Nursery optimization for kelp aquaculture in the Southern Hemisphere: the interactive effects of temperature and light on growth and contaminants

Figures & data

Figure 1. Bar plots of (a) sporophyte length and (b) sporophyte density on the seeded twine. Letters above the bars indicate significant differences based on the SNK-test (p < 0.05). Error bars show SEM, with n = 3.

Table 1. Sporophyte length per species. Summary of two-way ANOVA of the mean sporophyte length (mm) exposed to three temperatures (12°C, 15°C, and 18°C) and two light levels (30 and 60 μmol photons m⁻² s⁻¹), followed by a Student–Newman–Keuls (SNK) post-hoc test.

		Ecklonia radiata				Lessonia corrugata				Macrocystis pyrifera
Source of variation	df	MS	F	p	SNK	MS	F	p	SNK	MS	F	p	SNK
Temperature	2	7.68	41.31	<0.001		39.94	79.43	<0.001	§2	11.11	50.20	<0.001
Light	1	2.18	11.71	<0.001		0.01	0.02	0.88		19.85	89.71	<0.001
Temperature x Light	2	2.74	14.74	<0.001	§1	0.89	1.77	0.17		3.42	15.46	<0.001	§3
Residual	12	0.19				0.50				0.22

§1: 12°C 60 μmol m⁻² s⁻¹ < 12°C 30 μmol m⁻² s⁻¹ = 18°C 30 μmol m⁻² s⁻¹ = 15°C 60 μmol m⁻² s⁻¹ ≤ 18°C 60 μmol m⁻² s⁻¹ ≤ 15°C 30 μmol m⁻² s⁻¹

§2: 18°C < 15°C < 12°C.

§3: 18°C 60 μmol m⁻² s⁻¹ = 15°C 60 μmol m⁻² s⁻¹ = 18°C 30 μmol m⁻² s⁻¹ < 12°C 60 μmol m⁻² s⁻¹ = 15°C 30 μmol m⁻² s⁻¹ = 12°C 30 μmol m⁻² s⁻¹

Table 2. Sporophyte density per species. Summary of two-way ANOVA for the main and interactive effect of the mean number of sporophytes per cm of line, followed by a Student–Newman–Keuls (SNK) post-hoc test.

		Ecklonia radiata				Lessonia corrugata				Macrocystis pyrifera
Source of variation	df	MS	F	p	SNK	MS	F	p	SNK	MS	F	p	SNK
Temperature	2	136.01	2.56	0.12		154.19	5.58	0.02	§1	413.06	5.18	0.02	§2
Light	1	0.47	0.01	0.93		1.33	0.05	0.83		0.53	0.01	0.94
Temperature x Light	2	40.24	0.76	0.49		0.69	0.02	0.98		1.98	0.02	0.98
Residual	12	53.25				27.65				79.75

§1: 18°C < 15°C = 12°C.

§2: 18°C < 15°C = 12°C.

Figure 2. Boxplots of contamination score (between 0–5) for three kelp species. One asterisk (*) indicates a p value smaller than 0.05. Two asterisks (**) indicate a p value smaller than 0.01 as per Dunn’s post-hoc test.

Table 3. Contamination score per species. Scheirer–Ray–Hare test results for the main and interactive effects of a two-way non-parametric ANOVA.

	Temperature			Light level			Interaction
Species	df	H	p	df	H	p	df	H	p
Ecklonia radiata	2	11.45	0.003	1	1.61	0.205	2	0.41	0.813
Lessonia corrugata	2	12.72	0.002	1	0.08	0.782	2	0.15	0.926
Macrocystis pyrifera	2	9.90	0.007	1	1.36	0.244	2	1.16	0.560