Short research projects conducted for my "Doctorandus" degree at the University of Utrecht in The Netherlands fell in the areas of Landscape Ecology ("importance of forest/meadow edges for songbird densities"), Environmental Toxicology ("Dapnia magna food assimilation as a potential bioassay endpoint") and Population Genetics. Research for the latter was a part of the long-term Dutch study on the Great Tit (Parus major). This project, supervised by Arie van Noordwijk, was a quantitative genetic study that devised a method for measuring beak size in these birds and then went on to quantify the heritability of beak dimensions. This study resulted in the following publication:

• Van Noordwijk, A.J. and P.L. Klerks. 1983. Heritability of bill dimensions in the Great Tit. Institutes of the Royal Netherlands Academy of Arts and Sciences Progress Report 1982, Verh. K. Ned. Akad. Wet. Afd. Natuurk. Tweede Reeks 81: 7-12

Research for my Ph.D., conducted at Stony Brook University / State University of New York at Stony Brook (major advisor Jeffrey Levinton) was mainly focussed on the development of resistance in a species of oligochaete living at a site on the Hudson River that had a long history of contamination by metals (especially cadmium) caused by discharge from a cadmium-nickel battery factory. This site had extremely high levels of cadmium and was classified as an EPA Superfund site (and has since been cleaned up). Specific studies looked at the contamination at the time of the study, the occurrence of adaptation to metals in the oligochaete Limnodrilus hoffmeisteri, physiological methods underlying the resistance, and included a selection experiment in which laboratory populations were selected for an increased resistance. As part of this research I also reviewed the literature on the development of resistance to metals. The following publications resulted from this research:

• Levinton, J., P. Klerks, D. Martinez, C. Montero, C. Sturmbauer, L. Suatoni and W. Wallace. 1999. Running the gauntlet: Pollution, evolution and reclamation of an estuarine bay. Pp. 125-138. In: Aquatic Life Cycle Strategies: Survival in a Variable Environment. M. Whitfield, J. Mathews and C. Reynolds (Eds.) Marine Biological Association of the United Kingdom, Plymouth.
• Klerks, P.L. and J.S. Levinton. 1993. Evolution of resistance and changes in community-composition in metal-polluted environments: A case-study on Foundry Cove. Pp. 223-241, In: Ecotoxicology of Metals in Invertebrates. R. Dallinger and P.S. Rainbow (Eds.). CRC Press, Boca Raton.
• Klerks, P.L. and P.R. Bartholomew. 1991. Cadmium accumulation and detoxification in a Cd-resistant population of the oligochaete Limnodrilus hoffmeisteri. Aquat. Toxicol. 19: 97-112.
• Klerks, P.L. and J.S. Levinton. 1989. Effects of heavy metals in a polluted aquatic ecosystem. Pp. 41-67, In: Ecotoxicology: Problems and Approaches, S.A. Levin, M.A. Harwell, J.R. Kelly and K.D. Kimball (Eds.), Springer-Verlag, New York.
• Klerks, P.L. and J.S. Levinton. 1989. Rapid evolution of metal resistance in a benthic oligochaete inhabiting a metal-polluted site. Biol. Bull. 176: 135-141
• Klerks, P.L. 1989. Adaptation to metals in animals. Pp. 313-321, In: Heavy Metal Tolerance in Plants: Evolutionary Aspects, A.J. Shaw (Ed.), CRC Press, Boca Raton.
• Klerks, P.L. and J.S. Weis. 1987. Genetic adaptation to heavy metals in aquatic organisms: a review. Environ. Pollut. 45: 173-205.
• Knutson, A.B., P.L. Klerks and J.S. Levinton. 1987. The fate of metal contaminated sediments in Foundry Cove, New York. Environ. Pollut. 45: 291-304.

Research conducted during a postdoc (with Guritno Roesijadi) at the Chesapeake Biological Laboratory of the University of Maryland looked at various aspects of the induction of metallothioneins (metal-binding proteins involved in the detoxification of certain metals such as cadmium and copper) in the Eastern Oyster (Crassostrea virginica). This research resulted in the following publications:

• Roesijadi, G., M.M. Vestling, C.M. Murphy, P.L. Klerks and C.C. Fenselau. 1991. Structure and time dependent behavior of acetylated and nonacetylated forms of a molluscan metallothionein. Biochim. Biophys. Acta 1074: 230-236.
• Roesijadi, G., S. Kielland and P. Klerks. 1989. Purification and properties of novel molluscan metallothioneins. Arch. Biochem. Biophys. 273: 403-413.
• Roesijadi, G. and P.L. Klerks. 1989. A kinetic analysis of Cd-binding to metallothionein and other intracellular ligands in oyster gills. J. Exp. Zool. 251: 1-12.

