Assessing the Ecotoxicology of 4-nonylphenol Mixtures Across the Aquatic Food Chain
Principal Investigators: Heiko Schoenfuss and Matthew Julius, Assistant Professors, Department of Biological Sciences, St. Cloud State University, Kathy E. Lee US Geological Survey, Mounds View, MN, and Larry B. Barber Ph.D. Water Resources Division, US Geological Survey, Boulder, Colorado
Addtional Staff: Travis Bistodeau, Roberto Cediel, and Angela Allen, Department of Biological Sciences, St. Cloud State University
USGS-WRRI 104B/ CAIWQ Competitive Grants Program
September 2004 - February 2006
Environmental estrogens have been identified as an important source of endocrine disruption aquatic wildlife. In addition to potent natural and synthetic estrogens (estrone, estradiol, ethynylestradiol), alkylphenolic surfactants based on the parent compound 4-nonylphenol have been suggested as contributing to the estrogenicity of treated wastewater effluents and ultimately surface waters in the US. In this study, we developed sensitive methodology to assess the estrogenicity in two tiers of the aquatic food chain, a primary producer and a secondary consumer to determine whether exposure to 4-nonylphenol at environmentally relevant concentrations has adverse effects on aquatic organisms. The abundance and chemical nature of 4-nonylphenol suggests that organisms at different levels of the trophic cascade may experience differential effects that may be estrogen receptor independent (diatoms) or estrogen receptor mediated (fathead minnow). We chose Melosira varians as the primary producer for this study as this diatom is commonly found in North American surface waters and is a preferred food source for invertebrates (an intermediate step in the aquatic food chain) and fingerling fishes. The fathead minnow, Pimephales promelas was chosen as the other model organism for this study as it is a tier one screening organism for endocrine disrupting compounds by the US EPA as it reproduces year round and as it has several behavioral traits that facilitate the assessment of endocrine disrupting effects in this species. We used three parameters in an effects matrix to assess exposure effects of 4-nonylphenol on the diatom: cell growth, chlorophyll A content and lipid concentration after a 10-day stagnant exposure experiment. We calculated the lipid : chlorophyll A ratio for each exposure as it is well established that environmental pollution will stress diatoms and result in increased chlorophyll A production at the expense of lipid reserves. We chose a suite of endpoints to assess the effects of 4-nonylphenol on the fathead minnow. These included plasma vitellogenin induction, secondary sex characteristics, gonadal histology, and nest holding ability in direct competition with unexposed control males. We conducted several rounds of exposures at concentrations bracketing environmental concentrations of 4-nonylphenol in treated wastewater effluent for both model organisms. Our results indicate that 4-nonylphenol alters lipid : chlorophyll A content in diatoms at environmental concentrations of >80 μg/L 4-nonylphenol. Concentrations of 4-nonylphenol >10μg/L resulted in rapid vitellogenin mRNA induction in male fathead minnows and reducing nest holding ability in exposed male fathead minnows. Similar results were achieved when larval fathead minnows were exposed to nonylphenol for 60 days and then raised in clean water to adulthood. In summary, our study indicates that 4-nonylphenol at concentrations approaching environmental relevance can alter organisms in two tiers of the aquatic food chain and reduce the reproductive potential of exposed fathead minnows.
Refereed Scientific Journal Articles
Schoenfuss, H.L., S. E. Bartell, T. B. Bistodeau, R. A. Cediel, K. J. Grove, K. E. Lee, L. B. Barber. 2008. Impairment of the reproductive potential of male fathead minnows by environmentally relevant exposures to 4−nonylphenolf. Aquatic Toxicology 86(1): 91–98.
Bistodeau, T.J., L.B. Barber, S.E. Bartell, R.A. Cediel, K.J. Grove, J. Klaustermeier, J.C. Woodard, K.E. Lee and H.L. Schoenfuss. 2006. Larval exposure to environmentally relevant mixtures of alkylphenolethoxylates reduces reproductive competence in male fathead minnows. Aquatic Toxicology 79: 268−277.
