The influence of freshwater runoff on biomass, morphometrics, and production of Thalassia testudinum

Elizabeth Irlandi, Beth Orlando, Silvia Maciá, Patrick Biber, Tahzay Jones, Louis Kaufman, Diego Lirman, El Tanya Patterson

Research output: Contribution to journalArticle

23 Scopus citations


Efforts to restore more natural freshwater flows in South Florida will impact Biscayne Bay. In order to evaluate possible effects of decreased freshwater discharge on the seagrass Thalassia testudinum, we determined the biomass, density, morphometrics (width, length, number of blades per shoot) and production of T. testudinum twice a year for 2 year at sites exposed to varying degrees of freshwater runoff. Responses to freshwater discharge varied between the sampling years. The only morphometric variable to be influenced by freshwater runoff in both years was blade width with width of seagrass blades being less at sites influenced by freshwater runoff than at sites with limited influence of freshwater runoff. In 1996, no other parameters differed among the three freshwater conditions considered; canal discharge, sheet-flow runoff, and limited freshwater runoff. In addition, all measured parameters were greater in summer (wet season) than in winter (dry season) in 1996. In 1997, biomass, shoot weight, shoot production, and areal shoot production all were greater at sites on the eastern side of the bay that experience limited influence from freshwater runoff compared to sites on the western side of the bay that experience large amounts of freshwater runoff from sheet-flow and canal discharge. In 1997, only length of seagrass showed a significant increase from winter to summer. Factors thought to be responsible for these interannual differences are winter temperatures and seasonal rainfall amounts. The winter of 1996 was much colder than the winter of 1997, and 1997 experienced an unusually rainy dry season thus increasing the amount of time during the year that freshwater runoff would be influencing sites on the western side of the bay. Based on these results, reduced freshwater inflow to Biscayne Bay should have a positive effect on T. testudinum provided detrimental hypersaline conditions do not occur.

Original languageEnglish (US)
Pages (from-to)67-78
Number of pages12
JournalAquatic Botany
Issue number1
StatePublished - Feb 26 2002


  • Biomass
  • Freshwater
  • Morphometrics
  • Production
  • Salinity
  • Seagrass
  • Thalassia testudinum

ASJC Scopus subject areas

  • Aquatic Science
  • Plant Science

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    Irlandi, E., Orlando, B., Maciá, S., Biber, P., Jones, T., Kaufman, L., Lirman, D., & Patterson, E. T. (2002). The influence of freshwater runoff on biomass, morphometrics, and production of Thalassia testudinum. Aquatic Botany, 72(1), 67-78.