Which organisms carry out denitrification, converting nitrates into nitrogen gas in anaerobic conditions?

• A. Chlorophyll
• B. Disphotic Zone
• C. Biogeochemical Cycle
• D. Denitrifying Bacteria

Answer: (D)

Denitrification is the microbial process that uses nitrate as an alternative electron acceptor in the absence of oxygen, reducing nitrate all the way to nitrogen gas. The organisms that perform this transformation are denitrifying bacteria, which thrive in anaerobic or low-oxygen environments like waterlogged soils or marine sediments and help return nitrogen to the atmosphere.

Chlorophyll is the pigment used to capture light for photosynthesis, not to convert nitrates to nitrogen gas. The disphotic zone is a light-restricted layer of the ocean, not an organism or process. A biogeochemical cycle describes the pathways elements take through the environment, but it doesn’t specify the organisms carrying out a particular transformation.