Seasonal succession of a zooplankton metacommunity in the shallow ponds of the nature reserve

The pond complex is part of the De Maten nature reserve (50 degrees 57' N, 5 degrees 27' E) situated in the territory of Genk and Diepenbeek (Limburg province, Belgium; Figure 8.1). The area has been classified as a protected nature reserve since 1976 and now covers a surface of nearly 310 ha, of which 217 ha are managed by Natuurpunt vzw. The pond complex is a typical example of an ancient chain of fishing ponds. The ponds were created in the Middle Ages through peat digging and the construction of dykes. Fish farming continued until 1990 (Daniels 1998; W. Peumans, pers. comm.), but fish are still present in the ponds. All ponds studied are shallow (mean depth approximately 0.5 m) and eutrophied (except Pond 1). The pond complex is 3 Km long and 1.5 Km wide). There is a unidirectional flow of water from the upstream pond in the northeast corner of the nature reserve (Pond 32) at 55 m above sea level to the ponds in the southern end of the system at approximately 40 m above sea level. Almost half of the water in the system comes from two rivulets, and the remainder comes from ground water. The main rivulet, the Stiemerbeek, feeds Pond 32 and all downstream ponds. The second rivulet, the Heiweyerbeek, feeds a subset of ponds located in the northwest corner of the area and flows directly into Pond 18. At the southwest end of the pond complex, the water is diverted back into the Stiemerbeek, which flows into the Demer River. A subset of the pond complex (13 ponds, 8 from the upstream subgroup, and 5 from the downstream subgroup, with no direct water connection between the two subgroups) was sampled on 7 different dates between April 13 and July 17 1999, following an experimental manipulation of the different ponds (stocking with pike fingerlings and removing the water).