, Volume 11, Issue 5, pp 688–700 | Cite as

Ecosystem Structure and Function Still Altered Two Decades After Short-Term Fertilization of a Seagrass Meadow

  • D. A. Herbert
  • J. W. Fourqurean


An oligotrophic phosphorus (P) limited seagrass ecosystem in Florida Bay was experimentally fertilized in a unique way. Perches were installed to encourage seabirds to roost and deliver an external source of nutrients via defecation. Two treatments were examined: (1) a chronic 23-year fertilization and (2) an earlier 28-month fertilization that was discontinued when the chronic treatment was initiated. Because of the low mobility of P in carbonate sediments, we hypothesized long-term changes to ecosystem structure and function in both treatments. Structural changes in the chronic treatment included a shift in the dominant seagrass species from Thalassia testudinum to Halodule wrightii, large increases in epiphytic biomass and sediment chlorophyll-a, and a decline in species richness. Functional changes included increased benthic metabolism and quantum efficiency. Initial changes in the 28-month fertilization were similar, but after 23 years of nutrient depuration T. testudinum has reestablished itself as the dominant species. However, P remains elevated in the sediment and H. wrightii has maintained a presence. Functionally the discontinued treatment remains altered. Biomass exceeds that in the chronic treatment and indices of productivity, elevated relative to control, are not different from the chronic fertilization. Cessation of nutrient loading has resulted in a superficial return to the pre-disturbance character of the community, but due to the nature of P cycles functional changes persist.


phosphorus nitrogen nutrient retention seagrass diversity respiration productivity benthic metabolism eutrophication 



The authors recognize the efforts made by GVN Powell and WJ Kenworthy to initiate these experiments in the 1980s. This material is based upon work supported by the National Science Foundation-funded FCE-LTER program under Grant No. DBI-0620409 and Grant No. DEB-9910514. This is contribution number 383 from the Southeast Environmental Research Program at FIU.


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© Springer Science+Business Media, LLC 2008

Authors and Affiliations

  1. 1.Department of Biological Sciences and Southeast Environmental Research CenterFlorida International UniversityMiamiUSA
  2. 2.Fairchild Tropical Botanic GardenGoral GablesUSA

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