What are the key nitrogen cycling processes in estuaries and how do denitrification and nutrient inputs shape productivity?

• A. Nitrification, ammonification, assimilation, and denitrification; denitrification removes bioavailable nitrogen under anaerobic conditions, while nutrient inputs from rivers fuel productivity but can cause eutrophication.
• B. Only photosynthesis and respiration occur; denitrification does not occur in estuaries.
• C. Nitrification removes nitrogen entirely from water; eutrophication never occurs.
• D. Estuaries lack nitrogen cycling due to salinity.

Answer: (C)