The Belgian sandy beach ecosystem: a review

This paper reviews the available knowledge on sedimentology, hydrodynamics and five major ecosystem components (microphytobenthos, vascular plants, terrestrial arthropods, zoobenthos, and avifauna) of Belgian sandy beaches. It covers the area from the foredunes to the lower foreshore, takes an ecosystem approach to beaches of this specific geographic area. Morphodynamically, Belgian beaches are (ultra-)dissipative, macrotidal, and wide. Characteristic grain sizes are 160-380 mu m. The sand becomes coarser, beach slopes steeper and tidal range smaller towards the south-west, where beaches have also been frequently reshaped by human interference such as nourishment. Beach organisms are highly adapted to this unique environment and can reach high numbers. We show that even on a heavily populated coastline subjected to intense recreational and development pressure, beaches provide critical, yet threatened, habitats. Vascular plants growing near the drift line, on the dry beach and in the embryonic dunes are mostly short-lived and thalassochorous; the most common species include sea rocket (Cakile maritima), prickly saltwort (Salsola kali subsp. kali), and sea sandwort (Honckenya peploides). These zones are habitat to a highly diverse suite of terrestrial arthropods of halobiontic, halophilous and haloxene species; prominent members are sandhoppers (Talitrus saltator) and dipterans (flies). Microphytobenthos, mainly diatoms, is an important primary producer on Belgian beaches but is not well known. The meio- and macrobenthos of Belgian beaches contains specific assemblages such as the Scolelepis squamata-Eurydice pulchra community of the upper intertidal zone. Birds no longer nest on the beaches itself, but Belgian sandy shores continue to function as important resting and foraging areas for birds such as the sanderling Calidris alba. We identify several human pressures on the beach ecosystems arising from recreation, beach management and fisheries.