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11 July 2022 Trace Elements in Walleye Tissues and Dietary Components from an Impoundment Located Downstream of the Leadville Mining District, Colorado, I: Hg and Se
Scott J. Herrmann, Del Wayne R. Nimmo, Igor V. Melnykov
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Abstract

There is a paucity of studies focusing on how total mercury (THg) and total selenium (TSe) concentrations vary in walleye tissues and prey organisms from a reservoir that is downstream from a major mining district and whose basin consists of Cretaceous sedimentary Se-bearing outcroppings. Pueblo Reservoir in Colorado is fed by water from the upper Arkansas River, which has been polluted by trace metals and metalloids since mining began in 1859. Pueblo Reservoir is the only mainstem impoundment on the Upper Arkansas River and is located about 251 km downstream from the historic Leadville Mining District. Nearly all the contaminated colloids and sediment eventually reach Pueblo Reservoir and its walleye fishery. We compared THg and TSe concentrations among 15 walleye tissues clustered within “functional tissue groups,” and with walleye stomach contents and the walleye's primary forage fish (gizzard shad). We found that THg concentration in epaxial muscle and cardiac muscle ranked first and second, respectively, and results indicated a significant difference in THg between the 2 muscle types. Unlike THg, TSe levels were highest for liver, spleen, kidney, ovary/egg, and gill tissues, and TSe levels in all but 2 tissue pairings were significantly different. Significant differences occurred when THg and TSe in gizzard shad and stomach contents were compared to levels in each tissue. Our THg concentrations at the Pueblo Reservoir were generally lower than at other sites in western North America; however, TSe concentrations were higher and markedly different. The data indicate that THg tissue levels appear to be lower than established fish health benchmarks, yet many TSe tissue concentrations were above critical thresholds.

Son escasos los estudios centrados en cómo varían las concentraciones de mercurio total (THg) y selenio total (TSe) en los tejidos de luciopercas y en sus presas en un embalse situado aguas abajo de un importante distrito minero y cuya cuenca está formada por afloramientos sedimentarios cretácicos portadores de selenio. El embalse Pueblo Reservoir, en Colorado, se alimenta del agua del río Upper Arkansas, que ha sido contaminado por trazas de metales y metaloides desde el inicio de la explotación minera en 1859. El embalse Pueblo Reservoir es el único embalse del curso superior del río Arkansas, a unos 251 km aguas abajo del histórico distrito minero de Leadville. Casi todos los coloides y sedimentos contaminados llegan al embalse Pueblo Reservoir y a la zona pesquera de luciopercas. Comparamos las concentraciones de THg y TSe en 15 tejidos de luciopercas (agrupados en “grupos de tejidos funcionales”) con el contenido estomacal de la lucioperca y del sábalo molleja, principal presa de la lucioperca. Encontramos que el THg en el músculo epaxial y el músculo cardíaco ocupaban el primer y segundo lugar, respectivamente, y además los resultados indicaban una diferencia significativa entre los dos tipos de músculo. A diferencia del THg, los niveles de TSe fueron más altos en los tejidos del hígado, el bazo, el riñón, el ovario/óvulo y las branquias, y todos los pares de tejidos, excepto en dos, fueron significativamente diferentes. Se produjeron diferencias significativas cuando se comparó el contenido de la molleja y del estómago con el THg y el TSe en cada tejido. Nuestros resultados de THg fueron, en general, más bajos que en otros lugares del oeste de Norteamérica. Sin embargo, las concentraciones de TSe fueron más altas y notablemente diferentes. Los datos indican que los niveles de THg en los tejidos parecen ser inferiores a los puntos de referencia establecidos para la salud de los peces, aunque muchas concentraciones de TSe en los tejidos estaban por encima de los umbrales críticos.

© 2022
Scott J. Herrmann, Del Wayne R. Nimmo, and Igor V. Melnykov "Trace Elements in Walleye Tissues and Dietary Components from an Impoundment Located Downstream of the Leadville Mining District, Colorado, I: Hg and Se," Western North American Naturalist 82(2), 346-361, (11 July 2022). https://doi.org/10.3398/064.082.0209
Received: 7 June 2021; Accepted: 1 December 2021; Published: 11 July 2022
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