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- Taboada, Sergi, et al.
(författare)
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Long distance dispersal and oceanographic fronts shape the connectivity of the keystone sponge Phakellia ventilabrum in the deep northeast Atlantic
- 2023
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Ingår i: Frontiers in Marine Science. - : Frontiers Media S.A.. - 2296-7745. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Little is known about dispersal in deep-sea ecosystems, especially for sponges, which are abundant ecosystem engineers. Understanding patterns of gene flow in deep-sea sponges is essential, especially in areas where rising pressure from anthropogenic activities makes difficult to combine management and conservation. Here, we combined population genomics and oceanographic modelling to understand how Northeast Atlantic populations (Cantabrian Sea to Norway) of the deep-sea sponge Phakellia ventilabrum are connected. The analysis comprised ddRADseq derived SNP datasets of 166 individuals collected from 57 sampling stations from 17 different areas, including two Marine Protected Areas, one Special Area of Conservation and other areas with different levels of protection. The 4,017 neutral SNPs used indicated high connectivity and panmixis amongst the majority of areas (Ireland to Norway), spanning ca. 2,500-km at depths of 99-900 m. This was likely due to the presence of strong ocean currents allowing long-distance larval transport, as supported by our migration analysis and by 3D particle tracking modelling. On the contrary, the Cantabrian Sea and Roscoff (France) samples, the southernmost areas in our study, appeared disconnected from the remaining areas, probably due to prevailing current circulation patterns and topographic features, which might be acting as barriers for gene flow. Despite this major genetic break, our results suggest that all protected areas studied are well-connected with each other. Interestingly, analysis of SNPs under selection replicated results obtained for neutral SNPs. The relatively low genetic diversity observed along the study area, though, highlights the potential fragility of this species to changing climates, which might compromise resilience to future threats.
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| 2. |
- White, Martin, et al.
(författare)
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BENTHIC BOUNDARY LAYER CHARACTERISTICS IN CONTRASTING COLD-WATER CORAL ECOSYSTEMS
- 2008
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Ingår i: 4th International Symposium on Deep-Sea Corals, Wellington, New Zealand, December 2008.
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Konferensbidrag (refereegranskat)abstract
- B io lo g y : F ee d in g , G ro w th a nd R ep ro du c t io n Dynamics within the bottom boundary layer (BBL) are fundamental to the control of the overall benthic ecosystem functioning through processes of organic matter fluxes, turbulence, seabed frictional stresses, and re-suspension processes. Observations of BBL structure using high frequency HF-ADCPs have been made to estimate the frictional stresses within, and adjacent to, coral reef habitats. Measurements at the Tisler Reef, Skagerrak, both in and outside the coral reef have shown that the logarithmic layer approach to estimating bottom stresses can be used and is comparable to directly measured Reynolds stress measurements. Outside regions of live coral clumps, where the seabed is characterised by rubble material, friction velocities (u *, which determines the bottom stress, τ=ρ.u * 2 ) may reach values up to 2 cm s-1 with a mean of 1 cm s-1. A corresponding roughness length, characterising the boundary layer height generated by the seabed, is 2 cm. In contrast, within localized live coral stands, a higher BBL is generated with a roughness length scale of 50 cm and higher friction velocity – a mean of 2.5 cm s-1 and maximum of 5 cm s-1. Interestingly the friction velocities generated by the live reef are higher than those in a rubble area for any particular impinging flow speed, as a result of the greater turbulence generated by the larger bottom topography of the live reef system. This may result in an increased time period for particles to remain in suspension over a reef system compared to other seabed environments. The measurements have been contrasted to those made at a deep carbonate mound located west of Ireland. Here, two bottom landers equipped with HF-ADCPs were deployed near the summit of a mound and in the adjacent gully between two mounds. Boundary layer characteristics in the gully region are similar to those found in the rubble region for the Tisler reef measurements. Measurements near the mound summit indicated higher frictional velocities present compared to the gulley region, again similar to the shallow water observations. The values of frictional velocity generated per impinging flow speed, however, fall between those found for the Tisler observations in and outside the reef, reflecting the bottom topography, which consisted of smaller scale, and more widely dispersed, coral clumps than at the Tisler reef. The results have obvious implications for the fluxes of organic mater, material suspension (availability) and feeding behavior at a coral ecosystem and we suggest they require inclusion into micro habitat mapping and reef growth models.
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