My postdoc (with Peter Fraleigh) at the University of Toledo coincided with the proliferation of the introduced zebra mussel (Dreissena polymorpha) in Lake Erie. Research conducted during this period was aimed at finding methods to control this species (espcially problematic for cooling-water intakes and potable-water intakes on Lake Erie) and at understanding the impact of the exotic mussel on suspended matter levels in the lake and on the dynamics of heavy metals. The following publications resulted from this research:

• Klerks, P.L., P.C. Fraleigh and J.E. Lawniczak. 1997. Effects of the exotic zebra mussel on metal cycling in Lake Erie. Can. J. Fish. Aquat. Sci. 54: 1630-1638.
• Klerks, P.L. and P.C. Fraleigh. 1997. Uptake of nickel and zinc by the zebra mussel Dreissena polymorpha. Arch. Environ. Contam. Toxicol. 32: 191-197.
• Klerks, P.L., P.C. Fraleigh and J.E. Lawniczak. 1996. Effects of zebra mussels (Dreissena polymorpha) on seston levels and sediment deposition in western Lake Erie. Can. J. Fish. Aquat. Sci. 53: 2284-2291.
• Fraleigh, P.C., P.L. Klerks, G. Gubanich, G. Matisoff and R.C. Stevenson. 1993. Abundance and settling of zebra mussel (Dreissena polymorpha ) veligers in western and central Lake Erie. Pp. 129-142, In: Zebra Mussels: Biology, Impacts and Control. T.F. Nalepa and D.W. Schloesser (Eds.). Lewis Publishers, Boca Raton.
• Klerks, P.L. , P.C. Fraleigh and R.C. Stevenson. 1993. Controlling zebra mussel (Dreissena polymorpha ) veligers with three oxidizing chemicals: chlorine, permanganate, and peroxide + iron. Pp. 621-641, In: Zebra Mussels: Biology, Impacts and Control. T.F. Nalepa and D.W. Schloesser (Eds.). Lewis Publishers, Boca Raton.
• Lemma, A., L. Wolde-Yohannes, P.C. Fraleigh, P.L. Klerks and H.H. Lee. 1991. Endod is lethal to zebra mussels and inhibits their attachment. J. Shellfish Res. 10: 361-365.
• Klerks, P.L. and P.C. Fraleigh. 1991. Controlling adult zebra mussels with oxidants. Journal AWWA 83: 92-100.
• Fraleigh, P.C., G. Matisoff, G. Gubanich, G.L. Hoffman, P.L. Klerks, P.L. McCall, R.C. Stevenson, and M.E. Wenning. 1991. AWWA Zebra mussel research project results. Pp. 103-117, In: Proceedings of the American Water Works Association Annual Conference, June 23-27, Philadelphia.
• Matisoff, G., P. Fraleigh, A.B. Greenberg, G. Gubanich, G.L. Hoffman, P.L. Klerks, P.L. McCall, R.C. Stevenson, W. Van Cott, and M.E. Wenning. 1991. Controlling zebra mussels at water treatment plant intakes. I. Lake Erie veliger densities. Pp. 79-89, In: Proceedings of American Water Resources Association Spring Symposium "Surface and Groundwater Quality", February 24-27, Cleveland.
• Matisoff, G., P. Fraleigh, A.B. Greenberg, G. Gubanich, G.L. Hoffman, P.L. Klerks, P.L. McCall, R.C. Stevenson, W. Van Cott, and M.E. Wenning. 1990. Controlling zebra mussels at water treatment plant intakes. II. Veliger dose/response static tests. Pp. 59-70, In: Proceedings of the EPRI International Macrofouling Symposium, December 4-6, Orlando.

