Evaluation of toxicity of isolated cyanobacteria from the Khoor-e-Khooran mangrove ecosystem against shrimp larvae

Abstract

Climate change and human intervention have led to an increased occurrence of harmful cyanobacterial blooms in mangrove ecosystems, which can be considered a threat to the life of plant and animal species in this ecosystem. The aim of this study was to evaluate the biodiversity pattern of cyanobacterial populations living in mangrove forests and to investigate the toxicity of cyanotoxins extracted from shrimp larvae. The results of bacterial isolation from 3 water and sediment sampling stations using culture-based methods led to the isolation of 150 isolates. The biodiversity pattern of cyanobacteria based on morphological identification confirmed the presence of 5 distinct dominant genera including Phormidium, Spirulina, Oscillatoria, Microcystis, and Anabaena. The extracted cyanotoxins from the biomass of strains 2A, 7A, and 14C showed toxicity with LC50 of 173.2, 283.1, and 209 μg /ml against Artemia, respectively. The LC50 of these cyanotoxins against shrimp larvae was 310.3, 293.3, and 234.1 μg /ml, respectively. The presented results showed a high diversity of cyanobacteria and the presence of toxicogenic strains in the study area. Therefore, continuous monitoring programs in mangrove habitats, especially protected estuarine ecosystems, are recommended.

Keywords

• biodiversity
• cyanobacteria
• cyanotoxins
• mangrove