Biomass patterns in seagrass meadows of the Laguna Madre, Texas

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^-2; Syringodium filiforme, 138 g˙m^-2; Halodule 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 (