Seed burial in eelgrass Zostera marina: the role of infauna

Seed burial is a vital process that influences small- and large-scale plant population patterns and is frequently mediated by soil-dwelling invertebrates. Despite its importance in terrestrial systems, very little is known about seed burial in seagrasses. The goal of this work was to determine the role that benthic infauna play in the burial of Zostera marina seeds. Mesocosm experiments studying seed burial depth, seed burial rate, and particle burial and redistribution using beads, were conducted in defaunated sediment cores populated with single specimens of infauna with different modes of feeding and thus bioturbation effects: Amphitrite ornata (downward conveyor deposit feeder), Clymenella torquata and Pectinaria gouldi (upward conveyor deposit feeders), and Neanthes succinea (gallery biodiffuser). Seeds and beads in animal cores were significantly more likely to be buried than seeds in control cores in each experiment, although burial depths and rates varied by species. N. succinea and P. gouldi showed the most dramatic burial. N. succinea also showed evidence for actively burying seeds. Seed burial depths for A. ornata, C. torquata, and P. gouldi related well to individual bioturbation rates for those species. These results indicate that Z. marina seed burial is facilitated by infaunal bioturbation. Further, individual species have a different impact on burial patterns, and burial is rapid and occurs within days. Seed burial by infaunal bioturbation is relevant to seed survival by providing escape from predation, retention in suitable settlement sites, and movement to a sediment depth suitable for germination.