The present study provides information about the structure and temporal variations of the Bostrichietum complex in a Rhizophora racemosa and pelliciera rhizophorae dominated alluvial mangrove in the gulf of Montijo, western Panama. Twenty-one segments of one meter length of Rhizophora racemosa roots were randomly sampled below the high water mark and measured in terms of breadth (diameter) and surface area occupied by each species of the complex. In a second study, a year later, algal cover of thirty segments of roots were carefully removed and left to dry to a constant dry weight for a week after the collection date. Each species was weighted separately and biomass was expressed in mg/cm2 of root. The Bostrychietum complex was composed by three species of red algae, Bostrychia calliptera (Montagne) Montagne (Rhodomelaceae), Caloglossa leprieurii (Montagne) G. Martens (Delesseriaceae) and Catenella impudica (Caulacanthaceae). Bostrychia calliptera showed the broadest range of cover with 1.61 ± 0.04 m2 (81.8%) whereas Caloglossa leprieurii registered a cover of 0.35 ± 0.028 m2 (17.7%) and Catenella impudica only 0.009 ± 0.005 m2 (0.5%).  In the second study epiphytic biomass was measured in terms of the dry weight and the density of algal mass surrounding roots determined in both dry and rainy season. A total of 88.1 mg of algae were collected, 90.7% corresponding to Bostrychia calliptera and 9.3% to Caloglossa leprieurii.  Catenella impudica was not found.  Biomass of B. calliptera was relatively constant between dry and rainy season with mean density of 37.8 y 42.1 mg/cm² while C. leprieurii registered low values of 8.2 mg/cm² in the dry season and less of 1 mg/cm² in the rainy season.