Abstract:Selenium (Se) is a chemical of concern at many locations across North America and elsewhere, and site-specific conditions are important when evaluating its bioaccumulation and effects in aquatic ecosystems. Most regulatory criteria and guidelines are based on waterborne Se concentrations. In contrast, the draft water quality chronic criterion of the US Environmental Protection Agency (USEPA) is based on Se concentrations in whole-body fish, and current information suggests the agency will issue a new draft cri… Show more
“…Selenium's high bioaccumulation factor confounds water‐quality monitoring efforts, and many have criticized free Se water measurements in favor of ovary/egg measurements . Although these tissue‐quality measurements are an improvement over water measurements in estimating Se risk, site‐specific testing for Se may be necessary, particularly in multiple stressor situations . One common stressor is hypersalinity.…”
Anthropogenic disturbance of seleniferous soils can lead to selenium contamination of waterways. Although selenium is an essential micronutrient, bioaccumulation and maternal transfer of proteinaceous selenomethionine (SeMet) can result in embryo toxicity. Furthermore, as the climate changes, the salinity of spawning grounds in water-restrained estuaries is increasing. Although a small increase in salinity may not directly impact adult fish, it may alter the detoxification strategies of developing organisms. Previous research indicates that hypersalinity may potentiate SeMet embryo toxicity at an early developmental stage. However, embryonic development is a complex, spatiotemporal process with a constantly shifting cellular microenvironment. To generate thresholds and an adverse outcome pathway for the interactions between selenium and salinity, we sought to identify windows of susceptibility for lethality and deformities in the Japanese medaka (Oryzias latipes). Embryos were treated in freshwater or saltwater for 24 h with 0.5 μM, 5 μM, and 50 μM SeMet at 6 different developmental stages (9, 17, 25, 29, 34, and 38). Survival, hatch, deformities (total, type, and severity), and days to hatch were quantified. Selenium embryo tissue measurements were performed. Selenomethionine exposures of 5 μM and 50 μM significantly decreased survival and hatch at all stages. However, SeMet uptake was stage-dependent and increased with stage. Stage 17 (early neurulation) was identified as the most susceptible stage for lethality and deformities. Selenomethionine in saltwater caused significantly greater toxicity than freshwater at stage 25 (early organogenesis), suggesting a role for liver and osmoregulatory organogenesis in toxicity.
“…Selenium's high bioaccumulation factor confounds water‐quality monitoring efforts, and many have criticized free Se water measurements in favor of ovary/egg measurements . Although these tissue‐quality measurements are an improvement over water measurements in estimating Se risk, site‐specific testing for Se may be necessary, particularly in multiple stressor situations . One common stressor is hypersalinity.…”
Anthropogenic disturbance of seleniferous soils can lead to selenium contamination of waterways. Although selenium is an essential micronutrient, bioaccumulation and maternal transfer of proteinaceous selenomethionine (SeMet) can result in embryo toxicity. Furthermore, as the climate changes, the salinity of spawning grounds in water-restrained estuaries is increasing. Although a small increase in salinity may not directly impact adult fish, it may alter the detoxification strategies of developing organisms. Previous research indicates that hypersalinity may potentiate SeMet embryo toxicity at an early developmental stage. However, embryonic development is a complex, spatiotemporal process with a constantly shifting cellular microenvironment. To generate thresholds and an adverse outcome pathway for the interactions between selenium and salinity, we sought to identify windows of susceptibility for lethality and deformities in the Japanese medaka (Oryzias latipes). Embryos were treated in freshwater or saltwater for 24 h with 0.5 μM, 5 μM, and 50 μM SeMet at 6 different developmental stages (9, 17, 25, 29, 34, and 38). Survival, hatch, deformities (total, type, and severity), and days to hatch were quantified. Selenium embryo tissue measurements were performed. Selenomethionine exposures of 5 μM and 50 μM significantly decreased survival and hatch at all stages. However, SeMet uptake was stage-dependent and increased with stage. Stage 17 (early neurulation) was identified as the most susceptible stage for lethality and deformities. Selenomethionine in saltwater caused significantly greater toxicity than freshwater at stage 25 (early organogenesis), suggesting a role for liver and osmoregulatory organogenesis in toxicity.
