Evaluation of algicidal activity of isolated bacteria from coastal waters and sediments in the Hormozgan Province against Cochlodinium polykrikoides

Biological control using marine bacteria is part of the integrated management to control harmful algal blooms (HABs). The aim of the present study was to investigate the frequency and diversity of bacteria in HAB-exposed regions in Hormozgan province and to evaluate their algicidal activity against Cochlodinium polykrikoides. Seasonal frequency of bacteria in 10 stations throughout the coastal regions of Hormuz Island, Bandar Abbas, and Bandar Lengeh showed maximum frequency in St 1, St 6, and St 10 in spring. We identified 10 bacterial families in sediment samples, which dominantly belonged to Vibrionaceae, Entrobacteriaceae and Pseudomonadaceae with 29%, 14 %, and 12% frequency, respectively. While in seawater samples Entrobacteriaceae and Vibrionaceae were dominated with 23% among 6 identified families. Approximately, 13.33% of sediment-isolated bacteria and 9.09% of seawater-isolated bacteria were able to kill whole algal cells. The extracted metabolites of the active isolates exhibited significant algicidal activity with LC50 values ranging from 90.28±3.14 to 1029±45.94 µg/ml. This study presented an overview of the frequency and diversity of bacteria in the investigated areas and provided eight algicidal isolates for future studies on the biological control of HABs.