Impact of sand mining : release of fines during construction of an artificial island in the North Sea

Suspended matter (SPM) affects the ecosystem in a number of ways: 1. There is a direct impact on the primary production because SPM contributes to the turbidity (extinction) of the water. Hence the higher the SPM concentration, the lower the rate of primary production. Because the importance of SPM varies spatially and temporarily, the pattern and timing of primary production is affected. Since the primary production is the main driving force of the ecosystem, higher organisms will be affected by variations in primary production. 2. A change in the light regime affects not only the total primary production, but also the species composition of the phytoplankton community. As some species of phytoplankton provide a better source of food than others, there is also an effect on the rest of the ecosystem. 3. An increase in the contribution of SPM to the turbidity results in a decrease in the contribution by phytoplankton and organic material (enhanced light limitation by SPM on phytoplankton). The net effect on the total extinction or transparency of the water depends on the summation of these factors and again varies spatially and temporarily. Predators (fish; birds) hunting by eyesight may therefore also be affected by changes in SPM. 4. Variations in SPM concentrations are important to the inorganic part of the phosphorus cycle and hence also affect the primary production in phosphorus limited areas and periods (i.e. Wadden Sea; German Bight). 5. Increased inorganic SPM concentrations have a negative influence on the development of filter feeders because a certain amount of energy is necessary for handling the inorganic material. There are no benefits for the filter feeder. 6. SPM is also important to the kinetics of toxic substances: with increasing concentrations, more toxicants are bound and at least temporarily removed from the water phase. So it is clear that SPM affects the ecosystem both directly via the foodchain as well as indirectly via hindrance of filtration or visibility and via toxicants. During Phase 1 of Flyland it became clear that changes in SPM concentrations during the construction of the island due to the sand mining activities might impose important changes in the primary production and the species composition of the phytoplankton. However, with the existing knowledge we were unable to assess the magnitude of these changes within the rest of the foodchain because the necessary quantitative relationships have not been developed yet. Nor were we able to quantify the impacts on the filtration rates by hindrance or on top predators due to changes in transparency. Possible effects of toxicants were not considered at all, as these are not investigated within the framework of the Flyland marine ecology project. Furthermore, the estimate of the amount of SPM that would eventually end up in the North Sea system due to sand mining varied from 36 to 355 kg/s, i.e. equivalent to an input of fines (< 63