The beach of Lombardsijde, situated at the eastern side of the eastern palisade of Nieuwpoort, was nourished from March until September 2009. Approximately 650 000 m³ of sand was deposited on top of the beach over a distance of around 1200 m. The sand (grain size between 200 and 250 µm) originated from the new fair way to Oostende, more specifically from the zone situated seaward from the waiting zone border (1500 m seaward of the old western jetty). The nourishment was in full progress during this study so a clear overview of the ecological situation after completion of the works (t1 situation) remains to be obtained. Biotic (macrofauna) and abiotic data were sampled on the impact site (Lombardsijde) and its control site (Nieuwpoort-Bad) during the nourishment.
Every anthropogenic influence has an impact on the ecosystem. The scientific evaluation of ecological effects of such an influence, like beach nourishment, can only be done by comparing the status of the environment before (t0 situation) and after the influence has taken place. Four studies concerning the t0 situation have taken place during previous years (Speybroeck et al., 2003; Welvaert, 2005; Van Ginderdeuren et al., 2007; Vanden Eede et al., 2008). Each phase comprises a thorough study of the macrobenthos (organisms larger than 1 mm inhabiting the seafloor) and the physical-chemical environment. Only phase 3 (2006) and 4 (2008) contained enough relevant information to define the initial state of the current sites of interest.
The impact of beach nourishments on the intertidal and subtidal coastal ecosystems has been researched in the past (Speybroeck et al., 2004). On the short term, a negative influence is to be expected such as mortality of benthos due to the sand deposition. However, most macrobenthic organisms have planktonic or pelagic larvae and the adult populations are always situated nearby. An estimated period of 1 to 2 years is enough to renew most of the macrobenthic communities. Complete renewal takes around 4 to 5 years because long living organisms like Bivalvia and Echinodermata can’t reproduce successfully every year. If the environmental circumstances changed too drastic, renewal can even fail to occur. Especially changes in the median grain size and the beach profile have profound consequences.
The current study showed no notable changes on the beach of Lombardsijde between 2006 and 2009. We did find a rougher median grain size during autumn 2009 compared to the previous years. The beach profile of Lombardsijde was altered in such a way that it now resembles the beach profile of Nieuwpoort-Bad almost perfectly. No other distinct negative trends for the macrobenthos were found but we did show (again) that Nieuwpoort-bad is a better reference site for Lombardsijde than Koksijde-Oostduinkerke. The real effects of the beach nourishment on the macrofauna are yet to be discovered. Hopefully we manage this in future t1 studies
