The physiological response of the deep-sea coralSolenosmilia variabilisto ocean acidification

Abstract

Several forms of calcifying scleractinian corals provide important habitat complexity in the deep-sea and are consistently associated with a high biodiversity of fish and other invertebrates. How these corals may respond to the future predicted environmental conditions of ocean acidification is poorly understood, but any detrimental effects on these marine calcifiers will have wider impacts on the ecosystem. Colonies of Solenosmilia variabilis, a protected deep-sea coral commonly occurring throughout the New Zealand region, were collected during a cruise in March 2014 from the Louisville Seamount Chain. Over a 12-month period, samples were maintained in temperature controlled (∼3.5 °C) continuous flow-through tanks at a seawater pH that reflects the region’s current conditions (7.88) and an end-of-century scenario (7.65). Impacts on coral growth and the intensity of colour saturation (as a proxy for the coenenchyme tissue that covers the coral exoskeleton and links the coral polyps) were measured bimonthly. In addition, respiration rate was measured after a mid-term (six months) and long-term (12 months) exposure period. Growth rates were highly variable, ranging from 0.53 to 3.068 mm year−1 and showed no detectable difference between the treatment and control colonies. Respiration rates also varied independently of pH and ranged from 0.065 to 1.756 µmol O2 g protein−1 h−1. A significant change in colour was observed in the treatment group over time, indicating a loss of coenenchyme. This loss was greatest after 10 months at 5.28% and could indicate a reallocation of energy with physiological processes (e.g. growth and respiration) being maintained at the expense of coenenchyme production. This research illustrates important first steps to assessing and understanding the sensitivity of deep-sea corals to ocean acidification.

The Yellow Coral Dendrophyllia cornigera in a Warming Ocean

“…Predictions anticipate that ca. 70% of known CWCs reefs will be exposed to waters corrosive to aragonite before the end of 21st century (Tittensor et al, 2010) up to evoking negative to counteractive scenarios for their eventual survival (Maier et al, 2011;McCulloch et al, 2012;Gammon et al, 2018). However, some studies reveal that net calcification rates, as well as dissolution rates of exposed skeleton and respiration rates of different deep-sea coral species, do not significantly change when exposed to high seawater pCO 2 , with D. cornigera showing no physiological alterations (Movilla et al, 2014;Rodolfo-Metalpa et al, 2015;Reynaud and Ferrier-Pagès, 2019).…”

Solenosmilia variabilis-bearing cold-water coral mounds off Brazil

“…Desmophyllum pertusum versus Solenosmilia variabilis: the influence of the coral species on mound formation Growth rates of individual S. variabilis have been determined to vary between 0.8 and 1.25 mm yr -1 in live caught field samples (Fallon et al 2014) and between 0.5 and 3 mm yr -1 (1.5 mm on average) in cultivation experiments (Gammon et al 2018). These growth rates are similar to the AR determined here (30 cm kyr -1 ) and for S. variabilis reefs on SW Pacific seamounts (21 cm kyr -1 ; Fallon et al 2014).…”

“…However, S. variabilis occurrences appear typically between 3 and 4°C, which is at least 3°C colder than flourishing D. pertusum mounds (Fallon et al 2014;Flögel et al 2014;Gammon et al 2018). Moreover, S. variabilis habitats are found in less aragonite saturated waters (Thresher et al 2011;Bostock et al 2015;Gammon et al 2018) compared to flourishing D. pertusum reefs and mounds (Flögel et al 2014). Nevertheless, whether these different ecological tolerances enable S. variabilis to form mounds is unknown.…”

Influence of Water Masses on the Biodiversity and Biogeography of Deep-Sea Benthic Ecosystems in the North Atlantic

“…The capacity of CWCs to cope with OA has been related to their ability to increase internal pH at the site of calcification (McCulloch et al, 2012a;Raybaud et al, 2017). However, it remains unclear whether calcification can be sustained indefinitely, as this is an energy demanding process (20-30% of CWC energy budget; Cohen and Holcomb, 2009) and OA also affects the coral metabolism (Hennige et al, 2014) and, the loss of the tissue surrounding and connecting polyps (Gammon et al, 2018).…”