Cyanobacteria dynamics and microcystins: an emphasis on late autumn mass development of Woronichinia and Microcystis in the Zit-Emba reservoir, North-East Algeria
摘要
Although several studies have been conducted to investigate the dynamics of cyanobacteria, their toxicity, and the environmental factors that influence their proliferation in North African freshwater ecosystems, our current understanding is limited. This study focuses on the spatiotemporal dynamics of cyanobacteria in the Zit-Emba reservoir, as well as the role of environmental variables. From March 2015 to February 2016, sampling was conducted at four sampling points (S1-S4). The co-occurrence of two bloom-forming cyanobacteria, Microcystis and Woronichinia, as well as their rapid growth in autumn (9 × 104 cells.mL−1 and 8 × 104 cells.mL−1, respectively), was an unexpected phenomenon. Woronichinia is a little-studied cyanobacterium, with most reports coming from Europe and North America. During the monitoring period, microcystin levels ranged from 0.04—5.74 µg.L−1, with peaks observed during the cyanobacteria bloom. The PCA and correlation results revealed that water temperature and nutrient loading, particularly P-PO4 (max = 0.4 mg.L−1), were the most important contributing variables. This study emphasizes the importance of regularly monitoring cyanobacteria and their toxins, as well as implementing watershed management to reduce nutrient inputs in freshwater sources used for drinking water supplies.