Iron and manganese bacteria are non-pathogenic bacteria that feed on iron and manganese. They are naturally present in water, forming red-brown (iron) or black-brown (manganese) slime.

@ Eyram, black color of water are due to manganese and organic matter. Microbes like bacteria has a definite role in blackening the water.

Hi Eyram Norgbey , I agree with Lucia Bonadonna and J. C. Tarafdar and would like to put forward another potential contributor that touches on iron chemistry in particular.

I am not very familiar with "blackening" events but what I suspect is that the anoxia that comes with the consumption of DOC by aerobic heterotrophic bacteria could be creating conditions that support sulfate reduction. In that case, you would likely have ample elemental sulfur (which makes black globules) and sulfide-bearing minerals (many of which can take on a dark appearance) in addition to dissolved species being chelated with any remaining DOC. All of this can potentially be contributing to the blackening of water.

I further suspect that any microbes that store elemental sulphur when using sulphide as an electron donor may also be contributing to the colour, particularly if there is a bloom of anoxygenic photosynthetic purple/green bacteria that can survive at low light intensities.

This is an interesting phenomenon and I'd love to hear more about so please feel free to continue the discussion in this thread. I hope this is helpful,

Daniel

Thank you J. C. Tarafdar Lucia Bonadonna Daniel Gregoire . I appreciate your contribution, I will be glad if you share a research article to support your comment.

Daniel Gregoire , I agree with you. We have recorded ample amount of sulfur at our study area too. Can you kindly recommend an article for me to read for better explanations. Could you also help explain the process using chemical equations (sulfur)?

Furthermore, I want to perform an experiment on microbial analysis on the sediments below the bottom water layer of the reservoir. Can you guide me on how to do the microbial analysis to be able to determine the presence of the "green bacteria" you mentioned in your comments. This is also interesting hypothesis.

Thank you.

Another possibility could be sulfate reduction by bacteria and production of metal sulfides. Many of them are of black or dark color. I recommend to prove if biological sulfate production is possible in lake water. Everything depends on dissolved oxygen concentration, redox potential, presence of heterotrophic substrate and sulfate reducing bacteria.

Good luck

Vit

Thank you very much Vit Mateju for your suggestion. I am new in this field. I would like to know how i can prove if biological sulfate production is possible in lake water?