Resilience of Zostera noltii to burial or erosion disturbances

Dynamic environments like seagrass habitats are characterised by continuous local erosion and burial processes, which may induce seagrass decline if disturbances become too intense or frequent. We aim to quantify for Zostera noltii the resilience of both the edge of a meadow and individual propagules to local-scale burial and erosion events. In a set of mesocosm and in situ manipulation experiments, we varied the frequency (sudden vs. continuous rate) and intensity (different levels; −6 cm erosion to 6 cm burial) of sediment dynamics. Our results showed that the intensity of the disturbance event (−6 up to 6 cm) was negatively correlated with plant survival. Burial frequency also had a significant effect on plant survival, with sudden events having a stronger negative impact than continuous ones. Both experiments, on individual propagules and attached rhizomes at meadow edges, demonstrated a rapid acclimatization of seagrass plants to sediment dynamics within certain levels of disturbance (−6 up to 6 cm). After erosion or burial, all surviving plants in the field and mesocosm experiments were able to relocate their rhizomes to the preferential depth (from 0.3 to 0.8 cm), which was the depth at which the rhizomes of undisturbed plants were most frequently found in the field. In situ manipulation experiments showed that at the edge of the meadow, Z. noltii invaded experimentally created hollows more easily than hills. Overall, our results demonstrate that Z. noltii meadows can rapidly recover by clonal growth after modest sediment disturbance, thereby contributing to the current understanding of seagrass recovery mechanisms following disturbances (e.g. sediment dynamics).