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

Establishing historical water velocities is a goal of Everglades restoration because of their role maintaining landscape topographic relief. However, flows may also change the trophic state of marshes by phosphorus loading. I used fatty acid (FA) and stoichiometric data to quantify how increased sheet flow altered the relative heterotrophic and autotrophic contributions to aquatic consumers in a field experiment that introduced flowing water to an Everglades marsh in November, 2014. Algal taxonomic composition was different between pre-flow and flow sampling, marked by increases in the nutrient exploiting Mougeotia species (green algae) during flow sampling. Dietary tracer FAs in consumers reflected changes in algal resources, including an increase in green algae-derived and a decrease in bacteria-derived FAs. These food web responses indicate that establishing historic water velocity in degraded wetlands can shift the origins of organic matter from a more detrital to more algal supported web.