On the influence of cold‐water coral mound size on flow hydrodynamics, and vice versa

Cyr, Frédéric; Haren, Hans van; Mienis, Furu; Duineveld, G.C.A.; Bourgault, D.

doi:10.1002/2015gl067038

Cited by 46 publications

(70 citation statements)

References 42 publications

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“…The CWC communities on the mound consist of framework-building Lophelia pertusa and Madrepora oculata with associated macrofaunal such as polychaetes (e.g., Eunice norvegica), sponges (e.g., Hexadella dedritifera), and crinoids Van Soest and Lavaleye, 2005). Ambient bottom water temperatures on the coral mounds vary between 7-9 • C. The area is characterized by high bottom current velocities, internal tidal waves and hydraulic jumps Van Haren et al, 2014;Cyr et al, 2016).…”

Section: Study Site and Samplingmentioning

confidence: 99%

Benthic Oxygen and Nitrogen Exchange on a Cold-Water Coral Reef in the North-East Atlantic Ocean

et al. 2019

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Cold-water coral (CWC) reefs are distributed globally and form complex threedimensional structures on the deep seafloor, providing habitat for numerous species. Here, we measured the community O 2 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 noninvasive in situ aquatic 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 O 2 flux from a total reef area of up to 500 m 2 , with mean O 2 consumption rates ranging from 11.6 ± 3.9 to 45.3 ± 11.7 mmol O 2 m −2 d −1 (mean ± SE). CWC reef community O 2 fluxes obtained from the BC incubations ranged from 5.7 ± 0.3 to 28.4 ± 2.4 mmol O 2 m −2 d −1 (mean ± SD) while the O 2 flux measured by BC incubations on the bare sediment reference site reported 1.9 ± 1.3 mmol O 2 m −2 d −1 (mean ± SD). Overall, O 2 fluxes measured with AEC and BC showed reasonable agreement, except for one station with high habitat heterogeneity. Our results suggest O 2 fluxes 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 NH 4 + . Our data indicate that the amount of living corals and dead coral framework largely contributes to the observed variability in O 2 fluxes on CWC reefs. A conservative estimate, based on the measured O 2 and 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.

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Section: Study Site and Samplingmentioning

confidence: 99%

Benthic Oxygen and Nitrogen Exchange on a Cold-Water Coral Reef in the North-East Atlantic Ocean

et al. 2019

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“…The effect of tidal hydrodynamics on benthic fauna is the subject of ongoing research. Focusing on cold-water coral mounds on Rockall Bank, van Haren et al (2014) and Cyr et al (2016) observed and modelled topographically-trapped diurnal waves and turbulent mixing over the mounds, while Mohn et al (2014) correlated intensified near-bottom tidal currents to coral occurrence at these and other mounds in the Northeast Atlantic. Within Whittard Canyon, Robert et al (2015) used predictive habitat models to link the spatial variation in observed biological characteristics (e.g., megafaunal abundance, species richness, and biodiversity) to bathymetry-derived environmental variables (e.g., depth, slope, and roughness), but suggest that the addition of hydrodynamic variables related to internal tides may reduce the amount of unexplained variation.…”

Section: Biological Impactsmentioning

confidence: 99%

Partly standing internal tides in a dendritic submarine canyon observed by an ocean glider

