Distribution, growth rate, and carbonate production of non-geniculate and unattached coralline red algal beds (rhodoliths) were studied in the Gulfs of Panama and Chiriquí along the Pacific coast of Panama. This is the first attempt to quantify coralline carbonate production in this region based on a newly developed algorithm. Although situated at the same latitude, the two gulfs are characterized by distinctly different environmental conditions; Chiriquí is mesotrophic throughout the year, whereas the Gulf of Panama is eutrophic due to intense seasonal upwelling. Coralline algal carbonate production is ∼10× greater in the Gulf of Chiriquí (11.258 × 1010 gr CaCO3 yr−1) than in the Gulf of Panama (1.69 × 1010 gr CaCO3 yr−1), which is characterized mostly by siliciclastics with minor carbonates. Corallines display a patchy distribution in both gulfs being concentrated mainly around the islands. In Chiriquí, they occur as thin crusts as well as massive-nodular and open-branching growth types; encrusting types are most common in the Gulf of Panama. Growth rates of branching corallines were calculated based on annual growth bands matched to their skeletal Mg/Ca ratios. Ratios are higher in the less dense portions of growth bands corresponding to higher growth rates during the dry season, whereas both Mg/Ca ratios and growth rates in the dense portions (wet season) drop. Growth rates of branch tips in both sites are similar to those reported from other temperate-subtropical regions. Extremely slow growth rates combined with the old ages of individual thalli document the overall stability of this algal ecosystem.

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