Water Quality of the Long Fork Trout Pond at the Star Fire Site, Eastern Kentucky. C. Douglas R. Graham and David R. Wunsch

Transcription

1 Water Quality of the Long Fork Trout Pond at the Star Fire Site, Eastern Kentucky C. Douglas R. Graham and David R. Wunsch Kentucky Geological Survey Open-File Report OF August 26,

2 Abstract Water Quality of the Long Fork Trout Pond at the Star Fire Site, Eastern Kentucky Introduction of rainbow trout into a retention pond located on a reclaimed mountaintop-removal coal mine in eastern Kentucky resulted in observable stress upon the fish. The pond receives recharge directly from submerged springs supplied by highly mineralized groundwater within an adjacent body of thick mine spoil. Detailed waterquality analysis was performed for samples collected from the pond at various depths and locations over three lateral and one longitudinal transect. Results indicate that the dissolved solids content in the pond, although high, may not have been the primary cause of fish stress. The water-quality depth profiles identified the existence of a thermocline within the pond. Summer temperatures in the upper zone of the pond were too warm for the fish, whereas waters below the thermocline contained too little oxygen to support the fish. Introduction The Star Fire Mine consists of 17,000 acres in the Eastern Kentucky Coal Field (Fig. 1). A 1,000-acre area in the northwestern part has been mined and reclaimed through the mountaintop-removal method. The revegetated spoil is approximately 200 ft thick, covering two buried valleys and the mined-out ridge between them. Two water impoundments were created at the northwestern margin of the spoil to supply water for mine needs such as dust control and reclamation seeding. These ponds are incised into the bedrock and are fed by groundwater discharging from the mine spoil to the east (Wunsch and others, 1996). Long Fork Trout Pond is the larger of the two ponds, covering about 3 acres, and is approximately 23 ft deep. Flow from its outlet is nearly constant, and neither the outlet discharge nor the water level seems greatly affected by seasonable change nor by normal pumping of water from the pond. Figure 1. Location of Long Fork Trout Pond and other selected hydrologic sites, Star Fire Mine. Rainbow trout (Salmo gairdneri) were placed in the Long Fork Trout Pond on two occasions in 1996: January 25 and May 1. On both occasions the trout showed some distress, crowding to the shore of the pond, before 2

3 apparently adjusting to the pond water and swimming into the depths of the pond. The first release was a success for anglers; however, few, if any, fish were caught from the pond after the second release (D. Schindler, Kentucky Fish and Wildlife Service, personal communication). The Kentucky Fish and Wildlife Service requested the help of the Water Resources Section of the Kentucky Geological Survey in determining the reason for the fish s distress. Members of the Water Resources Section sampled the pond outfall in July of 1996, then in August began a program of profiling and sampling the Long Fork Trout Pond on a quarterly basis. Sampling/profiling events took place in August, December, February, and June. Trout were released to the pond on April 27, 1997, and Section personnel were on hand to profile the pond, take samples, and measure the temperature, ph, electrical conductance, and dissolved oxygen of the hatchery water in the truck. Background Behavior of Lakes One of the most important characteristics of ponds and lakes is thermal stratification (i.e., the differentiation of a lake into a deeper, denser, colder zone the hypolimnion and a shallower, lighter, and warmer zone affected by sun and wind the epilimnion). This is largely a summer phenomenon, and is caused by the density differences between warm water and cold water. The metalimnion separates the upper and lower layers of the lake, and is defined as the zone of marked vertical temperature change (the thermocline). Some mixing and diffusion of chemical constituents takes place in the metalimnion, but the layers remain quite distinct as long as their densities remain different. The stratification of a lake in a temperate climate continues through summer, and as winter approaches and the uppermost layer of water cools to the point that it is heavier and denser than the bottom, the body of water will overturn ; the surface water will sink and the water at the bottom will rise, and the lake s waters mix thoroughly. The chemical characteristics of the warm surface water of a lake in summer and the cool water at depth are very different. Physical aeration of the surface by waves and the diffusion of oxygen, nitrogen, and carbon dioxide from the air into the water means that the content of dissolved gases at the surface will usually be greater than at depth. Of equal importance are the biological processes. In general, the epilimnion is the most biologically active, because light and dissolved carbon dioxide and nitrogen allow plant life (particularly algae) to exist in greatest abundance. Plant life, including microscopic algae, provides a basis for animal life such as plankton and invertebrates, both of which in turn affect the chemical quality of the water by the uptake of certain nutrients and generating other nutrients as waste products. In the cooler hypolimnion, lower light means less plant life and lower oxygen content, and a concomitant increase in dissolved nutrient concentrations and of dissolved solids. Water-Quality Requirements of Rainbow Trout Trout is a popular species for both angling and human consumption, and trout are successfully raised and stocked in many places in the United States. A number of manuals and government-produced guides exist for the culture of trout and for the recognition of suitable habitat (Eipper, 1960; Raleigh and others, 1984; Brannon, 1991). Many of these publications list desirable ranges of water-quality parameters, but are not always in full agreement with each other. Heinen (1996) reviewed a selection of papers that deal with water-quality criteria and discussed the contradictions and inadequacies of the various works. The term water-quality criteria in the context of this paper refers to the maximum concentrations of elements or ions, or ranges of other water-quality parameters (such as temperature and ph), that must be considered when selecting or treating water to be used for trout habitat; they are based on laboratory studies that subject living trout to various water-quality conditions to test toxicity. Our report relies heavily on the evaluation by Heinen (1996). Temperature and dissolved oxygen are important controls on trout habitat. Temperatures above 18 or 19 C are, at the least, stressful to rainbow trout (Elliot, 1981). Concentration of dissolved oxygen (which has an inverse relationship with temperature warmer waters reach oxygen saturation at lower concentration than cool waters) is at its optimum above 7 mg/l, and between 5 and 7 mg/l is tolerable to trout only at cool temperatures (Hess, 1974; Raleigh and others, 1984). Certain heavy metals are toxic to trout at relatively low concentrations. Water-quality criteria (in mg/l) have been developed from toxicity studies for these elements: cadmium, 0.006; copper, 0.006; zinc, 0.005; 3