Hall

Aslam

Huvenne

2017

Deep Sea Research Part I: Oceanographic Research Papers

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An autonomous ocean glider is used to make the first direct measurements of internal tides within Whittard Canyon, a large, dendritic submarine canyon system that incises the Celtic Sea continental slope and a site of high benthic biodiversity. This is the first time a glider has been used for targeted observations of internal tides in a submarine canyon. Vertical isopycnal displacement observations at different stations fit a one-dimensional model of partly standing semidiurnal internal tides – comprised of a major, incident wave propagating up the canyon limbs and a minor wave reflected back down-canyon by steep, supercritical bathymetry near the canyon heads. The up-canyon internal tide energy flux in the primary study limb decreases from 9.2 to 2.0 kW m−1 over 28 km (a dissipation rate of View the MathML source), comparable to elevated energy fluxes and internal tide driven mixing measured in other canyon systems. Within Whittard Canyon, enhanced mixing is inferred from collapsed temperature-salinity curves and weakened dissolved oxygen concentration gradients near the canyon heads. It has previously been hypothesised that internal tides impact benthic fauna through elevated near-bottom current velocities and particle resuspension. In support of this, we infer order 20 cm s−1 near-bottom current velocities in the canyon and observe high concentrations of suspended particulate matter. The glider observations are also used to estimate a 1 °C temperature range and 12 μmol kg−1 dissolved oxygen concentration range, experienced twice a day by organisms on the canyon walls, due to the presence of internal tides. This study highlights how a well-designed glider mission, incorporating a series of tide-resolving stations at key locations, can be used to understand internal tide dynamics in a region of complex topography, a sampling strategy that is applicable to continental shelves and slopes worldwide

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“…Processes in the water column such as internal wave motions and turbulence can have major implications (i.e., oxygen and nutrient supply) on the functioning of ecosystems populating the slopes of underwater topography (Cyr et al, 2016;van Haren et al, 2017). In the case of Saba Bank, dissolved inorganic nutrients were depleted in the near-surface layer where the shallow water coral reefs are located.…”

Section: Internal Wave Observations Off Saba Bankmentioning

confidence: 99%

“…Observations above seamounts and raised atolls in other ocean areas showed that motions in the ocean interior are important for the replenishment of oxygen and nutrients to deep-sea organisms ranging from microbes to corals and sponges. An example is the breaking of internal waves on steep sloping sides of underwater mounts influencing cold-water coral reef growth (e.g., Genin et al, 1986;Wang et al, 2007;Chen et al, 2016;Cyr et al, 2016;van Haren et al, 2017). The generally stable density stratification in the ocean, a result of the dominant solar insolation storing large amounts of potential energy, hinders but does not prevent the vertical diapycnal exchange of suspended and dissolved matter.…”

Section: Introductionmentioning

confidence: 99%

Internal Wave Observations Off Saba Bank

2019

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The deep sloping sides of Saba Bank, the largest submarine atoll in the Atlantic Ocean, show quite different internal wave characteristics. To measure these characteristics, two 350 m long arrays consisting of primary a high-resolution temperature T-sensor string and secondary an acoustic Doppler current profiler were moored around 500 m water depth at the northern and southern flanks of Saba Bank for 23 days. We observed that the surrounding density stratified waters supported large internal tides and episodically large turbulent exchange in up to 50 m tall overturns. However, an inertial subrange was observed at frequencies/wavenumbers smaller than the mean buoyancy scales but not at larger than buoyancy scales, while near-bottom non-linear turbulent bores were absent. The latter reflect more open-ocean than steep sloping topography internal wave turbulence. Both the Banks' north-side and south-side slopes are locally steeper 'supercritical' than internal tide slope angles. However, the three times weaker north-side slope showed quasi-mode-2 semidiurnal internal tides, not high-frequency solitary waves occurring every 12 h, over the range of observations, centered with dominant nearinertial shear around 150 m above the bottom. They generated the largest turbulence when touching the bottom and providing off-bank flowing turbid waters. In contrast, the steeper south-side slope showed quasi-mode-1 internal tides occasionally having excursions > 100 m crest-trough, with weak inertial shear and smallest buoyancy scale turbulence periodicity occurring near the bottom and about half-way the water column, below abundant coral reefs in shallow <20 m deep waters.

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On the influence of cold‐water coral mound size on flow hydrodynamics, and vice versa

Cited by 46 publications

References 42 publications

Benthic Oxygen and Nitrogen Exchange on a Cold-Water Coral Reef in the North-East Atlantic Ocean

Benthic Oxygen and Nitrogen Exchange on a Cold-Water Coral Reef in the North-East Atlantic Ocean

Partly standing internal tides in a dendritic submarine canyon observed by an ocean glider

Internal Wave Observations Off Saba Bank

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