Impact of Oil and a Tropical Cyclone on an Omnivore and Herbivore Population in Salt Marshes of Louisiana

Abstract

Terrestrial arthropods are the ideal ecological indicators for the health of a salt marsh. Salt marshes are under extreme continuous stressors including climate change, land loss, oil spills, and tropical cyclones. Such stressors impact trophic and species level interactions, food resources, dispersal and population size of insects. In the present study, we collected terrestrial arthropods from eleven sites around Barataria Bay, five sites were oiled and five sites were unoiled, to determine the impact of the redistribution of oil from the Deepwater Horizon oil spill. Site C6 was excluded from the oiled and unoiled data because it was in close proximity to site C5 and we wanted equal replicates for comparison. Samples were collected from January 2012 to December 2013 to determine how the population size of an omnivore and a herbivore were impacted by Hurricane Isaac. The results show that the herbivore, Ischnodemus, was directly and indirectly affected by Hurricane Isaac. While the omnivore, Crematogaster, was not affected by the hurricane but instead impacted by the seasons. In both the herbivore and omnivore weight, length, and head width was affected by the DWH oil. Although the differences were small and it is assumed insect species do recover, long-term monitoring of terrestrial arthropod communities is needed to better understand the recovery and natural succession of marsh ecosystems.