Effects of thermal acclimation and photoacclimation on lipophilic pigments in an invasive and a native cyanobacterium of temperate regions

Figures & data

Table 1. Optimized binary gradient system for the separation of phytoplankton lipophilic pigments on Waters Symmetry C18 column. Eluent A was 45 : 45 : 10 methanol : acetonitril : 1 M ammonium acetate (v/v/v) +3% 0.1 M ammonium acetate (v/v). Eluent B was 45 : 55 acetonitril : acetone (v/v).

Time (min)	Eluent A (%)	Eluent B (%)
0	100	0
0.5	100	0
4.5	80	20
6.0	80	20
11.0	0	100
16.5	0	100
17.5	100	0
25	100	0

Fig. 1. Mean content of the major lipophilic pigments chlorophyll a (Chl a), 4-hydroxymyxol glycoside (4-OH-Myxol), myxol glycoside (Myxol), echinenone (Echi) and β-carotene (β-Car) per dry weight (DW) (mg g⁻¹) and carotenoid to chlorophyll a ratios (mg mg⁻¹) of three temperate (hatched bars) and three tropical C. raciborskii strains (grey bars). Strains were grown at different combination of temperature (°C) and light intensity (µmol photons m⁻² s⁻¹) displayed as temperature/light intensity. Pigment content is given as mean and standard deviation of one replicate of three strains each (n = 3). Asterisks mark significant differences between temperate and tropical strains.

Fig. 2. Content of major lipophilic pigments per dry weight (DW) (mg g⁻¹) and ratios of carotenoids (Car) to chlorophyll a (Chl a) (mg mg⁻¹) of C. raciborskii strain 24G7 (A, C) and A. gracile strain 16D11 (B, D) grown at 80 µmol photons m⁻² s⁻¹ and seven temperatures from 10 to 35°C. Lines represent temperature-dependent growth curves (day⁻¹) (A, B).

Table 2. Content of major lipophilic pigments per dry weight (DW) (mg g⁻¹) and growth rates (day⁻¹) of C. raciborskii strain 24G7 (C) and A. gracile strain 16D11 (A) acclimated to different temperatures and 80 µmol photons m⁻² s⁻¹. Mean and standard deviation of three pigment samples taken at different time-points during steady-state growth are given (n = 3). Differences of the pigment contents between the two species were tested for significance with t-test for independent samples and Mann–Whitney U-test. Abbreviations: ^ns non significant; *P ≤ 0.05; ^** P ≤ 0.01; ^*** P ≤ 0.001.

	Growth rate		Chlorophyll a		Total carotenoids		4-Hydroxymyxol glycoside		Myxol glycoside		Echinenone		β-Carotene
	(day^−1)		(mg g^−1 DW)		(mg g^−1 DW)		(mg g^−1 DW)		(mg g^−1 DW)		(mg g^−1 DW)		(mg g^−1 DW)
Temperature (°C)	C	A	C	A	C	A	C	A	C	A	C	A	C	A
10 ± 0.5	−0.01	0.15	2.96***	6.29	2.87**	1.69	2.10***	0.64	0.08**	0.30	0.45**	0.32	0.10*	0.25
15 ± 0.5^a	0.11	0.17	5.82	10.04	2.94	2.15	1.96	0.79	0.25	0.29	0.50	0.39	0.20	0.47
20 ± 0.5	0.25	0.27	10.69**	14.79	2.47*	1.85	1.24**	0.53	0.20^ns	0.16	0.55*	0.45	0.43^ns	0.55
25 ± 0.5	0.31	0.27	12.08**	14.71	2.51^ns	2.34	1.14*	0.72	0.17**	0.31	0.64*	0.51	0.52^ns	0.66
27.5 ± 0.5	0.33	0.29	12.94*	14.16	2.63^ns	2.46	1.14**	0.78	0.21***	0.45	0.73***	0.49	0.50^ns	0.62
30 ± 0.5	0.33	0.26	12.73**	11.45	2.55^ns	2.27	1.06**	0.76	0.17***	0.39	0.72***	0.48	0.54^ns	0.52
35 ± 0.5	0.11	–	8.08	–	3.11	–	1.72	–	0.06	–	0.88	–	0.37	–
^aNo statistical tests were done at 15°C as only two filters were available for C. raciborskii.

