Plant cover in semiculture enclosures was studied in Punta Gavilan (PG) and Banco Chinchorro (BCH) in order to determine the phytobenthíc biomass and potential Coad availability oC queen conch Strombus gigas. Samples were collected monthly from two habitats: "Thalassia" (T) and "Thalassia-Sand" (T-A), from October 1993 to March 1994. In PG the mean biomass oC TluJlassia and . Thalassia epiphytes, were 40.5 ± 18.5 dw.g.m,2 in T, and 29.4 ± 9.2 dw.g.m,2 in T-A, while in BCH. these values were 23.3 ± 5.3 dw.g.m'2 (T) and 16.2 ± 6.0 dw.g.m,2 (T-A). In BCR Halimeda spp biomass was more significant than the biomass oC TluJlassia and Thalassia epiphytes. In PG shell marginal increment was larger in T-A hábitat (2.1 ± 0.9 mmlmonth), while in BCH mean shell growth was 1.5 ± 0.4 mmlmonth, without any significant difCerence between hábitats. Although potential food was available for conchs in T and T-A, shell marginal increment was highest in "Sand" (A) and "Coral" (C) hábitats. It is necessary to study the microfloral biomass and detritus from bottom sediments in these hábitats and lO relate them with the growth of S. gigas