Photosynthesis presents a paradox of solar energy: the maximum quantum efficiency of photosystem II likely surpasses that of any engineered system, but in environments with high solar flux, photosynthetic organisms are famously wasteful and resource inefficient. For example, even in agricultural systems bred for maximum resource efficiency such as switch grass and maize, only a few percent of the energy of the solar resource becomes accessible, fixed carbohydrate in the mature plants.  Surprisingly, giant clams, which are symbiotic with unicellular algae at extreme solar flux intensities that close to the solar constant, may be the most solar-resource-efficient organisms on Earth.

Our prior experimental work on this system supports the hypothesis that the clam/algae system absorbs nearly all the solar flux incident on them at the equator and transduces that energy into photosynthate with maximal efficiency and minimal photoinhibition. Our theory talk will briefly outline those earlier results, and then focus on presenting a new, analytical explanation of how the system accomplishes this, and why it may represent a true optimum design for solar resource utilization efficiency using biological photosynthesis.