Mercury and Selenium in Fountain Creek Fish Tissues: An Update

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from the Study Group at the Aquatic Research Center, Colorado State University-Pueblo

In March of 2006, then Senator Ken Salazar put forth his vision that Fountain Creek could become a recreational amenity between Colorado Springs and Pueblo. The title of his vision was “The Fountain Creek Crown Jewel Project”. After connecting with about one hundred stakeholders from six Southern Colorado counties, he found support for the project to be very positive. A plan was soon developed with several priorities stated in the vision statement. First, two key components needed to be addressed in preparation for a successful project. One was to fix problems associated with Fountain Creek and its tributaries, including flood control and water quality. The second was to ensure that policy makers and community leaders in the region work cooperatively to carry out the vision.

Of interest to us here at CSU-Pueblo was a component highlighted in the vision being the broad issue of water quality. To our study group, it seemed that we could define what biological problems exist in the watershed relative to water quality. The timing for Colorado State University’s involvement in Fountain Creek issues could not have been better, as the initial funding for water quality studies in the Creek’s watershed came in the fall of 2006. Principle support came from the Lower Arkansas Valley Water Conservancy District for the purchase of an Inductively-Coupled Plasma Mass Spectrometer (ICP-MS). With this instrument came the University’s ability to detect 30 elements at trace (sub parts-per-billion or µg/kg) concentrations in water, sediment, plant or animal tissues. Additional funding has been received from the City and County of Pueblo, and the Pueblo Board of Water Works. As a result of continuous funding, hundreds of samples for analysis of trace elements have been obtained from the watershed. From the data collected thus far, two elements seem to be important for future monitoring and study: mercury and selenium.

The CSU-Pueblo study appears to fill a unique gap in the literature. To our knowledge and review of available literature, there are no reports showing concentrations of mercury or selenium, or any others, in resident biota of the Fountain Creek watershed. For this report, as an example of our investigation, we focus on mercury and selenium in the tissues of fish from Fountain Creek and its main tributary Monument Creek.

The project did not begin by studying mercury and selenium in fish tissues. Rather, we focused on these elements in water, sediments and plants. After some initial samples were analyzed, we directed our attention towards selenium for three reasons. First, it was listed as an element causing impairment within Fountain Creek in the 2008 Colorado 305(b) report. Second, U. S. Senator Salazar listed selenium as a priority in his original vision statement. Third, we found the element to be omnipresent in our samples. However, following additional sampling and analysis, it became imperative to also address the element mercury in the watershed.

 
Figure 1 – Fountain Creek Watershed showing the 14 sample site locations.

Fourteen sites in the Fountain Creek Watershed were established in late 2006 (Figure 1). Our initial question concerned the detection of selenium in water, its movement, and whether we could demonstrate site-to-site differences in its concentration in the watershed. Our second question concerned whether aquatic mosses, deployed “in-stream”, could concentrate the metalloid enough to be detected by instrumentation. Results gathered from samples of water and sediment, and use of the mosses, confirmed selenium increasing as the creek flowed toward it’s confluence with the Arkansas.

The surprise was the mercury detected in the plants at about half of the 14 sampling sites in the watershed in the fall study even though this element was not detectable, by ICP-MS, in water at all sites. This prompted us to survey mercury in fish, keeping in mind that the ICP-MS instrument detects additional elements as well.

 
Figure 2 – Colorado Division of Wildlife and Colorado State University-Pueblo personnel electro-shocking fish at LF-1, the Lower Fountain Creek site below the confluence of Upper Fountain and Monument Creeks in Colorado Springs.

For the survey, sampling each site was a joint effort between personnel from the Colorado Division of Wildlife and CSU-Pueblo using an electro shocker (Figure 2). Initial samples were taken from March to May of 2009. During this time, multiple species were collected: brown trout, creek chubs, flathead chubs, longnose and white suckers, and stonerollers. Although, we were not able to collect a single fish species at all locations for comparison between sites. Of particular interest, the fish species in upper Fountain Creek, i.e., sites UF-1 to UF-4, were mostly brown trout.

Moving downstream, the results showed selenium in the watershed generally increased in whole fish, regardless of species, whereas mercury generally decreased (Figures 3 and 4). Another finding was the differences between selenium and mercury in selected tissues of fishes. Where ovarian tissue was present, the liver, skin and muscle in fish were individually dissected and analyzed separately. Results suggested that the ovaries and livers were highest in selenium whereas mercury was highest in muscle. As little ovarian tissue is present in the spring, we consulted with Division of Wildlife personnel in order to arrange a fall study. We conducted the survey of trout during October of 2010. Tissues from this survey are currently being analyzed.

 
Figure 3 – Selenium concentrations are expressed as micrograms per kilograms (µg/kg) dry weight in whole fish. Upper Fountain Creek sites are indicated by UF-1 through UF-4; Monument Creek, MC-1 through MC-5; and Lower Fountain Creek by LF-1 through LF-5.
 
Figure 4 – Mercury concentrations are expressed as micrograms per kilograms (µg/kg) dry weight in whole fish. Upper Fountain Creek sites are indicated by UF-1 through UF-4; Monument Creek, MC-1 through MC-5; and Lower Fountain Creek by LF-1 through LF-5.

In addition to selenium and mercury in fish, other elements and sites in the watershed are being investigated. At present, we are addressing the influence of zinc, copper, arsenic, chromium, lead, and uranium on fish. Questions that we aim to answer include: Is it possible to show correlations between elements in fish tissues and in earlier studies when elements were found in fish-food organisms and plants addressed above? Can we corroborate elements in water, sediments, plants and fish tissues? This current investigation positions us to recognize additional problems in the watershed, and to understand their importance in the overall “water quality” component of the vision for establishing Fountain Creek as a Crown Jewel stream in Colorado.

Investigators:

Colorado State University-Pueblo Aquatic Research Center:
J. Carsella, S. Herrmann, D. Lehmpuhl, B. Vanden Heuvel, C. Kinney, P. Cabot, K. McGarvy, D. Nimmo
Colorado Division of Wildlife, Colorado Springs Office:
G. Dowler and P. Foutz