Effects of seawater sulfur starvation and enrichment on Gracilaria gracilis growth and biochemical composition

• Published in: Scientific reports Vol. 12; no. 1; p. 11095
• Main Authors: Mensi, Fethi, Ben Ghedifa, Aziz, Rajhi, Hayfa
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 30-06-2022; Nature Publishing Group; Nature Portfolio
• Subjects: 704/158; 704/47; 704/829; Algae; Biochemical composition; Chemical analysis; Coastal zone; Gracilaria gracilis; Growth rate; Humanities and Social Sciences; Laboratory culture; Lagoons; Marine aquaculture; multidisciplinary; Science; Science (multidisciplinary); Seawater; Sulfates; Sulfur; Water analysis
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-022-15303-6

The genus Gracilaria, largest biomass producer in coastal regions, encompasses a wide range of species including
Gracilaria gracilis
. Nowadays, there is a spate of interest in its culture in lagoon where the water sulfate concentration is variable. A laboratory culture was carried out to determine the sulfate concentration effect on their growth as well as their biochemical composition, which were 2.5, 27 or 50 mM, referred to as SSS (sulfur starved seawater), SW (seawater) and SES (sulfur enriched seawater).We found that the sulfate content of the surrounding medium is a key parameter influencing both the alga growth and its composition. However, seawater proved to be the most suitable environment to sustain alga growth, proteins, R-phycoerythrin and agar yields, but sulfur enrichment and starvation affects them. The sulfate degree of agar and therefore its quality is related to the medium sulfate concentration. We conclude that sulfur starvation (2.5 mM) for three weeks, led to severe growth retardation, lower agar yield and quality and indicated the limit potential of
G. gracilis
for mariculture under these conditions. These results demonstrated that the success of
G. gracilis
culture in the lagoon is feasible if sulfate concentration is closer to that of seawater.