mercury and selenium concentrations in the muscle
tissue of twelve (12) northern pike (Esox lucius) from each of five (5)
specific drainages within the Northern Unit of the Innoko National Wildlife
Refuge (Kaiyuh Flats).
2. Determine the total mercury and selenium concentrations in surface water of five (5) specific drainages of the Northern Unit of the Innoko National Wildlife Refuge (Kaiyuh Flats).
3. Collect surface water samples and fish tissues from drainages that have, and have not, had prior lode ore and gold placer mining activities.
4. Sample surface waters for specific water quality parameters.
5. Collect biological data from sample fish.
METHODS AND MATERIALS
Sample Sites
Sample sites represent areas that are downstream of former placer mining activities,
and also non-mining areas for control and comparison purposes (Figure 1). A
discrepancy between creek names was found on the USGS Nulato (B-4) Quadrangle
map and a map used for a trapping pattern study by the Alaska Department of
Fish and Game (ADF&G) Subsistence Division (Robert 1984). Bonanza Creek on the
USGS Nulato (B-4) Quadrangle map originates in the Camp Creek drainage. It appears
that Bonanza Creek is correctly labeled as Camp Creek on the ADF&G map. USFWS
has referred to this sample site as Bonanza Creek, sample site 5 (Snyder-
Figure 1. Map of sample sites within the Kaiyuh Flats study area.
#3 Bishop Creek
#5 Camp Creek
#11 Bonanza Creek
#12 North Creek/American Creek
#13 Yukon Creek
Conn et al 1992b). Eddy Creek on the USGS Nulato (B-4) Quadrangle map is renamed
as Bonanza Creek on the ADF&G map. North Creek is renamed American Creek on
the ADF&G map at approximately Township 13S, Range 5E, and Section 4, SW 1/4.
The ADF&G map, because it is consistent with the local knowledge and place names
of the area, was used for this study. Description of sites in Figure 1 are as
follows:
Site 3. Bishop Creek. USGS Nulato (C-3) Quadrangle. Township 9S, Range 8E, Section 35. Water samples collected. No fish captured in this drainage.
Site 5. Camp Creek. USGS Nulato (B-4) Quadrangle. Township 12S, Range 6E, Section 17, NE 1/4. Water and fish were collected immediately below the fork of Camp Creek in the NE 1/4 of Section 17.
Site 11. Bonanza Creek. USGS Nulato (B-4) Quadrangle. Township 12S, Range 5E, Section 35, NE 1/4. Water samples were collected in Section 35, NE 1/4. Fish were captured from Bonanza Creek within Sections 35 and 26.
Site 12. North Creek. USGS Nulato (B-4) Quadrangle. Township 13S, Range 5E,
Section 9, NW 1/4. Water samples collected.
Site 12A. American Creek. USGS Nulato (B-4) Quadrangle. Township 12S, Range
5E, Section 30, SW 1/4. Fish captured.
Site 13. Yukon Creek. USGS Nulato (B-5) Quadrangle. Township 13S, Range 3E, Section 3, NW 1/4. Water samples and fish were collected within Yukon Creek immediately before the confluence with 22-Mile Slough (Khotol River).
All field work and sampling was conducted between 23-27 August, 1993. Of the five separate drainages sampled, Camp Creek has a history of gold placer mining, and Bishop Creek has a history of lead-silver production. North/American Creek, Bonanza Creek, and Yukon Creek have no documented mining history.
Permits applied for and received for this project included: 1) a conditional State of Alaska Department of Fish and Game Scientific Permit for collecting fish with a gill net, and 2) a conditional United States Department of the Interior Fish and Wildlife Service Refuge Special Use Permit.
A unique identification number was given to each fish captured and each water sample collected. The system used for this project is based on a system used by the USFWS within the Northern Unit of the Innoko National Wildlife Refuge. The identification number describes the area, sample site number, type of sample, sample number, and type of tissue. An example for a fish tissue sample would be as follows: NIN05PO01M, where NIN is the Northern Unit of the Innoko National Wildlife Refuge, 05 is the sample site, P is northern pike, 001 is sample number, and M is muscle tissue. An example for a surface water sample would be as follows: NIN 11 H2O 01, where NIN is the Northern Unit of the Innoko National Wildlife Refuge, 11 is the sample site, H20 is a surface water sample, and 01 is the sample number.
