Nieuwe waarnemingen van Tolypella (Charophyceae) in België

Three Tolypella species (T. glomerata, T. intricata and T. prolifera) have been recorded in Belgium, all of them only sparingly and with most observations dating from the 19th C. We document new records of T. glomerata and T. intricata from stagnant fresh water in the Flemish region and discuss the general ecology and distribution of these rare species, as well as possibilities for site management. Three sites are small, more or less periodic water bodies, where either T. glomerata or T. intricata occur as winter-spring annuals, a fourth one is a stratified sand extraction pit where T. intricata grows at considerable depth. Extensive cattle grazing and trampling sustains T. glomerata in a wet polder grassland influenced by brackish seepage and continuation of this management is recommended. Both other sites with this species, a shallow pond and a ditch-like depression, are of more recent origin and the species is likely to have arrived here by bird transport or revitalisation of buried oospores. Competition by other submerged plants or dense growth of Typha latifolia and planned land conversion are immediate threats here. Two ponds with T. intricata are situated within a nature reserve and presumably support the remainder of an older population occurring in this alluvial setting. Given considerate management and, perhaps, the creation of additional habitat they provide good prospects for this species. The deep-water site with T. intricata shows a continuous salinity rise since 2005, presumably due to infiltration of brackish water from a nearby container dock connected to the Scheldt Estuary. Judging from near-surface salinity and conductivity measurements and considering its limited salt tolerance, conditions already appeared to be quite suboptimal for T. intricata at the time it was last observed here. However, salinity possibly remained more favourable close to the bottom in some places due to freshwater seepage. If T. intricata is still present at the moment, expectations for its persistence are very bleak because a further salinity rise appears likely. For those populations where local management cannot guarantee suitable conditions, translocation to more appropriate sites nearby appears to be the only option.