Research conducted in my lab at the University of Louisiana at Lafayette can be grouped in several different topics:

1) Research on acclimation and adaptation in invertebrates and fish exposed to environmental contaminants.  This included research determining the presence of genetic variation for resistance differences ("heritability of resistance"), comparing resistance among different natural populations, performing laboratory selections for an increased resistance, investigating overall genetic variation in laboratory populations following selection, and investigating resistance mechanisms in resistant laboratory populations.  This research was conducted in collaboration with many colleagues and graduate students (including Lingtian Xie, Paul Leberg and others - see names of co-authors below), and resulted in the following publications:

• Giridhar Athrey, N. R., P.L. Leberg & P.L. Klerks. 2007. Laboratory culturing and selection for increased resistance to cadmium reduce genetic variation in the least killifish, Heterandria formosa. Environ. Toxicol. Chem. 26: 1916-1921.
• Xie, L., and P.L. Klerks. 2004. Changes in cadmium accumulation as a mechanism for cadmium resistance in the least killifish Heterandria formosa. Aquat. Toxicol. 66: 73-81.
• Xie, L., and P.L. Klerks. 2004. Metallothionein-like protein in the least killifish Heterandria formosa and its role in cadmium resistance. Environ. Toxicol. Chem. 23: 173-177.
• Xie, L., and P.L. Klerks. 2004. Fitness costs of resistance to cadmium in the least killifish (Heterandria formosa). Environ. Toxicol. Chem. 23: 1499-1503.
• Xie, L. and P.L. Klerks. 2003. Responses to selection for cadmium resistance in the least killifish Heterandria formosa. Environ. Toxicol. Chem. 22: 313-320.
• Klerks, P.L. 2002. Adaptation, ecological impacts and risk assessment: Insights from research at Foundry Cove, Bayou Trepagnier and Pass Fourchon. Human Ecol. Risk. Assessm. 8: 971-982.
• Millward, R.N. and P.L. Klerks. 2002. Contaminant-adaptation and community tolerance in ecological risk assessment: Introduction. Human Ecol. Risk. Assessm. 8: 921-932.
• Klerks P.L. and C.J. Moreau. 2001. Heritability of resistance to individual contaminants and to contaminant mixtures in the sheepshead minnow (Cyprinodon variegatus). Environ. Toxicol. Chem. 20: 1746-1751.
• Klerks, P.L. 1999. Acclimation to contaminants by the grass shrimp Palaemonetes pugio: individual contaminants vs. mixtures. Ecotoxicology 8: 277-286.
• Klerks, P.L. 1998. The influence of contamination complexity on adaptation to environmental contaminants. Pp. 103-121, In: Genetics and Ecotoxicology. V. Forbes (Ed.). Taylor & Francis, Philadelphia.
• Klerks, P.L. and S.A. Lentz. 1998. Resistance to lead and zinc in the western mosquitofish Gambusia affinis inhabiting contaminated Bayou Trepagnier. Ecotoxicology 7: 11-17.
• Klerks, P.L., P.L. Leberg, R.F. Lance, D. J. McMillin and J. C. Means. 1997. Lack of development of pollutant-resistance or genetic differentiation in darter gobies (Gobionellus boleosoma) inhabiting a produced-water discharge site. Mar. Environ. Res. 44: 377-395.

2) Research on heat tolerance in aquatic organisms.  This includes research in zebra mussels (lead by Curt Elderkin) with the overall goal of understanding whether this introduced species is likely to do well in the southern U.S..  This research looked at genetic differentiation along the north-south range of its distribution in the Mississippi River, at differences in heat tolerance along this range, and at the presence of genetic variation in temperature tolerance at the larval (veliger) stage.  This research  resulted in the following publications:

• Elderkin, C.L., and P.L. Klerks. 2005. Variation in thermal tolerance among three Mississippi River populations of the zebra mussel, Dreissena polymorpha. J. Shellfish Res. 24: 221-226.
• Elderkin, C.L, E.J. Perkins, P.L. Leberg, P.L. Klerks, and R.F. Lance. 2004. Amplified fragment length polymorphism (AFLP) analysis of the genetic structure of the zebra mussel, Dreissena polymorpha, in the Mississippi River. Freshwat. Biol. 49: 1487-1494.
• Elderkin, C.L., J.A. Stoeckel, D.J. Berg, and P.L. Klerks. 2004. Heritability of heat tolerance in zebra mussel veligers. J. Great Lakes Res. 30: 360-366.
• Elderkin, C.L., P.L. Klerks and E. Theriot. 2001. Shifts in allele and genotype frequencies in zebra mussels, Dreissena polymorpha, along the latitudinal gradient formed by the Mississippi River. J. Nrd. Am. Benthol. Soc. 20: 595-605.

