Nitrous oxide (N₂O) is an ozone-depleting greenhouse gas that has 300 times higher global warming potential than carbon dioxide. Although the oceans contribute about 21% of atmospheric global N₂O emissions, we know little about N₂O dynamics in nearshore systems. Here, we document the four-fold increase in the abundance of a large N₂O-producing invertebrate (Herdmania grandis) over two decades in warming reefs that were previously dominated by carbon-capturing kelp but have since become tropicalised. Temperature manipulation experiments revealed that N₂O production by Herdmania also increased significantly with temperature. By upscaling our results to a coastal region of Australia impacted by warming, we estimate that under future warming scenarios, subtropical reefs will produce more N₂O than adjacent estuaries. Our findings suggest that we are severely underestimating N₂O production from coastal systems, and further tropicalisation of subtropical and temperate reefs in the future may increase greenhouse gas emissions on a global scale.

Primary Presenter: Zuhairah Dindar, University of New South Wales (zuhairah.dindar@unsw.edu.au)

Authors:

Zuhairah Dindar, UNSW Sydney  (zuhairah.dindar@unsw.edu.au)

Dirk Erler, Southern Cross University  (dirk.erler@scu.edu.au)

Stephanie Gardner, University of Sydney  (steph.gardner@sydney.edu.au)

Hamish Malcolm, Department of Primary Industries, New South Wales Fisheries  (hamish.malcolm@dpi.nsw.gov.au)

Michael Sutherland, Department of Planning and Environment, Waters, Wetlands and Coastal Science  (michael.sutherland@environment.nsw.gov.au)

Adriana Verges, UNSW Sydney  (a.verges@unsw.edu.au)