Outline the main steps of the nitrogen cycle in coastal ecosystems and where sediment processes fit.

• A. Nitrogen fixation converts N2 to usable forms; nitrification turns ammonium to nitrate; assimilation incorporates nitrate into organic matter; ammonification returns ammonium from organic matter; denitrification converts nitrate to N2 gas; Sediments host anoxic conditions enabling denitrification and anaerobic ammonium oxidation, coupling with microbial processes.
• B. The nitrogen cycle includes photosynthesis and respiration.
• C. Sediments prevent any nitrogen transformations.
• D. Only nitrogen fixation occurs in coastal systems.

Answer: (B)