The Future of Giant Clam-Dominated Lagoon Ecosystems Facing Climate Change

Abstract

Several small isolated Pacific Ocean atoll lagoons were characterized by their unique abundances of giant clams for at least 35 years, but they were recently affected by massive mortalities. We review evidences that confirm collapses in the past 10 years, discuss the likely causal factors based on current knowledge, and assess the consequences for management. Recent in situ and modeling research have focused on how management, natural processes, and climate change can influence the population trajectories. Projections suggest increasing risks with limited management options to reverse the trend. The various documented cases support the hypothesis that mass mortalities of giant clams are triggered by climate variability, enhanced by the geomorphological specificities of these atolls. The exact mechanisms leading to mortalities and consequences for the whole ecosystem remain unknown and are probably case-dependent. These collapsing ecosystems represent well the fast impact that climate change can have on reef ecosystems.