4 manganese, 0.01; aluminum, 0.01; arsenic, 0.05; chromium, 0.011; lead, 0.02; mercury, ; selenium, 0.01; and thallium, 0.04 (Heinen, 1996). Very little is known about the toxic effect of combinations of these metals in an aquatic environment. Heinen (1996) noted the possibility of additive, synergistic, or antagonistic effects on toxicity in water containing significant levels of two or more of these metals. Alkalinity, ph, and hardness of water have a pronounced effect on the toxicity of heavy metals (Heinen, 1996). Maximum allowable concentrations of various metals are different for waters of different hardness. Hardness is a measure of the reaction of certain waters to sodium soap, and is reported as mg/l of equivalent CaCO 3 (Drever, 1988). The effect is due to the concentration of two common cations: calcium and magnesium. Concentrations of these constituents can be converted to hardness by the formula (Drever, 1988) Hardness, as equivalent CaCO 3 = 2.5x(mg/L Ca) + 4.1x(mg/L Mg). The total loads of both suspended and dissolved solids can also affect rainbow trout. A common upper limit for maximum total suspended solids is 80 mg/l (Brannon, 1991; Heinen, 1996). Heinen (1996) recommended a maximum of 400 mg/l total dissolved solids, but noted that minimum values from the literature range from 15 to 5,000 mg/l. Methods and Instruments The Kentucky Geological Survey studied the chemistry of the water of the Long Fork Trout Pond with regard to the water-quality requirements of rainbow trout. The pond was not known to be thermally stratified, but was believed to be deep enough to show differences in the water column, particularly in temperature. It was important to get an accurate picture of the vertical temperature profile. Other water-quality parameters of interest were dissolved oxygen (DO), ph, and electrical conductance (EC). A flat-bottomed boat was used as a sampling platform, and the boat was held in place for water sampling by a rope tied between the north and south shores of the pond. The temperature profile and the water-quality measurements were carried out from opposite ends of the boat so as not to interfere with each other (Fig. 2). Figure 2. Pump and meter configuration for measuring unstable water-quality parameters in a lake. 4

