2.1. Simulation of S. obliquus sp. C1S biomass
productivity in different ecoregions of South America
Previous studies suggested that the average algal productivity in summer
(high productivity season) and winter (low productivity season) could be
a good estimator of average annual productivity in any region[14,25]. To further confirm the appropriateness of
this simplification, we calculated the S. obliquus average
productivity of biomass, lipids or carbohydrates in the four seasons in
Buenos Aires, La Quiaca, Posadas (Argentina) and Fortaleza (Brazil) and
compared them against the average values considering only summer and
winter (Figure S1, Supporting information). Strong positive correlations
(r = 0.86; 0.87; or 0.96; P <0.0001, for biomass,
carbohydrates or lipids, respectively) suggested that a simplified model
based on summer and winter productivities would provide a good
estimation for mean annual productivities across a broad range of
simulated-climates.
Figure 1 shows the average summer and winter biomass productivity in
20-cm deep simulated ponds of cultures supplemented with
CO2. The calculated mean annual productivities were
16.76 ± 1.88; 13.72 ± 3.11; 13.03 ± 1.39; 10.61 ± 2.43; 10.56 ± 3.70;
and 7.36 ± 4.48 g · m- 2 · d-1 in
Fortaleza (Brazil), Paita (Peru), Caracas (Venezuela), Posadas, Buenos
Aires, and Comodoro Rivadavia (Argentina), respectively. The overall
mean annual productivity in South America was 12 ± 4 g ·
m- 2 · d-1 (n=24 ).
Seasonal variability between summer and winter was lower in Tropical and
Subtropical regions for summer to winter productivity ratios of 1.2:1;
1.4:1; 1.2:1; 1.5:1 in Fortaleza, Paita, Caracas, Posadas, respectively.
Our simulations suggest potential biomass productivities in summer, from
18.25 ± 0.54 g · m- 2 · d-1 to 11.24
± 0.2 g · m- 2 · d-1 in Fortaleza
(the highest in this study) and Comodoro Rivadavia (the lowest in this
study), respectively and a large seasonality and low productivity in
winter in Comodoro Rivadavia (3.49 ± 0.04 g · m- 2 ·
d-1).
Under nutrient-sufficient and short-cycle cultivation conditions,S. obliquus only presented low levels of lipids at 13.4 ± 2.9%
(w/w) across these simulations. Only a minor increase in lipids
accumulation was observed in the coldest condition analyze, which
corresponded to Comodoro Rivadavia winter simulated-climate, at 22.57 ±
0.23% (w/w). Carbohydrates also remained at low levels across the study
at about 29.3 ± 13.1% (w/w) and a mild tendency to increase in warmer
conditions at 32.1 ± 2.7% and 34.4 ± 4.4%, in the summer simulated-
climate of Paita and Fortaleza, respectively (Table S1, Supporting
information).