Under future increased CO2 concentrations, seagrasses are predicted to perform better as a result of increased photosynthesis, but the effects in carbon balance and growth are unclear and remain unexplored for early life stages such as seedlings, which allow plant dispersal and provide the potential for adaptation under changing environmental conditions. Furthermore, the outcome of the concomitant biochemical changes in plant-herbivore interactions has been poorly studied, yet may have important implications in plant communities. In this study we determined the effects of experimental exposure to current and future predicted CO2 concentrations on the physiology, size and defense strategies against herbivory in the earliest life stage of the Mediterranean seagrass Posidonia oceanica. The photosynthetic performance of seedlings, assessed by fluorescence, improved under increased pCO2 conditions after 60 days, although these differences disappeared after 90 days. Furthermore, these plants exhibited bigger seeds and higher carbon storage in belowground tissues, having thus more resources to tolerate and recover from stressors. Of the several herbivory resistance traits measured, plants under high pCO2 conditions had a lower leaf N content but higher sucrose. These seedlings were preferred by herbivorous sea urchins in feeding trials, which could potentially counteract some of the positive effects observed.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: E. Cerezo, E. Oliver, and D. Rita helped with set up and sample preparation. GH was supported by the Graduate Fellowship Program co-funded by the European Social Fund and the Government of the Balearic Islands (Conselleria d´Educació, Cultura i Universitats). LR was supported during this experiment by Becas Chile fellowship program from Comisión Nacional de Investigación Científica y Tecnológica de Chile (CONICYT). This study was supported by POSIPLANT (CTM2011-27377) to JT and FT, EstresX project (CTM2012-32603) and MedSeA (FP7-ENV-2010-265103) to CMD and the Ramón y Cajal Program to FT.