Developmental carry over effects of ocean warming and acidification in corals from a potential climate refugium, Gulf of Aqaba

Abstract

Coral reefs are degrading from the effects of anthropogenic activities, including climate change. Under these stressors, their ability to survive depends upon existing phenotypic plasticity, but also transgenerational adaptation. Parental effects are ubiquitous in nature, yet empirical studies of these effects in corals are scarce, particularly in the context of climate change. This study exposed mature colonies of the common reef-building coral Stylophora pistillata from the Gulf of Aqaba to seawater conditions likely to occur just beyond the end of this century during the peak planulae brooding season (Representative Concentration Pathway 8.5: pH −0.4 and +5°C beyond present day). Parent and planulae physiology were assessed at multiple time points during the experimental incubation. After 5 weeks of incubation, the physiology of the parent colonies exhibited limited treatment-induced changes. All significant time-dependent changes in physiology occurred in both ambient and treatment conditions. Planulae were also resistant to future ocean conditions, with protein content, symbiont density, photochemistry, survival and settlement success not significantly different compared with under ambient conditions. High variability in offspring physiology was independent of parental or offspring treatments and indicate the use of a bet-hedging strategy in this population. This study thus demonstrates weak climate-change-associated carryover effects. Furthermore, planulae display temperature and pH resistance similar to those of adult colonies and therefore do not represent a larger future population size bottleneck. The findings add support to the emerging hypothesis that the Gulf of Aqaba may serve as a coral climate change refugium aided by these corals' inherent broad physiological resistance.

Feeding increases the number of offspring but decreases parental investment of Red Sea coral Stylophora pistillata

“…In addition, temperatures of 32°C, 4°C above ambient, reduced time to settlement from 4 to 3 days in four broadcast spawning species from Okinawa and the Great Barrier Reef (Heyward & Negri, 2010) and increased mortality in P. damicornis from Taiwan (ambient 25°C, elevated temperature 29°C; Putnam, Mayfield, Fan, Chen, & Gates, 2013). Resistance of adult corals to above ambient temperatures has previously been identified in this population (Bellworthy & Fine, 2017;Fine et al, 2013;Krueger et al, 2017) and, in the absence of effects of temperature changes predicted within the next century upon planulae (see also Bellworthy et al, 2019), the current data begin to imply a similar resistance to ocean warming exists during early life history. It still however remains unknown whether postsettlement development may be a future bottleneck to the persistence of this climate change resilient population.…”

“…25°C). These temperatures represent an extension to which planulae from this population have previously been experimentally exposed (Bellworthy et al, ). Regardless of temperature, median time to settlement in U planulae was 24 hr postrelease, the first observation time point.…”

“…Likewise, experiments exposing adult S. pistillata to temperatures far beyond the assumed 28°C local bleaching threshold (1°C above maximum monthly mean temperature 26.75°C; Bellworthy & Fine, ) for up to 6 weeks did not result in any significant change in typical physiological indicators (Bellworthy & Fine, ; Fine et al, ; Krueger et al, ). A 5‐week parental exposure to ocean acidification (pH 7.6) and higher temperature (5°C above ambient) did not induce significant changes in either POI or offspring physiology, further attesting to the resistance of S. pistillata from the GoA both during early life stages and induction of carry over effects (Bellworthy et al, ). It has therefore been hypothesized that this region may act as a coral reef refuge from global climate change (Fine et al, ; but see Genevier, Jamil, Raitsos, Krokos, & Hoteit, ).…”

“…For example, reef‐building corals are the foundation organisms of the coral reef ecosystem and yet their persistence is threatened by the environmental consequences of increasing global carbon dioxide levels. Experimental studies of carry over effects, which manipulate the parental environment, are few in scleractinian corals (Bellworthy, Menoud, Krueger, Meibom, & Fine, ; Putnam & Gates, ; Putnam, Ritson‐Williams, Cruz, Davidson, & Gates, ). This is likely attributed to corals' relatively long time to sexual maturity, extended gametogenesis period, as well as typically a single annual reproductive cycle, and an inability to reliably induce spawning ex situ (but see Craggs et al, ).…”

“…These questions were addressed in this study with an experiment where S. pistillata colonies were fed for 5 months during gametogenesis, fertilization, and brooding, and the resulting effect on maternal condition, POI, and physiology were assessed. It was hypothesized that fed maternal colonies will produce planulae with greater POI but that this will not influence planulae thermal response in this thermally resistant population (Bellworthy & Fine, 2017;Bellworthy et al, 2019;Fine et al, 2013;Krueger et al, 2017). Time to settlement and survival of planulae were assessed under exposure to a broad thermal gradient ranging from 22 to 31°C where ambient seawater temperature was ca.…”