Surface Water
Surface water grab samples were collected at each site using 500 ml Nalgeneā
bottles just below the water surface and upstream of the collector. At the time
surface water samples were collected, surface water temperature (o
C) was recorded using a hand-held alcohol thermometer. pH was recorded using
a Whatman model PHA300 portable pH meter. The meter was calibrated before each
measurement with standard buffer solutions of pH 4.01 and pH 7.01. Water samples
were chilled on blue ice and brought back from the field for analysis of turbidity,
hardness, and conductivity. A duplicate surface water grab sample was collected
at each site using a 500 ml plastic bottle provided by Columbia Analytical Services
(CAS). The bottle contained nitric acid for the purpose of fixing the water
sample to a pH of less than 2.0. The duplicate sample was shipped to CAS in
for metals analyses.
Turbidity was measured in nephelometer turbidity units (NTU) using a Hach Portable Turbidimeter Model 2100P, calibrated with Hach Gelex secondary standards for 1, 10, and 100 NTU. Hardness was measured in parts per million (ppm) of calcium carbonate (CaCO3) using Hach hardness and digital titration methods and color endpoints. Conductivity was measured in umhos/cm using a Hach DREL/5â Conductivity meter with automatic temperature compensation. The USFWS Ecological Services, Fairbanks, provided the instruments for these measurements.
Fish
Fish were captured using conventional hook and line techniques. The target number
of twelve (12) northern pike (Esox lucius) captured per sample site was
achieved at four (4) of the five (5) sample sites for a total sample size of
forty eight (48) specimens. Although effort was put forth, no fish were captured
at Bishop Creek.
Total length (mm), fork length (mm), and weight (grams) were recorded for each fish prior to field dissection. Weight was measured using either a 2 kg, 5 kg, or 15 kg Chatillon hand-held scale. After fish metrics were recorded for each specimen, the same specimen was placed on a polyethylene dissection board that was pre rinsed with distilled water. Upon dissection, skin-off dorsal muscle tissue was removed from the right side of the specimen using a sterile stainless steel scalpel blade. The tissue sample was then placed into a new 125 ml plastic bottle and sealed. The corresponding identification number was recorded into a field notebook and written in permanent ink on the bottle. Each bottle was placed into a cooler with blue ice.
After each tissue sample was collected, the sex of each fish was recorded along with a cursory stomach content analysis. Scales and vertebrae were collected from each specimen for age analysis. Aging of vertebrae and scales was performed by the ADF&G Sportfish Division, Fairbanks, AK.
Prior to dissection of the next specimen, the dissection board was rinsed with distilled water and wiped dry with a disposable paper towel. A new sterile stainless steel scalpel blade was used for each tissue sample removed. A new pair of talc-free plastic surgical gloves was used when handling and dissecting each specimen.
Aware that livers, kidneys, intestines, and sex organs are routinely consumed by Kaiyuh Flats area residents, dorsal muscle was chosen for metals analysis due to the much greater amount of edible tissue provided per fish. The fact that individual body organs, such as the liver, may contain higher or lessor concentrations of contaminants is noted.
Upon return to Fairbanks, dry ice was placed in each cooler and the tissue and water samples were sent to Columbia Analytical Services (CAS) in Kelso, Washington for analysis of total mercury and total selenium.
Quality Assurance/ Quality Control (QA/QC)
Methods used by Columbia Analytical Services (CAS) for total mercury and selenium analyses were cold vapor atomic absorption, and graphite furnace atomic absorption, respectively. EPA methods used for analysis of total mercury and selenium in water samples were #7470 and #7740, respectively. EPA methods used for analysis of total mercury and selenium in fish tissues were #7471 and #7740, respectively. Total mercury analysis of surface water samples was completed within the required 28-day holding time (APHA et al. 1989).
Quality control screening used by CAS resulted in acceptable precision and accuracy for each metal analyzed in both fish tissue and water samples. The laboratory tested duplicate samples for relative percent difference (RPD), spiked duplicate samples for percent spike recovery, and analysis of standard reference materials (commercially provided tissue of known metal concentration). Therefore, the confidence level is high for the validity of the analysis results. The QA/QC laboratory report is presented in Appendix B.