Bioaccumulation of Selenium by the Bryophyte Hygrohypnum ochraceum in the Fountain Creek Watershed, Colorado

Abstract

Aquatic bryophytes, Hygrohypnum ochraceum, were deployed "in situ" at 14 sites in the Fountain Creek Watershed, spring and fall, 2007 to study selenium (Se) accumulation. Dissolved, total, and pore (sediment derived) water samples were collected and water quality parameters determined while plants were exposed to the water for 10 days. There was a trend showing plant tissue-Se uptake with distance downstream and we found a strong correlation between Se in the water with total hardness in both seasons. There was a modest association between Se-uptake in plants with hardness in the spring of 2007 but not the fall. Plants bioconcentrated Se from the water by a factor of 5.8 × 10(3) at Green Mountain Falls and 1.5 × 10(4) at Manitou Springs in the fall of 2007. Both are examples of the bioconcentration abilities of the plants, primarily in the upper reaches of the watershed where bioconcentration factors were highest. However, the mean minima and maxima of Se in the plants in each of the three watershed segments appeared similar during both seasons. We found direct relationships between the pore and dissolved Se in water in the spring (R (2) = 0.84) and fall (R (2) = 0.95) and dissolved Se and total hardness in the spring and fall (R (2) = 0.92). The data indicate that H. ochraceum was a suitable indicator of Se bioavailability and Se uptake in other trophic levels in the Fountain Creek Watershed based on a subsequent study of Se accumulation in fish tissues at all 14 sites.

Mercury and selenium in fish of Fountain Creek, Colorado (USA): possible sources and implications

“…Similarly, Turner ( 2009 ) found dissolved Se in water from site LF-4 (Lower Fountain Creek, Pueblo, CO, Table 1 ) averaging 9.7 µg/l in spring and 18.6 µg/l in the fall. As part of an extensive monitoring study Herrmann et al ( 2012 ) found bioconcentration factors in the aquatic plant, H. ochraceum , exposed for 10 days in-stream, as high as 5.8 × 10 3 at Green Mountain Falls site (UF-1) and 1.5 × 10 4 at the Manitou Springs site (UF-2) in the fall of 2007. The main conclusion by Herrmann et al ( 2012 ) was that the aquatic plants ( H. ochraceum ) used in the study were suitable indicators of Se-bioavailabilty and that Se potentially would enter additional trophic levels, including fish, in Fountain Creek.…”

“…Among other issues were flash floods leading to erosion, resulting in questions about the sources of Se, the movement and varying concentrations of Se in the watershed, and was there uptake of the metalloid into the stream biota including fish? Because of an earlier study by Nimmo et al ( 2006 ) who showed the cadmium and zinc accumulation by an aquatic plant species, Hygrohypnum ochraceum, in the upper Arkansas River, Colorado, we used H. ochraceum as an indicator organism to determine Se-uptake in the Fountain Creek watershed (Herrmann et al 2012 ). Four findings of this effort were that the: (1) plants obtained more Se in the basin with travel-distance downstream, (2) plants showed a trend to take up more Se with total hardness in the spring versus the fall, (3) bryophytes accumulated Se thousands of times above the Se-concentration in ambient water, particularly noticeable in the upper reaches of the watershed in the fall, and most important, (4) the bryophytes appeared to be a suitable indicator of Se bioavailability to other trophic levels.…”

“…Upper Fountain Creek flows through sand, gravel, and boulders underlain with sandstone and shale; after leaving the mountains, it becomes a typical meandering sandy-bottom warm-water stream free of any impoundments, dams or reservoirs along its course. Herrmann et al ( 2012 ) found Fountain Creek to be a well-oxygenated stream with median dissolved oxygen concentrations of 14 sites (11.2 mg/l in the spring and 8.7 mg/l in the fall). A major tributary to Fountain Creek, Monument Creek, originates in the Rampart Range of Colorado flowing easterly until it leaves the front range mountains then the tributary turns south eventually confluencing with the upper Fountain Creek at America the Beautiful Park in downtown Colorado Springs, Colorado.…”

“…1 . Both Fountain and Monument Creeks are perennial streams and sampling sites were established in the watershed by Herrmann et al ( 2012 ); their locations indicated by global positioning system (GPS) and map descriptions are in Table 1 . It is important to note that Fountain Creek is a major tributary to the lower Arkansas River in Colorado.…”

“…The 2 years of sampling, 2007–2009 included 161 total (unfiltered), 205 dissolved (0.45 µM filter) and 113 pore (interstitial) water samples. The pore water samples were obtained using a mechanical vacuum-operated pore-water extractor similar to that described by Winger and Lasier ( 1991 ) and sampling method described by Herrmann et al ( 2012 ). All samples were placed on ice, and transported to the laboratory where total and dissolved water samples were acidified with Ultrex (ultra-pure) concentrated HNO 3 and stored at 4 °C until analysis.…”