Browsing by Author "Vergara, J. J."
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- Nitrogen load and irradiance affect morphology, photosynthesis and growth of Caulerpa prolifera (Bryopsidales : Chlorophyta)Publication . Malta, Erik-jan; Ferreira, D. G.; Vergara, J. J.; Perez-Llorens, J. L.The effect of nitrogen (N) load and irradiance on morphology, growth and photosynthetic performance was studied in the green macroalga Caulerpa prolifera (Forsskal) J. V. Lamouroux from the Gulf of Cddiz (south Spain). Constant growth rates were obtained for thalli growing at different N loads, which could be fitted to tissue N using the Droop equation, rendering a maximum growth rate of 0.09 d(-1), a minimum tissue N level of 1.71 % dry weight (DW) and a critical tissue N of 5.2 % DW. N limitation had no effects on F-v/F-m (maximum quantum yield of chlorophyll a fluorescence). Stolon production was significantly highest at low N loads; a reverse trend was observed for assimilator production. In a second experiment, algae were subjected to combinations of high and low N loads (HN and LN) and irradiance (HL and LL) levels. Highest growth rates were observed in the HNLL treatment, whereas the reverse combination rendered the lowest growth rate. High irradiance and high N load both led to increased biomass allocation to assimilators; at low N, the bulk of the biomass (> 75 % in the HLLN treatment) was allocated to the stolons. HN had a positive effect on F-v/F-m and HL had a negative effect. HL algae had a higher capacity for non-photochemical quenching. Despite its prolific nature, C. prolifera should be characterised as a slow-growing, but highly nitrophilic alga which has the capacity to forage for nutrients by allocating biomass to the stolons.
- 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.