To estimate the macrobenthic biomass production of the Faro/Ancão artificial reef in the Algarve region of Portugal, we carried out a study on two artificial reef groups, arranged in two layers, deployed in May 2003. Concrete cubic units (15 × 15 × 15 cm) were used
to test, on the horizontal and vertical surfaces of the reefs, the effect of depth (16 and 20 m depth) and relative position within the reef (upper and lower layer) on macrobenthic biomass. Both artificial reef groups were dominated by Balanus amphitrite Darwin, 1854. Furthermore, Bugula
neritina (Linnaeus, 1758) was a typical species at 16 m, particularly on the upper layer of the artificial reef, whereas Anomia ephippium Linnaeus, 1758 was particularly common at 20 m, especially on the lower layer. At both depths, biomass was higher on the top than the bottom
of horizontal surfaces. Biomass on the vertical surfaces was similar for both layers and depths.
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