Recovery of the eelgrass Zostera marina following intense Manila clam Ruditapes philippinarum harvesting disturbance in China: The role and fate of seedlings

•A recovery of an annual eelgrass bed after clam harvesting in Moon Lake, Shandong, China was observed.•The disturbed annual eelgrass bed was recovered via seedling recruitment.•The recovery of the annual bed was probably mainly dependent on the seeds originating from the nearby perennial bed. Manila clam Ruditapes philippinarum (Adams & Reeve 1850) harvesting has been observed to damage the eelgrass Zostera marina L. meadow in Moon Lake, Shandong Peninsula, China. An annual eelgrass bed was found bordering the perennial meadow. We monitored the morphology, growth and survival of Z. marina in both annual (AB, disturbed site) and perennial beds (PB, reference site) in Moon Lake from December 2012 to January 2014. Nearly all eelgrass shoots in AB were removed or buried in sediments due to clam harvesting, which occurred during low tides in the winter and early spring of 2012–13. Seedlings were observed in February 2013 right after the end of the clamming season. They were less abundant but exhibited higher survival rates in AB than in PB. In June, the newly established seedlings in the AB formed numerous patches, indicating that the disturbed site recovered via seedling recruitment. However, these annual plants could not survive the winter of 2013–14 as perennials did, including those free from clamming disturbance in experimental enclosures. The annual Z. marina bed had smaller plant size and much lower biomass, density and potential seed production than the perennial stand. The recovery of the disturbed bed probably mainly depended on seeds recruited from the nearby perennial bed where the potential seed production was much higher.