The relationship between occurrence of invasive bryozoan Pectinatella magnifica (Leidy 1851) and parameters of the aquatic environment in the Biosphere Reserve Třeboňsko (Czech Republic)

Abstract

In the period from 2012 to 2014, twenty localities with a varying density level of the invasive bryozoan Pectinatella magnifica were investigated in the Třeboň region. These localities included water bodies ranging from eutrophic-hypertrophic fishponds to mesotrophic-oligotrophic flooded sandpits. The aim of the study was to investigate and compare the water bodies’ physical, hydrochemical and hydrobiological parameters. Control localities (localities with absence of P. magnifica) were found to be significantly different from localities with occurrence of P. magnifica in most of the measured parameters. Also shown was that P. magnifica tends to form colonies in localities showing above-average qualitative parameters within the Třeboň region: balanced oxygen and pH regime, low concentration of suspended solids (Secchi depth over 1 m) and nitrogen forms (mean TN 1.5 mg L−1), chlorophyll-a mean concentration 54 µg L−1, and zooplankton mean density 117 ind L−1 and biomass 2 mg of wet weight L−1. Furthermore, P. magnifica was also found in brown humic waters. While the sites with P. magnifica occurrence are often mesotrophic flooded sandpits and fishponds under nature protection, fishponds for recreational use, and those with low intensity of fishery management (without formation of massive cyanobacterial water blooms, oxygen regime fluctuations, etc.), localities unoccupied by invasive bryozoans are mostly strictly eutrophic-hypertrophic, semi-intensified, carp fishponds.