“…It is possible to use relationships between tissue types to estimate ovary/egg Se concentrations from nonreproductive tissues of the same species (e.g., nonlethal muscle biopsy samples); however, care should be taken because intertissue selenium concentration relationships are species dependent and may also vary among sites or seasons within species [45]. Therefore, conversion of data from other tissues to estimate ovary/egg concentrations should be based on site-and species-specific relationships [44].…”
Section: Sources Of Variability and Implications For Selenium Monitormentioning
confidence: 99%
“…Mature eggs and/or ovaries are the target for selenium analysis to evaluate potential reproductive effects [44]. It is possible to use relationships between tissue types to estimate ovary/egg Se concentrations from nonreproductive tissues of the same species (e.g., nonlethal muscle biopsy samples); however, care should be taken because intertissue selenium concentration relationships are species dependent and may also vary among sites or seasons within species [45].…”
Section: Sources Of Variability and Implications For Selenium Monitormentioning
Previous studies conducted in the Elk River watershed showed that selenium concentrations are higher in aquatic biota in lentic compared to lotic habitats of the system having similar water selenium concentrations. Studies have also shown that water selenium concentrations have increased over time (~10% per year) and recent annual average concentrations have ranged up to 0.044 mg/L in areas downstream from mine discharges. For the present study, trophic transfer of selenium was characterized in lotic versus lentic habitats using concentrations measured in field-collected samples and assuming a three-step food chain of water to the base of the food web (biofilm), to benthic invertebrates, and then to westslope cutthroat trout (WCT) ovaries. Food chain models were developed for each habitat type (lotic and lentic) by combining linear regression equations for the three transfer relationships, allowing for prediction of fish ovary concentrations from water concentrations. Greater accumulation of selenium in lentic areas was mostly attributable to greater uptake at the base of the food chain compared to lotic areas. Enrichment/trophic transfer factors for selenium at all levels of the lotic and lentic food chains decreased and then became near constant as exposure concentrations increased. The lotic model predicted little increase in WCT ovary selenium concentrations over an eightfold increase in water concentrations (~0.005-0.040 mg/L), accounting for the lack of observed increase in within-area fish tissue concentrations over time despite increasing trends in water concentrations.
“…Once mobilized, Se becomes bioavailable and in high concentrations leads to accumulation in plants and wildlife in aquatic ecosystems [21]. Se has four oxidative states: Selenate (Se 6+ ), Selenite (Se 4+ ), elemental Se (Se 0 ), and Selenide (Se 2− ), and the oxidative state of Se determines its bioavailability [22]. Selenate, the more oxidized state, and some organic forms of selenium are more soluble and, therefore, more available for plant uptake [23].…”
Selenium (Se) contamination of public lands and water is a result of irrigated agriculture and mining activities in areas rich in Se geologic deposits. Pariette Draw is part of the northern Colorado Plateau and is an area of concern for Se contamination in the Pariette Wetlands. Pariette Wetlands, a wetland built in the 1970s to provide wildlife habitat, is distinguished by its arid climate and a short growing season of hot dry summers followed by cold winters with several months below freezing. An understanding of how Se is mobilized and removed within the wetland will provide management strategies that minimize and mitigate Se contamination and promote sustainable ecosystem services. The data collected in 2012 and 2014 was the first comprehensive spatial and temporal analysis of Se in all environmental compartments (bird eggs, macroinvertebrates, plants, sediments, and water) of an arid wetland ecosystem in the Colorado Plateau. Water, sediment, and plant tissue samples were collected and analyzed to determine Se’s spatial and temporal variation in Pariette Wetlands. Se concentrations in water, sediment, and plants were evenly distributed throughout wetlands. No significant differences were found in plant Se concentrations between samples collected in 2012 (447 ± 44 ug kg−1) or 2014 (541 ± 42 μg kg−1), indicating that plant Se did not vary temporally during sampling. Aquatic plant species (e.g., pondweed (Potamogeton filiformis), 743 ± 66 μg kg−1 and watermilfoil (Myriophyllum spicatum), 874 ± 122 μg kg−1) accumulated more Se than plant species growing at the edges of the ponds (e.g., hardstem bulrush (Schoenoplectus acutus), 368 ± 37 μg kg−1 and cattail (Typha), 420 ± 43 μg kg−1). Plant roots (1045 ± 110 μg kg−1) accumulated more Se than aboveground vegetation (flowers, 228 ± 17 μg kg−1 or stems, 224 ± 19 μg kg−1). Relative to Se retained by sediments (75%), plants were not an extensive reservoir of wetland Se (<5%) but still may pose a risk to animals feeding on plant tissue. Thus, phytoremediation of Se does not appear to be a viable tool for Se mitigation in wetlands of arid climates with a short growing season, such as those located in the Colorado Plateau.
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