Why do Turbinaria algae float?

Macroalga Turbinaria ornata can grow individually or in aggregations (clumps). When growing in aggregations, Turbinaria adults receive less light and may have less access to nutrients and gases that they need to grow, but they also have air bladders that make them float. Floating helps individuals get enough light by keeping them spaced out and preventing stacking in the aggregation.

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Stewart et al. 2007