Wageningen Marine Research is studying the long-term development of a number of individual intertidal mussel beds in the Dutch Wadden Sea to identify the characteristics that determine the survival of such beds. The study is being carried out as part of the WOT theme Nature Information Infrastructure. A large proportion of the mussel beds have been able to maintain themselves since the beginning of the study. About a year after new mussel beds are formed they gradually decline in area, coverage and population density, and the proportions of empty shells, macroalgae and barnacles increase. The decline in size and coverage is occasionally reversed by a good mussel spatfall, after which the process starts again. Japanese oysters have settled in most beds, leading to higher coverage of shellfish and a decline in mussel biomass.