We present a new method for quantifying spatio-temporal O 2 distribution and dynamics at biologically active surfaces with a complex surface topography. Magnetized O 2 optode microparticles (*80-100 lm) containing the NIR-emitting luminophore platinum (II) meso-tetra (4-fluorophenyl) tetrabenzoporphyrin (PtTPTBPF; ex. max. 615 nm; em. max. 780 nm) were distributed across the surface tissue of the scleractinian coral Caulastrea furcata and were held in place with a strong magnet. The O 2 -dependent luminescence of the particles was mapped with a lifetime imaging system enabling measurements of the lateral surface heterogeneity of the O 2 microenvironment across coral polyps exposed to flow. Mapping steady-state O 2 concentrations under constant light and O 2 dynamics during experimental light-dark shifts enabled us to identify zones of different photosynthetic activities within a single coral polyp linked to the distribution of coral host pigments. Measurements under increasing irradiance showed typical saturation curves of O 2 concentration and estimates of gross photosynthesis that could be spatially resolved at *100 lm pixel resolution. The new method for O 2 imaging with magnetized optode particles has much potential to be used in studies of the surface microenvironment of other aquatic systems such as sediments, biofilms, plant, and animal tissue.