Clams have a lifespan of 100 years or more and their bright colors are the result of living algae in their bodies. Interesting! These incredible creatures are filled with unique characteristics and an addition to them came with a recent experiment. Researchers discovered that giant clams can make solar energy more efficient.
Photosymbiotic giant clams have vertical columns of single-celled algae that absorb sunlight. It has forward-scattered light-scattering cells called iridocytes. Inspired by the geometry observed in the clams, researchers have created an analytical model. It can calculate the performance of the system as per a system with a similar geometry as clams.
Highlights: Giant Clams Can Make Solar Energy More Efficient Experiment
- In intense tropical sunlight, the quantum efficiency of clams can reach up to 43% relative to the solar resource.
- Clams use a fixed geometry of light-dilution strategy.
- It is possible that the solar-transformer geometry of the clam could be useful for solar energy conversion.
- With a simple physical model, researchers are trying to understand the relation between the evolved tissue structure of clams and the optimization of solar-resource efficiency.
- 67% photosynthetic light-use efficiency under natural tropical light was achieved by the system model.
Researchers studied the photosynthetic efficiency of a complex biological system. It includes symbiotic giant clams hosting single-celled algae in their tissues. A simple model of a solar transformer was prepared on the same logic as that of these clams.
This model achieved around 67% photosynthetic light-use efficiency under natural tropical light. It is possible that living clams can exceed this efficiency as per additional mechanisms explained by the researchers. According to this, it is possible to design a sustainable biomass system with intense natural sunlight to generate renewable power.
Cultivating Unicellular Algae
The modern economy runs on photosynthetic products gathered over geologic time. To collect large-scale quantities of non-fossil liquid fuels and chemical feedstocks on an industrial scale, unicellular algae are cultivated.
Applicable for Efficient Solar Conversion
Generally, the efficiency of biological photosynthesis increases with decreasing flux. It is possible that the solar-transformer geometry of the clam could be useful for solar energy conversion.
Clams’ Illumination and Application in the Real World
Internal artificial lights can lead to greater per-cell and system productivity. However, these lead to high electricity bills relative to using ambient sunlight as an energy source.
About the Experiment
The demonstration is also based on the reanalysis of experimental data from a 1985 paper. It helps in demonstrating that large clams photosynthesize at near-perfect rates in the initial oxygen-evolution step of photosynthesis.
To explain the unprecedented efficiency achieved by these clams, a simple physical model of light scattering, and photo conversion was developed.
Purpose Of the Experiment
Researchers want to understand the plausibility of large-scale resource-level efficiencies for photosynthesis in the solar-transformer design. Thus, they have developed a simple framework for this. To address how light-efficient area-spanning system for algal cultivation under ambient sunlight can be. For this, the giant clams (genus Tridacna) were considered.
The Experiment: How Can Clams Improve Renewable Efficiency
The clam system was presented as a vertically oriented cylinder.
- Along the inner vertical wall, light incident on the horizon’s circular top surface was uniformly redistributed.
- The isolated dilute suspension of algae from a giant clam was used on the walls of the cylinder to perform photosynthesis-irradiance behavior.
- This setup helps to explore resource efficiency by using the parameter of the rate of O2 evolution per area, over a day.

Evaluating the Performance of Simple Model
For this, the cylindrical system’s performance was compared with another system, which was similar in size and same number of algae cells. The only difference was the arrangement of algae throughout the volume.
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Effects of Multiple Scattering Phenomenon Used by Clams
To explore this, the simple analytical model was compared to a light-scattering numerical model of a realistic model. That model has discrete realistic cell positions and the geometry system which was too similar to the clam system.
Points Discovered: Better Energy Efficiency With Giant Clams
To achieve 70% quantum efficiency, the geometry of a simple-cylinder system can be modulated with light intensity. This can be done via the inflation and deflation cycles of the mantle tissue. Which will further cause expansion and contraction of the effective cylinder radius with light intensity. Thus, the system can effectively harvest solar energy.
About Giant Clams
They are symbiotic unicellular algae from the dinoflagellate genus Symbiodinium. Here, algae living in the mantle tissue perform photosynthesis, contributing energy to the host. The energy supplied is in the form of small organic molecules. With its large filter-feeding apparatus, giant clams supply nitrogen and other nutrients to the system.
Qualities of Giant Clams (Unicellular Algae)
- They can grow at high densities in liquid culture.
- Many species readily deposit most of the photosynthesized carbon into intracellular oil droplets rather than complex extracellular polymers.
- Their efficiency is strongly dependent on the intensity of light. Many cells experience too high light density to be efficient. Whereas several of them experience too low intensity of light to be highly productive.
- They live throughout the Indo-Pacific oceans in shallow coral reef environments.
- They are free spawning, and their larvae develop in the water column and feed on phytoplankton.
- They develop into small clams with photosynthetic algae in their mantle tissue after ingesting algae cells.
- As they grow, unicellular algae multiply and develop into an array of vertical columnar structures.
- The diameter of these algal columns is around 100 µm and 150 µm in distance.
How Clams Illuminate?
- Algae are visible in clam tissue beneath and around their mantle tissues and superficial iridocytes, appearing saturated black.
- These forward-scattering iridocytes become transparent under strong directional lateral illumination.
- It then reveals densely packed microalgae in columnar arrays.
- This array is visible within the mantle tissues, leading to the appearance of saturated black mantle tissue present under overhead illumination.
The Clam’s Approach Observed in the Experimented Model
Mantle tissue’s inflation and deflation is a major part of clam’s behavior which is mostly observed in a flinching response to perturbation.
- In high light, the mantle should be deflated relatively. Radial spacing between columns will be affected by this and it will increase the light diluting factor and decrease the parameter.
- In dim/low light, to increase the effective radial column spacing, the mantle should be inflated. This decreases light dilution and increases the parameter.
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Conclusion
The numerical model accurately captured the phenomenon of multiple scattering in columns with randomly organized algae. This demonstrates a comparable level of efficiency to the simpler analytical model. It shows that there is a possible solution to increase the efficiency of PV systems, but researchers have to cover a long route.
All the qualities offered by the model system are amenable to further engineering and modelling. The productivity of 60 000 l per hectare per year of fuel of a large system can be exceeded if its physical principles are similar to the giant clam.
Thus, researchers conclude that giant clams can make solar energy more efficient, and the experimental model is considered to be a useful tool. It can help in designing future schemes for efficient photosynthetic biomass cultivation. Most probably it will be applicable for the production of algal biofuels. Also, it can minimize land use for sustainable biomass harvesting for any organic PV or arbitrary photosynthetic system.
Source: Simple Mechanism for Optimal Light-Use Efficiency of Photosynthesis Inspired by Giant Clams