Semester of Graduation
Master of Science (MS)
Tidally influenced coastal marshes provide numerous important ecosystem services, but these habitats are experiencing extreme habitat loss. Louisiana’s coastal marshes in particular are vulnerable to land loss resulting from both anthropogenic and natural causes, but especially to subsidence and relative sea-level rise. In response, the Louisiana Coastal Restoration and Protection Authority has outlined and is currently implementing the largest ever attempt at habitat restoration. A major component of this habitat restoration attempt is the use of freshwater and sediment diversions to increase the input of low salinity water, sediment, and nutrients needed to slow marsh loss and build land. Coastal marsh plant communities are primarily stratified by salinity and their distributions and salt tolerances are relatively well understood. However, the insect communities that are associated with these plant communities are less well known. Few inventories of Louisiana’s coastal insects have been made, and those that exist did not adequately sample the breadth of the tidally influenced marsh vegetation types. The goals of this study were to create a year-long, family-level inventory of the insects present in the Spartina dominated intermediate, brackish, and saline marshes of coastal Louisiana and to determine indicator plant species for each marsh vegetation type for potential environmental monitoring efforts. The objective was to provide baseline data that can be used to both quickly assess marsh type to determine habitat risk to threats such as oil spills or hurricanes and to enable the long-term monitoring of the health of these marshes. Insects and plant ground cover data were collected from July 2018 through June 2019 from 18 sites across Barataria Bay and Caillou Bay in coastal Louisiana. A total of 71 insect families were collected with 61 from intermediate marsh, 64 from brackish marsh, and 39 from saline marsh sites. Family-insect diversity was negatively correlated with salinity for multiple diversity indices. Salinity, seasonality, total ground cover, and ground cover of four plant species were found to be important factors in determining the distribution of insect families within Louisiana’s coastal marshes. Additionally, the abundances of insects belonging to different feeding guilds were found to vary between marsh vegetation types. Families likely to contain useful indicator species were identified to the species level when possible and an Indicator Value Analysis was performed on the species abundance data to determine potential bioindicators. A total of 26 species (from 17 families) were found to be significant indicators for a marsh vegetation type or a combination of marsh habitats. Of these bioindicator species, 11 were indicators of intermediate marsh, 2 were indicators for the combination of intermediate and brackish marsh, 4 were indicators for brackish marsh, 4 were indicators for the combination of brackish and saline marsh, and 5 were indicators for saline marsh.
Aker, Benjamin G., "The Collection of Baseline Data on Insect and Plant Communities Across Multiple Salinity Zones Within Louisiana's Tidal Marshes" (2020). LSU Master's Theses. 5203.