Nutrition
 
 

Explanations for possible reasons for poor growth of sea urchins Tripneustes on a diet of seagrass Thalassia:

The sea urchins might be eating much less of the seagrass than of the other plants. No. Consumption is actually highest for seagrass, and decreases in the following order: Thalassia > Sargassum > Padina > Dictyota > Ulva. For whatever reason, the soft membranous green-alga Ulva is eaten least.

Absorption of nutrients in the gut may be relatively low on a seagrass diet. Yes, this is true. Absorption of nutrients was least on the seagrass diet: Ulva > Padina > Dictyota > Sargassum >Thalassia.

Use of the absorbed seagrass-derived nutrients for growth may be relatively low. Yes, this is true. Use of absorbed nutrients for growth declines in the order: Ulva > Padina > Dictyota > Sargassum >Thalassia. So, not only are relatively fewer nutrients absorbed on a diet of seagrass, but those that are absorbed are less good for growth.

Cost of eating and/or processing the seagrass food might be relatively high. No, this does not appear to be the case. Although tested for only 2 of the diets, costs are much less on a seagrass diet, even though more of it is eaten.

NOTE measured as oxygen consumed by the sea urchin as it eats and digests the food

 
 
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