Cold-water coral reef frameworks, megafaunal communities and evidence for coral carbonate mounds on the Hatton Bank, north east Atlantic

Abstract

Offshore banks and seamounts sustain diverse megafaunal communities including framework reefs formed by cold-water corals. Few studies have quantified environmental effects on the alpha or beta diversity of these communities. We adopted an interdisciplinary approach that used historical geophysical data to identify topographic highs on Hatton Bank, which were surveyed visually. The resulting photographic data were used to examine relationships between megafaunal communities and macrohabitat, the latter defined into six categories (mud, sand, cobbles, coral rubble, coral framework, rock). The survey stations revealed considerable small-scale variability in macrohabitat from exposed Late Palaeocene lava flows to quiescent muddy habitats and coral-built carbonate mounds. The first reported evidence for coral carbonate mound development in UK waters is presented, which was most pronounced near present day or former sites of topographic change suggesting that local current acceleration favoured coral framework growth and mound initiation.Alpha diversity varied significantly across macrohabitats, but not between rock and coral rubble, or between smaller-grain sized categories of cobbles, sand and mud. Community composition differed between most macrohabitats, and variation in beta diversity across Hatton Bank was largely explained by fine-scale substratum. Certain megafauna were clearly associated with particular macrohabitats, with stylasterid corals notably associated with cobble and rock habitats and coral habitats characterised by a diverse community of suspension-feeders. The visual surveys also produced novel images of deep-water megafauna including a new photographic record of the gorgonian coral Paragorgia arborea, a species not previously reported from Rockall Plateau.Further interdisciplinary studies are needed to interpret beta diversity across these and other environmental gradients on Hatton Bank. It is clear that efforts are also needed to improve our understanding of the genetic connectivity and biogeography of vulnerable deep-water ecosystems and to develop predictive models of their occurrence that can help inform future conservation measures.

Deep, diverse and definitely different: unique attributes of the world's largest ecosystem

“…Cidaris spp., Gorgonocephalus sp.) (Hovland, 2008;Roberts et al, 2006Roberts et al, , 2008. Although the inventory is ever growing, currently over 1300 species have been reported from cold-water coral reefs, some of which are new to science (Myers and Hall-Spencer, 2004;Mortensen and Fosså, 2006;Henry and Roberts, 2007;Guerra-Garcia, 2008).…”

“…Although the inventory is ever growing, currently over 1300 species have been reported from cold-water coral reefs, some of which are new to science (Myers and Hall-Spencer, 2004;Mortensen and Fosså, 2006;Henry and Roberts, 2007;Guerra-Garcia, 2008). There are also biogeogrpahic variations in the species found associated to Lophelia and an overall biodiversity decrease from south to north (Hall-Spencer et al, 2002Roberts et al, 2008). The Lophelia reefs found in the NE Atlantic are complex habitats with coral colonies up to ca.…”

Progress in marine geoconservation in Scotland’s seas: assessment of key interests and their contribution to Marine Protected Area network planning

“…Biogenic sediment mounds are elevated features composed of the skeletal remnants of scleractinian cold-water corals (mainly Lophelia pertusa and Madrepora oculata) and a veneer of sands, muds and silts. The largest are the giant carbonate mounds, for example on the margins of the Rockall Trough and Plateau (Mienis et al, 2007;Roberts et al, 2008), that can be over 300 m high. Their location depends on the relatively strong currents that sweep the upper part of the slope in this region, providing a food supply for the cold water coral L. pertusa.…”

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

“…The aragonite skeleton of the polyps increases habitat complexity both at and above the seafloor (Rogers, 1999). Dead coral polyps provide hard substrate for sessile filter-feeding organisms (López Correa et al, 2004), with the complexity of the reef morphology providing refuge for mobile organisms such as fish (Husebø et al, 2002;Costello et al, 2005;Ross and Quattrini, 2007;Ballion et al, 2012;D'Onghia et al, 2012), shrimp and other crustaceans (Reed et al, 1982;Mortensen et al, 1995;Krieger and Wing., 2002; Roberts et al, 2008;Le Guilloux et al, 2010;D'Onghia et al, 2012). Local hydrodynamic flow may be influenced by coral structure, enhancing or reducing local depositional rates across a reef, or entrapping suspended material in turbidity loops above the reef structure (Mortensen et al, 1995White, 2007;Wagner et al, 2011).…”