The quantity of shell grit and sand extracted from the Zeeland Banks is increasing due to the growing demand for sand for coastal defences and domestic use. IMARES is looking into the effects on seabed fauna before and after extraction.
The Zeeland Banks off the coast of the province of Zeeland form part of an extensive area of shallow sandbanks stretching along the English Channel from France and Belgium to the Netherlands. The sandbanks run south-west to north-east and started to form centuries ago as a result of the working of tidal flows. This has led to an immense variation in currents, water depths, and seabed types. Despite its long history, the top layers of the seabed remain extremely dynamic and there are large differences in sediment categories.
Sand from the Zeeland Banks is extracted from clearly defined concession areas. All seabed organisms in these areas are sucked up together with the sand and removed by dredgers. What remains is a long, hollowed out, shallow trench in which the seabed fauna can recover and adjust to the new circumstances.
IMARES is researching the original and resulting seabed fauna from samples taken using various techniques, including a grab dredger and a box corer, which both bring up fixed quantities of sediment to the surface, together with all the organisms that happen to be on the seabed at the time.
The species in the samples are sorted and give an indication of the development of communities of seabed fauna over a period of years. The effect of extraction on this highly dynamic ecosystem is determined by taking samples from locations where sand is removed and locations that are left undisturbed.