The influence of mechanical habitat disturbance on the infauna of Zostera marina L. meadows

Abstract

Eelgrass (Zostera marina) meadows are a common feature in shallow waters along the Norwegian coast, where they provide a habitat for an infaunal community with a high biodiversity. A field experiment, comprised of two different disturbance events, was conducted to investigate the effects mechanical habitat disturbances have on the infauna of Z. marina. The disturbances included the cutting of all the Z. marina leaves at the sediment surface and the removal of entire plants including the rhizomes. This experiment was conducted in three eelgrass meadows in the inner Oslofjord. The faunal composition of macrofauna and meiofauna in the sediment was analyzed after a recovery time of ten months to investigate the effects of the treatments. The infaunal abundance of macrofauna and meiofauna varied between the three studied locations, with the fewest individuals at Sætrepollen, followed by Sandspollen and Hallangspollen with the highest infaunal abundance. The infauna of the cut treatments could not be separated from control samples by univariate or multivariate statistical analysis. The removed treatment resulted in a higher abundance of the gastropod Peringia ulvae and the bivalve Mya arenaria than in the control samples. Each of the Z. marina meadows was characterized by a different abundance and composition of its infauna. Z. marina meadows in the removed patches did not regrow within ten months, what has the potential to change the functioning of the infaunal community. This should be considered for an appropriate management of Zostera marina.