Colonization and initial succession on artificial substrates over spatial and temporal gradients in a Caribbean coral reef ecosystem
Human activity and higher frequencies of disturbance have increased coral reef degradation and created barren substrates with the opportunity for primary colonization. The pioneer microorganisms determine the subsequent community composition, as many organisms require specific substrates and environmental conditions to recruit. Considering that coral recruits more effectively on hard substrates (including crustose coralline algae, polychaete tubes, and other encrusted invertebrates), examining colonization on artificial substrates is increasingly important for coral recruitment. This study documented the pioneer species and early succession on introduced substrates on the fringing reef in Kralendijk, Bonaire, Dutch Caribbean. Ceramic tiles were used as the artificial substrate, and data was collected and analyzed weekly over a period of four weeks. Tiles were placed in three different environments in the reef ecosystem: the sand flat, reef crest, and reef slope. Tiles were analyzed in the laboratory using stereomicroscopy for organism colonization. Turf algae, and brown and green algal filaments were present on all tiles over the experimental time period, but there was no fleshy macroalgal growth. Strong increasing trends of invertebrate abundance and diversity occurred in all environments over the four-week research period. Microfauna including polychaetes, oligochaetes, bivalves, gastropods, crustaceans, bryozoans and foraminiferans were the main pioneer organisms observed. According to other studies, these organisms are also present on artificial substrates over the time period of two to five months. Therefore, these benthic invertebrates likely dominate substrates for several months before further succession occurs allowing organisms such as crustose coralline algae and coral recruits to settle.