Figure 1.
Phenometrics ePBR schematic diagram.
Light intensity is controlled using a white light LED array and culture temperature is controlled with a Peltier controlled temperature jacket. The PBR is comprised of a magnetically-stirred chamber, filled with a 10% v/v N. oculata stock culture inoculum in f/2 medium. Aeration with ambient air is supplied through a gas dispersion tube. Dissolved oxygen (pO2) is measured optically (PyroScience) and pH is measured electrochemically (Phenometrics).
Figure 2.
Measurements of N. oculata growth.
N. oculata grown in Phenometrics ePBRs under two different temperature regimes: constant temperature (circles) in A-C and sinusoidal temperature (triangles) in D-F. Growth was measured by microscopic cell counts (A, D), Chl a extraction (B, E) and in vivo fluorometry (C, F). For constant temperatures n = 4, for sinusoidal temperatures n = 3; error bars represent ±1 standard error. A logistic fit based on the method of least squares [45] was used to model algal growth (B, C, E, F; solid line). Linear regression was used to model subsequent Chl a depletion, which occurred after the exponential growth phase (B, C; dotted line).
Figure 3.
Constant temperature pO2 profiles.
Dissolved oxygen profiles of N. oculata when exposed to constant temperature. Two representative PBRs are shown (A, B, C and D, E, F). Top panels (A, D) display the entire experiment, middle panels (B, E) present in more detail the pO2 profile during the exponential growth phase (day 4 to day 8), and bottom panels (C, F) highlight a single day (day 5). White regions represent the sinusoidal light regime, thin red lines give the smoothed culture temperature and thick blue lines show the pO2 profile. Large spikes on even-numbered days are caused by short interruptions to the air supply during periodic oxygen evolution measurements.
Figure 4.
Sinusoidal temperature pO2 profiles.
Dissolved oxygen profiles of N. oculata when exposed to sinusoidal temperature. Two representative PBRs are shown (A, B, C and D, E, F). Top panels (A, D) display the entire experiment, middle panels (B, E) present in more detail the pO2 profile during the exponential growth phase (day 4 to day 8), and bottom panels (C, F) highlight a single day (day 5). White regions represent the sinusoidal light regime, thin red lines give the smoothed culture temperature and thick blue lines show the pO2 profile. Large spikes on even-numbered days are caused by short interruptions to the air supply during periodic oxygen evolution measurements.
Figure 5.
Constant temperature pH profiles.
Smoothed (moving average) pH profiles of N. oculata when exposed to constant temperature. Two representative PBRs are shown (A, B and C, D). Top panels (A, C) display the entire experiment, while bottom panels (B, D) present in more detail the pH profile during the exponential growth phase (day 4 to day 8). White regions represent the sinusoidal light regime, thin red lines give the smoothed culture temperature and thick green lines show the pH profile.
Figure 6.
Sinusoidal temperature pH profiles.
Smoothed (moving average) pH profiles of N. oculata when exposed to sinusoidal temperature. Two representative PBRs are shown (A, B and C, D). Top panels (A, C) display the entire experiment, while bottom panels (B, D) present in more detail the pH profile during the exponential growth phase (day 4 to day 8). White regions represent the sinusoidal light regime, thin red lines give the smoothed culture temperature and thick green lines show the pH profile.
Figure 7.
Quantum yield of photosystem II and net photosynthesis under constant temperature.
Algal physiology parameters, including: the quantum yield of photosystem II (YII) measured using PAM fluorometry (A, circles), the rate of oxygen concentration change when positive, representing net photosynthesis (B, crosses), and net photosynthesis normalised against Chl a content (C, triangles). Data were collected on alternate days, at 6 time points throughout the diel cycle. White areas represent the sinusoidal light regime.
Figure 8.
Quantum yield of photosystem II and net photosynthesis under sinusoidal temperature.
Algal physiology parameters, including: the quantum yield of photosystem II (YII) measured using PAM fluorometry (A, circles), the rate of oxygen concentration change when positive, representing net photosynthesis (B, crosses), and net photosynthesis normalised against Chl a content (C, triangles). Data were collected on alternate days, at 6 time points throughout the diel cycle. White areas represent the sinusoidal light regime.