A tale of two Enso Events: carbonate budgets and the influence of two warming disturbances and intervening variability, Uva Island, Panama

Numerous changes have occurred at the Uva Island reef since the original calcium carbonate budget model was published (Eakin, 1996). Minor bleaching events occurred during the 1990s and a widespread event occurred in 1997–98. In 1989 and 1993, reef flat exposures bleached and killed corals that had recruited to the reef flat. Since 1983 erosion by sea urchins and infauna have eliminated much of the structure that previously existed in the seaward reef base. Earlier work reported that the reef was largely depositional before 1983 (8600 kg CaCO₃ yr−1 net), and highly erosional in the early 1990s (−4800 kg CaCO₃ yr−1 net). New data related to post-1983 disturbances are presented and incorporated into the calcium carbonate model. Modeling suggests that the reef has remained erosional, varying from around −3000 to −18,000 kg CaCO₃ yr−1 net. The reef budget varies substantially with changes in community composition, topographic complexity and echinoid density. La Niña-driven low tidal exposures had more influence on the budget than the 1997–98 El Niño. As the carbonate framework in the reef base eroded, sea urchin density declined and corals began to recover. Climate factors, mediated by biological processes, continue to influence the course of the Uva Island reef ecosystem and its physical structure.