Nutrition
 
 

Explanations for answers to quiz on the greater efficiency of light-utilisation for photosynthesis in deep-dwelling boulder corals. The nonsense entry is highlighted:

 

Zooxanthellae numbers increase with depth. No. Although this would be a logical choice, there is no significant difference in numbers of zooxanthellae between the shallow and deep colonies.

 

Chlorophyll content per zooxanthella is greater in deep colonies. Yes, this is one of the true statements. In fact, there is 6-fold more chlorophyll per zooxanthella in colonies at 50m depth as compared with ones near the surface.

graph comparing chlorophyll content of zooxanthellae in shallow and deep boulder corals

There is more red wavelength-utilising chlorophyll in zooxanthellae in the deeper colonies. If you selected this as the NONSENSE ENTRY, then you are correct. Any SCUBA-diver will know that red wavelengths are the first to be absorbed with depth, so more red wavelength-using chlorophyll at depth could be of no benefit.

 

There is more blue wavelength-utilising chlorophyll in zooxanthellae in the deeper colonies. Yes, this is one of the true statements. In fact, the ratio of blue- to red-utilising chlorophyll goes from about 1:6 at the surface to about 1:1 at 50m depth (SCUBA-divers know that blue wavelengths penetrate deeper into water). So, not only do the deep colonies have more chlorophyll per zooxanthella (the 2nd point on the quiz), but the type of chlorophyll they have is additionally "photo-adapted" for depth.

graph comparing ratio of blue-red wavelength-utilising chlorophyll in shallow and deep boulder corals
 
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