Current Research Projects
The impacts of sub-lethal pesticide concentrations on trophic cascades in marine and freshwater communities
Agricultural and residential chemicals find their way into ponds, rivers, and estuaries through run-off where they can have a number of impacts on aquatic communities. Crustaceans, such as crabs and crayfish, are often particularly vulnerable to pesticides which target their insect cousins and recent research suggests that even non-lethal low levels of these chemicals can influence animal behavior, altering community level interactions. Importantly, these keystone crustaceans also have significant impacts on aquatic communities suggesting low level pesticide concentrations may have important impacts on the structure and function of aquatic communities. To investigate if sub-lethal pesticide concentrations influence crustacean behavior and aquatic trophic cascades, we are comparing the impact of pesticides on a freshwater and marine trophic cascade. This project is funded by the Louisiana Board of Regents Research Competitiveness Subprogram (RCS).
Agricultural and residential chemicals find their way into ponds, rivers, and estuaries through run-off where they can have a number of impacts on aquatic communities. Crustaceans, such as crabs and crayfish, are often particularly vulnerable to pesticides which target their insect cousins and recent research suggests that even non-lethal low levels of these chemicals can influence animal behavior, altering community level interactions. Importantly, these keystone crustaceans also have significant impacts on aquatic communities suggesting low level pesticide concentrations may have important impacts on the structure and function of aquatic communities. To investigate if sub-lethal pesticide concentrations influence crustacean behavior and aquatic trophic cascades, we are comparing the impact of pesticides on a freshwater and marine trophic cascade. This project is funded by the Louisiana Board of Regents Research Competitiveness Subprogram (RCS).
Does copper tape used to manipulate periwinkle behavior produce experimental artifacts?
Periwinkle snails are notorious for not cooperating with experimental manipulations. They can climb out of tanks and cages at will. To corral perwinkles, copper tape has been used as gastropods famously don't cross copper barriers. This is why you can use copper tape, pennies, and wire to keep slugs out of your garden. However, preliminary experiments suggested copper used in copper tape may leach and cause experimental artefacts. Recent experiments performed in our lab have examined if copper used in these experimental manipulations is actually altering snail behavior.
Periwinkle snails are notorious for not cooperating with experimental manipulations. They can climb out of tanks and cages at will. To corral perwinkles, copper tape has been used as gastropods famously don't cross copper barriers. This is why you can use copper tape, pennies, and wire to keep slugs out of your garden. However, preliminary experiments suggested copper used in copper tape may leach and cause experimental artefacts. Recent experiments performed in our lab have examined if copper used in these experimental manipulations is actually altering snail behavior.
The impacts of water hyacinth on estuarine communities and predator prey interactions
Invasive water hyacinth (Eichornia crassipes) is a freshwater floating plant that can temporarily occupy estuarine habitats when it breaks free from mats and floats down the rivers to the coasts. In coastal estuaries, small to moderate patches of water hyacinth can be found against the marsh edge where they can sit for weeks. These floating plants can provide habitat structure for a variety of estuarine species, but there is limited data on how water hyacinth can influence estuarine communities.
Invasive water hyacinth (Eichornia crassipes) is a freshwater floating plant that can temporarily occupy estuarine habitats when it breaks free from mats and floats down the rivers to the coasts. In coastal estuaries, small to moderate patches of water hyacinth can be found against the marsh edge where they can sit for weeks. These floating plants can provide habitat structure for a variety of estuarine species, but there is limited data on how water hyacinth can influence estuarine communities.
Previous Research Projects
How does nutrient enrichment methodology influence Spartina alterniflora production and allometry?
The impacts of nutrient enrichment on Spartina above and belowground production are somewhat controversial, but very important to marsh preservation and restoration efforts on the Louisiana coast. Some studies demonstrate adding nutrients reduces belowground biomass while others show an increase. To understand what may be causing these differences, we are examining how nutrient enrichment methodologies influence Spartina plant production, plant allometry, and herbivory. In collaboration with Brian Roberts at LUMCON, we will also examine how C,N, P are allocated in Spartina under different nutrient methodologies.
