Fig 1.
Changes in temperature over the course of the experiment exposing Symbiodiniaceae cultures to heat stress.
Parent cultures were acclimated for 30 days at 26°C. At the start of the experiment parent cultures were aliquoted in 250 mL triplicate bottles for each temperature and were subjected to increases in steps of 2°C every second day. After 4 h and 72 h of exposure to the final temperature, the photosynthetic parameters were measured, and samples were taken for ROS production estimates and flow cytometric characterization (see S2 Fig).
Fig 2.
Minimum haplotype network for the Symbiodiniaceae ITS 2 unique sequences.
Hatch marks on the lines represent a single nucleotide polymorphism (SNPs) and black dots represent indel sites. Haplotypes that did not match any previously defined ITS 2 types are color labeled according to the best hit identity obtained using Blastn. (a) Symbiodinium (b) Cladocopium.
Fig 3.
Responses of three Symbiodiniaceae cultures (Cladocopium sp. CCMR 0093; Symbiodinium sp. CCMR0095; Symbiodinium sp. CCMR0100) to thermal stress.
Each column of graphs represents one Symbiodiniaceae strain. Rows represent each variable measured using flow cytometry (a to c): average green fluorescence of the whole symbiont cell population stained with DCF; (d to f): proportion of ROS-positive cells i.e. cells above the green fluorescence threshold for DCF (see S2 Fig); (g to i): average green fluorescence of the ROS-positive cell population stained with DCF; (j to l): relative cell size expressed as average forward scattering light (FSC) signal of the whole non-stained symbiont cell population; (m to o): average chlorophyll fluorescence of the whole non-stained symbiont cell population. (#): Significant difference compared to the control group at 26°C (t-test; adjusted.p<0.1); (*): Significant difference compared to the same temperature and culture at 4 h and 72 h (t-test; adjusted.p<0.1). a.u.: arbitrary units.
Fig 4.
Photochemical performance obtained from PAM fluorometer analysis.
Strains are represented in columns, and variables as rows. a to c: maximum quantum yield measurements; d to f: Effective quantum yields; and g to i: NPQ. The colors indicate the moment of sampling (4 h, red; 72 h, blue).