Environmental factors related to the occurrence of Cylindrospermopsis raciborskii (Nostocales, Cyanophyta) at the north-eastern limit of its geographical range.

摘要

Cylindrospermopsis raciborskii has recently attracted wide attention owing to its toxigenicity and its capacity for rapid invasion of new geographical regions. We studied the spatial distribution of C. raciborskii in western Poland and the environmental variables related to its occurrence near the border of its current temperate geographical range. We also identified the typical phytoplankton assemblages in which C. raciborskii occurs. Forty-six lakes were sampled once during the summers of 2008 and 2009. C. raciborskii was present in 43% of the samples and its biomass accounted for 0.1-13.9% of the total phytoplankton biomass found in the lakes. A General Linear Model (GLM) analysis and t-tests showed that the lakes in which C. raciborskii occurred were significantly shallower, more turbid and more eutrophic than the lakes from which it was absent. Redundancy Analysis (RDA) and GLM analyses showed that C. raciborskii biomass correlated positively with total nitrogen (TN), total phosphorus (TP) and conductivity. It correlated negatively with temperature, ammonium (NH₄+) and orthophosphate (PO₄3-). According to Detrended Correspondence Analysis (DCA), C. raciborskii often co-occurred with Aphanizomenon ovalisporum, which is rarely observed in the studied region (common in subtropical regions, like C. raciborskii), rather than with the more common A. aphanizomenoides or the native A. gracile. Moreover, Planktothrix agardhii, the most common species in the studied region, was weakly associated with C. raciborskii. Overall, C. raciborskii was frequently present in the temperate lakes of western Poland, but it was most abundant in eutrophic lakes with high conductivity and high concentrations of TN and TP but low concentrations of NH₄+ and PO₄3-.