Ontwikkeling van enkele droogvallende mosselbanken in de Nederlandse Waddenzee : periode 1995 tot en met 2023

Samenvatting

Development of intertidal mussel beds in the Dutch Wadden Sea: Period 1995–2023 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 mussel beds. The study is being carried out as part of the WOT theme Nature Information Infrastructure. The data show that the older mussel beds in the programme (continuously present for at least the last 18 years) are vital structures capable of maintaining themselves. Younger beds are more prone to disappear. This is illustrated by the disappearance between 2022 and 2023 of most young beds in the programme that were formed in or after 2018. A new mussel bed formed from mussel spat that settled in 2023 has been included in the programme. After formation, new mussel beds gradually decline in area, coverage and population density, while the proportion of empty shells increases. Annual mussel spatfalls in existing banks stop this decline over time and a mussel population consisting of multiple year classes is formed. The species composition also changes with bed age; some species largely disappear (cockles, sea lettuce, for example) and others emerge (Pacific oyster, bladderwrack and shrimp, for example). If the loss of mussels is not compensated by the accretion of new mussel spat, the bank disappears after several years. Establishment of Pacific oysters in existing mussel beds appears to be a common phenomenon, resulting in an increase in shellfish cover and a decrease in mussel biomass and average mussel length.