971

North American Journal of Fisheries Management 21:971–975, 2001q Copyright by the American Fisheries Society 2001

Influence of Stream Flow on Hydrogen SulfideConcentrations and Distributions of Two Trout Species

in a Rocky Mountains Tailwater

MATTHEW R. DARE*1 AND WAYNE A. HUBERT

U.S. Geological Survey, Wyoming Cooperative Fish and Wildlife Research Unit,2

University of Wyoming, Laramie, Wyoming 82071-3166, USA

JOSEPH S. MEYER

Department of Zoology and Physiology, University of Wyoming,Laramie, Wyoming 82071-3166, USA

Abstract.—Geothermal springs in or adjacent tostreams can contribute hydrogen sulfide (H2S) and affectdistributions of fish. We assessed the effects of H2S,relative to discharge, on the locations and movementsof cutthroat trout Oncorhynchus clarki and brown troutSalmo trutta in a regulated river in northwestern Wyo-ming. Concentrations of H2S as low as 0.13 mg/L pre-vented upstream passage and habitation by trout over a4.2-km reach of the river. The location of the down-stream terminus of the H2S plume was relatively sta-tionary; it varied little when discharge was stable atmoderate flows (13.7–14.8 m3/s) and moved within a300-m reach when flows were declining from 20.9 to5.7 m3/s. Changes in water temperature and riffle areaappeared to be the major mechanisms controlling theconcentration and downstream influence of H2S.

Geothermal effluents are present in many wa-tersheds of the Rocky Mountains. Geothermalsprings in or adjacent to streams can cause in-creased water temperatures and inputs of chemi-cals that might harm aquatic life (Goldstein 1999).The toxicity of one such chemical, hydrogen sul-fide (H2S), has been studied extensively (EPA1976; NRC 1979). Most research has concentratedon H2S in paper mill effluents (Colby and Smith1967) and the effects of H2S on invertebrates (Os-eid and Smith 1974) and sedentary life stages offishes (Adelman and Smith 1970; Smith et al.1976). Little research has been conducted on theeffects of geothermal sources of H2S on fish, andwe are unaware of any studies that have attemptedto assess the relationship between discharge andthe instream dynamics of H2S.

* Corresponding author: mattdare@biomark.com1 Present address: Biomark, Inc., 149 South Adkins

Way, Suite 104, Meridian, Idaho 83642, USA.2 The Unit is jointly supported by the University of

Wyoming, Wyoming Game and Fish Department, U.S.Geological Survey, and Wildlife Management Institute.

Received October 23, 2000; accepted April 27, 2001

DeMaris Springs is a cluster of geothermalsprings that contribute approximately 1.8 m3/s ofH2S-enriched water to the Shoshone River, a reg-ulated river in northwestern Wyoming (Figure 1).Discharge from Buffalo Bill Dam is substantiallyreduced each fall at the end of the agriculturalgrowing season and inputs from DeMaris Springsduring fall and winter can constitute 10–20% ofthe total discharge. Pedlar (1985) reported that, atdischarges ranging from 2.8 to 45.3 m3/s, H2S con-centrations directly downstream from DeMarisSprings often exceeded 0.025 mg/L, the lethal con-centration for trout (EPA 1976).

The fish community downstream from DeMarisSprings primarily consists of cutthroat trout On-corhynchus clarki and brown trout Salmo trutta,but rainbow trout O. mykiss and mountain white-fish Prosopium williamsoni are also present in theriver. Managers have noted low overwinter reten-tion of trout within the 5-km reach directly down-stream from the H2S plume beginning approxi-mately 4 km downstream from DeMaris Springs(Vogt and Annear 1991). One hypothesized mech-anism for the overwinter losses of trout is in-creased downstream influence of H2S at low dis-charge and corresponding downstream fish move-ment.

