WALTERS, LJ; BEACH, KS; WICK, LA; BORGEAS, HB; Univ. of Central Florida, Orlando; Univ. of Tampa; Guana Tolomato Matanzas National Estuary Reserve; Univ. of Tampa: Coral Reef Community Ecology: Interactions Between the Brown Alga Dictyota and Fishes, Macroalgae and Invertebrates in the Florida Keys

The brown macroalga Dictyota is the dominant species on Conch Reef (northern FL Keys reef tract) at 7 and 21 m, and its abundance has significantly increased during the past decade. Although the cause of this increase is still under debate, Dictyota, primarily D. menstrualis and D. pulchella, impacts community structure in a number of ways. Many species of reef fishes avoid areas with dense Dictyota cover and/or reject rather than consume bites of this chemically-defended alga. 49% of reef fishes rejected bites of Dictyota at our 7 m site and 70% of bites were rejected at 21 m. 100% of the fish-generated fragments attached to sand grains via microscopic rhizoids and continued to grow clonally. Dictyota can also impact sessile reef flora and fauna by overgrowing them. To determine the probability an organism will be overgrown by Dictyota, we: 1) monitored entanglement around reef organisms, and 2) held Dictyota in contact with sessile species with fine-gauge stainless steel wire to determine if it can permanently attach to these potential hosts. Entanglement was ≥ 20% for 4 species: the sponge Agelas wiedenmyeri, the fire coral Millepora alcicornis, and the macroalgae Halimeda tuna and D. menstrualis. Within 3 d, ≥ 25% of fragments permanently attached to the sponges Iotrochota birotulata, Aplysina cauliformis, Niphates digitalis and A. wiedenmyeri; the macroalgae D. menstrualis and H. tuna; and the soft coral Briareum asbestinum.