Biomarker evidence for anammox in the oxygen minimum zone of the Eastern Tropical North Pacific

► Ladderane fatty acids (FAs) were found in the oxygen minimum zone of the ETNP. ► Ladderane FA concentration in the ETNP was compared with those in other OMZs. ► The anammox process may play an important role in the nitrogen cycle of the ETNP. ► Nitrite concentration likely limits anammox in the ETNP.