Our objective was to determine whether low dis-charge from the upriver Buffalo Bill Reservoirduring fall and winter resulted in downstream mi-gration of the H2S plume from DeMaris Springsand attendant downstream movement of trout. Todo this, we compared the H2S discharge rate andthe area affected downstream, hypothesizing thatat static discharge, the downstream terminus of theplume would remain relatively stable. However,we expected that with decreasing discharge, theproportionally greater contributions of DeMarisSprings would cause downstream migration of the

972 DARE ET AL.

FIGURE 1.—Sampling locations (A–G) in the Shoshone River, Wyoming, where the dispersion of hydrogen sulfidefrom DeMaris Springs was examined and related to discharge rates from Buffalo Bill Dam.

H2S plume, resulting in downstream movement oftrout.

Methods

We monitored H2S concentrations at seven sam-pling sites in the Shoshone River from Octoberthrough February of 1997–1998 and 1998–1999.Discharge during the winter of 1997–1998 wasrelatively stable at 13.7–14.8 m3/s. To determinethe dynamics of the H2S plume during decreasingdischarge from Buffalo Bill Reservoir, we moni-tored the position of the downstream terminus ofthe H2S plume from DeMaris Springs during thewinter of 1998–1999 (beginning in December) atdeclining discharges of 20.9, 13.9, 8.2, and 5.7m3/s. Each discharge was maintained for 2–3weeks.

Concentration of total reactive sulfide at eachsite was measured weekly using the MethyleneBlue Method (APHA 1995) and a Bausch andLomb Spectronic Mini-20 spectrophotometer. Theminimum detectable level of total reactive sulfideusing this technique was 0.01 mg/L, which wasbelow the 0.025 mg/L lethal concentration fortrout. The spectrophotometer was calibrated every2 weeks during the study. Water samples, collectedwith plastic containers from the middle of the wa-ter column at midchannel, were processed on site.Three subsamples were taken and measured fromeach water sample, and we averaged these values

to obtain an estimate of total reactive sulfide. Wemeasured the pH of each water sample with anelectronic meter, monitored water temperature us-ing continuously recording thermometers at eachsampling site, and took weekly measurements ofdischarge upstream and downstream from DeMarisSprings.

To determine the location of the downstreamterminus of the H2S plume (sulfide ,0.01 mg/L)in 1998–1999, we sampled total reactive sulfideevery 100 m downstream from site D (Figure 1),where the Wyoming Game and Fish Departmenthas consistently captured fish during fall andspring electrofishing surveys (S. Yekel, WyomingGame and Fish Department, personal communi-cation). We calculated, using the first and seconddissociation constants for H2S (Langmuir 1997),pH, and water temperature, the proportion of totalsulfide that was H2S.

Movements of radio-tagged fish were monitoredfrom December 1998 through February 1999. Us-ing electrofishing gear, we collected cutthroat troutand brown trout (20–30 cm total length) duringthe last week of November from a 2.4-km sectionof the Shoshone River extending from about 0.5km upstream from site E downstream to site F(Figure 1). Each fish was surgically implanted witha radio transmitter (Advanced Telemetry Systems#357) according to the technique of Bidgood(1980) and released near its point of capture fol-

973MANAGEMENT BRIEFS

TABLE 1.—Total sulfide and hydrogen sulfide (H2S)concentrations measured at seven sampling sites below thesource (DeMaris Springs) in the Shoshone River, Wyo-ming, during winter of 1997–1998.

SiteDistance below

source (km)Sulfide

(mean; mg/L)

H2S (mg/L)

Mean Range

ABCDEFG

0.22.24.26.28.7

11.3

,0.010.600.250.12

,0.01,0.01,0.01

,0.010.540.210.10

,0.01,0.01,0.01

0.35–0.910.13–0.320.05–0.21

FIGURE 2.—Hydrogen sulfide concentrations at threesampling sites in the Shoshone River, Wyoming (seeFigure 1), having detectable levels of H2S during thewinter of 1997–1998. The dashed line denotes the con-centration of H2S that is lethal to trout.

FIGURE 3.—Downstream distance from DeMarisSprings (Shoshone River, Wyoming) of the terminus ofthe hydrogen sulfide plume versus discharge (by date)from Buffalo Bill Reservoir.

lowing a 30–90 min acclimation period. Each fishwas relocated every 3–4 d through the winter. Fishpositions were plotted on a topographic map anddistance and direction of movements between ob-served locations were recorded.

