Mixed approach on Chroodactylon ornatum (Stylonematophyceae, Rhodophyta) tolerance to hyposalinity: growth, photosynthetic performance and carbohydrate analysis

ABSTRACT

Chroodactylon ornatum is a cosmopolitan non-Florideophycean red alga with a simple morphology, generally described as a euryhaline species. Herein, we compared the response of a marine strain under exposure to different salinities (3, 7.5, 15 and 30 psu) through the analyses of growth, morphology, chlorophyll a fluorescence, floridean starch properties, and mucilage composition. In 3 psu, the cultures consisted of solitary cells whereas the typical pseudofilamentous morphology of increasing length was found at higher salinities. The species grew in the whole range of salinities, although growth response together with photosynthetic efficiency were maximum in full seawater. The maximum relative electron transport rate (rETR) was significantly lower under hyposaline conditions, concomitant with the increase in photophysical decay but not in non-photochemical quenching of chlorophyll fluorescence (NPQ). Higher phycocyanin content at the highest salinity tested (30 psu) could be related to a more efficient energy transfer to the reaction centre. The amylopectin:amylose ratios were higher in 7.5 and 30 psu. Agarans extracted at different salinities showed similar sulphation degrees, but there was an increase in xylose content in the mucilage from lower salinities. This could be related to a change in physical properties of the sheath polysaccharide, yielding a polymer with lower gelling capacity which hampered the formation and/or elongation of pseudofilaments.

KEYWORDS:

• Agaran
• Floridean starch
• PAM fluorometry
• Photosynthetic yield
• Salinity

Acknowledgements

The authors are grateful to the University of Buenos Aires (UBACyT20020170100037BA and 20020170100255BA), CONICET (PIP 298/14), and ANPCyT (PICT 2017-01675) for granting this project. JMR developed this work with a fellowship from CONICET (Argentina). MGL and CAS are Research Members of CONICET (Argentina). MCR and CAS would like to dedicate this paper to the memory of Dr Alberto S. Cerezo.

AUTHOR CONTRIBUTIONS

Y. Daglio: growth experiments, LM images, pigment and carbohydrate analyses and editing of the manuscript; J.M. Romero: chlorophyll fluorescence experiments, data analysis and editing manuscript; M.G. Lagorio: chlorophyll fluorescence analysis and editing manuscript; C.A. Stortz: carbohydrate analyses and editing of the manuscript; M.C. Rodríguez: growth experiments design, project direction, supervision of experiments, data analysis, drafting and editing of the manuscript.

DISCLOSURE STATEMENT

No potential conflict of interest was reported by the authors(s).

SUPPLEMENTARY MATERIAL

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Additional information

Funding

This work was supported by the Agencia Nacional de Promoción Científica y Tecnológica [PICT 2017-01675]; CONICET [PIP 298/14]; Secretaría de Ciencia y Técnica, Universidad de Buenos Aires [UBACyT20020170100037BA and 20020170100255BA].