Ecosystem engineering in intertidal sand by the lugworm Arenicola marina

Large-scale permanent experimental exclusion of bioturbating lugworms (Arenicola marina) from intertidal sand revealed manifold implications of this polychaete for ecosystem functioning. Sediment properties, biogeochemical processes and the benthic community were analysed over a three year period on six lugworm exclusion areas, each 400 m2, and corresponding lugworm populated plots. Lugworms reduced microphytobenthic biomass and prevented a clogging of the sediment with fine particles maintaining sediment permeability and facilitating sediment-water exchange. Changes in sediment properties caused a functional shift in the benthic community from tube-building worms to discretely motile worms. Sediment mediated effects of an ecosystem engineer on associated species appear to be subtle and contingent in a variable environment.