Benthic primary production and mineralization in a High Arctic Fjord:In situ assessments by aquatic eddy covariance

• Published in: Marine Ecology Progress Series
• Main Authors: Attard, Karl M., Hancke, Kasper, Sejr, Mikael K., Glud, Ronnie N.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2016
• Subjects: Aquatic eddy covariance; Arctic; Benthic macrofauna; Benthic primary production; Carbon cycling; Arctic Ocean; Greenland; Phytoplankton
• Online Access: https://pure.au.dk/portal/en/publications/99ebdbac-c5fc-468b-8a74-6ed65f75f967; https://doi.org/10.3354/meps11780; http://www.scopus.com/inward/record.url?scp=84980407589&partnerID=8YFLogxK

Coastal and shelf systems likely exert major influence on Arctic Ocean functioning, yet key ecosystem processes remain poorly quantified. We employed the aquatic eddy covariance (AEC) oxygen (O 2 ) flux method to estimate benthic primary production and mineralization in a High Arctic Greenland fjord. Seabed gross primary production (GPP) within the 40 m deep photic zone was highest at 10 m (29 mmol O 2 m- 2 d -1 ) and decreased to 5 mmol O 2 m- 2 d -1 at 40 m, while nighttime community respiration (CR) ranged from 11 to 25 mmol O 2 m- 2 d -1 . CR decreased to ∼2.5 mmol O 2 m- 2 d -1 at 80 m and remained constant with further depth. Fauna activity accounted for ∼50% of the CR at depths ≤60 m but was <15% at depths ≥80 m. Benthic GPP and CR were comparable when scaled to the outer fjord area ≤40 m depth (2.7 and 3.1 t C d -1 ), and here the seabed was twice as important as the pelagic compartment for primary production. However, when scaled to the entire outer fjord area of which 80% is >40 m, benthic GPP was 26% of the pelagic production. CR was 2-fold higher than GPP over this region (5.7 t C d -1 ) and thus net heterotrophic. By scaling AEC-derived Arctic benthic GPP to the entire Arctic Ocean using modelled seabed light data, we estimate an annual Arctic Ocean benthic GPP of 11.5 × 10 7 t C yr -1 . On average, this value represents 26% of the Arctic Ocean annual net phytoplankton production estimates. This scarcely considered component is thus potentially important for contemporary and future Arctic ecosystem functioning.