5 A Yellow Springs Instrument model 33 S-C-T meter was fitted with a probe on a 50-ft cord that could be lowered to various depths in the lake for purposes of temperature profiling. This set of measurements was carried out independently from the measurement of the other water-quality parameters. A Horiba water-quality checker, model U-10, measured ph, dissolved oxygen, electrical conductance, and temperature of the water at the probes. Water chemistry could not be measured in situ with the handheld meter because of the depth of the pond. Therefore, a weighted, flexible tube with a measuring tape attached to one end was hung from a peristaltic pump, and water was drawn up to a measuring chamber. In this way, the various waterquality probes were kept isolated from the atmosphere, and therefore atmospheric effects on the water sample were minimized. The chamber was fitted with a port for a millivolt probe or ph probe attached to a Yellow Springs Instruments model 3500 water-quality monitor (see Figure 2). This arrangement allowed backup instrumentation to be used along with the primary (Horiba) water-quality meter. Water-quality samples sent to the laboratory for constituent analysis were also drawn using the peristaltic pump and tubing assembly. Wetted foam insulation was placed around the excess suction hose and over the top of the measuring chamber, which was itself suspended in the lake water to minimize change in water temperature and concomitant change in water-quality parameters from their in situ state. The pond was divided into three transects across the narrow dimension (Fig. 3). The transects measured were at approximately 150, 300, and 500 ft from the lake outlet and roughly perpendicular to the long axis of the lake (Fig. 3). Each transect had three stations: one corresponding to the center of the lake, one 40 ft from the north shore, and one 40 ft from the south shore. Total water depth at each station was determined, and a depth-temperature profile was measured at 2- or 3-ft depth intervals. Water-quality parameters were measured at 2- to 5-ft depths. Care was exercised not to draw lake-bottom sediment into the pumping tube; typically, the deepest water-quality samples were drawn 3 to 5 ft above the bottom of the lake. 5

6 Figure 3. Location of profile lines in Long Fork Trout Pond. Water-quality samples collected for laboratory analysis were drawn at the upper end (500 ft from the outlet) and the lower end (150 ft from the outlet) of the lake at the center of each transect. Samples were taken at shallow (2 ft deep) and deep (18 ft deep) intervals and submitted to the laboratory as separate samples. Results The measurement of water-quality parameters showed that the pond is clearly stratified, and that the stratification is accompanied by chemical distinctions between water near the surface and water near the bottom. Figure 4 shows a typical profile of ph, dissolved oxygen, and temperature versus depth in the lake. Figure 5 is a profile of the lake from the head of the lake to the outlet, and demonstrates the lateral homogeneity of the pond s water. Electrical conductivity did not vary significantly with either depth (Fig. 6) or lateral position in the lake. The lake s water was remarkably clear; the stainless-steel probe used to measure water depth was visible to nearly 15 ft below the water surface. 6

7 Figure 4. Transect of Long Fork Trout Pond at 150 ft from lake outlet (west end of lake), showing ph and temperature versus depth. 7

8 Figure 5. Longitudinal profile of Long Fork Trout Pond center line, showing ph and temperature versus depth. 8

9 Figure 6. Long Fork Trout Pond: electrical conductivity versus depth for all transects. The variation of dissolved oxygen around the pond is shown in Figures 7 through 9. Lateral variation for this parameter is considerably less than vertical variation. The lowest dissolved oxygen values at both the 18- and 2- ft depths are at the north and south ends of the 300-ft transect. Both sites were near the highwalls of the lake pit, relatively sheltered from wind and away from shoal areas with underwater plant growth. This apparent correlation must be considered cautiously, however: data were not collected systematically with respect to distance from nearshore vegetation nor with respect to windward/leeward fetches of the pond. 9

10 Figure 7. Transect of Long Fork Trout Pond at 150 ft from lake outlet (west end of lake), showing dissolved oxygen and temperature versus depth. 10

11 Figure 8. Transect of Long Fork Trout Pond at 300 ft from lake outlet (central part of lake), showing dissolved oxygen and temperature versus depth. 11

12 Figure 9. Transect of Trout Pond at 500 ft from lake outlet (east end of lake), showing dissolved oxygen and temperature versus depth. Diurnal variation of dissolved oxygen due to physical/chemical factors or biological activity is a welldocumented process in lakes (Goldman and Horne, 1983, Fig. 7-7). Repeated dissolved oxygen measurements at a single station were made on both August 28 and August 29, 1996, bracketing the times over which the lake was sampled for dissolved oxygen. Figure 10 shows the results of the sampling, and also the level of dissolved oxygen that would be present if the water were at full saturation. The water of the lake is clearly undersaturated in oxygen, and the saturation decreases with depth. 12

