The influence of salinity on seagrass growth, survivorship, and distribution within Biscayne Bay, Florida: Field, experimental, and modeling studies

Diego Lirman, Wendell P. Cropper

Research output: Contribution to journalArticle

72 Scopus citations

Abstract

We evaluate if the distribution and abundance of Thalassia testudinum, Syringodium filiforme, and Halodule wrightii within Biscayne Bay, Florida, are influenced by salinity regimes using, a combination of field surveys, salinity exposure experiments, and a seagrass simulation model. Surveys conducted in June 2001 revealed that while T. testudinum is found throughout Biscayne Bay (84% of sites surveyed), S. filiforme and H wrightii have distributions limited mainly to the Key Biscayne area. H. wrightii can also be found in areas influenced by canal discharge. The exposure of seagrasses to short-term salinity pulses (14 d, 5-45‰) within microcosms showed species-specific susceptibility to the salinity treatments. Maximum growth rates for T testudinum were observed near oceanic salinity values (30-40‰) and lowest growth rates at extreme values (5‰ and 45‰). S. filiforme was the most susceptible seagrass species; maximum growth rates for this species were observed at 25‰ and dropped dramatically at higher and lower salinity. H. wrightii was the most tolerant, growing well at all salinity levels. Establishing the relationship between seagrass abundance and distribution and salinity is especially relevant in South Florida where freshwater deliveries into coastal bays are influenced by water management practices. The seagrass model developed by Fong and Harwell (1994) and modified here to include a shortterm salinity response function suggests that freshwater inputs and associated decreases in salinity in nearshore areas influence the distribution and growth of single species as well as modify competitive interactions so that species replacements may occur. Our simulations indicate that although growth rates of T. testudinum decrease when salinity is lowered, this species can still be a dominant component of nearshore communities as confirmed by our surveys. Only when mean salinity values are drastically lowered in a hypothetical restoration scenario is H. wrightii able to outcompete T. testudinum.

Original languageEnglish
Pages (from-to)131-141
Number of pages11
JournalEstuaries
Volume26
Issue number1
DOIs
StatePublished - Feb 1 2003

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ASJC Scopus subject areas

  • Environmental Chemistry
  • Environmental Science(all)
  • Aquatic Science

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