Omnibus Research Projects: 2016-2018 

The Louisiana Sea Grant College Program (LSG) intends to support eight research projects for the funding period beginning Feb. 1, 2016. Below is a synopsis of the projects, along with a list of the principal investigators and their affiliations.

Impacts of Ocean Acidification on Natural Phytoplankton Communities, Oyster Development and Trophic Interactions

Principal Investigator: Sibel Bargu (LSU)
Associate Investigators: Reagan Errera (LSU) and Achim Hermann (LSU)
Collaborator: John Supan (LSU AgCenter and Louisiana Sea Grant)

Estuarine systems within Louisiana are critical for coastal ecosystem function. These waterbodies where a river meets the tide are essential habitats for freshwater and marine species of finfish and invertebrates, and they support a healthy regional economy. Although crucial to Louisiana, very little research has focused on the impact global climate change may have on coastal estuaries. The goal of this project is to better understand the impacts of multiple stressors associated with changing climate (sea surface warming, ocean acidification and nutrient enrichment) on coastal water quality and the health of the eastern oyster, which is an economically and ecologically important species along the Gulf coast. It will focus on the impact of ocean acidification on coastal water quality and the producer/consumer trophic link between phytoplankton and oysters. Research will concentrate on two locations – Barataria Bay, where poor water quality during high river discharge and runoff impacts the state’s oyster hatchery programming, and Fourleague Bay, which receives three percent of the Atchafalaya River, causing an increase in freshwater input and declining salinities. Data generated from this project will be critical in evaluating potential vulnerability of the eastern oyster to ocean acidification and nutrient enhancement.

Migratory Movements and Fishing Mortality of the Louisiana Blue Crab Spawning Stock

Principal Investigator: M. Zachary Darnell (Nicholls State University)

The blue crab fishery in Louisiana is the third-largest fishery in the state, with a dockside value of roughly $51 million. Blue crabs have a migratory life cycle, inhabiting different estuarine and offshore habitats at different life stages. Female blue crabs mate in the lower-salinity waters of the upper-estuary and must migrate to the higher-salinity waters of the lower-estuary to spawn. Although the harvest of ovigerous (egg-bearing) females is prohibited in Louisiana, harvest of non-ovigerous mature females is permitted. Since blue crabs spawn multiple clutches of eggs, many of these females may be captured when they are between clutches, representing an under-recognized source of spawning stock mortality. An understanding of the spawning migration and the processes contributing to blue crab mortality during this critical period is necessary for accurate spawning stock assessment and management plans that ensure the sustainability of the fishery.

The researcher will examine the timing and route of crab migration using a mark-recapture study focusing on females that have recently molted to maturity. The crabs will be captured in collaboration with local commercial crabbers and marked with individually numbered tags. Tags will be printed with a unique ID number, contact information, a request for recapture data and an offer of small monetary reward.

This project has four objectives: 1. Determine the timing and route of migration of mature female blue crabs in the Pontchartrain and Terrebonne basins. 2. Quantify spatial and temporal variability in fishing mortality of female blue crabs in the Pontchartrain and Terrebonne basins. 3. Assess the potential for sperm limitation in the Louisiana blue crab spawning stock. 4. Quantify reproductive effort, output and future reproductive potential of crabs recaptured while ovigerous.

Impacts of Labor Policy Changes on Louisiana Seafood Processing and Production

Principal Investigators: Maria Bampasidou, (LSU AgCenter)
Associate Investigator: J. Matthew Fannin, (LSU AgCenter)

Louisiana seafood processors and producers indicate that the employment of foreign workers admitted to the United States for a limited time (called “nonimmigrant foreign workers”) is essential to seafood production in the state. Nonimmigrant labor policy holds potentially serious consequences for the state’s seafood industry and can affect its competitiveness in the global market. H-2A visas are issued for those engaged in agricultural work, which includes crawfish and alligator production. H-2B visas are issued to those engaged in non-agricultural work, which includes seafood processing like peeling crawfish and crabs. However, the federal government issues a limited number of visas each year. Not only has nonimmigrant labor been reportedly in short supply in recent years, but there has been pressure at the federal level to raise the required wage for nonimmigrant labor.

