Environmental variability and biodiversity of megabenthos on the Hebrides Terrace Seamount (Northeast Atlantic)

Abstract

We present the first remotely operated vehicle investigation of megabenthic communities (1004–1695 m water depth) on the Hebrides Terrace Seamount (Northeast Atlantic). Conductivity-temperature-depth casts showed rapid light attenuation below the summit and an oceanographic regime on the flanks consistent with an internal tide, and high short-term variability in water temperature, salinity, light attenuation, aragonite and oxygen down to 1500 m deep. Minor changes in species composition (3–14%) were explained by changes in depth, substratum and oceanographic stability, whereas environmental variability explained substantially more variation in species richness (40–56%). Two peaks in species richness occurred, the first at 1300–1400 m where cooler Wyville Thomson Overflow Water (WTOW) mixes with subtropical gyre waters and the second at 1500–1600 m where WTOW mixes with subpolar mode waters. Our results suggest that internal tides, substrate heterogeneity and oceanographic interfaces may enhance biological diversity on this and adjacent seamounts in the Rockall Trough.

Population genetic structure and connectivity of deep‐sea stony corals (Order Scleractinia) in the New Zealand region: Implications for the conservation and management of vulnerable marine ecosystems

“…However, the extent of damage to corals caused by bottom trawling is not quantified, although qualitative estimates indicate that such damage can be extensive, in particular in localized areas around fishing hotspots, such as the seamounts where corals are predominantly found (Althaus et al, 2009;Clark & Rowden, 2009;Parker et al, 2009). Other factors, including environmental factors such as depth-dependent water temperature, pH, calcite and aragonite saturation concentrations, are also likely to contribute both historically and contemporaneously (Henry et al, 2014;Miller, Rowden, Williams, & Häussermann, 2011;Tracey et al, 2013), but are thought to be of lesser importance than fishing pressure in modern times. However, the most recent study of possible impacts of fishing activity on deep-sea corals (Miller & Gunasekera, 2017) reported that genetic diversity of S. variabilis and the solitary cup coral Desmophyllum dianthus on fished and unfished seamounts was similar.…”

Biological Communities on Seamounts and Other Submarine Features Potentially Threatened by Disturbance

“…Studies have highlighted the ability of live cold-water corals to maintain calcification at reduced pH (Maier et al, 2009; Form and Riebesell 2012) but synergistic effects with increasing temperature and longer-term effects on resource allocation and reproduction remain unknown. It is becoming clear that deep-water ecosystems may experience more natural variability in carbonate chemistry than was previously supposed (Findlay et al, 2013;Findlay et al, 2014) and that calcareous species can persist even in under-saturated conditions on Tasmanian seamounts (Thresher et al, 2011). However, undersaturated waters will be corrosive to dead coral skeletons that provide structural habitat for many other species, a factor potentially explaining the limited scleractinian coral reef framework on the Hebrides Terrace Seamount (Henry et al, 2014).…”

“…It is becoming clear that deep-water ecosystems may experience more natural variability in carbonate chemistry than was previously supposed (Findlay et al, 2013;Findlay et al, 2014) and that calcareous species can persist even in under-saturated conditions on Tasmanian seamounts (Thresher et al, 2011). However, undersaturated waters will be corrosive to dead coral skeletons that provide structural habitat for many other species, a factor potentially explaining the limited scleractinian coral reef framework on the Hebrides Terrace Seamount (Henry et al, 2014). Increased carbon dioxide and reduced pH may also directly affect marine organisms' physiology, growth, and behaviour (Wicks and Roberts, 2012).…”

Three‐Dimensional Dynamics of Baroclinic Tides Over a Seamount

“…There is evidence that seamounts form hot spots of biological activity in the oceans (Lavelle & Mohn, 2010;Morato et al, 2010). Analysis done by Rogers (1994) indicates that higher species richness detected at seamounts compared to coastal or oceanic areas can be a consequence of enhanced oceanic dynamical activity in these areas (Henry et al, 2014).…”