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Coral Bio-optics

We employ diverse techniques to study coral optical properties. Extracting them is complex due to high density and scattering in coral tissue. Adapted from biomedical optics, methods like reflection spectroscopy, radiative transfer modeling, and optical coherence tomography aid in understanding coral light interactions.

Diffuse Reflectance Spectroscopy

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The lateral attenuation of diffuse reflectance can be mapped over a photosynthetic tissue. Diffusion theory can then be used to extract the scattering and absorption coefficient. The image shows the mapping of lateral light attenuation over the heterogeneous coral surface. 

Integrating Sphere

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The integrating sphere allows for mesaurements of total diffuse refelctance and transmittance of a sample. These values can be matched to theory to calcuate the scattering coefficient of a sample.

Optical Coherence Tomography (OCT)

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OCT measures characteristic patterns of directly elastically backscattered (low coherent ballistic and near ballistic) photons from different reflective layers in a sample, e.g. at refractive index mismatches between tissue compartments with different microstructural properties. Signal contrast in OCT thus depends on the optical scattering properties of the investigated material, where light scattering creates good image contrast, while highly NIR absorbing media result in poor images. Recently, OCT imaging has been applied in the environmental sciences in order to understand the structure and function of biofilms, higher plants, aquatic vertebrates and corals.

Related Publications:

Tuchin, V.V. 2007. Tissue optics: light scattering methods and instruments for medical diagnosis(Vol. 13). Bellingham: SPIE press.

Wang, L., Jacques, S.L. and Zheng, L., 1995. MCML—Monte Carlo modeling of light transport in multi-layered tissues. Computer methods and programs in biomedicine, 47(2), pp.131-146.

Wangpraseurt, D., Jacques, S.L., Petrie, T. and Kühl, M., 2016. Monte Carlo modeling of photon propagation reveals highly scattering coral tissue. Frontiers in plant science, 7.

Wangpraseurt, D., Wentzel, C., Jacques, S.L., Wagner, M. and Kühl, M., 2017. In vivo imaging of coral tissue and skeleton with optical coherence tomography. Journal of The Royal Society Interface, 14(128), p.20161003.

Bollati E, Kuhl M, Wiedenmann J, Wangpraseurt D*. Green fluorescent protein-like pigments optimise the internal light environment in symbiotic reef-building corals 2022. Elife 11, e73521.

Kramer N, Tamir R, Ben-Zvi O, Jacques SL, Loya Y & Wangpraseurt D*, 2021. Efficient light harvesting in mesophotic corals is facilitated by coral optical traits (Functional Ecology, https://doi.org/10.1111/1365-2435.13948)

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