venerdì 19 maggio 2017, ore 13:30, aula U7-06, edificio U7
Luciana Migliore, Dipartimento di Biologia, Università Tor Vergata, Roma
The increasing rate of human-induced environmental changes on coastal ecosystems has created the demand for effective monitoring and management strategies. In particular, descriptors stating the conservation status of seagrass meadows are necessary due to their widespread regression. Beyond the standard methods (fenology, density, etc.), to this end in our laboratory several approaches were followed in the last years including proteomics and enzymatic analyses, synthesis of secondary metabolites and photosynthetic activity. Among the more affordable there are plant secondary metabolites. Furthermore, the plant-associated microbial communities can deserve interesting cues, being so tightly linked to the plants to be considered an integrated structure, the ‘holobiont’.
Total phenols and photosynthetic pigments were measured in 4 seagrass species (Posidonia oceanica, Mediterranean Sea; Cymodocea nodosa and Zostera noltii, Atlantic Ocean; Halophila stipulacea, Red Sea). These demonstrated their effectiveness at different time scales (from days to years), and under different growth conditions (in situ and mesocosm) and environmental pressures (eutrophication to acidification/global warming). The variation of total phenols is associated with environmental stress conditions and thus with a decreasing state of conservation of the meadows. The amount of chlorophyll and carotenoids is a quick response to water column conditions (turbidity). Overall, the results indicate the effectiveness and versatility of the two descriptors: they were able to represent the eco-physiological state of different species under different environmental conditions. Both descriptors should be included in seagrass monitoring to deepen this field, quite unexplored.
Microbial communities play an important role in seagrass meadow dynamics participating in nutrient cycling, nitrogen fixation and detoxification of sulfide in sediments. Plant’s epiphytic microbial communities are probably involved in the supply of nutrients to the plants and their alteration could affect plant growth and survival. The study of the microbial metagenome by different molecular techniques allows a good and quick taxonomic identification, improving the knowledge of these communities. Two different molecular techniques were applied to study the plant’s epiphytic microbial community of Cymodocea nodosa (SSCP fingerprinting) and Halophila stipulacea (pyrosequencing). The microbial community analyses (bacterial diversity, taxonomic composition and phylogenetic relationships) revealed significant differences between above- and below-ground plant compartment; as expected, the environmental conditions drive the composition of epiphytic bacterial assemblages. Different microbial community assemblages were found also on the plants exposed to different environmental conditions. The microbial community composition needs further investigation, to deepen our knowledge about their structure, functions and relationship with the plant. However, it represents a promising tool to be associated with the biochemical descriptors and included in seagrass monitoring.
Ospite: Davide Seveso