GRASSMET - Climate change effects on seagrass secondary metabolism: ecological implications
Summary
This project aims to answer a relevant but yet unexplored question concerning the implications of climate change on seagrass communities: what will be the impact of changes in the relative availability of carbon and nitrogen in the plant’s primary and secondary metabolite profiles and how will this affect seagrasses capacity to defend themselves against oxidative stress and against epiphytes and herbivores? Seagrasses form some of the world's most productive marine ecosystems, with a very high ecological and economical importance and yet little is known regarding the physiological and ecological consequences of climate change on these plants. Most climate change scenarios predict that atmospheric CO2 concentrations will reach values in excess of 700 ppm before 2100, changing the relative availabilities of carbon and other nutrients, with foreseen important impacts on plant metabolism. Based on what is known for land plants, it is expected that C assimilation and N use efficiency will increase with rising CO2 availability, with direct consequences to the C:N balance in plant tissues. In this scenario, it is likely that seagrasses defence capacity be significantly affected, since the molecules involved in defense processes are also rich in carbon and/or nitrogen and share metabolic pathways with carbohydrates and amino acids synthesis. The antioxidant system depends on the activity of several enzymes, phenolic compounds and alkaloids, molecules with distinct compositions. While polyphenols, a large group of phenolic compounds, are N free, alkaloids are N containing compounds. In addition, phenolics, alkaloids and antioxidants, all play important roles in allelopathy and in the plant-epiphytes-herbivores relationships. Therefore, changes in carbon and nitrogen availabilities have the potential to affect not only seagrasses stress responses, but also the settlement of epiphytic communities and the grazing activity. To address this complex question, we designed a stepwise plan, that starts by optimizing the analytical methodologies for the screening and identification of the phenolic compounds, alkaloids, amino acids and soluble sugars in seagrasses, focusing on the molecules known to be relevant to defensive mechanisms, due to their antioxidant, allelopathic or anti-herbivory activity. The second step will be to investigate the effect of high CO2 and different nitrogen concentrations on the phenolics:alkaloids balance. This will be done through a series of manipulative experiments to be conducted in the mesocosm facility already in place at the CCMAR marine station and also by sampling plants at the vicinity of submarine volcanic vents in the Mediterranean where C. nodosa plants are exposed to naturally high CO2 and low nitrogen concentrations. Finally, we will investigate how different metabolite profiles will affect plants-epiphytes-herbivores relationships, again using a series of mesocosm manipulative experiments. To acomplish the ambitious worklplan, we assembled a team that largely derives from two previous sucessful projects that have set the stage for this natural followup, the European Science Foundation COST action "Seagrass productivity: From genes to ecosystem management" (ES0906) and the FCT-funded project "High-CO2 effects on seagrass photosynthetic ecophysiology" (PTDC/MAREST/ 3687/2012). The seagrass Cymodocea nodosa was selected as a model species, for which the team has recently sequenced the full transcriptome, making available a large amount of molecular resources. Methodologically, we shall use an innovative combination of ecophysiological tools, coupled to genetic techniques, in order to link the biochemical processes to the underlying transcriptional responses. Previous work by the team, relating functional genomics with ecophysiology, has revealed new perspectives about how marine angiosperms respond to environmental pressures and have paved the way for this next step.
SZN role
Participant Institution for the genetic characterization of Cymodocea nodosa individuals in situ and in mesocosms experiment and for assessment of gene expression in situ and controlled conditions.
Partners
University of Algarve, Portugal; Stazione Zoologica Anton Dohrn, Italy
Project lifetime
2015-2016
P. I.
Gabriele Procaccini
Project coordinator: Joao Silva (University of Algarve, Portugal)
Funding Institution
Ministerio da Educacao e Ciencia - Portugal
