Cyanobacteria in small water bodies: The effect of habitat and catchment area conditions.

Cyanobacteria are an important component of microalgae communities in aquatic ecosystems, however, their response to environmental factors in different habitats and catchment areas of small water bodies is still not well recognised. We examined ponds from two types of surroundings (field vs. forest) in order to find the best triggers for the distribution of cyanobacteria species, and analysed different habitats (open water and macrophyte-dominated zones) to find the habitat preferences of cyanobacteria species. Our results underline the important role of habitats in the determination of the abundance of cyanobacteria species in small water bodies. Cyanobacteria as a group preferred macrophyte-dominated sites with stable water column conditions, which to lesser extent were inhabited by representatives of other systematic groups of algae. The co-occurrence of many cyanobacteria species and zooplankton in the studied ponds may have indirectly resulted from biotic interactions in the food web. In the open water a positive relationship between zooplankton and cyanobacteria suggests stimulation of their development through the elimination of smaller edible taxa or by nutrient resupply through zooplankton excretion. The type of catchment area also impacted the cyanobacterial community. Field ponds with significantly higher values of pH and NO were characterised by a higher abundance of cyanobacteria compared with ponds within the forest catchment. A positive relationship between pH and cyanobacteria indicates that they raise pH during photosynthesis. However, some species were negatively associated with water temperature and occurred exclusively only in forest ponds. The study revealed that cyanobacteria in small water bodies can be a valuable indicator of important ecosystem conditions. Despite the fact that their prevalence in agricultural ponds may confirm their potential as an indicator of pollution, their high diversity associated with macrophytes contributes to an increase of overall landscape biodiversity.