Presence and distribution of heterotrophic denitrifying bacteria in the Eastern Tropical North Pacific oxygen minimum zone in relation to environmental parameters

Abstract

[Author's Abstract] The marine nitrogen cycle plays an important role in primary productivity by supplying primary producers with the essential nutrient nitrate. The expansion of oxygen minimum zones in the oceans is causing increasing concerns about its implications for nutrient cycles such as the nitrogen cycle. Oxygen minimum zones are sites of a process called heterotrophic denitrification, which results in the removal of large amounts of biologically reactive nitrogen from the oceans. Heterotrophic denitrifying bacteria perform this process by converting nitrate into dinitrogen gas. Dinitrogen gas is not very soluble in seawater and escapes to the atmosphere. I investigated the presence of heterotrophic denitrifying bacteria in the Eastern Tropical North Pacific oxygen minimum zone to assess their contribution to nitrogen removal in this area. I found heterotrophic denitrifying bacteria at two different stations and evidence of active heterotrophic denitrification at multiple stations. This suggests that heterotrophic denitrifying bacteria play an active role in nitrogen removal in the Eastern Tropical North Pacific oxygen minimum zone.