Title page for ETD etd-08252011-120545

Type of Document Master's Thesis
Author Lockfield, Konner Chadwick
Author's Email Address klockf1@lsu.edu
URN etd-08252011-120545
Title Population-Level Responses of the Mummichog, Fundulus Heteroclitus, to Chronic Nutrient Enrichment in a New England Salt Marsh
Degree Master of Science (M.S.)
Department Biological Sciences
Advisory Committee
Advisor Name Title
Fleeger, John Committee Chair
Baltz, Donald Committee Member
Brown, Ken Committee Member
  • growth
  • fundulus heteroclitus
  • mummichog
  • eutrophication
  • wire tags
  • salt marsh
Date of Defense 2011-07-27
Availability unrestricted
Mummichog (Fundulus heteroclitus) responses to chronic whole-ecosystem nutrient enrichment were examined near Plum Island Sound, Massachusetts. Dissolved fertilizer was released into replicate salt marsh creeks over 6 growing seasons to simulate agricultural run-off (bottom-up effects). Density, biomass, secondary production, growth rate, and condition factor were estimated in fertilized and reference creeks. Mummichog densities were also used to determine if mummichog growth or health varied with density. Over 7,600 mummichogs were marked and released into the treatment and control areas to measure responses. Over 900 mummichogs were recovered. Mummichog abundance was higher (p = 0.055) in nutrient-enriched creeks than reference creeks (0.81 0.04 fish m-2 and 0.59 0.07 fish m-2 respectively). Nutrient enriched-creek biomass of 522.9 36.1 mg dw m-2 was significantly higher (p=0.028) than control-creek biomass of 338.5 26.7 mg dw m-2. However, reference-creek growth rates of 0.105 0.091 were significantly higher (p=0.04) than the nutrient enriched-creek growth rates of 0.073 0.065 mm d-1. Secondary production and condition factor of mummichogs did not differ with nutrient enrichment. Nutrient enrichment likely stimulated primary production causing bottom-up effects in the food web, which increased mummichog abundance and biomass. However, as abundance increased, mummichog growth rates decreased, suggesting a density-dependent response, likely caused by either intraspecific competition or behavioral changes causing dietary shifts.
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