Results and Discussion

Lethal concentrations of H2S were consistentlyobserved at sites B, C, and D in 1997–1998 (Table1). Although they varied considerably within agiven site (Figure 2), H2S concentrations at sitesB, C, and D were consistently five times or morethe lethal limit for trout (EPA 1976). No H2S wasdetected at or downstream from site E (Table 1).The H2S plume emanating from DeMaris Springsremained stationary when discharge was held rel-atively constant during the winter of 1997–1998.The downstream terminus of the plume was ap-proximately 4.7 km downstream from DeMarisSprings. We determined the plume’s position in1997–1998 by sampling at 100-m intervals down-stream from site D. Because surface turbulencecauses rapid release of H2S into the overlying air(NRC 1979), a large riffle directly downstreamfrom site D probably enhanced this process, al-though microbial and chemical oxidation of H2Smight also have contributed.

The H2S plume migrated slightly downstreamas discharge was reduced during the winter of1998–1999. When discharge was 20.9 m3/s in De-cember 1998, the downstream terminus of theplume was approximately 4.5 km downstreamfrom DeMaris Springs. The terminus was 0.2 kmfurther downstream when discharge was decreasedto 13.9 m3/s (Figure 3), and it remained at thislocation when discharge was reduced to 8.2 m3/s.However, the plume moved upstream approxi-mately 0.3 km about 10 d after discharge was re-duced to 5.7 m3/s.

Two factors probably affected the downstream

terminus of the plume when discharge was de-creased: (1) an increasing proportion of streamflow composed of water from DeMaris Springs,and (2) an increase in water temperature in Feb-ruary 1999. Decreasing discharge results in a de-crease in water velocity (Kraft 1972; Cushman1985). It is likely that decreased water velocity(associated with flow reduction in the ShoshoneRiver) and the proportionally greater contributionof H2S-infused water from DeMaris Springscaused the downstream movement of the plume inJanuary 1999. We noted an increase in the lengthof two riffles located between DeMaris Springsand site D when discharge was reduced from 8.2to 5.7 m3/s. However, given the delayed upstreammigration of the plume in February 1999, it isunlikely that increased surface turbulence when

974 DARE ET AL.

FIGURE 4.—Water temperatures recorded downstreamfrom DeMaris Springs (Shoshone River, Wyoming) dur-ing the winters of 1997–1998 and 1998–1999.

FIGURE 5.—Distributions of cutthroat trout (solidbars) and brown trout (open bars) downstream fromDeMaris Springs (Shoshone River, Wyoming) on foursampling dates during the winter of 1998–1999.

discharge was 5.7 m3/s resulted in greater H2S re-lease into the atmosphere.

A probable explanation for the upstream move-ment of the plume about 10 d after discharge wasreduced to 5.7 m3/s on 1 February, is a 4.58C in-crease (from about 8.08C to 12.58C) in the meandaily water temperature at DeMaris Springs thatoccurred early in February 1999 (Figure 4). Be-cause (1) the aqueous solubility of H2S gas de-creases with increasing temperature and (2) therate of diffusion of gases increases as temperatureincreases (Morel and Hering 1993), H2S was prob-ably lost to the air more rapidly at the higher watertemperatures causing the upstream migration ofthe H2S plume. However, microbial and chemicaloxidation of H2S might have also increased athigher water temperatures.

We did not record downstream movements oftrout as discharge was reduced during the winter1998–1999. Although we recorded radio-taggedtrout within 1 km of the downstream terminus ofthe H2S plume throughout the fall and winter, wedid not record any upstream movements of troutthrough the plume. The distribution of radio-tagged trout downstream from the H2S plume didnot seem to be affected during the second winter(Figure 5).

