Plasticity and remodelling of lipids support acclimation potential in two species of low-intertidal macroalgae, Fucus serratus (Phaeophyceae) and Palmaria palmata (Rhodophyta)

Abstract

This study aimed to investigate the seasonal changes in the lipid and pigment profiles of two macroalgae, Fucus serratus (Phaeophyceae) and Palmaria palmata (Rhodophyta). The two species displayed distinct differential seasonal patterns of lipid partitioning when collected from their natural habitat at times when species-specific maxima and minima in total fatty acids (TFA) concentrations occurred. F. serratus contained highest levels of TFA (40.07mgg−1DW) and triacylglycerols (TAG) (26.83mgg−1DW) during summer (July), in association with lowest levels of polyunsaturated fatty acids (PUFA, 30.2% of TFA) and pigments (1.44mgg−1DW chlorophyll a). In P. palmata, high levels of TFA (13.00mgg−1DW) were observed during spring (May), with high levels of polar lipids (10.00mgg−1DW) rich in PUFA (52.3% of TFA), and high levels of pigments (1.25mgg−1DW chlorophyll a and 10.88mgg−1DW phycoerythrin). The results suggest that summer-acclimated F. serratus diverted excess energy into storage lipids (TAG), while P. palmata was more sensitive and susceptible to degradation of its chloroplast membranes, resulting in a decrease in TFA, PUFA-rich polar lipids and pigments, and a release of FFA. The ability to accumulate TAG may be a key factor allowing acclimation to environmental stressors for F. serratus, a species with broader vertical distribution than P. palmata which is restricted to low-intertidal and upper subtidal shores in western Ireland.