Title page for ETD etd-06102008-194156

Type of Document Master's Thesis
Author Moerschbaecher, Matthew Korbel
Author's Email Address mmoers1@lsu.edu, matthewmoe@hotmail.com
URN etd-06102008-194156
Title The Impact of the Caernarvon Diversion on Above- and Belowground Marsh Biomass in the Breton Sound Estuary after Hurricane Katrina
Degree Master of Science (M.S.)
Department Environmental Studies
Advisory Committee
Advisor Name Title
Day, John W. Committee Co-Chair
Wilson, Vince Committee Co-Chair
Wascom, Mike Committee Member
White, John R. Committee Member
  • Caernarvon
  • redox potential
  • Hurricane Katrina
  • porewater
  • estuarine gradient
  • belowground biomass
  • aboveground biomass
Date of Defense 2008-03-14
Availability unrestricted
The purpose of this project was to monitor the recovery of marsh vegetation following Hurricane Katrina in the Breton Sound estuary, which is directly influenced by the Caernarvon freshwater diversion. From March 2006 until October 2007, we measured above- and belowground biomass, soil porewater nutrients (NOx, NH4, and PO4), porewater salinity, porewater sulfide concentrations, and soil redox potential bimonthly at duplicate Near (N), Intermediate (M), and Far (F) sites (with respect to the diversion), as well as at a Reference (C) site. End of season live (EOSL) below and above ground biomass was measured at 26 separate stations where vegetation studies had been done previously. Peak standing crop ranged from 423 g/m2/yr at site M2 to 1515 g/m2/yr at F1. Aboveground biomass was significantly greater at N1 than at N2, M1, or M2. Peak belowground biomass ranged from 8315 g/m2/yr at C2 to 17890 g/m2/yr at N1. Multiple regression analysis showed that sulfide levels were related to the amount of belowground biomass (p < 0.05; R2=0.13). PO4 concentration was related to the amount of aboveground biomass (p<0.05; R2=0.09). Short term vertical marsh accretion measurements ranged from 0.49 cm y-1 at N2 to 1.25 cm y-1 at N1, suggesting that all the study sites are stable or accreting at a rate which offsets local RSLR. Analysis of the results of short term accretion compared to regional relative sea level rise (RSLR) indicates that all Caernarvon sites are keeping pace with RSLR. Analysis of porewater parameters showed that stress on plants was low to moderate while nutrient concentrations were greatest at the Near sites.
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