Recent Research

Environmental Effects of Selenium

Adrian M. H. deBruyn and Peter M. Chapman, Selenium Toxicity to Invertebrates: Will Proposed Thresholds for Toxicity to Fish and Birds Also Protect Their Prey? Environmental Science & Technology, volume 41 (2007), pages 1766-1770.

Efforts to manage the environmental risks of selenium (Se) in freshwater ecosystems have focused primarily on fish and birds, with invertebrates most often considered only as dietary sources of Se to higher trophic levels. Relatively little attention has been given to the risk of Se toxicity to invertebrates. Based on a review of 156 aqueous, dietary, or internal Se concentrations associated with toxic effects in 29 macroinvertebrate species, we found that water concentrations associated with acute lethality varied >1000-fold among taxa, whereas toxic dietary concentrations varied ~100-fold and toxic internal concentrations varied about 30-fold. Sublethal effects occurred at ~10-fold lower concentrations than lethality. Sublethal effects occurred at 1-30 g Se/g dry weight in invertebrate tissue, a range that encompasses proposed dietary thresholds for toxicity to fish and water birds, suggesting that Se may cause toxic effects in some invertebrate species at concentrations considered to be "safe" for the organisms consuming them.

The journal is available at libraries and the article may be purchased on-line at: http://pubs.acs.org/cgi-bin/abstract.cgi/esthag/2007/41/i05/abs/es062253j.html

Robert W. Van Kirk, Sheryl L. Hill, Modeling Predicts Trout Population Response to Selenium Based on Individual-Level Toxicity, Idaho State University, Final Project Report to Greater Yellowstone Coalition, Idaho Falls, Idaho, December 11, 2006.

We model the cutthroat trout life cycle explicitly, based on demographic data from the upper Snake River basin, U.S.A., the southeast Idaho portion of which is susceptible to selenium contamination associated with phosphate mining. Individual-level responses, limited to pre-winter juvenile mortality and growth reduction, were modeled by functions determined from published laboratory data; density dependence, applied only to juvenile winter survival, was modeled by a compensatory survival rate function. Long-term population size relative to carrying capacity decreased sigmoidally with increasing concentration, and affected populations initialized at carrying capacity stabilized at sub-carrying capacity equilibria after a period of decline. Toxicity-related juvenile mortality was the primary cause of population size decrease, and individual-level response was greater than population-level response until individual-level mortality exceeded 70%. Populations compensated for increased pre-winter mortality via decreased density-dependent winter mortality at selenium concentrations below about 10 μg/g (whole-body, dry weight). At higher concentrations, equilibrium population size declined in the stochastic environment not because average juvenile survival rates declined but because variance in survival rates declined, preventing high survival during years in which fry production was low relative to carrying capacity. Our results suggest a protective tissue-based criterion for cutthroat trout of between 5.5 and 7.4 μg/g, higher than some that have been proposed based on individual-level effects but lower than USEPA’s proposal of 7.91 μg/g. Selenium concentrations observed in trout collected in the southeast Idaho phosphate mining area indicate high potential for population-level effects, but a statistically rigorous study of concentrations and population sizes throughout the phosphate patch would be required assess actual effects.

Full study>> http://www.greateryellowstone.org/media/pdf/van-kirk_selenium_report.pdf

Jorgelina R. Muscatello, Pamela M. Bennett, Kevin T. Himbeault, Andrew M. Belknap, and David M. Janz, Larval Deformities Associated with Selenium Accumulation in Northern Pike (Esox lucius) Exposed to Metal Mining Effluent, Environmental Science & Technology, volume 40 (2006), pages 6506-6512.

