Seagrass community dynamics in a subtropical estuarine lagoon

The temporal and spatial distribution of major plant and animal species were investigated for 4 years in south Biscayne Bay including Card Sound, Florida, a subtropical estuarine lagoon. This was part of a larger study including chemical, physical and geological investigations. The major species of plants were Thalassia testudinum Banks ex Konig, turtle grass, Laurencia poitei (Lamour.) Howe, a red macroalga and the green algae Penicillus capitatus Lamarck and Halimeda incrassata (Ellis) Lamour. Standing crop and production of plant material taken bi-weekly is given in detail for 16 stations in Card Sound for the 4-year period and for eight stations in Biscayne Bay for a 1-year period. The major animal species were not equally distributed; in the near-shore Thalassia community, species of Pagurus, Neopanope, Hippolyte, Cerithium, Bulla, Prunum and Modulus were dominant. In mid-bay, where patchy Thalassia plus green algae occurred, Thor and Chondrilla were the dominant animals. Near the fringing islands, where tidal flow caused more oceanic conditions, the community was dominated by sponges, urchins and corals. This highlights the structural differences in what is now termed the “ Thalassia community”. Comparisons with other known Thalassia communities are made.