Biomass patterns in seagrass meadows of the Laguna Madre, Texas

Bulletin of Marine Science
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Abstract

The Laguna Madre of Texas supports the most extensive seagrass meadows in the western Gulf of Mexico, In 1988 seagrasses covered 730 km2 or about three-quarters of the embayment. Halodule wrightii dominated the entire upper laguna, and total biomass was quite uniform near 160 g˙m-2 throughout. Four species shared dominance in the lower laguna. Where present mean biomass of Thalassia testudinum was 373 g˙m-2Syringodium filiforme, 138 g˙m-2Halodule wrightii, 78 g˙m-2; and Halophila engelmannii, 6 g˙m-2. Macroalgae were widespread, at 71 g˙m-2 where present. Halodule wrightii was dominant and biomass was low on sand flats of the barrier island separating the laguna from the gulf. Halophila engelmannii was limited to the deep edges of meadows. Biomass >300 g˙m-2 was limited to one extensive T. testudinum meadow at the south end of the laguna at all vegetated depths and two small areas with S. filiforme dominant at intermediate depths. Laguna Madre was similar in biomass to the two regions of extensive development of seagrasses in the eastern gulf: the Big Bend region of Florida (Iverson and Bittaker, 1986) and Florida Bay (Iverson and Bittaker, 1986; Zieman, et al., 1989). The laguna differed from the eastern gulf sites in more turbid waters and much shallower maximum depths of occurrence of seagrasses (<2 m compared to 8–11 m), higher contribution of H. wrightii to system-wide biomass (although H. wrightii's share has rapidly diminished in Laguna Madre as it has been displaced by S. filiforme and T. testudinum [Quammen and Onuf, 1993]), and much higher macroalgal biomass (limited to the section of the lower laguna receiving agricultural inflows). Similarities in the environments of Laguna Madre and inner Florida Bay suggest that, if cover and biomass of Thalassia continue to increase, the laguna may become vulnerable to mass mortalities as are now occurring in Florida Bay.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Biomass patterns in seagrass meadows of the Laguna Madre, Texas
Series title Bulletin of Marine Science
Volume 58
Issue 2
Year Published 1996
Language English
Publisher Ingenta
Contributing office(s) Wetland and Aquatic Research Center, National Wetlands Research Center
Description 17 p.
First page 404
Last page 420
Country United States
State Texas
Other Geospatial Laguna Madre