Abstract
Cold-water corals are associated with high local biodiversity, but despite their importance as ecosystem engineers, little is known about how these organisms will respond to projected ocean acidification. Since preindustrial times, average ocean pH has decreased from 8.2 to ~8.1, and predicted CO2 emissions will decrease by up to another 0.3 pH units by the end of the century. This decrease in pH may have a wide range of impacts upon marine life, and in particular upon calcifiers such as cold-water corals. Lophelia pertusa is the most widespread cold-water coral (CWC) species, frequently found in the North Atlantic. Here, we present the first short-term (21 days) data on the effects of increased CO2 (750ppm) upon the metabolism of freshly collected L. pertusa from Mingulay Reef Complex, Scotland, for comparison with net calcification. Over 21 days, corals exposed to increased CO2 conditions had significantly lower respiration rates (11.4±1.39 SE, µmolO2g−1tissuedryweighth−1) than corals in control conditions (28.6±7.30 SE µmolO2g−1tissuedryweighth−1). There was no corresponding change in calcification rates between treatments, measured using the alkalinity anomaly technique and 14C uptake. The decrease in respiration rate and maintenance of calcification rate indicates an energetic imbalance, likely facilitated by utilisation of lipid reserves. These data from freshly collected L. pertusa from the Mingulay Reef Complex will help define the impact of ocean acidification upon the growth, physiology and structural integrity of this key reef framework forming species.
Highlights
Cold-water corals are among the most three-dimensionally complex deep-sea habitats known and are associated with high local biodiversity (Roberts et al, 2006, 2009)
From CTD casts in June 2012, salinity increased with depth at Mingulay whereas temperature slightly decreased from the surface to the reef crest (Table 2)
Deeper CTD casts taken in July 2011 at the side of the Mingulay Reef mounds correlate with Table 1; such that AT and CT increased with depth (AT 2332.771.18; DIC 2149.072.08 at 172 m)
Summary
Cold-water corals are among the most three-dimensionally complex deep-sea habitats known and are associated with high local biodiversity (Roberts et al, 2006, 2009) Their remoteness and the relatively short history of ecological research in these habitats mean that to date, we have little information on how these ecosystems will fare in the face of predicted future climate change. Similar to their tropical counterparts, cold-water corals (referred to as CWC ) are under potential threat from increasing sea temperatures and ocean acidification. The aragonite saturation depth or ‘horizon’ (ASH) (Guinotte et al, 2006) is predicted to become shallower (shoal), making it more difficult for calcifying organisms near this depth to
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