Imaging of surface O sub(2) dynamics in corals with magnetic micro optode particles

We present a new method for quantifying spatio-temporal O sub(2) distribution and dynamics at biologically active surfaces with a complex surface topography. Magnetized O sub(2) optode microparticles (80-100 mu m) 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 sub(2)-dependent luminescence of the particles was mapped with a lifetime imaging system enabling measurements of the lateral surface heterogeneity of the O sub(2) microenvironment across coral polyps exposed to flow. Mapping steady-state O sub(2) concentrations under constant light and O sub(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 sub(2) concentration and estimates of gross photosynthesis that could be spatially resolved at 100 mu m pixel resolution. The new method for O sub(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.