Structural complexity governs seagrass acclimatization to depth with relevant consequences for meadow production, macrophyte diversity and habitat carbon storage capacity.

Analyses of the integrated seagrass response to depth support the previously documented low plasticity and consistent shade-adapted leaf physiology of a habitat-builder that dominates well-illuminated reef environments. Two structural responses, "canopy-opening" and "below-ground-mass-depletion", govern the photoacclimatory response and facilitate, respectively, light penetration within the canopy and functional adjustments in whole-plant carbon balances. Conversely, "canopy-closing" may also explain dense canopies formed close to the waterline, as they provide shade and photoprotection to a susceptible leaf physiology under high-light.

Leaf photoacclimatory responses of the tropical seagrass Thalassia testudinum under mesocosm conditions: a mechanistic scaling-up study.

Here, the leaf photoacclimatory plasticity and efficiency of the tropical seagrass Thalassia testudinum were examined. Mesocosms were used to compare the variability induced by three light conditions, two leaf sections and the variability observed at the collection site. The study revealed an efficient photosynthetic light use at low irradiances, but limited photoacclimatory plasticity to increase maximum photosynthetic rates (P(max)) and saturation (E(k)) and compensation (E(c)) irradiances under high light irradiance.