When there is a detectable odor in the air above

a stream, the concentration of H2S is 0.25 mg/Lor greater (EPA 1979). Because we always noticeda strong odor of H2S in the air between DeMarisSprings and site D, the downstream attenuation ofH2S as water flowed through several riffles in thatreach suggests that surface turbulence effects theremoval of H2S from the Shoshone River. Duringboth winters, H2S always became undetectablewithin 0.5 km downstream of the large riffle down-stream from site D. The apparent importance ofriffles in controlling H2S concentrations in theShoshone River suggests that water quality and theupstream boundary of the trout fishery could beenhanced by installing structures that promotedsurface turbulence downstream from DeMarisSprings. However, because the H2S inputs are nat-ural rather than anthropogenic (e.g., paper mills),such management might not be appropriate.

Acknowledgments

We thank M. Clark, S. Rothmeyer, and M. Stich-ert for assistance in the field and S. Yekel and R.McKnight of the Wyoming Game and Fish De-partment in Cody for providing equipment. N. Nib-blelink and S. Yekel provided thoughtful com-ments on the manuscript. The Wyoming Game andFish Department funded this project. Reference totrade names does not constitute an endorsement.

ReferencesAdelman, I. R., and L. L. Smith, Jr. 1970. Effect of

hydrogen sulfide on northern pike eggs and sac fry.

975MANAGEMENT BRIEFS

Transactions of the American Fisheries Society 99:501–509.

APHA (American Public Health Association). 1995.Standard methods for the examination of water andwastewater. Port City Press, Baltimore, Maryland.

Bidgood, B. F. 1980. Fish surgical procedure for im-plementation of radio tags in fish. Alberta Divisionof Fish and Game, Fisheries Research Board Report20, Edmonton.

Colby, P. J., and L. L. Smith. 1967. Survival of walleyeeggs and fry on paper fiber sludge deposits in theRainy River, Minnesota. Transactions of the Amer-ican Fisheries Society 96:278–296.

Cushman, R. M. 1985. Review of ecological effects ofrapidly varying flows downstream from hydroelec-tric facilities. North American Journal of FisheriesManagement 5:330–339.

EPA. 1976. Effects of hydrogen sulfide on fish and in-vertebrates. Part 1, Acute and Chronic ToxicityStudies. EPA Publication 600/3-76-062, Washing-ton, D.C.

EPA. 1979. Methods for chemical analysis of water andwastes. EPA Publication 600/4-79-020, Washing-ton, D.C.

Goldstein, J. N. 1999. Effects of geothermal effluentson rainbow trout and brown trout in the FireholeRiver, Yellowstone National Park, Wyoming. Mas-ter’s thesis. University of Wyoming, Laramie.

Kraft, M. E. 1972. Effects of controlled flow reductionon a trout stream. Journal of the Fisheries ResearchBoard of Canada 29:1405–1411.

Langmuir, D. 1997. Aqueous environmental geochem-istry. Prentice-Hall, Upper Saddle River, New Jer-sey.

Morel, F. M. M., and J. G. Hering. 1993. Principles andapplications of aquatic chemistry. John Wiley andSons, Inc., New York.

NRC (National Research Council), Subcommittee onHydrogen Sulfide. 1979. Hydrogen sulfide. Uni-versity Park Press, Baltimore, Maryland.

Oseid, D. M., and L. L. Smith, Jr. 1974. Chronic toxicityof hydrogen sulfide to Gammarus pseudolimnaeus.Transactions of the American Fisheries Society 103:819–822.

Pedlar, D. 1985. Hydrogen sulfide concentrations inShoshone River below Buffalo Bill Reservoir. Wy-oming Game and Fish Department, Fish Division,Adminstrative Report, Cheyenne.

Smith, L. L., Jr., D. M. Oseid, G. L. Kimball, and S. M.El-kandelgy. 1976. Toxicity of hydrogen sulfide tovarious life history stages of bluegill (Lepomis ma-crochirus). Transactions of the American FisheriesSociety 105:442–449.

Vogt, G. F., and T. C. Annear. 1991. Shoshone Riverinstream flow report. Wyoming Game and Fish De-partment. Fish Division, Administrative Report,Cheyenne.