Influence of hydrological conditions on zooplankton of oxbow lakes (old riverbeds) of the Lower Vistula in the city of Toruń (Poland). (original) (raw)

2009, Limnological Papers v. 4,

" The research on zooplankton was being conducted during the vegetation season from April to October 2006, in three different types of oxbow lakes of the Lower Vistula – (isolated site 1, site 2 connected with the Vistula River by an inlet, and site 3 artificially isolated by a concrete embankment), as well as in the river - site 4 at the 736th km of its course. Zooplankton of the oxbow lakes was qualitatively and quantitatively much richer as compared to potamoplankton of the Vistula River - a higher number of species (sites 1, 2 and 3 - 44 species and site 4 – 25 species), the count (site 1-3 – on average 426 specimens/dm3 and site 4 – 94 specimens/dm3), as well as biomass (site 1-3 – on average 0.966 mg m.m./dm3 and site 4 – 0.066 mg m.m./dm3). More stable hydrological conditions prevailing in oxbow lakes are favourable to the development of zooplankton. When investigating the subsequent oxbow lakes, the following was found: the higher number of species (34 and 29) and higher average frequencies, as well as biomass at the sites isolated from the rapid exchange of water or sites completely isolated - site 2 (721 specimens/dm3, 1.220 mg m.m./dm3) and site 1 (443 specimens/dm3, 1.566 mg m.m./dm3). Based on the results presented in the publication, a conclusion can be drawn that the more the oxbow lake is isolated from the riverbed (more stable hydrological conditions) the richer the zooplankton gets. Although the delicate washing of the oxbow lake with waters of the Vistula River can enrich it with Rotifera (site 2). "