Fig. 3. Mean content of the major pigments per dry weight (DW) (mg g⁻¹) and light-dependent growth curves (day⁻¹) of three German C. raciborskii strains (left) and three German A. gracile strains (right) grown at 20 and 15°C and four different light intensities. The growth curve is given as a fit of growth rates of the three strains each.

Fig. 4. Ratios of total carotenoids (Total Car), 4-hydroxymyxol glycoside (4-OH-Myxol), myxol glycoside (Myxol), echinenone (Echi) and β-carotene (β-Car) to chlorophyll a (Chl a), given as mean and standard deviation of three German C. raciborskii strains (black boxes) and three German A. gracile strains (open boxes). Cultures were grown at 20°C (left panels) and 15°C (right panels) and four different light intensities. Linear regression was performed without the carotenoid content at the lowest light intensity. The slope b of the regression curve and the coefficient of determination R ² are displayed in standard font for C. raciborskii and in italics for A. gracile.

Table 3. Content of major lipophilic pigments per dry weight (DW) (mg g⁻¹) and growth rates (day⁻¹) of three German C. raciborskii (C) and three German A. gracile (A) strains acclimated to 15 and 20°C and different light intensities. Pigment content is given as the mean and standard deviation of one sample for each of three strains of each species (n = 3). Differences of the pigment contents between the two species were tested for significance with t-test for independent samples and Mann–Whitney U-test. Abbreviations: ^ns non significant; *P ≤ 0.05; ^** P ≤ 0.01; ^*** P ≤ 0.001.

	Growth rate		Chlorophyll a		Total carotenoids		4-Hydroxymyxol glycoside		Myxol glycoside		Echinenone		β-Carotene
	(day^−1)		(mg g^−1 DW)		(mg g^−1 DW)		(mg g^−1 DW)		(mg g^−1 DW)		(mg g^−1 DW)		(mg g^−1 DW)
Light intensity (µmol photons m^−2 s^−1)	C	A	C	A	C	A	C	A	C	A	C	A	C	A
20°C
20 ± 2	0.09	0.09	16.23^ns	15.53	5.16*	3.01	2.94**	1.16	0.33^ns	0.18	1.00*	0.53	0.85^ns	0.98
82 ± 11	0.25	0.29	11.67^ns	13.42	3.29*	1.67	1.76*	0.48	0.37^ns	0.14	0.62*	0.38	0.51^ns	0.52
169 ± 11	0.39	0.38	9.26^ns	10.51	3.72*	2.49	1.93**	0.78	0.47^ns	0.41	0.70*	0.46	0.59^ns	0.63
282 ± 30	0.34	0.42	7.50^ns	7.47	4.17*	2.62	2.39*	0.69	0.45*	0.60	0.76*	0.44	0.55^ns	0.55
15°C
25 ± 5	0.05	0.07	9.55^ns	13.11	6.25***	2.18	4.22***	0.89	0.47*	0.10	0.99**	0.47	0.51^ns	0.56
66 ± 8	0.11	0.15	7.35*	9.85	3.73*	1.54	2.45*	0.59	0.36^ns	0.15	0.59*	0.29	0.29^ns	0.35
101 ± 11	0.14	0.20	6.67*	9.63	4.49*	2.57	2.95**	0.96	0.50^ns	0.40	0.68*	0.40	0.36**	0.58
308 ± 31	0.16	0.28	4.99^ns	7.06	4.56*	2.89	3.01***	0.85	0.59^ns	0.75	0.62*	0.43	0.33**	0.57

Fig. 5. Non-photochemical quenching of fluorescence (NPQ) plotted against photosynthetically active radiation (PAR) emitted by the PHYTO-PAM device. Three C. raciborskii (left panel) and three A. gracile (right panel) strains were grown at 88 µmol photons m⁻² s⁻¹ and 15°C (open symbols) and 20°C (closed symbols), respectively. NPQ is given as mean and standard deviation of the measurements of three different strains per species.