The objectives of this study are to determine: 1. The extent of uses of H-2A and H-2B labor in crawfish and alligator production and in seafood processing in Louisiana. 2. The consequences incurred by Louisiana crawfish and alligator production firms and seafood processing firms under various scenarios of labor shortages and wage increases. 3. The reasons why producers and processors hire nonimmigrant labor. 4. The value of H-2A and H-2B labor to producers of crawfish and alligators and to seafood processors in Louisiana. 5. The full costs incurred by firms in using H-2A and H-2B labor in crawfish and alligator production and in seafood processing in Louisiana. Data will be collected via a mailed survey sent to all known Louisiana crawfish and alligator producers and seafood processors in the state.

Genomic Variation and Local Adaptation among Natural Stocks of Easter Oysters (Crassostrea virginica) in Coastal Louisiana

Principal Investigators: Morgan Kelly (LSU) and Jerome LaPeyre (LSU AgCenter)

Louisiana’s eastern oyster fishery is the nation’s largest. Oysters in the Gulf of Mexico also provide critical ecosystem services – stabilizing shorelines, providing nursery and foraging habitat for other species, and improving water quality. For any fishery, natural genetic variation among and within stocks is critically important, however, there are no comprehensive data on genetic variation among or within Louisiana oyster socks. This limits managers’ ability to choose stock for successful aquaculture or to predict the ways that environmental change might differentially impact stocks with varying environmental histories. This study seeks to quantify genetic and phenotypic variation among and within stocks of Louisiana oysters, both at the genomic level and in key traits affecting their environmental distribution.

The research will address four questions: 1. How much genomic variation exists among oysters from geographically separated sites with differing environmental conditions? 2. Do genetic differences among sites translate into differences in growth and survival among stocks translocated among sites? 3. Does post-settlement selective mortality differ among sites? 4. Do the larvae of adults from different sites vary in their salinity tolerances?

Expansion of Black Mangroves on Trophic Dynamics in Coastal Louisiana: Implication of Climate Change and Coastal Restoration to Estuarine Fisheries

Principal Investigator: Michael Polito (LSU)
Associate Investigator: Melissa Baustian (The Water Institute of the Gulf)

Climate change, winter warming and drought conditions in coastal Louisiana are projected to increase the northward spread of tropical black mangrove trees (Avicennia germinas) into salt marshes traditionally dominated by the grass Spartina alterniflora. In addition, recent coastal restoration efforts in Louisiana’s marshes have promoted the use and planting of black mangroves as a method to reduce coastal erosion by trapping sediment in the trees’ dense root structures. Once mangroves become well established in a salt marsh zone, they may potentially change the physical, biological, geological and chemical structure of the habitat.

This research will investigate how salt marsh-dependent commercially and recreationally valuable nekton species, such as crab and shrimp, may be affected by transitioning marsh habitats and shifts in basal carbon sources. Determining how climate-driven changes in the carbon sources influence trophic dynamics (the transfer of energy from one part of the ecosystem to another) in Louisiana’s productive estuaries will fill an important gap in the current understanding of healthy coastal ecosystems and habitats, including the sustainability of fisheries. Estuarine-dependent fisheries in Louisiana support a multimillion-dollar industry, and the data collected in this research will help inform coastal restoration management and fisheries policy on the effects of mangrove expansion to the estuarine ecosystem, including food web dynamics.

Evaluation of Blue Carbon Accumulation Potential in Created Marshes of Louisiana

Principal Investigator: Tracy Quirk (LSU)
Associate Investigator: Ronald DeLaune (LSU)

Salt marshes are sinks for atmospheric carbon and play an important role in the global carbon cycle and offsetting carbon emissions. This high rate of carbon accumulation in saline marsh soils is associated with high primary production, anaerobic conditions and accretion in response to sea level rise. A growing stock of carbon in marsh soils increases the potential for long-term sequestration of “blue” carbon, which is the carbon captured by living coastal and marine organisms and stored in coastal ecosystems. However, wetland loss and degradation result in the export and remineralization of stored carbon pools, as well as the loss of capacity to function as blue carbon sinks.

This project seeks to inform the large data gap on the value of coastal marsh restoration to soil carbon development and long-term sequestration of blue carbon by testing the hypothesis that blue carbon stores increase with time in restoration sites, but varies spatially, depending on species composition, mineral sediment accumulation, elevation, hydrology, redox potential and soil texture. The two objectives are: 1. Investigate plant-soil interactions and soil organic carbon development in a chronosequence of created marshes, and paired created and natural marshes across coastal Louisiana. 2. Develop empirical and spatial models of labile and refractory carbon development in restoration sites based on significant species-specific and environmental controls.

