Thesis (M.S.)--Georgia Southern University, 2004. / "A thesis submitted to the Graduate Faculty of Georgia Southern University in partial fulfillment of the requirements for the degree Master of Science" ETD. INDEX WORDS: Palaemonetes pugio, microphallus turgidus, host-parasite interaction, single-strand conformation polymorphism, gene flow. Includes bibliographical references (p. 26-26) and appendices.

Ammonia is known to be toxic to aquatic organisms. The national water quality criteria for ammonia in the marine environment have been established to protect aquatic organisms from the toxicity of ammonia. Discharge into Chesapeake Bay has not yet been regulated under this criteria. Ammonia limits of 1-2 mg/L total ammonia have been proposed for the marine waters in Virginia based on the national criteria of 0.035 mg/L of un-ionized ammonia. The limits have been questioned because the criteria were calculated using toxicity data from both freshwater and saltwater species, rather than solely from saltwater species. More ammonia toxicity tests need to be conducted to expand the database with saltwater species in order to develop a reliable and appropriate limits for ammonia discharge. Two saltwater species, one marine fish, Atlantic silverside (Menidia menidia), and one marine invertebrate, ghost shrimp (Palaemonetes pugio), were tested in acute and 7-day chronic tests. The acute tests for the Atlantic silverside were performed at three levels of salinity in order to develop a better understanding of the relationship between ammonia toxicity and salinity levels. The acute LC50values for both species were determined and compared to values in the literature. The 48-hour LC50 values for the Atlantic silverside were 1.50, 1.17, and 1.08 NH3 mg/L at salinities of 14, 22, and 30 ppth, respectively. The 96-hour LC50 for the ghost shrimp was 1.66 NH3 mg/L. The species mean acute values (SMAVs) for the Atlantic silverside (2% difference) and the ghost shrimp (31% difference) were compared to previous test results. The no-observed-effect-concentration (NOEC) was 0.48 NH3 mg/L for the Atlantic silverside based on growth, and 0.33 NH3 mg/L for the ghost shrimp based upon growth. The acute-chronic ratio for the ghost shrimp was 7.56. The refined national chronic criterion of un-ionized ammonia was 0.056 mg/L according to the test data from this research. / Master of Science

Estuaries, an important facet of coastal regions, are highly productive natural systems, frequently acting as drainage basins for various pollutants such as agricultural runoff. The estuarine grass shrimp, Palaemonetes pugio, has been shown to be a sensitive indicator of pesticide exposure. In this study, emphasis was placed on the quantification of the lethal and sublethal effects of aldicarb on three different life stages of P. pugio. Acute 96-h toxicity tests were conducted with newly hatched larvae, 22-d old larvae and adult grass shrimp to determine lethal toxicant ranges. LC₅₀ values were 85.0 ug/L for newly hatched larvae, 70.7 ug/L for 22-d old larvae and 125.4 ug/L for adults. The impact of aldicarb on specific neurological functions in the grass shrimp was examined using an acetylcholinesterase assay. Acetylcholinesterase (AChE) activity was reduced in the larvae after exposure to acute concentrations of aldicarb. Mean whole-body AChE activity for the newly hatched and 22-d larvae was significantly lower from the controls (P=0.009). Conversely, mean whole body AChE activity in the adult shrimp was not significantly different from the controls at any concentration (P=0.401), although there was a trend towards reduced activity at 50 and 100 ug/L exposures. A behavioral study was conducted to examine the ability of adult grass shrimp to detect and avoid aldicarb-treated seawater. Behavioral responses were measured in a modified steep gradient chamber. A partition divided the chamber, creating three distinct areas: 1) seawater 2) aldicarb-treated seawater and 3) mixing. There were significant differences between the control and exposed adult shrimp in the amount of time spent in the mixing area (P<0.05). Aldicarb exposed shrimp spent, on the average, 20% more time in the mixing area than the controls. Additionally, exposed shrimp spent significantly more time facing downstream, away from the toxicant source (P<0.05). Exposed shrimp displayed increasing hyperactivity and attempted to jump out of the chamber. / Master of Science