3) Research on the effects of chemicals used in treating oil spills (a dispersant and a cleaner) on the toxicity to aquatic organisms.  This research used laboratory microcosms to look at the influence of these treatments and at changes in toxicity over time.  This research was conducted in collaboration with Andy Nyman and Sucharita Bhattacharyya, and resulted in the following publications:

• Nyman, J.A., P.L. Klerks, and S. Bhattacharyya. 2007. Effects of chemical additives on hydrocarbon disappearance and biodegradation in freshwater marsh microcosms. Environ. Pollut. 149: 227-238. 
• Bhattacharyya, S., P.L. Klerks and J.A. Nyman. 2003. Toxicity to freshwater organisms form oils and oil spill chemical treatments in laboratory microcosms. Environ. Pollut. 122: 205-215.
• Klerks, P.L., J.A. Nyman, and S. Bhattacharyya. 2004. Relationship between hydrocarbon measurements and toxicity to a chironomid, fish larva and daphnid for oils and oil spill chemical treatments in laboratory freshwater marsh microcosms. Environ. Pollut. 129: 345-353.

4) Research on bioluminescence in the dinoflagellate Pyrocystis lunula.  These dinoflagellates emit light, e.g. when disturbed.  One part of this research investigated the use of this system for toxicity testing, and included an analysis of the senstivity of this essay to changes in environmental variables (pH, salinity and temperature).  Another component of this research investigated the more basic aspects of bioluminescence regulation in this species.  This research was conducted in collaboration with Kirsten Heimann and Jacky Craig (né Matuszewski), and resulted in the following publications:

• Heimann, K., P.L. Klerks & K.H. Hasenstein. In press. Involvement of actin and microtubules in regulation of bioluminescence and translocation of chloroplasts in the dinoflagellate Pyrocystis lunula. Bot. Mar.
• Craig, J.M., P.L. Klerks, K. Heimann and J.L. Waits. 2003. Effects of salinity, pH and temperature on re-establishment of bioluminescence and copper or SDS toxicity in the marine dinoflagellate Pyrocystis lunula using bioluminescence as an endpoint. Environ. Pollut. 125: 267-275.
• Heimann, K., J.M. Matuszewski and P.L. Klerks. 2002. Effects of metals and organic contaminants on the recovery of bioluminescence in the marine dinoflagellate Pyrocystis lunula (Dinophyceae). J. Phycol. 38: 482-492.

5) Some smaller projects dealt with related topics such as the interplay between genetic variation and contaminant tolerance, interactions between contaminants, metal detoxification, and the influence of bioturbators on metal cycling   These dinoflagellates emit light, e.g. when disturbed.  This research was conducted in collaboration with several colleagues and students, and resulted in the following publications:

• Klerks, P.L., D.L. Felder, K. Strasser, and P.W. Swarzenski. 2007. Effects of ghost shrimp on zinc and cadmium in sediments from Tampa Bay, FL. Mar. Chem. 104:17-26.
  
• Lewis, S.S., P.L. Klerks and P.L. Leberg. 2001. Relationship between allozyme genotype and sensitivity to stressors in the western mosquitofish Gambusia affinis detected for elevated temperature but not for mercury. Aquat. Toxicol. 52: 205-216.
• Mitra, S., P.L. Klerks, T.S. Bianchi, J. Means and K.R. Carman. 2000. Effects of estuarine organic matter biogeochemistry on the bioaccumulation of PAHs by two epibenthic species. Estuaries 23: 864-876.
• Deeds, J.R. and P.L. Klerks. 1999. Metallothionein-like proteins in the freshwater oligochaete Limnodrilus udekemianus and their role as a homeostatic mechanism against cadmium toxicity. Environ. Pollut. 106: 381-389.
• Moreau, C., P.L. Klerks and C.N. Haas. 1999. The interaction between phenanthrene and zinc in toxicity to the sheepshead minnow (Cyprinodon variegatus). Arch. Environ. Contam. Toxicol. 37: 251-257.

Contact information: Dr. Paul L. Klerks, Department of Biology, University of Louisiana at Lafayette, Box 42451, Lafayette, LA 70504, USA. E-mail: klerks@louisiana.edu 

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