GoMRI RFP-V: Horse fly populations & food web dynamics as stress indicators on coastal marsh (Foil)

Claudia Husseneder gives an overview of the project at the Gulf of Mexico Oil Spill & Ecosystem Science Conference January 2016

A Study of horse fly (Tabanidae) populations and their food web dynamics as indicators of the effects of environmental stress on coastal marsh health project is lead by P.I. Lane Foil, Louisiana State University Ag Center.

Within the tidal marshes of Louisiana the PAH levels in subsurface water in the marsh locations remained high enough to have lethal effects on fish for up to two months, and it has been shown that high levels of oil were retained in the sediment of oiled marsh for much longer. Whether oil components remain in sediments of certain tidal marsh habitats and what effect these residues or degradation caused by oiling have on the invertebrate food web of vertebrates and invertebrates is now an important question. The aftermath of the oil spill provides unprecedented research opportunities for years to come. Tools must be developed not only to assess the impact of a particular oil spill but also to provide screening methods for time- and cost-efficient assessments of marsh health after future environmental insults to help guide remediation efforts. For future unpredicted insults on tidal marshes such as oil spills, techniques for rapid and intensive baseline sample collections with minimum impact on the fragile ecosystem will be needed.

During a two year period beginning immediately after the spill, we conducted studies on the abundance of greenhead horse fly populations at four locations (Grand Bayou and Grand Isle which were oiled and Cypremort Point and Cameron which remained pristine). Horse fly abundance estimates showed severe crashes of adult tabanid populations as well as reduced numbers of larvae recovered from the soil in oiled areas. We propose to follow up that study with a longitudinal population genetic study of horse flies as bioindicators of marsh health and recovery. In 2011, we conducted surveys of tabanid larvae and their surrounding sediment, and specimens were archived to initiate studies on establishing the food web within the sediments. We propose to use those and future collections for metagenetic analyses to compare the micro- and meiofauna community in larval guts to that in the immediate soil environment where tabanid larvae are either present or absent. Based on this knowledge we will develop a time- and cost-efficient PCR-based diagnostic method to differentiate between healthy and biologically depleted marsh soil for use in intensive sampling.

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This project was funded by the Gulf of Mexico Research Initiative (GoMRI) in the RFP-V funding program.

The Gulf of Mexico Research Initiative (GoMRI) is a 10-year independent research program established to study the effect, and the potential associated impact, of hydrocarbon releases on the environment and public health, as well as to develop improved spill mitigation, oil detection, characterization and remediation technologies. An independent and academic 20-member Research Board makes the funding and research direction decisions to ensure the intellectual quality, effectiveness and academic independence of the GoMRI research. All research data, findings and publications will be made publicly available. The program was established through a $500 million financial commitment from BP. For more information, visit http://gulfresearchinitiative.org/.