The impacts of nutrient enrichment on Spartina above and belowground production are somewhat controversial, but very important to marsh preservation and restoration efforts on the Louisiana coast. Some studies demonstrate adding nutrients reduces belowground biomass while others show an increase. To understand what may be causing these differences, we are examining how nutrient enrichment methodologies influence Spartina plant production, plant allometry, and herbivory. In collaboration with Brian Roberts at LUMCON, we will also examine how C,N, P are allocated in Spartina under different nutrient methodologies.
Does fear influence pollinator behavior and flower visitation?
Pollinators across the globe are declining leading to an increased need to understand what factors influence pollinator abundance and distribution. In collaboration with Dr. Natalie Clay, we are examining whether avian visual cues (bird models) influence the behavior of insects such as butterflies and bees and their visitation on ornamental plants.
Pollinators across the globe are declining leading to an increased need to understand what factors influence pollinator abundance and distribution. In collaboration with Dr. Natalie Clay, we are examining whether avian visual cues (bird models) influence the behavior of insects such as butterflies and bees and their visitation on ornamental plants.
The impacts of exotic Asian tiger shrimp (Penaeus monodon) on Gulf Coast estuarine animals
Recently, tiger shrimp, Penaeus monodon, have been identified as a new threat to Gulf of Mexico estuarine ecosystems. The tiger shrimp’s broad diet, aggressive omnivory, large body size, and overlapping distribution with native shrimp and other invertebrates suggest that this species may compete with or consume native, commercially important shrimp species and be highly disruptive to community structure. However, there is no knowledge of how tiger shrimp interact with local species, or even species in their native range, which impedes predictions of their ecological or economic impacts. We are currently partnering with commercial shrimpers to obtain live tiger shrimp and then performing laboratory mesocosm experiments to examine how tiger shrimp will interact with local species. This project was funded by Mississippi-Alabama Sea Grant.
Recently, tiger shrimp, Penaeus monodon, have been identified as a new threat to Gulf of Mexico estuarine ecosystems. The tiger shrimp’s broad diet, aggressive omnivory, large body size, and overlapping distribution with native shrimp and other invertebrates suggest that this species may compete with or consume native, commercially important shrimp species and be highly disruptive to community structure. However, there is no knowledge of how tiger shrimp interact with local species, or even species in their native range, which impedes predictions of their ecological or economic impacts. We are currently partnering with commercial shrimpers to obtain live tiger shrimp and then performing laboratory mesocosm experiments to examine how tiger shrimp will interact with local species. This project was funded by Mississippi-Alabama Sea Grant.
The impacts of eutrophication, wave action, and climate-driven sea level rise on grazer abundance and Spartina alterniflora above and below-ground biomass
Salt marshes are an important ecosystem currently eroding at high rates due to coastal development and other anthropogenic impacts. Current efforts to stop salt marsh erosion include the use of barriers, such as man-made oyster reefs, to attenuate wave action and increase sedimentation rates. However, in coastal Alabama, such barriers have had limited success in stopping salt marsh erosion potentially because of rising sea levels, wave action, and eutrophication. In collaboration with Dr. Ken Heck, Dr. Hill and the Heck Lab performed multiple field experiments investigating the impacts of submergence, wave action, and nutrients on the production of Spartina above and belowground biomass and grazer abundance. |
The influence of avian predators on fish behavior and indirect effects to seagrass communities
Seagrasses are threatened habitats disappearing worldwide due to overfishing, eutrophication, and coastal development. As such, many methods have been developed to restore seagrass beds including bird stakes, where bird perches or stakes are placed in disturbed or damaged seagrass beds to increase local nutrients through bird guano and promote the growth and distribution of seagrasses. However, bird stakes can also increase traffic of predatory birds such as cormorants, herons, and pelicans that may influence the distribution of fishes through NCEs and cause multiple indirect effects. Since the influence of predatory birds on fish behavior or distribution had not previously been examined in estuarine systems, Dr. Hill in collaboration with the Heck lab performed empirical lab and field experiments to investigate: a) if avian predators influence fish behavior and distribution; and b) if avian predators cause any indirect effects on seagrass invertebrate fauna and epiphyte biomass. The results of this study were recently published in OIKOS in June of 2015. |