Changes in benthic cover in the south atoll of tubbataha reefs due to possible eutrophication

Abstract

The Tubbataha Reefs Natural Park is of global and local importance and is a benchmark and aspirational model for the condition of reefs within an MPA. Recently, small but significant overall declines in hard coral cover (HCC) and increases in algae were detected in Tubbataha. Changes were most consistent in Site 4 at the South Atoll, where lagoon waters drain through during ebb tide. Space available to corals here was covered by cyanobacteria in 2018, and then by sponges in 2019. These sponges have begun to overgrow coral. These changes in Site 4 are likely due to an increase in guano-derived nutrients in the lagoon waters of the South Atoll. They may initiate a continuing decline in corals and, thus, require enhanced monitoring.