Schoenfuss, H.L., T.J. Bistodeau, and L.B. Barber. 2006. Larval exposure to environmentally relevant mixtures of alkylphenolethoxylates reduces reproductive competence in male fathead minnows. SETAC North America 27th Annual Meeting, Montreal, Canada, November 5−9, 2006. Abstract #333 pg. 73.
Schoenfuss, H.L. and T.J. Bistodeau. 2006. Effects of Alkylphenol Polyethoxylates AP Alone and in Mixture on Two Life Stages of the Fathead Minnow Pimephales promelas. Minnesota Water 2006 and Annual Water Resources Joint Conference, Brooklyn Center, MN, October 24−25, 2006.
Allen, A.K., T. Loes and H.L. Schoenfuss. 2006. Assessing two species of cypriniform fish for signs of endocrine disruption in a historically estrogenic wastewater outfall. Poster Presentation. 2006 Midwest SETAC Meeting, St. Cloud, MN March 20−22, 2006.
Gamble, C., A. Gikineh and M.L. Julius. 2006. The effects estradiol and nonylphenol on Melosira varians, a common tycho planktonic diatom. Oral Presentation. 2006 Midwest SETAC Meeting, St. Cloud, MN March 20−22, 2006.
Koch, J.K., M. Minger, and H.L. Schoenfuss. 2006. Education as environmental stewardship: Developing inquiry−based learning modules for high school science teachers. Poster Presentation. 2006 Midwest SETAC Meeting, St. Cloud, MN March 20−22, 2006.
Schoenfuss, H.L. and T.J. Bistodeau. 2006. Effects of alkylphenol polyethoxylates AP alone and in mixture on two life stages of the fathead minnow Pimephales promelas. Oral Presentation. 2006 Midwest SETAC Meeting, St. Cloud, MN March 20−22, 2006.
Bistodeau, T.J., Cediel, R.A., Grove, K.J., Klaustermeier, J.A. and Schoenfuss, H.L. 2005. The reproductive consequences of an environmentally relevant exposure of alkylphenol polyethoxylates on fathead minnow larvae. SETAC North America 26th Annual Meeting, Baltimore, MD, November 13−17, 2005. Abstract # WP022 pg. 285.
Schoenfuss H. L. 2005.Concentration dependent effects of 4−nonylphenol on male fathead minnows in a competitive reproductive assay. 2005 MN Water Conference Oral Presentation, Minneapolis, MN, October 25−26, 2005.
Schoenfuss H. L. 2005.Concentration dependent effects of 4−nonylphenol on male fathead minnows in a competitive reproductive assay. 2005 MN Water Conference Oral Presentation, Minneapolis, MN, October 25−26, 2005.Concentration Dependent Effects of 4−Nonylphenol on Male Fathead Minnows in a Competitive Reproductive Assay. Oral Presentation. 2005 Midwest SETAC Meeting, Madison, WI, April 5, 2005.
Bistodeau, T., R. Cediel, K. Groove, J. Klaustermeier, H. L. Schoenfuss. 2005. Reproductive Consequences of Environmentally Relevant Exposures of Fathead Minnow Larvae to a Mixture of Alkylphenol Ethoxylates. Poster Presentation. 2005 Midwest SETAC Meeting, Madison, WI, April 5, 2005.
Schoenfuss, H.L. 2005. Biological Effects of Biologically Active Compounds: Experimental Considerations in the Study of Endocrine Disrupting Chemicals. Symposium Presentation at the Annual Meeting of the American Oil Chemists Society, Salt Lake City, UT, May 3, 2005.
Schoenfuss, H.L. 2004. Simple Questions − Complex Answers: Investigating the Effects of Alkylphenols on Aquatic Organisms. Invited Seminar, University of Nebraska, Omaha.