Benthic O₂ uptake of two cold-water coral communities estimated with the non-invasive eddy correlation technique

The community respiration of 2 tidally dominated cold-water coral (CWC) sites was estimated using the non-invasive eddy correlation (EC) technique. The first site, Mingulay Reef Complex, was a rock ridge located in the Sea of Hebrides off Scotland at a depth of 128 m and the second site, Stjernsund, was a channel-like sound in Northern Norway at a depth of 220 m. Both sites were characterized by the presence of live mounds of the reef framework-forming scleractinian Lophelia pertusa and reef-associated fauna such as sponges, crustaceans and other corals. The measured O<inf>2</inf> uptake at the 2 sites varied between 5 and 46 mmol m^-2 d^-1, mainly depending on the ambient flow characteristics. The average uptake rate estimated from the ∼24 h long deployments amounted to 27.8 ± 2.3 mmol m^-2 d^-1 at Mingulay and 24.8 ± 2.6 mmol m^-2 d^-1 at Stjernsund (mean ± SE). These rates are 4 to 5 times higher than the global mean for soft sediment communities at comparable depths. The measurements document the importance of CWC communities for local and regional carbon cycling and demonstrate that the EC technique is a valuable tool for assessing rates of benthic O<inf>2</inf> uptake in such complex and dynamic settings.