Physiological responses of the red algae Gracilaria caudata (Gracilariales) and Laurencia catarinensis (Ceramiales) following treatment with a commercial extract of the brown alga Ascophyllum nodosum (AMPEP)

Abstract

Extracts of brown algae are used commercially for agricultural crops due to their plant growth-promoting effects and they can also be applied to help improve seaweed cultivation. Gracilaria caudata is commercially exploited as a raw material for agar production in Brazil, and Laurencia catarinensis is a source of halogenated terpenoids with several biological activities. Investigations to understand the development of seaweeds of biotechnological interest are required in order to improve their cultivation and the sustainability for biomass production on an industrial scale. The aim of the present study was to evaluate the effects of Ascophyllum/Acadian marine plant extract powder (AMPEP), a commercial, water-soluble extract of the brown alga Ascophyllum nodosum, on the growth, branching development, and pigment content of G. caudata and L. catarinensis. Four concentrations of AMPEP (0, 0.1, 1.0, and 5.0 mg L−1) were added to sterilized seawater (seawater+AMPEP), and to a medium comprised of half-strength von Stosch solution (VSES/2+AMPEP). Experiments were performed under conditions of 23 ± 2 °C, a light:dark cycle of 14:10 h, salinity at 32 psu, and photon flux densities of 60 ± 10 μmol photons m−2 s−1. Data were analyzed by one-way ANOVA, followed by a posteriori multiple comparison, Student-Newman-Keuls’ test. Treatments of seawater+AMPEP at concentrations of 0.1 and 1.0 mg L−1 stimulated the growth rates of G. caudata when compared to the control. However, the effects of seawater+AMPEP and VSES/2+AMPEP on the branching architecture of the thalli were not significant for either species. Concentrations of phycoerythrin, phycocyanin, allophycocyanin, and chlorophyll-a in L. catarinensis were stimulated by the highest concentration of VSES/2+AMPEP (i.e., 5.0 mg L−1). This is the first study to report the stimulatory effect of AMPEP on the phycobiliprotein contents of selected red algae. Furthermore, seawater+AMPEP in concentrations of 0.1 and 1.0 mg L−1 stimulated growth rates of G. caudata, which could be applied in its large-scale cultivation. The results obtained for G. caudata and L. catarinensis, an agar-producing and a terpenoid-producing species, respectively, contributed to extending the knowledge of the beneficial uses of a brown seaweed-derived extract with biostimulatory properties for use with cultivated, economically important red algae.