The research I have undertaken so far in my career has been wide and varied but is currently focused on three separate projects.

The first assessing the concentrations of total and unionized ammonia produced in sediment pore water as a result of Asian clam (Corbicula fluminea) die-offs. Asian clams occur in most drainages of the southeastern United States. These clam populations can reach high densities and may be subject to rapid die-offs, particularly under conditions of low water flow and warm temperatures during summer droughts. Since the clams are infaunal, the sediment interstitial zone may be subject to elevated levels of ammonia and reductions in dissolved oxygen that could affect organisms such as native mussels that also use this habitat. Laboratory experiments were conducted to assess concentrations of total and unionzed ammonia in the sediment pore and overlying waters as a result of clam die-offs under varying conditions (temperature, water flow, clam density, sediment type). Overall the results indicated that the ammonia production in the sediment interstitial zone in addition to the associated reductions in dissolved oxygen could pose a risk to other sediment dwelling organisms such as native mussels that also inhabit this zone.

The second project is assessing the potential, in terms of time and cost, of utilizing an amphibian (Xenopus laevis) oocyte maturation germinal vesicle breakdown (GVBD) test to evaluate levels of endocrine disruption in a suite of different chemicals. Using previously developed techniques we are able to induce final maturation (GVBD) of Xenopus oocytes in vitro. Under normal conditions Xenopus oocytes undergo final maturation when induced by progesterone via a membrane bound receptor (OMPR) or by androgens via a classical intracellular receptor (AR). Our results thus far have indicated that the GVBD test is a 24-h rapid assay for identifying alterations in progestin/anti-progestin activity in Xenopus oocytes as a result of exposure to a wide range of classes of chemicals and therefore could be useful in high throughput endocrine disruptor screening.

The third project is attempting to determine the relatedness and possibly source population/s of a recently introduced population of Zebra mussels, Dreissena polymorpha, to an Oklahoma lake using the microsatellites technique.

Previous work:

• The use of cholinesterase activity and ecologically-relevant behavioral parameters to indicate chlorpyrifos exposure in the Asian clam, Corbicula fluminea.
• Assessing the impact of a lead smelter in Spencer Gulf, South Australia, on the genetic diversity of the marine isopod, Platynympha longicaudata.