Tropical reef ecosystems lie at the interface of productive, populated terrestrial coastlines and unproductive, oligotrophic oceanic waters. Corals and other dominant reef organisms maintain complex symbiotic interactions with both surficial and planktonic aquatic microbial communities, but the processes defining the composition and life history of these communities are poorly understood.

Water motion has wide-ranging effects on scleractinians, particularly during thermal bleaching when increased flow may aid in resistance to high temperature. Increased flow removes photosynthetically-derived oxygen radicals, causing greater efficiency of PSII and conferring resistance to bleaching. However, enhanced flow can have both positive and negative effects on coral photophysiology (light-adapted yield, QY). Modest increases in flow benefit QY, while larger increases can have detrimental effects, suggesting that there is a threshold effect in QY along a flow continuum.

The objective of this study was to test the effect of light (sand and CCA) and dark (macroalgae) substrata on the photosynthetic efficiency of coral tissues adjacent to these surfaces. The study was motivated by the conspicuous effects of macroalgae in “darkening” the submarine light fields of reefs, an effect we demonstrated through spectral analysis of the light microenvironment using an underwater spectrophotometer.

In the face of a changing global climate, being able to predict the response of organisms and to assess their vulnerability is essential for the development of successful management and conservations strategies. We hope to study the impacts of ocean acidification on two important members of the Moorea coral reef ecosystem: the sea urchin Echinometra mathaei and the coral Pocillopora damicornis.

Zooplankton were 3 to 8 times more abundant near the surface than elsewhere in the water column during the day over a 1 to 2.4 m deep back reef in Moorea, French Polynesia. Zooplankton were also significantly more abundant near the surface at night although gradients were most pronounced under moonlight.