Browsing by Author "Brun, F. G."
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- Leaf-fracture properties correlated with nutritional traits in nine Australian seagrass species: implications for susceptibility to herbivoryPublication . de los Santos, Carmen B.; Brun, F. G.; Onoda, Yusuke; Cambridge, Marion L.; Bouma, Tjeerd J.; Vergara, Juan J.Seagrasses are exposed to the constant risk of structural damage due to abiotic factors, such as waves and currents, and biotic factors, e.g. herbivory. Leaf mechanical resistance is therefore essential in protecting plants from structural failure and may also have ecological consequences. For example, mechanical traits of seagrass leaves may play an important role in plant− herbivore interactions and food-preferences of herbivores in these ecosystems, as widely reported for terrestrial plants. However, little is known about leaf mechanical resistance against structural damage in seagrasses and how it varies with other traits such as their nutritional value. We analysed the correlation between fracture properties relevant to herbivory and the nutritional value of seagrass leaves, testing the general assumption that species that invest heavily in mechanical resistance (toughening of the leaves) will present low nitrogen and high carbon and fibre contents. Direct measurements of leaf traits were conducted on 9 seagrass species from south-western Australia: (1) leaf-fracture properties from shearing and tearing tests, (2) nutritional values (carbon to nitrogen ratio and fibre content) and (3) morphological and structural traits (specific leaf area and leaf thickness). Results showed that leaf-fracture properties in seagrasses were tightly correlated to their C:N ratio, which reflects their nutritional value, thus supporting the general assumption that C investment is inversely correlated to N content. This close correlation suggested that patterns of seagrass consumption may be influenced not only by the C:N ratio but also by the leaf-fracture properties. Among co-existing seagrasses, we found a continuous spectrum of mechanical and nutritional traits across species, which provides fundamental information about species assembly, herbivore behaviour and ecosystem functions.
- The morphometric acclimation to depth explains the long-term resilience of the seagrass Cymodocea nodosa in a shallow tidal lagoonPublication . Peralta, G.; Godoy, O.; Egea, L. G.; de los Santos, Carmen B.; Jiménez-Ramos, R.; Lara, M.; Brun, F. G.; Hernandéz, I.; Olivé, I.; Vergara, J. J.; González-Ortiz, V.; Moreno-Marín, F.; Moris, E. P.; Villazán, B.; Pérez-Lloréns, J. L.Cadiz Bay is a shallow mesotidal lagoon with extensive populations of the seagrass Cymodocea nodosa at intertidal and shallow subtidal elevations. This work aims to understand the mechanisms behind the resilience of this species to gradual sea level rise by studying its acclimation capacity to depth along the shallow littoral, and therefore, to gradual variations in the light environment. To address this objective, these populations have been monitored seasonally over a 10 year period, representing the longest seasonal database available in the literature for this species. The monitoring included populations at 0.4, − 0.08 and − 0.5 m LAT. The results show that C. nodosa has a strong seasonality for demographic and shoot dynamic properties – with longer shoots and larger growth in summer (high temperature) than in winter (low temperature), but also some losses. Moreover, shoots have different leaf morphometry depending on depth, with small and dense shoots in the intertidal areas (0.4 m) and sparse large shoots in the subtidal ones (− 0.08 and 0.5 m). These differences in morphometry and shoot dynamic properties, combined with the differences in shoot density, explain the lack of differences in meadow production balance (i.e. meadow growth – meadow losses) between the intertidal (0.4 m) and the deepest population (− 0.5 m), supporting the long term resilience of Cymodocea nodosa in Cadiz Bay. This study contributes to the understanding of the mechanisms behind seagrass stability and resilience, which is particularly important towards predicting the effects of climate change on these key coastal ecosystems, and also highlights the value of continuous long-term monitoring efforts to evaluate seagrass trajectories.