GCRC Project Summary |
Effects of Eutrophication on Marsh Plant Community Structure in Four Sea Grant States
PIs: Steve C. Pennings* (formerly: Marine Institute, Sapelo Island, Georgia, USA) and J. Stephen Brewer (Dept of Biology, Univ of Mississippi) *currently - Dept of Biology and Biochemistry, Univ of Houston, Texas.
Support: Georgia Sea Grant College Program (R/HAB-6)
Timeframe: 3/1/98 - 2/28/00 (complete)
Project
Overview:
This project was designed to test the hypothesis that eutrophication will alter
salt marsh plant community composition, zonation, and diversity in 3 southern
states. Sites in Alabama, Georgia, and Mississippi were fertilized, plants were
monitored non-destructively through 2 growing seasons and then harvested, dried
and weighed.
Findings:
After one year of fertilizer application, all plots showed obvious signed of
enhance nutrient availability. Vegetation was taller and greener. No signs of
"burning" due to fertilizer application were noted. Enhanced growth
and color were discretely limited to the boundaries of the plots, indicating
that fertilizer was not spreading to adjacent areas during high tides.
Vegetation responses to fertilization suggest that shifts in species dominance will occur in fertilized plots. In particular, Spartina alterniflora appears to be increasing in fertilized plots, often at the expense of co-occurring species.
Experiments were performed at the borders of S. alterniflora and Juncus roemerianus in all three states. The response (after one year of fertilization) appears similar in all three states: S. alterniflora appears to be increasing whereas Juncus roemerianus does not. This suggests that similar plant mixtures may respond similarly to fertilization in each state, despite differences in tidal regime between geographic regions.
Publications:
SC Pennings, LE Stanton, JS Brewer. Nutrient effects on the composition
on salt marsh plant communities along the Atlantic and Gulf coasts of the United
States. Submitted.