Broad Thermal Tolerance in the Cold-Water Coral Lophelia pertusa From Arctic and Boreal Reefs

Abstract

Along the Norwegian coasts and margins, extensive reefs of the stony coral Lophelia pertusa act as hotspots for local biodiversity. Climate models project that the temperature of Atlantic deep waters could rise by 1-3 • C by 2100. In this context, understanding the effects of temperature on the physiology of cold-water species will help in evaluating their resilience to future oceanic changes. We investigated the response of L. pertusa to stepwise short-term increases in temperature. We sampled corals from four reefs, two located north of the Arctic circle and two at the mid-Norwegian shelf (boreal). In on-board experiments (one per reef), the sampled fragments were exposed to increasing temperatures from 5 to 15 • C over 58 h. Respiration increased linearly by threefold for a 10 • C increase. The short-term temperature increase did not induce mortality, cellular (neutral red assay for lysosome membrane stability; but one exception) or oxidative stress (lipid peroxidation assay) -to a few exceptions. However, the variability of the respiration responses depended on the experiment (i.e., reef location), possibly linked to the genetic structure of the individuals that we sampled (e.g., clones or siblings). The corals from the Arctic and boreal regions appear to have a high tolerance to the rapid temperature fluctuations they experience in the field. Over extended periods of time however, an increased metabolism could deplete the energy stored by the corals, if not met by an increased food availability and/or uptake. Empirical data on organisms' thermal performance curves, such as the one presented in this study for L. pertusa, will be useful to implement predictive models on the responses of species and populations to climate change.

The carbon and nitrogen budget of Desmophyllum dianthus—a voracious cold-water coral thriving in an acidified Patagonian fjord

“…The metabolic flexibility of D. dianthus could allow colonization of different habitats, from shallow areas of fjords with a high variability of food, temperature, salinity and pH, to the environmentally more stable, deep CWC habitats ( Freiwald et al, 2004 ). Global warming increases the metabolic rate of CWCs ( Dodds et al, 2007 ; Gori et al, 2016 ; Dorey et al, 2020 ), which could cause severe energetical constraints for this and other CWC species.…”

Cold-Water Coral Reefs in the Langenuen Fjord, Southwestern Norway—A Window into Future Environmental Change

“…Due to surface warming in spring and summer, the seasonal isopycnal reaches~100 m. The uppermost CWCs on the wall reef setting (at 80-100 m, HH) experience temperatures >12 • C in late summer before the water is mixed in late autumn. This is~4 • C warmer than the mean temperature at these shallow reefs and likely enhances the metabolism of L. pertusa and increases their energetic demand [36,41]. Together with strong flow speeds (limiting prey capture rates in L. pertusa), seasonal high temperatures could restrict the upper limit of the CWCs on the fjord wall.…”

“…The summer thermocline with temperatures >12 • C would reach depths >100 m by the year 2100. The warming within the past 40 years has likely already increased the energy demand of CWCs compared to that in the 1970s, with possible effects on coral energy reserves and reproductive output if these are not met by increased food uptake rates [41]. The warming of coastal waters caused by climate change has likely led to a decreased frequency of intrusions of dense, oxygen-rich North Atlantic water with relatively high Ω Ar levels and has caused a general oxygen decline in the basin waters of some western Norwegian fjords with shallow sills (i.e., <100 m) [45,116].…”

“…CWCs are usually found in waters with temperatures <12 • C [13,29,39], but occasionally they thrive in warmer waters of~15 • C [15,40]. Even though CWCs can tolerate substantial fluctuations in temperature [41,42], a rise of only 2 • C for a few hours will significantly increase its energy demands [36,41], which could deplete energy stores if they are not met by increased food availability and/or uptake rates [35]. Ocean warming can also indirectly affect CWCs by changing primary production patterns [43] and reducing oxygen availability [44].…”

Benthic foraminiferal faunas associated with cold‐water coral environments in the North Atlantic realm

“…The main parameter controlling the development of CWCs is food availability. Furthermore, substrate availability, temperature, pH, salinity and oxygen availability also play a role (Davies & Guinotte, 2011;Davies et al, 2008;Dorey et al, 2020;Duineveld et al, 2012;Flögel et al, 2014;Maier et al, 2019;Mienis et al, 2012;Naumann et al, 2014;Taviani et al, 2005;Van Engeland et al, 2019). Food availability is in itself governed by a number of environmental variables, such as surface productivity, export production, upwelling and bottom-water currents (De Clippele et al, 2018;Hebbeln et al, 2016;Van Oevelen et al, 2009;White et al, 2005).…”