13 Figure 10. Diurnal variation of dissolved oxygen at Long Fork Trout Pond, station 500, 115. Long Fork Trout Pond Water Quality in Regard to Rainbow Trout The water of the Long Fork Trout Pond on the days it was measured and sampled (August 28 and 29, 1996) was stratified into a lower layer that was, at best, marginally cool enough for trout but without sufficient dissolved oxygen, and an upper layer that was more oxygenated but had temperatures in the range that cause trout acute stress (Elliot, 1981). Data from a single later-summer set of measurements are not sufficient to reflect the structure of the pond s waters in other reasons, particularly with regard to temperature, dissolved oxygen, and ph. Continued monitoring would be necessary to assess the pond s seasonal trends. Chemical analysis of samples taken at two different surface locations, two depths at each location (four samples total), on the above dates, indicates that the water is very high in total dissolved solids (Table 1). Of particular interest are the levels of calcium, magnesium, sodium, potassium, sulfate, manganese, and thallium. Table 2 compares the mean concentrations of each of these constituents to the water-quality criteria discussed by Heinen (1996). Table 2. Water-quality criteria versus average analytical results of samples. Units in mg/l. Constituent Long Fork Trout Pond (mean of August 28, 1996) Water-Quality Criteria* (from Heinen, 1996) Ca Mg <15 (28) Na (<1500) K SO 4 2,125 <50 (<850) TDS 3,460 <400 (15 5,000) Mn 2.15 <0.01 (<1.0) Tl 1.31 <0.40 *Different criteria have been published, and are included with the appropriate constituent. Ranges printed are optimum ranges. 13

14 The mean concentrations of these constituents are clearly above the indicated criteria. They indicate a number of reasons for the distress of trout released to the Long Fork Trout Pond in the spring of An examination of the supporting literature cited by Heinen (1996) reveals that simple toxicity of any single constituent cannot be held responsible for distress or mortality of trout in the pond. Piper and others (1982, p ) stated variously that trout will tolerate 30 parts per thousand dissolved solids (30,000 mg/l) and 7,000 mg/l of total dissolved solids. TDS of the Long Fork Trout Pond is less than those levels and should be tolerable by trout. Concentrations of dissolved calcium, magnesium, sodium, and potassium in the pool are also greater than the stated criteria. McKee and Wolfe (1963, p. 114), however, stated that mixtures of salts [in water] have become progressively less toxic when to sodium chloride has been added calcium chloride, potassium chloride, and finally magnesium chloride. The action of calcium and magnesium reduces the toxicity of heavy metals (McKee and Wolf, 1963; Heinen, 1996); perhaps they protect against ill effects of potassium and sodium as well. Concentrations of sulfate, manganese, and thallium at the Long Fork Trout Pond are well above the suggested water-quality criteria. The geochemical reaction that leads to high sulfate values (the oxidation of pyrite in the mined rock) would be expected to contribute greatly to the acidity of the water of the pond, but the high buffering capacity of the water (as shown by the high bicarbonate concentration) prevents the ph from becoming extreme. Heinen (1996, p. 22) stated: Unpublished sources, believed to be reliable, indicate that sulfate levels up to at least about mg/l are suitable for trout grow-out. It is unclear from the literature what effect high levels of calcium and magnesium have on the toxicity of manganese and thallium. One hypothesis is that the pond s load of total dissolved solids is simply too high for hatchery-raised trout, even though major metallic constituents (calcium and magnesium) simultaneously reduce the toxic effects of various other constituents in the water. Piper and others (1982), in their discussion of the tolerance of rainbow trout to high total dissolved solids, stressed that a period of acclimation to steadily increasing dissolved loads was necessary for trout to live in water with content of high dissolved solids. Trout raised at a hatchery are probably accustomed to fresher water, and the introduction of the fish to the more mineralized water of the trout ponds causes unaccustomed stress. The fact that few of the trout in the second release were ever caught might indicate that the increased temperature of the lake enhanced the toxicity of certain dissolved elements to trout (McKee and Wolf, 1963). Conclusions 1. Daytime temperatures in late August are too high for rainbow trout to live in the more shallow part of the pond; the deeper part of the pond has too little dissolved oxygen to support fish. Mixing between the two parts of the pond is prevented by thermal stratification. 2. High content of dissolved solids in the water of the pond may be stressful to fish that are not acclimated. Although high levels of certain constituents (calcium, magnesium) are desirable to ameliorate the effects of other constituents (sulfate, heavy metals), it is not clear from our results whether the toxicity of the undesirable constituents is sufficiently reduced. Increased temperature of the water increases the stress that toxins exert on trout. 3. Continued monitoring on a quarterly basis for a full year would be necessary to evaluate the chemistry of the Long Fork Trout Pond for fish habitat. This would include the measurement of water-quality parameters such as ph, temperature, dissolved oxygen, and conductance at various depths in longitudinal and lateral traverses. Simultaneous samples should be taken at four of these stations to be analyzed for major anions and dissolved metals. 4. Further releases of rainbow trout should probably be confined to the late winter and early spring months, based on information from the first trout release in the spring of 1996, after which trout were caught from the pond. Temperature and dissolved oxygen content should be monitored closely to ensure that a segment of the pond s depth profile has water below 19 C and a dissolved oxygen content above 5.0 mg/l. References Cited Brannon, E.L., 1991, Trout culture, in Stickney, R.R., ed., Culture of salmonid fishes: Boca Raton, Fla., CRC Press, p Drever, J.A., 1988, The geochemistry of natural waters [2d ed.]: Englewood Cliffs, N.J., Prentice-Hall, 437 p. 14