The objective of this study was to investigate selenium toxicosis in larval northern pike (Esox lucius) originating from reproductively mature pike collected downstream of a uranium milling operation in northern Saskatchewan, Canada. Eggs were obtained from female pike collected from a reference site and three sites representing an exposure gradient (approximately 2, 10, and 15 km downstream of effluent discharge). Embryos were incubated following a two-way (crossover) analysis of variance experimental design that allowed discrimination between effects due to maternal transfer to eggs and effects due to site water exposure in the developing embryos. The major finding of this study was a significant increase in the frequencies of individual deformities (skeletal curvatures, craniofacial deformities, and fin deformities) and edema in fry originating from high and medium exposure site females (mean selenium concentrations of 48.23 and 31.28 g/g egg dry weight and 38.27 and 16.58 g/g muscle dry weight, respectively) compared to reference site females. Selenium concentrations resulting in a 20% increase in total deformities above background levels (EC20s) were 33.55 and 21.54 /g dry weight in eggs and muscle, respectively. Mathematical conversion of the egg- and muscle-derived relationships to whole body selenium levels resulted in similar EC20s of 15.56 and 17.72 g/g dry weight, respectively. These relationships between tissue selenium levels and larval deformities suggest that northern pike are within the same range of sensitivity to selenium as the majority of warm water (e.g., centrarchids and cyprinids) and cold water (e.g., salmonids) fish species studied to date.

The journal is available at libraries and the article may be purchased on-line at: http://pubs.acs.org/cgi-bin/abstract.cgi/esthag/2006/40/i20/abs/es060661h.html

Mark Wayland, Robert Crosley, Selenium and Other Trace Elements in Aquatic Insects in Coal Mine–Affected Streams in the Rocky Mountains of Alberta, Canada, Archives of Environmental Contamination and Toxicology, volume 50 (2006), pages 511–522.

We determined levels of Se, As, Cd, Pb, and Zn in aquatic insects at coal mine–impacted and reference sites in streams in the Rocky Mountain foothills of west central Alberta from 2001–2003. Selenium levels were greater at coal mine–impacted sites than at reference sites in caddisflies but not in mayflies or stoneflies. Arseniclevels were greater at coal mine–impacted sites than at reference sites in caddisflies and stoneflies but not in mayflies. Zn levels were higher at coal mine–impacted sites than at reference sites in all three groups of insects. At coal mine–impacted sites, Se levels in mayflies and caddisflies were greater than those in stoneflies while at reference sites mayflies contained greater concentrations of Se than either caddisflies or stoneflies. Arsenic levels in mayflies were greater than those in caddisflies at reference and coal mine–impacted sites and were greater than those in stoneflies at reference sites. At both types of sites Cd differed amongst insect taxa in the order of mayflies > caddisflies > stoneflies. The same was true of Zn at coal mine–affected sites. At reference sites, stoneflies had greater concentrations of Zn than both mayflies and caddisflies. At both types of sites, Pb levels were greater in mayflies and caddisflies than they were in stoneflies. Of the five trace elements considered in this study, only Se was sufficiently elevated in aquatic invertebrates to be of potential concern for consumers such as fish and aquatic birds. Such was the case at both coal mine–impacted and reference sites.

The journal is available at libraries and the article may be purchased on-line at http://www.springerlink.com/content/y...

J.D. Latshaw, T.Y. Morishita, C.F. Sarver and J. Thilsted, Selenium Toxicity in Breeding Ring-Necked Pheasants (Phasianus colchicus), Avian Diseases, vol. 48 (2004), pages 935-939.

A flock of breeding pheasants received feed that contained a high level of selenium (9.8 parts per million) due to a mixing error in preparing the feed. Within 4 days, the rate of egg production began to decrease and 12% of the hens died with a week. Hatchability of the eggs laid was 35%, compared to >80% in normal eggs. Approximately 10% of the chicks that hatched had deformed beaks and abnormal eyes. Many of the chicks that died in the shell had deformities, bringing the total fraction of deformed chicks to more than 50% of all embryos that developed.

The journal is available on-line and the article may be found at the following link:http://avdi.allenpress.com/avdionline/...

S.J. Teh, X. Deng, D.-F. Deng, F.-C. Teh, S.S.O. Hung, T.W.-M. Fan, J. Liu and R.M. Higashi, Chronic Effects of Dietary Selenium on Juvenile Sacromento Splittail (Pogonichthys macrolepidotus), Environmental Science & Technology, vol. 38 (2004), pages 6085-6093.

