Benthic oxygen and nitrogen exchange on a cold-water coral reef in the North-East Atlantic Ocean
de Froe; Rovelli; Glud, R.N.; Maier, S.R.; Duineveld, G.; Mienis, F.; Lavaleye, M.; van Oevelen, D. (2019). Benthic oxygen and nitrogen exchange on a cold-water coral reef in the North-East Atlantic Ocean. Front. Mar. Sci. 6. https://dx.doi.org/10.3389/fmars.2019.00665Additional data: In: Frontiers in Marine Science. Frontiers Media: Lausanne. e-ISSN 2296-7745, more |   |
| Author keywords | cold-water coral; biogeochemistry; benthic respiration; nitrogen cycling; carbon cycling |
| Abstract | Cold-water coral (CWC) reefs are distributed globally and form complex three-dimensional structures on the deep seafloor, providing habitat for numerous species. Here, we measured the community O2 and dissolved inorganic nitrogen (DIN) flux of CWC reef habitats with different coral cover and bare sediment (acting as reference site) in the Logachev mound area (NE Atlantic). Two methodologies were applied: the non-invasive in situaquatic eddy co-variance (AEC) technique, and ex situ whole box core (BC) incubations. The AEC system was deployed twice per coral mound (69 h in total), providing an integral estimate of the O2 flux from a total reef area of up to 500 m2, with mean O2 consumption rates ranging from 11.6 ± 3.9 to 45.3 ± 11.7 mmol Om–2 d–1 (mean ± SE). CWC reef community Ofluxes obtained from the BC incubations ranged from 5.7 ± 0.3 to 28.4 ± 2.4 mmol Om–2 d–1 (mean ± SD) while the Oflux measured by BC incubations on the bare sediment reference site reported 1.9 ± 1.3 mmol Om–2 d–1 (mean ± SD). Overall, Ofluxes measured with AEC and BC showed reasonable agreement, except for one station with high habitat heterogeneity. Our results suggest Ofluxes of CWC reef communities in the North East Atlantic are around five times higher than of sediments from comparable depths and living CWCs are driving the increased metabolism. DIN flux measurements by the BC incubations also revealed around two times higher DIN fluxes at the CWC reef (1.17 ± 0.87 mmol DIN m–2 d–1), compared to the bare sediment reference site (0.49 ± 0.32 mmol DIN m–2 d–1), due to intensified benthic release of NH4+. Our data indicate that the amount of living corals and dead coral framework largely contributes to the observed variability in Ofluxes on CWC reefs. A conservative estimate, based on the measured Oand DIN fluxes, indicates that CWC reefs process 20 to 35% of the total benthic respiration on the southeasterly Rockall Bank area, which demonstrates that CWC reefs are important to carbon and nitrogen mineralization at the habitat scale. |
|
