Results of an experiment on post-settlement survival for Porites corals in Palau

The early life-history stages of marine invertebrates, including corals, are subject to high mortality. Numerous environmental and biological factors serve as bottlenecks, restricting recruitment and connectivity of populations. We conducted a lab experiment to determine the influence of temperature and light on post-settlement mortality of massive Porites corals in April 2023. Adult massive Porites corals were collected from six sites in Palau immediately prior to their spawning season. Collected corals were held in individual plastic containers (4.2 L; 17 x 13 x 19 cm) in ambient unfiltered flow-through seawater tanks at the Palau International Coral Reef Center (PICRC). Three days post fertilization, larvae were settled on glass microscope slides with crushed crustose coralline algae used as a settlement cue. Slides were randomly distributed among two temperature treatments (30° C, 33° C) and two light levels (ambient, high) in a 2-way crossed design. Immediately after settlement and every two days throughout the experiment, slides were photographed individually using a Nikon D850 camera with a macro lens. Living settlers were counted in each image to track settler survival over time. Temperature and light level in each treatment were logged using Hobo pendants (Onset, Wareham, USA).