Interactive Effects of Ocean Acidification and Warming on Growth, Fitness and Survival of the Cold-Water Coral Lophelia pertusa under Different Food Availabilities

Abstract

Cold-water corals are important bioengineers that provide structural habitat for a diverse species community. About 70% of the presently known scleractinian cold-water corals are expected to be exposed to corrosive waters by the end of this century due to ocean acidification. At the same time, the corals will experience a steady warming of their environment. Studies on the sensitivity of cold-water corals to climate change mainly concentrated on single stressors in short-term incubation approaches, thus not accounting for possible long-term acclimatisation and the interactive effects of multiple stressors. Besides, preceding studies did not test for possible compensatory effects of a change in food availability. In this study a multifactorial long-term experiment (6 months) was conducted with end-of-the-century scenarios of elevated pCO 2 and temperature levels in order to examine the acclimatisation potential of the cosmopolitan cold-water coral Lophelia pertusa to future climate change related threats. For the first time multiple ocean change impacts including the role of the nutritional status were tested on L. pertusa with regard to growth, "fitness," and survival. Our results show that while L. pertusa is capable of calcifying under elevated CO 2 and temperature, its condition (fitness) is more strongly influenced by food availability rather than changes in seawater chemistry. Whereas growth rates increased at elevated temperature (+4 • C), they decreased under elevated CO 2 concentrations (∼800 µatm). No difference in net growth was detected when corals were exposed to the combination of increased CO 2 and temperature compared to ambient conditions. A 10-fold higher food supply stimulated growth under elevated temperature, which was not observed in the combined treatment. This indicates that increased food supply does not compensate for adverse effects of ocean acidification and underlines the importance of considering the nutritional status in studies investigating organism responses under environmental changes.

Climate‐induced changes in the suitable habitat of cold‐water corals and commercially important deep‐sea fishes in the North Atlantic

“…Indeed, multiple studies link reduced food availability to reduced physiological performance (e.g. calcification and respiratory metabolism) and condition of cold-water corals (Büscher et al, 2017;Larsson, Lundälv, & van Oevelen, 2013;Naumann, Orejas, Wild, & Ferrier-Pagès, 2011), as well as their ability to cope with ocean change (Büscher et al, 2017;Georgian et al, 2016;Gomez et al, 2019;Maier et al, 2016;Wood, Spicer, & Widdicombe, 2008). In contrast, the direct link between POC flux and deep-sea fish abundances has proven difficult to demonstrate (Bailey, Ruhl, & Smith, 2006), despite some evidence that increased surface production may fuel key fish prey taxa such as benthic invertebrates (Bailey et al, 2006;Drazen, Bailey, Ruhl, & Smith, 2012;Ruhl & Smith, 2004).…”

Paradise lost: End‐of‐century warming and acidification under business‐as‐usual emissions have severe consequences for symbiotic corals

“…Although it is known that elevated temperature and OA together impact coral health, metabolism, and skeleton formation, the underlying interactive mechanisms of these factors are crucial in the assessment of the impact and magnitude of future changes (Bay, Rose, Logan, & Palumbi, 2017;Dove et al, 2013;Schoepf et al, 2019). The number of studies investigating the individual and combined effects of temperature and pCO 2 in an orthogonal design has steadily increased in recent years (Büscher, Form, & Riebesell, 2017;Edmunds et al, 2012;Reynaud et al, 2003;Schoepf et al, 2013). However, not many orthogonal studies address extreme warming and acidification conditions (Hoadley et al, 2016) such as under the RCP8.5 emission scenario, which predicts a rise of approximately +3.5°C and +570 µatm CO 2 for non-El Niño years by 2100 compared to present-day (PD) levels (Meinshausen et al, 2011;van Vuuren et al, 2011).…”

The Fate of Cold-Water Corals in a Changing World: A Geological Perspective

“…However, MPA provide no protection against threats induced by ongoing global change (Jackson et al, 2014) such as ocean warming, acidification, deoxygenation and decreasing particulate organic matter fluxes to the seabed as these cannot be controlled locally (e.g., Sweetman et al, 2017). In addition, this range of environmental parameters might be even more critical for the proliferation or survival of CWC considering a combined effect of multiple stressors (e.g., Büscher et al, 2017). Thus, to assess the vulnerability of CWC to future global change, there is an indispensable need to comprehensively understand their sensitivity to changing environmental conditions.…”

“…However, recent discoveries of hitherto unknown CWC reefs that exist today under rather "extreme" conditions [e.g., in terms of temperature or oxygen (Ramos et al, 2017)], force us to shift the upper and lower thresholds of environmental parameters beyond formerly described values. In addition, laboratory experiments conducted on several common CWC species (e.g., Lophelia pertusa, Madrepora oculata, and Dendrophyllia) provided additional information on their ecological requirements (e.g., in terms of temperature, carbonate system, food supply, and oxygen) (e.g., Tsounis et al, 2010;Gori et al, 2014;Movilla et al, 2014;Naumann et al, 2014;Maier et al, 2016;Büscher et al, 2017) and also indicate region-specific adaptations of CWC to particular environmental parameters (Dodds et al, 2007;Lunden et al, 2014). Furthermore, exceeding/undercutting such environmental thresholds ("tipping point") causing a local extinction of CWC so far has never been documented by field observations.…”