Ecological characteristics of scale‐bearing chrysophytes in a small eutrophic pond in The Netherlands

In a pool near Nijmegen (The Netherlands) a study was carried out regarding the ecological characteristics of scale-bearing chrysophytes (species and groups of species). The results confirm the relatively new thought, that chrysophytes are not indicating oligotrophic waters only, but the wider range of oligotrophic to eutrophic water. In this pool ammonia and nitrate appeared to be the most important chemical variables, determinatting the development of chrysophyte species. Total and ortho-phosphorus were important variables in the second place. From the physical factors, pH-value here had less influence, while conductivity and alkalinity had none at all. However, some species of Mallomonas are able to develop at higher levels of conductivity than usually assumed. In high concentrations, ammonia could be toxic. Confirming the knowledge from literature, temperature variation is an important factor for the quantitative development of species. In particular, high abundancies occur at temperatures below around 12–14°C, which explains the decrease of chrysophytes in summertime. The presence of organic matter complicates the results and must be taken into account in future studies. For biological assessment of water quality, the results underline the necessity of having knowledge of the ecological characteristics of the individual species.