Temperature Effects on the Growth Rates and Photosynthetic Activities of Symbiodinium Cells

Abstract

Coral bleaching is caused by environmental stress and susceptibility to bleaching stress varies among types of coral. The physiological properties of the algal symbionts (Symbiodinium spp.), especially extent of damage to PSII and its repair capacity, contribute importantly to this variability in stress susceptibility. The objective of the present study was to investigate the relationship between the growth rates and photosynthetic activities of six cultured strains of Symbiodinium spp. (clades A, B, C, D, and F) at elevated temperature (33 °C). We also observed the recovery of photodamaged-PSII in the presence or absence of a chloroplast protein synthesis inhibitor (lincomycin). The growth rates and photochemical efficiencies of PSII (Fv/Fm) decreased in parallel at high temperature in thermally sensitive strains, B-K100 (clade B followed by culture name) and A-Y106, but not in thermally tolerant strains, F-K102 and D-K111. In strains A-KB8 and C-Y103, growth declined markedly at high temperature, but Fv/Fm decreased only slightly. These strains may reallocate energy from growth to the repair of damaged photosynthetic machineries or protection pathways. Alternatively, since recoveries of photo-damaged PSII at 33 °C were modest in strains A-KB8 and C-Y103, thermal stressing of other metabolic pathways may have reduced growth rates in these two strains. This possibility should be explored in future research efforts.

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.…”

“…There is some evidence from in hospite and cultured studies that temperature regimes may influence local availability of thermally tolerant (clades D and F, Sawall et al, 2014) vs. thermally sensitive Symbiodinium types [A and B, although A1 is thermo-tolerant (e.g., Karim et al, 2015)]. Biogeographic patterns may also follow water quality gradients, as high levels of suspended sediments change light environments and nutrient levels (Storlazzi et al, 2015).…”

Revealing changes in the microbiome of Symbiodiniaceae under thermal stress

“…The four Symbiodiniaceae strains investigated within this experiment exhibited varying thermal sensitivities based on changes in maximum quantum yield of PSII ( F v /F m ) and growth rates. The largest reduction (80%) in F v /F m over the experimental period (T0 to TE) occurred for Breviolum strain B1 under heat stress, supporting previous findings that Breviolum contains thermally sensitive species (e.g., Robison and Warner, ; McGinley et al ., ; Karim et al ., ; Goyen et al ., ; Grégoire et al ., ). In contrast, Durusdinium strain D1a appeared to be the most thermally tolerant strain (as per Karim et al ., ; Goyen et al ., ), yet the temperature stress treatment still resulted in significant declines in F v /F m and growth rates relative to the control by TE.…”

“…The largest reduction (80%) in F v /F m over the experimental period (T0 to TE) occurred for Breviolum strain B1 under heat stress, supporting previous findings that Breviolum contains thermally sensitive species (e.g., Robison and Warner, ; McGinley et al ., ; Karim et al ., ; Goyen et al ., ; Grégoire et al ., ). In contrast, Durusdinium strain D1a appeared to be the most thermally tolerant strain (as per Karim et al ., ; Goyen et al ., ), yet the temperature stress treatment still resulted in significant declines in F v /F m and growth rates relative to the control by TE. While declines in PSII photochemical efficiency commonly reflects the thermal sensitivity of Symbiodiniaceae both in hospite (e.g., Warner et al ., ; Goyen et al ., ; Nitschke et al ., ) and ex hospite in cultures (e.g.…”

Phylogenetic signature of light and thermal stress for the endosymbiotic dinoflagellates of corals (Family Symbiodiniaceae)

“…Now, those phylotypes of Symbiodinium spp. representing multiple phenotypes with different rates of photosynthesis, capacity to photoacclimatize, stress tolerance, and metabolic interchange with their hosts (Iglesias‐Prieto and Trench , ; Banaszak et al ; Robison and Warner ; Reynolds et al ; Hennige et al ; Brading et al ; Buxton et al ; Karim et al ; Warner and Suggett ) can be placed within the context of the revised phylogeny. One of these phenotypic character states, the production of reactive oxygen species (ROS) and the activities of antioxidants such as the enzyme superoxide dismutase (SOD), known to differ among phylotypes in the cladal phylogeny (Suggett et al ; Lesser ; McGinty et al ; Roberty et al , ; Kreuger et al ), can also be re‐examined as it relates to the new phylogeny, and the phenomenon of coral bleaching.…”