Ephemeral neustonic macrofaunal communities on floating seaweeds

Completed: October 2002 - September 2006

Floating seaweeds form the most important natural component of all floating material found on the surface of oceans and seas. Two types of floating seaweed can be discerned: (1) the permanently floating Sargassum, from which the associated fauna are already intensively studied, and (2) short-lived clumps formed by seaweeds detached from their rocky substrates. Notwithstanding the absence of natural rocky shores, seaweed clumps of the second type are frequently encountered along the Belgian coast. There are, however, very few data on the ecological value and dynamics of these floating seaweeds. Preliminary research indicates that the fauna associated with floating seaweeds off the Belgian coast shows a higher diversity and density compared to the surrounding water column. Moreover, the data indicate that floating seaweeds may function as a nursery for larval and juvenile stages of macrofauna, and that they can play a role in the dispersal of rocky shore fauna towards the artificial hard substrates of the Belgian coast. This study aims to investigate the dynamics and ecological value of floating seaweeds off the Belgian coast and will address the following aspects: (1) Temporal and spatial variation in density, biomass and diversity of associated macrofauna, (2) Importance of floating seaweeds and their fauna for birds and fish, (3) Nursery function of floating seaweeds, (4) Influence of seaweed species as structuring variable, (5) Abundance, lifespan, origin and route of clumps and (6) dispersal of associated fauna to the Belgian coast.