15 Eipper, A., 1960, Managing farm ponds for trout production: Cornell, N.Y., New York State College of Agriculture, Extension Bulletin 1036, 29 p. Elliot, J.M., 1981, Some aspects of thermal stress on freshwater teleosts, in Pickering, A.D., ed., Stress in fish: London, Academic Press, p Goldman, C.R., and Horne, A.J., 1983, Limnology: New York, McGraw-Hill, 464 p. Heinen, J.M., 1996, Water quality criteria, uptake, bioaccumulation, and public health considerations for chemicals of possible concern in West Virginia mine waters used for the culture of rainbow trout: Shepherdstown, W.Va., The Conservation Fund s Freshwater Institute, prepared for U.S. Department of Agriculture, Agricultural Research Service, under grant agreement , 55 p. Hess, L., 1974, The summer catch, vertical distribution, and feeding habits of trout in Spruce Knob Lake: Proceedings, West Virginia Academy of Science, v. 46, p , McKee, J.E., and Wolf, H.W., eds., 1963, Water quality criteria [2d ed.]: Prepared for the California State Water Quality Control Board with assistance from Division of Water Supply and Pollution Control, U.S. Public Health Service, Department of Health, Education, and Welfare: The Resources Agency of California, 548 p. Piper, R.G., McElwain, I.B., Orme, L.E., McCraren, J.P., Fowler, L.G., and Leonard, J.R., 1982, Fish hatchery management: U.S. Fish and Wildlife Service, 517 p. Raleigh, R.F., Hickman, T., Solomon, R.C., and Nelson, P.C., 1984, Habitat suitability information: Rainbow trout: U.S. Department of the Interior, Fish and Wildlife Service, FWS/OBS-82/10.60, 64 p. Wunsch, D.R., Dinger, J.S., Taylor, P.B., Carey, D.I., and Graham, C.D.R., 1996, Hydrogeology, hydrogeochemistry, and spoil settlement at a large mine-spoil area in eastern Kentucky: Star Fire tract: Kentucky Geological Survey, ser. 11, Report of Investigations 10, 49 p. 15

16 Station Date Time (24- hr) Temp (C) ph Eh (mv) DO (mg/l) Table 1. Chemical data for Long Fork Trout Pond (dissolved constituents, mg/l) Cond. (µs) Ca Mg Na K Cl SO 4 HCO 3 Fe F PO 4 Ba Br TDS* Hardness as CaCO 3 * Pond outlet 7/12/ , < <1 3,520 3, x115x18 8/28/ , , ,460 2, x115x18 8/28/ , , ,494 2, x115x2 8/28/ , , ,425 2, x115x2 8/28/ , , , n max , , ,520 3,080 min , , ,425 2,653 avg 380 3, , ,472 2,834 std dev. CV(%) *Total dissolved solids calculated by summation; hardness calculated from Ca and Mg concentrations. Station Date Time (24-hr) NO 3 Si Li Mn Ni P Se Ag Sr S Tl Sn V Zn pond outlet 7/12/ < <0.129 < <0.426 < x115x18 8/28/ <0.049 <0.121 <0.129 < <0.426 <0.004 < x115x18 8/28/ < <0.129 < <0.426 <0.004 < x115x2 8/28/ < <0.129 < <0.426 <0.004 < x115x2 8/28/ < <0.129 < <0.426 <0.004 <0.004 n max min avg std. dev CV(%)