Microhabitat and shrimp abundance within a Norwegian cold-water coral ecosystem

Cold-water coral (CWC) reefs are heterogeneous ecosystems comprising numerous microhabitats. A typical European CWC reef provides various biogenic microhabitats (within, on and surrounding colonies of coral species such as Lophelia pertusa, Paragorgia arborea and Primnoa resedaeformis, or formed by their remains after death). These microhabitats may be surrounded and intermixed with non-biogenic microhabitats (soft sediment, hard ground, gravel/pebbles, steep walls). To date, studies of distribution of sessile fauna across CWC reefs have been more numerous than those investigating mobile fauna distribution. In this study we quantified shrimp densities associated with key CWC microhabitat categories at the Røst Reef, Norway, by analysing image data collected by towed video sled in June 2007. We also investigated shrimp distribution patterns on the local scale (<40 cm) and how these may vary with microhabitat. Shrimp abundances at the Røst Reef were on average an order of magnitude greater in biogenic reef microhabitats than in non-biogenic microhabitats. Greatest shrimp densities were observed in association with live Paragorgia arborea microhabitat (43 shrimp m−2, SD = 35.5), live Primnoa resedaeformis microhabitat (41.6 shrimp m−2, SD = 26.1) and live Lophelia pertusa microhabitat (24.4 shrimp m−2, SD = 18.6). In non-biogenic microhabitat, shrimp densities were <2 shrimp m−2. CWC reef microhabitats appear to support greater shrimp densities than the surrounding non-biogenic microhabitats at the Røst Reef, at least at the time of survey.

Microhabitat and shrimp abundance within a Norwegian cold-water coral ecosystem

Cold-water coral reefs are highly heterogeneous ecosystems comprising of a range of diverse microhabitats. In a typical European cold-water coral reef various biogenic habitats (live colonies of locally common coral species such as Lophelia pertusa, Paragorgia arborea and Primnoa resedaeformis, dead coral structure, coral rubble) may be surrounded and intermixed with non-biogenic habitats (soft sediment, hardground, gravel/pebbles, steep walls). To date, studies of distribution of sessile fauna across these microhabitats have been more numerous than those investigating mobile fauna distribution. In this study we quantified shrimp densities associated with key CWC habitat categories at the Røst reef, Norway, by analysing image data collected by towed video sled. We also investigated shrimp distribution patterns on the local scale (<40 cm) and how these may vary with habitat. We found shrimp abundances at the Røst reef to be on average an order of magnitude greater in biogenic reef habitats than in non-biogenic habitats. Greatest shrimp densities were observed in association with live Paragorgia arborea habitats (43 shrimp m−2, SD = 35.5), live Primnoa resedaeformis habitats (41.6 shrimp m−2, SD = 26.1) and live Lophelia pertusa habitats (24.4 shrimp m−2, SD = 18.6). In non-biogenic habitats shrimp densities were <2 shrimp m−2. We conclude that CWC reef habitats clearly support greater shrimp densities than the surrounding non-biogenic habitats on the Norwegian margin.

Ages and growth rates of some deep-sea gorgonian and antipatharian corals of Newfoundland and Labrador

Using bomb-14C dating and growth ring counting methods, we calculate life spans and growth rates of six species of deep-sea corals collected at depths of between 400 and 900 m from the continental slope of Newfoundland and Labrador. Bamboo corals ( Acanella arbuscula , Keratoisis ornata ) and antipatharians ( Stauropathes arctica ) secrete concentric growth rings in their axial skeletons, which were proven to form annually for K. ornata and S. arctica. These species had the lowest radial growth rates of 33 ± 11 to 75 ± 11 μm·year–1. Primnoa resedaeformis and Paramuricea spp. had higher radial growth rates of 83 ± 6 to 215 ± 37 μm·year–1. Paragorgia arborea had the highest radial growth rate of 830 ± 120 μm·year–1. Axial growth rates ranged from 0.56 ± 0.05 cm·year–1 for a specimen of Paramuricea spp. to 2.61 ± 0.45 cm·year–1 for a specimen of Primnoa resedaeformis . Life spans ranged from 18 ± 4 years for a live-collected P. resedaeformis to 200 ± 30 years for a subfossil specimen of K. ornata. Because all of the corals were from heavily fished areas, it is likely that age distributions are biased towards smaller and younger colonies. Recovery of deep-sea corals from fishing-induced damage will take decades to centuries.