Microbial population changes in the polluted coastal sediments of the Gulf of Finland, Baltic Sea

This study has been undertaken to characterize microbial population and ecological changes regulated by pollution pressure in coastal sediments of the Eastern Gulf of Finland, Baltic Sea. Culturable bacterial population showed a significant spatial variation and ranged between 10
⁵
-10
⁸
CFU g
^-1
dry weight of the sediment. The number of total heterotrophic culturable bacteria showed an increase from northern to southern part of the coast and was found to be highest in the Neva Bay. There was no significant pattern of fungal distribution within the sediment samples. The long-term accumulation of heavy metals in sediments of the Gulf of Finland provides the microbial community time to adapt to these contaminants. The study revealed high heavy metal concentration and high number of metal-tolerant microorganisms in sediment samples. It is observed that fungi were the predominant group among metal-tolerant microorganisms compared to bacteria. The reduced microbial diversity was found in contaminated sediments. The results suggest that, exposure to heavy metals has a negative effect on the culturable heterotrophic microbial community in sediments. Changes in the structure of this important component of the microbial assemblages have the potential to profoundly impact the biogeochemical cycling and trophic relationships of the aquatic ecosystem.