Results indicate that survivals, growth, changes of tissue selenium concentrations and histopathology of juvenile splittail were dose-dependent, but their response thresholds to dietary selenium concentrations differed and depended on treatment concentrations and duration of exposure. Chronic exposure to 6.6 milligrams of selenium per kilogram in the diet (6.6 parts per million) induced deleterious health effects that can potentially impact survival of these fish.

The journal is available at libraries and the article may be purchased on-line at http://pubs3.acs.org/acs/journals/doilookup...

J.H. Roe, W.A. Hopkins, J.A. Baionno, B.P. Staub, C.L. Rowe and B.P. Jackson, Maternal Transfer of Selenium in Alligator Mississippiensis Nesting Downstream from a Coal-Burning Power Plant, Environmental Toxicology and Chemistry, vol. 23 (2004), pages 1969-1972.

Over a four-year period, the authors collected three clutches of eggs of the American alligator (A. mississippiensis) from a single nest at a site contaminated with selenium and compared egg and hatchling selenium concentrations and clutch viability from this nest to nests downstream from the contaminated site and at a reference site (two clutches from two nests at each site). Eggs and hatchlings from the nest at the selenium-contaminated site and downstream nests have elevated selenium concentrations (2.1-7.8 parts per million, ppm) and low viability (30-54%) compared to reference nests (1.4-2.3 ppm and 67-74% viability) despite the fact that selenium concentrations did not exceed reproductive toxicity thresholds set for other egg-laying vertebrate species. These data suggest that the alligator may be more sensitive to the effects of selenium that other species and further studies on the uptake, accumulation and reproductive success of alligator embryos exposed to excessive selenium are warranted.

The journal is available in libraries, the abstract of the article may be viewed on-line at
http://entc.allenpress.com/entconline/?request=get-abstract...
and the full text purchased at the same link.

 

A.S. Stewart, S.N. Luoma, C.E. Schlekat, M.A. Doblin and K.A. Hieb, Food Web Pathway Determines How Selenium Affects Aquatic Ecosystems: A San Francisco Bay Case Study, Environmental Science & Technology, vol. 38 (2004), pages 4519-4526.

The authors show that a combination of food web structure and the physiology of trace element accumulation are required to explain why some species in San Francisco Bay are threatened by a relatively low level of selenium contamination. Bivalves and crustacean zooplankton form the base of two dominant food webs in estuaries such as the San Francisco Bay. The dominant bivalve in the San Francisco Bay has a 10-fold slower rate constant for elimination of selenium than do the common crustaceans. The result is much higher selenium concentrations in the bivalve than in the crustaceans. Consequently, several predators of bivalves have tissue concentrations of selenium that exceed thresholds thought to be associated with teratogenesis or reproductive failure (liver selenium concentrations greater than 15 micrograms per gram (15 parts per million) dry weight). Deformities typical of selenium-inducted teratogenesis were observed in one of these species.

The journal is available at libraries and the article may be purchased on-line at
http://pubs3.acs.org/acs/journals/...

D.J. Hoffman, C.M. Marn, K.C. Marois, E. Sproul, M. Dunne and J.P. Skorupa, Sublethal Effects in Avocet and Stilt Hatchlings form Selenium-contaminated Sites, Environmental Toxicology and Chemistry, vol. 21 (2002), pages 561-566.

Excessive selenium in the aquatic food chain is embryotoxic and teratogenic to avocets, stilts and other waterbirds. American avocet and black-necked stilt eggs were collected from three sites in the Tulare Lake Basis on California, USA and hatched in the laboratory. Yolk sac-free hatching weights and bone lengths were less and liver weights and liver to body weight ratios were greater in avocets at the site that had the highest levels of selenium. Oxidative stress, increasing with selenium concentrations in the birds, was also evident in avocet hatchlings from the site with the highest selenium water concentrations.

The journal is available in libraries, the abstract of the article may be viewed on-line at
http://entc.allenpress.com/entconline/?request... and the full text purchased at the same link.