Summary Marine Crenarchaeota are among the most abundant microbial groups in the ocean, and although relatively little is currently known about their biogeochemical roles in marine ecosystems, recognition that Crenarchaeota posses ammonia monooxygenase ( amoA ) genes and may act as ammonia‐oxidizing archaea (AOA) offers another means of probing the ecology of these microorganisms. Here we use a time series approach combining q...