The Macroalgal Composition Differs Among Depths and Zones in Cuban Mesophotic Coral Reef Eosystems

Previously the algal community of Cuban mesophotic coral reef ecosystems (MCEs) has not been characterized quantitatively. The objective of this study was to explore the distribution of macroalgae around Cuba and their depth profiles within the mesophotic zone (30−150 m). Data on the algal community were obtained in 2017 during 43 ROV (remotely operated vehicle) dives around Cuba’s shelf. Scientists specializing in algal taxonomy watched the live ROV video on board the ship and recorded algal presence every ~5—10 min in a database. Algae were identified to the lowest possible taxa, and algal presence/absence was analyzed in 20 m depth intervals between 30 and 150 m. Differences in algal composition among zones and depths were observed. Macroalgae were more diverse at shallower depths (30—69 m). Changes in algal composition were observed as depth increased to 89 m; at greater depths, no differences in algal composition were observed. The deepest algae were crustose forms of Chlorophyta and Rhodophyta, capable of capturing the low light levels reaching the bottom. Differences among geographical zones were observed, where the most algal categories (16—22) occurred in the southwest, northwest, and northcentral zones. The least number were in the southcentral zone (10 categories). In addition to their major role as primary producers, mesophotic macroalgae are no doubt important to structuring MCEs in Cuba and merit more study to better elucidate and quantify their multiple roles at these depths.