Physiological response to elevated temperature and pCO2 varies across four Pacific coral species: Understanding the unique host+symbiont response

Abstract

The physiological response to individual and combined stressors of elevated temperature and pCO2 were measured over a 24-day period in four Pacific corals and their respective symbionts (Acropora millepora/Symbiodinium C21a, Pocillopora damicornis/Symbiodinium C1c-d-t, Montipora monasteriata/Symbiodinium C15, and Turbinaria reniformis/Symbiodinium trenchii). Multivariate analyses indicated that elevated temperature played a greater role in altering physiological response, with the greatest degree of change occurring within M. monasteriata and T. reniformis. Algal cellular volume, protein, and lipid content all increased for M. monasteriata. Likewise, S. trenchii volume and protein content in T. reniformis also increased with temperature. Despite decreases in maximal photochemical efficiency, few changes in biochemical composition (i.e. lipids, proteins, and carbohydrates) or cellular volume occurred at high temperature in the two thermally sensitive symbionts C21a and C1c-d-t. Intracellular carbonic anhydrase transcript abundance increased with temperature in A. millepora but not in P. damicornis, possibly reflecting differences in host mitigated carbon supply during thermal stress. Importantly, our results show that the host and symbiont response to climate change differs considerably across species and that greater physiological plasticity in response to elevated temperature may be an important strategy distinguishing thermally tolerant vs. thermally sensitive species.

Symbiodinium mitigate the combined effects of hypoxia and acidification on a noncalcifying cnidarian

“…Survival of symbiotic organisms ultimately depends on the physiological limitations of both the host and their symbionts. Maximum photochemical efficiency values of Symbiodinium were low relative to those previously observed for Symbiodinium in hospite of cnidarians (e.g., Enochs et al, 2014;Hoadley et al, 2015; including polyps of Cassiopea sp. Klein, Pitt, & Carroll, 2016) numbers and productivity, but natural population sizes were also substantially increased in proximity to a natural CO 2 vent (Suggett et al, 2012).…”

“…Survival of symbiotic organisms ultimately depends on the physiological limitations of both the host and their symbionts. Maximum photochemical efficiency values of Symbiodinium were low relative to those previously observed for Symbiodinium in hospite of cnidarians (e.g., Enochs et al., ; Hoadley et al., ; including polyps of Cassiopea sp. Klein, Pitt, & Carroll, ) and could reflect a number of biological (e.g., high light fields, chlororespiration), or measurement artefacts (e.g., lower values expected with imaging PAM; Levin, Suggett, Nitschke, Oppen, & Steinberg, ) that cannot presently be ascertained.…”

Temperature and Water Quality-Related Patterns in Sediment-Associated Symbiodinium Communities Impact Symbiont Uptake and Fitness of Juveniles in the Genus Acropora

“…More rapid rates of infection in juveniles exposed to Rib and Davies (central offshore) sediment treatments may reflect an increased capacity of A3, C15, and C to infect and proliferate within coral juveniles. The presence of A3, both when dominant or at background levels of abundance, also strongly impacted F v /F m in juveniles and provides corroborative support that numerically rare background symbionts contribute to changes in the photophysiological performance of their hosts (Erwin et al, 2012;Hoadley et al, 2015;Karim et al, 2015;Mortzfeld et al, 2015). Lower F v /F m values in juveniles that acquired symbionts from offshore sediments and spikes in chlorophyll fluorescence may indicate that the symbionts acquired were adapted to higher light environments (due to increased sediment particle size or decreased turbidity) and a stress response (Shapiro et al, 2016), respectively.…”

Ecophysiology of mesophotic reef‐building corals in Hawai‘i is influenced by symbiont–host associations, photoacclimatization, trophic plasticity, and adaptation

“…P. speciosa hosted mainly Symbiodinium type C across its depth range (0–60 m), whereas S. hystrix hosted Symbiodinium type D1a at shallow depths (0–20 m) and Symbiodinium C type at deeper depths (10–45 m; Cooper et al ). Interestingly, S. hystrix had an increase in metabolic costs when hosting Symbiodinium C compared to type D1a while exposed to higher irradiances, suggesting that metabolic demands may depend on Symbiodinium type (Hoadley et al ; Leal et al ; Pernice et al ). In the Red Sea, Symbiodinium densities and ratios of photoprotective and photosynthetic pigments decreased with depth (0–60 m) in Porites , Leptoseris , Pachyseris, and Podabacia.…”