Vulnerability of the seagrass "Cymodocea nodosa" to simulated herbivory levels

Abstract

Herbivory may affect the performance and fitness of seagrasses. The seagrass Cymodocea nodosa creates meadows of great ecological relevance. We tested whether the vulnerability of Cymodocea nodosa to a natural simulated stressor (high consumption by herbivores) differed among three seagrass meadows (Arinaga, Gando and El Castillo del Romeral). Three levels of herbivory were simulated by clipping the leaves within experimental 1-m2 plots: high herbivory (approximately 80% of leaf canopy removed), moderate (approximately 40% of leaf canopy removal) and low (no clipping; natural levels). Clipping was performed periodically (every 3-4 weeks) during 4 months throughout the summer season (June to September of 2016). At the end of the experiment, plant traits at physiological (leaf growth), morphological (number of leaves per shoot, leaf length and leaf width) and demographic (shoot density) levels were measured to assess plant responses to simulated levels of herbivory. Simulated herbivory on the three meadows of Cymodocea nodosa produced physiological, morphological and demographic changes on the plant. Moderate herbivory facilitated the growth of leaves in Arinaga and Gando meadows, what resulted in longer leaves within moderate intensity plots at these two meadows. In contrast, intense levels of herbivory delayed growth, what resulted in shorter leaves. At El Castillo meadow, however, recovery was fast; growth and leaf length did not differ between plots of varying herbivory levels. In summary, large differences in plant responses to simulated herbivory were detected among seagrass meadows.