Factors modulating herbivory patterns in Cymodocea nodosa meadows

Abstract

In coastal marine food webs, seagrass-grazer interactions play a fundamental role in ecological processes by regulating the structure and functioning of plant communities. Therefore, assessing the strength of these seagrass-grazer links and identifying the mechanisms that regulate these relationships are crucial to increasing our understanding of community and ecosystem structure and dynamics. Herbivory on the temperate seagrass Cymodocea nodosa was evaluated in four locations with contrasting abiotic and biotic factors (i.e., depth; meadow size; seagrass shoot density, productivity, and leaf traits; and herbivore presence) using cross-transplantation experiments carried out once per season to account for seasonal variation. Patterns of feeding rates on C. nodosa meadows showed high temporal variability, with peaks occurring in spring and summer. Results indicate that between 46.59% and 74.08% of the annual leaf production is lost to herbivory at the locations sampled in this study. Herbivory rates increased with higher nitrogen content and shoot density for all types of consumers (mesograzers, fishes, and sea urchins). This work highlights the need to integrate the abiotic and biotic factors modulating herbivory patterns, particularly in a foundation species like C. nodosa, for which changes in plant traits and grazer abundance may trigger trophic cascades with far-reaching consequences for associated species.