Acute survivorship of the deep-sea coral Lophelia pertusa from the Gulf of Mexico under acidification, warming, and deoxygenation

Abstract

Changing global climate due to anthropogenic emissions of CO 2 are driving rapid changes in the physical and chemical environment of the oceans via warming, deoxygenation, and acidification. These changes may threaten the persistence of species and populations across a range of latitudes and depths, including species that support diverse biological communities that in turn provide ecological stability and support commercial interests. Worldwide, but particularly in the North Atlantic and deep Gulf of Mexico, Lophelia pertusa forms expansive reefs that support biological communities whose diversity rivals that of tropical coral reefs. In this study, L. pertusa colonies were collected from the Viosca Knoll region in the Gulf of Mexico (390 to 450 m depth), genotyped using microsatellite markers, and exposed to a series of treatments testing survivorship responses to acidification, warming, and deoxygenation. All coral nubbins survived the acidification scenarios tested, between pH of 7.67 and 7.90 and aragonite saturation states of 0.92 and 1.47. However, net calcification generally declined with respect to pH, though a disparate response was evident where select individuals net calcified and others exhibited net dissolution near a saturation state of 1. Warming and deoxygenation both had negative effects on survivorship, with up to 100% mortality observed at temperatures above 14 • C and oxygen concentrations of approximately 1.5 ml·l −1 . These results suggest that, over the short-term, climate change and OA may negatively impact L. pertusa in the Gulf of Mexico, though the potential for acclimation and the effects of genetic background should be considered in future research.

Intra-Specific Variation Reveals Potential for Adaptation to Ocean Acidification in a Cold-Water Coral from the Gulf of Mexico

“…Previous work indicates relatively low levels of clonality among distinct coral colonies at this site as compared to L. pertusa populations in the North Atlantic (Waller and Tyler, 2005;Lunden et al, 2014a). To ensure that distinct genotypes were used in our experiments, each coral fragment was genotyped according to methods used previously in a similar study of L. pertusa (Lunden et al, 2014a). Briefly, coral genotypes were determined using 10 L. pertusa microsatellite loci (Morrison et al, 2008; Molecular Ecology Resources database entry 51059) from total DNA extracted from coral polyps.…”

“…The average weight of the fragments at the start of the experiment was 15.81 ± 7.39 g. For the long-term experiment, net calcification rates were averaged monthly to yield a total of six time points. Percent net calcification per day was calculated by the equation described in Lunden et al (2014a):…”

“…In the lowest pH treatment, skeletal dissolution was Rates were calculated as the difference between initial weight and weight at the time of measurement for each fragment, and are presented as % increase in calcification day −1 . For comparative purposes, the calcification rates from the studies by Lunden et al (2014a) and Georgian et al (2016b) conducted with Lophelia pertusa from the Gulf and Mexico, and Form and Riebesell (2012) conducted with L. pertusa from the North Atlantic. observed at a rate of −0.033 ± 0.032% day −1 (Table 3, Figure 1) Table 4), indicating that different genotypes had different responses to the three pH treatments.…”

“…Moreover, these species naturally exhibit slow growth and calcification rates, which range between ∼2 to 9 mm year −1 (Brooke and Young, 2009;Larcom et al, 2014;Lartaud et al, 2014) making them particularly vulnerable to the effects of future ocean acidification. Nevertheless, recent evidence from experimental studies suggests that cold-water corals can be resistant to low aragonite saturation states, and may even be able to calcify in undersaturated conditions (Form and Riebesell, 2012;Maier et al, 2013;Hennige et al, 2015), though at a reduced rate (Maier et al, 2009;Lunden et al, 2014a). The ability to maintain calcification under lowpH conditions has been explained by the capacity of cold-water corals to upregulate the pH of their internal calcifying fluid by up to 0.8 units (McCulloch et al, 2012;Wall et al, 2015).…”

“…Standing variation to acidification has been investigated in a number of marine organisms, including bryozoans (Pistevos et al, 2011), oysters (Parker et al, 2012), coccolithophores (Langer et al, 2009;Lohbeck et al, 2012), and sea urchins (Kelly et al, 2013). Notably for cold-water corals, Lunden et al (2014a) found that Lophelia pertusa individuals from the Gulf of Mexico exhibited a highly variable calcification response to reduced pH conditions, suggesting that certain acidification-resistant genotypes may provide such an adaptive capacity.…”