Towards Continuous Updates to Topography, Bathymetry, and Surface Characteristics for Louisiana Surge Guidance and Related Coastal Studies

Principal Investigator: Scott Hagen (LSU)
Collaborators: Carola Kaiser (LSU) and Maurice Wolcott (LSU AgCenter)

From running models in near real-time, to modeling impacts of proposed coastal protection and restoration projects, to conducting studies for the revision and improvement of flood insurance programs, the need for accurate computer modeling in coastal Louisiana is ever increasing. The ADvanced CIRCulation model (ADCIRC) is a system of computer programs that can be used to predict tide, wind-wave and hurricane storm surge. During a potential storm surge threat to the Louisiana coast, simulations are performed to estimate inundation with various forecasts of the hurricane wind and pressure fields. However, the Louisiana coast is constantly changing from both natural forces and from manmade alterations, like higher levees constructed in the wake of the 2010 hurricane season. In order to inform local governing agencies and institutions on accurate flooding scenarios, the storm surge model must include all relevant features. The interactive website CERA (Coastal Emergency Risk Assessment) is a tool for the presentation of ADCIRC model results.

This project will update an existing ADCIRC model mesh representation of topography (including levees and other flood control structures) and bathymetry by applying prior elevation data and data that is acquired as the project progresses. Researchers will also update representations of surface characteristics, including bottom friction, canopy and wind-reduction factors. They will use existing CERA technology to validate changes to the ADCIRC model; to ensure stable, reliable and accurate data outputs; and to communicate directly with their target audience. Three historical storms (Hurricanes Isaac, Rita and Katrina) will be used to test and validate any changes made to the ADCIRC model. Researchers will establish a framework for continuous model updates based on all available, high-quality levee and roadbed surveys and by working closely with local emergency managers and relevant decision makers through annual workshops. The over-arching goal is to develop a meshing framework so that continuous adjustments may be made to the ADCIRC model as coastal Louisiana evolves morphologically and ecologically and from engineered improvements.

From Physics to Oysters: An Integrated Modeling Study of the Potential Impacts of Future Large Sediment Diversions on Louisiana Eastern Oyster

Principal Investigator: Haosheng Huang (LSU)
Co-Principal Investigators: Dubravko Justic (LSU), Kehui Xu (LSU), Megan LaPeyre (LSU) and Jerome LaPeyre (LSU AgCenter)

Coastal Louisiana has experienced massive wetland loss, and controlled river diversions that release pulses of sediment-laden fresh water into wetlands are increasingly used for coastal restoration.

Louisiana’s Comprehensive Master Plan for a Sustainable Coast proposes to use river diversions that would convey much more fresh water to the coastal wetlands than existing diversions. However, one of the controversies that arises with diversions is the displacement and salinity stress they may cause to commercially and recreationally important fish and shellfish, especially oysters. Mississippi River diversions have a potential to dramatically influence salinity gradients, as well as turbidity and water quality, in Louisiana estuaries. Diversions may increase nutrient inputs and thus alter the spatial and temporal dynamics of productivity within the system.

This project will provide a quantitative tool for assessing the effects of river diversions for coastal restoration. One of the final products will be spatial distribution of coastal environments which is most favorable for the growth of oysters when large diversions are open. This information will help site selections of future oyster farms and aid economists in better estimating the costs and benefits of sediment diversions, including the corresponding increased fishery effort due to possible seaward shifts of oyster reefs.

Researchers will investigate the effect of ongoing small and future large freshwater and sediment diversions on the populations of eastern oyster in the Breton Sound estuary. Researchers will combine existing hydrodynamic, water quality, sediment transport and individual-based dynamic energy budget oyster models into a single integrated modeling system to study the impacts of various diversion scenarios on: 1. Salinity distribution and its seasonal and annual variations in the Breton Sound estuary and adjacent continental shelf. 2. Corresponding turbidity and water quality changes. 3. The effects of timing, extent and magnitude of habitat freshening and water quality variations on growth and mortality of the eastern oyster population.