UCB Moorea Class: Biology and Geomorphology of Tropical Islands

Abstract. Zooplankton is an essential component of every coral reef system, not only because it is the base of many marine food chains, but also because it is an important stage in many marine animals’ life cycles. While by definition plankton is free floating, zooplankton ha been known to move in predictable patterns. This includes a daily diel vertical migration towards the surface at night and back to the depths during the day and fluctuations in abundance over the lunar cycle, usually peaking around the full moon. This study aimed to look at the amount of control plankters have in choosing their horizontal position over the reef by looking at substrate preferences of demersal zooplankton in the fringing reef. It was found that zooplankton emerge in the largest numbers from branching coral followed by coral rubble and sand and in significantly lower numbers from smooth coral. This suggests that demersal zooplankton is able to select the substrate on which it seeks shelter during the day. Little evidence was found suggesting specific taxa prefer specific substrates. The study also compared plankton emerging from the substrate of the reef with those in the water above it. A zooplankton from the genus Lucifer was found to be dominant in the water column above the reef, but was not seeking shelter in the reef substrate during the day. Lastly, fluctuations in abundance were observed throughout the lunar cycle with a peak in numbers occurring 6-11 days after the full moon.